Biology as Scheme of Work
Content
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Scheme of work
Cambridge International AS and A Level
Biology
9700
For examination from 2016
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Contents
Overview ........................................................................................................................................................................................................................................................... 3
Key concepts ............................................................................................................................................................................................................................................... 3
Practical work .............................................................................................................................................................................................................................................. 4
Suggested teaching order............................................................................................................................................................................................................................ 5
Teacher support........................................................................................................................................................................................................................................... 8
Unit 1: Biological molecules ............................................................................................................................................................................................................................ 11
Unit 2: Cells as the basic units of life .............................................................................................................................................................................................................. 27
Unit 3: DNA and the mitotic cell cycle ............................................................................................................................................................................................................. 40
Unit 4: Transport and gas exchange............................................................................................................................................................................................................... 48
Unit 5: Disease and protection against disease ............................................................................................................................................................................................. 66
Unit 6: The diversity of life .............................................................................................................................................................................................................................. 79
Unit 7: Genetics, population genetics and evolutionary processes ................................................................................................................................................................ 92
Unit 8: Molecular biology and gene technology ............................................................................................................................................................................................ 111
Unit 9: Respiration ........................................................................................................................................................................................................................................ 129
Unit 10: Mammalian physiology, control and coordination ........................................................................................................................................................................... 140
Unit 11: Plant physiology and biochemistry .................................................................................................................................................................................................. 156
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
2
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Overview
This staged teaching scheme of work provides ideas about how to construct and deliver a two-year course of study with all of the AS Level syllabus taught in Year 1
and the remainder of the A Level syllabus taught in Year 2. The syllabus has been broken down into teaching units, which incorporate one or more of the syllabus units,
with suggested teaching activities and learning resources to use in the classroom.
Recommended prior knowledge
Learners should have attained at least a grade C in IGCSE or O Level Biology, or the equivalent in another award such as Co-ordinated Science.
Outline
Whole class (W), group work (G), pair (P) and individual activities (I) are indicated, where appropriate, within this scheme of work. Suggestions for homework (H) and
formative assessment (F) are also included. The activities in the scheme of work are only suggestions and there are many other useful activities to be found in the
materials referred to in the learning resource list.
Opportunities for differentiation are indicated as basic and challenging; there is the potential for differentiation by resource, length, grouping, expected level of
outcome, and degree of support by the teacher, throughout the scheme of work. Length of time allocated to a task is another possible area for differentiation.
Where a learning objectives has been divided so that part of that learning objective content is taught at a different time to the rest of the learning objective, these are
identified by (i) or (ii), etc., and the specific part of the learning objective is in bold.
Key concepts
The key concepts on which the syllabus is built are set out below. These key concepts can help teachers think about how to approach each topic in order to encourage
learners to make links between topics and develop a deep overall understanding of the subject. As a teacher, you will refer to these concepts again and again to help
unify the subject and make sense of it. If mastered, learners can use the concepts to solve problems or to understand unfamiliar subject-related material.
Cells as the units of life
A cell is the basic unit of life and all organisms are composed of one or more cells. There are two fundamental types of cell: prokaryotic and eukaryotic.
Biochemical processes
Cells are dynamic: biochemistry and molecular biology help to explain how and why cells function as they do.
DNA, the molecule of heredity
Cells contain the molecule of heredity, DNA. Heredity is based on the inheritance of genes.
Natural selection
Natural selection is the major mechanism to explain the theory of evolution.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
3
Organisms in their environment
All organisms interact with their biotic and abiotic environment.
Observation and experiment
The different fields of biology are intertwined and cannot be studied in isolation: observation and enquiry, experimentation and fieldwork are fundamental to
biology.
Some of the ideas in this syllabus can take time to be fully understood. By linking them together through the key concepts, learners will have more opportunity for
those ideas to make sense to them and how they connect to other areas of the syllabus. The key concepts themselves will not be directly assessed; rather they are
themes that learners will be able to use to order their thoughts, themes and knowledge to express answers in examinations and interviews for work or the next stage of
their study.
As learners progress through the course, it is important that they do not regard the different topics as being totally self-contained and unconnected, studied in complete
isolation from one another. By keeping the key concepts to the fore at all stages of your teaching, you can strongly encourage learners to regard the subject as a set of
interconnected themes.
Learners should be aware that an ability to see how different strands of the syllabus can be pulled together within one key concept is a high-level transferable skill.
Linking different areas of their knowledge through a common thread of ideas, or ways of understanding and explaining, is enhancing their higher-order thinking skills.
These skills are the building blocks of deeper and broader learning, those that universities look for in their students and which allow learners to answer examination
questions fully and with links from more than one part of the syllabus.
Teachers can introduce key concepts as an integral part of their teaching approach and consolidate them when appropriate. This will help their learners to appreciate
that some themes and theories are revisited and built upon during the course and that, by bringing together very different areas of the syllabus, these themes are
fundamental to our understanding of the subject.
Focussing on these concepts will improve learners’ self-confidence in their ability to progress, as well as enabling them to revise more effectively; learners could make
mind maps across the syllabus on each of the key concepts as a way of revising. By visualising the subject as being formulated from these basic ideas, they will
become better prepared for interviews and future study at university, or be more adaptable to themes currently under research and development in industrial and
academic institutions.
There is also merit in showing learners how, during the course, they will be biologists studying in a number of inter-related fields that can be drawn together by the key
concepts. Examples of these fields - cell biology, biochemistry, physiology, genetics, evolutionary biology, microbiology, epidemiology, immunology, biotechnology,
ecology, population biology and conservation biology - can be discussed and linked to the different areas of the syllabus.
The key concepts are listed under the relevant learning objectives, those in bold are where the coverage of the learning objective makes a significant contribution to the
key concept.
Practical work
Practical work is an essential part of science. Scientists use evidence gained from prior observations and experiments to build models and theories. Their predictions
are tested with practical work to check that they are consistent with the behaviour of the real world. Learners who are well trained and experienced in practical skills will
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
4
be more confident in their own abilities. The skills developed through practical work provide a good foundation for those wishing to pursue science further, as well as for
those entering employment or a non-science career.
Twelve Practical Booklets have been developed for this syllabus, six for Paper 3 and six for Paper 5, and are available on Teacher Support at http://teachers.cie.org.uk
and are referenced within this scheme of work.
The Teaching A Level Science Practical Skills booklet is also available on Teacher Support at http://teachers.cie.org.uk which contains useful information and
suggestions for teaching A Level practical skills.
Suggested teaching order
The learning objectives and activities in this scheme of work are arranged in a suggested teaching order rather than the order that they appear in the syllabus. It has
been written for the staged route, with Units 1 to 5 covering the learning objectives to be studied by all learners in the first year, and which can be assessed by the AS
Level qualification. This is followed by Units 6 to 11 which cover all learning objectives that will be assessed by the full A Level qualification at the end of the second
year of the course.
For classes taking the linear route, where all learners take the full A Level, this allows for the integrated teaching of AS and A Level learning objectives across both
years of the A Level course. The linear route is not covered in this scheme of work.
The units within this scheme of work are:
Suggested time allocation (%)
AS Level
A Level
Unit 1. Biological molecules
Water
Carbohydrates
Lipids
Proteins
Biochemical tests
Nucleic acids
Enzymes
Unit 2. Cells as the basic units of life
Cells and microscopy
Size and magnification calculations
Plant and animal cells
Bacteria
Prokaryotic versus eukaryotic cell structure
v2.1 5Y02
2.3.d
2.2.b, 2.2.a, 2.2.c, 2.1.a(i), 2.1.b, 2.2.d, 2.2.e
2.2.f, 2.2.g, 2.1.a(ii)
2.1.a(iii), 2.3.a, 2.3.b, 2.3.c
2.1.a
6.1.a, 6.1.b
3.1.a, 3.1.b, 3.1.c, 3.1.d, 3.2.a, 3.2.b, 3.2.c, 3.2.d
1.1.d, 1.1.a, 1.1.c
1.1.b, 1.1.e
1.2.b, 1.2.c, 1.2.a
1.2.d
1.2.e
Cambridge International AS & A Level Biology (9700) – from 2016
10
9
5
Viruses
Cell membrane structure and function
Transport across membranes
Unit 3. DNA and the mitotic cell cycle
Chromosome structure
The mitotic cell cycle - overview
The mitotic cell cycle – DNA replication
The mitotic cell cycle – mitosis and cytokinesis
Protein synthesis, introduction to genes and mutation
Unit 4. Transport and gas exchange
Plant anatomy and histology
Transport of water and mineral ions
Transport of assimilates
Structure to function: plants
The mammalian circulatory system
The mammalian heart
The human gas exchange system
Carriage of respiratory gases
Unit 5. Disease and protection against disease
Disease and smoking
Infectious disease
Antibiotics
The immune response
Antibodies
Vaccination
Unit 6. The diversity of life
Definitions
Classification
Biodiversity
Fieldwork
Conservation, population control and maintaining
v2.1 5Y02
1.2.f
4.1.a, 4.1.b, 4.1.c
4.2.a(v), 4.2.c, 4.2.a(i), 4.2.d, 4.2.b, 4.2.a(ii), 4.2.a(iii), 4.2.f,
4.2.e, 4.2.a(iv)
5.1.a
5.1.c
6.1.c, 5.1.d
5.1.b, 5.1.e, 5.2.a, 5.2.b
6.2.a, 6.2.b, 6.2.c, 6.2.d
7.1.a, 7.1.b, 7.1.c
7.2.a, 7.2.c, 7.2.b, 7.2.d, 7.2.e, 7.2.f
7.2.g, 7.2.h, 7.2.i
7.1.d
8.1.a, 8.1.b, 8.1.c, 8.1.d, 8.1.e
8.2.a, 8.2.b, 8.2.c, 8.2.d
9.1.a, 9.1.b, 9.1.c, 9.1.d
8.1.f, 8.1.g, 8.1.h
10.1.a, 9.2.a, 9.2.b
10.1.b, 10.1.c, 10.1.d, 10.1.e
10.2.a, 10.2.b, 10.2.c
11.1.d, 11.1.a, 11.1.b, 11.1.e, 11.1.c, 11.1.f
11.2.a, 11.2.b, 11.2.c
11.2.d, 11.2.e
18.1.a
18.2.a, 18.2.b, 18.2.c, 18.2.d
18.1.b
18.1.c, 18.1.d, 18.1.e, 18.1.f
18.3.a, 17.3.e, 18.3.b, 18.3.g, 18.3.c, 18.3.d, 18.3.e, 18.3.f,
Cambridge International AS & A Level Biology (9700) – from 2016
7
14
10
6
6
biodiversity
18.3.h
Unit 7. Genetics, population genetics and evolutionary processes
Understanding terms
16.1.a, 16.1.b, 16.2.a(i)
Meiotic cell division and heredity
16.1.c, 16.1.d, 16.1.e
Genetic crosses
16.2.a(ii), 16.2.b, 16.2.c, 16.2.d
Biological variation
17.1.a, 17.1.c, 17.1.b, 16.2.e, 16.2.f, 16.2.g
Natural selection and population genetics
17.1.d, 17.2.a, 17.2.b, 17.2.c, 17.2.d
Evolution and speciation
17.3.a, 17.3.b, 17.3.c, 17.3.d
Artificial selection
17.2.e, 17.2.f
Unit 8. Molecular biology and gene technology
The control of gene expression
16.3.b, 16.3.a, 16.3.c, 19.1.i
Recombinant DNA technology
19.1.a, 19.1.b, 19.1.h, 19.1.e, 19.1.f, 19.1.g, 19.2.c, 19.3.a,
19.3.b, 19.3.c
Molecular biology techniques
19.1.c, 19.1.d, 19.2.g
Bioinformatics
19.2.a, 19.2.b
Prevention and treatment of inherited conditions.
19.2.d, 19.2.e, 19.2.f
Unit 9. Respiration
Energy and ATP
12.1.a, 12.1.b
Aerobic respiration and ATP synthesis
12.2.a, 12.2.b, 12.2.c, 12.2.d, 12.2.e, 12.1.c, 12.2.g, 12.2.f,
12.1.e(i), 12.1.d, 12.2.i
Anaerobic respiration
12.2.k, 12.2.l
Comparing anaerobic and aerobic respiration
12.2.j
Yeast practical
12.2.h
Respiratory substrates, RQs and respirometers
12.1.f, 12.1.g, 12.2.m, 12.1.h
Unit 10. Mammalian physiology, control and coordination
Communication systems
15.1.a
The nervous system
15.1.b, 15.1.c, 15.1.d, 15.1.e, 15.1.f, 15.1.g, 15.1.h
Muscle contraction
15.1.i, 15.1.j, 15.1.k
Homeostasis
14.1.a, 14.1.b, 14.1.c
Excretion of nitrogenous waste and osmoregulation
14.1.d, 14.1.e, 14.1.f, 14.1.g
Control of blood glucose concentration
14.1.h, 14.1.i, 14.1.j
Detection of biological molecules in blood and urine
14.1.k, 14.1.l
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
10
9
7
10
7
Hormones of the menstrual cycle
Unit 11. Plant physiology and biochemistry
Photosynthesis overview
The light dependent stage
The light dependent stage - chemiosmosis
The light independent stage
The chloroplast
Factors affecting photosynthesis.
Control and coordination in plants.
15.1.l, 15.1.m
13.1.b
13.1.c, 13.1.d, 13.1.e, 13.1.f
12.1.e(ii)
13.1.a, 13.1.g, 13.1.h
13.3.a
13.2.a, 13.2.b, 13.2.c, 13.2.d, 13.2.e, 13.3.b
15.2.a, 14.2.a, 14.2.b, 14.2.c, 15.2.b, 15.2.c, 15.2.d, 16.3.d
8
Suggested teaching order
AS Level
Unit 1, Biological molecules, could be studied either before or after Unit 2, Cells as the basic units of life. Learners with a good chemistry background will cope well with
Unit 1, others will probably find the subject matter in Unit 2 to be more approachable. If Unit 2 is covered first, then learners will need a reminder of previous knowledge
of biological molecules learned in earlier studies or a brief introduction to lipids and proteins. Knowledge and understanding from both of these will be used and applied
in the rest of the course. The role of DNA in the mitotic cell cycle, Unit 3, follows on quite logically from the work done in Units 1 and 2. Unit 5, Disease and protection
against disease is best taught after Unit 4, Transport and gas exchange, as there is a link between mammalian transport and gas exchange in mammals in Unit 4 and
non-infectious disease and cells of the immune system in Unit 5. There is much work that can be done in improving data extraction and data analysis skills in Unit 5,
where there are fewer opportunities to carry out practical work. As this unit is taught at the end of the AS Level course, teachers may wish to allocate some time to
consolidate practical skills gained earlier in the course and prepare learners fully for Paper 3.
A Level
Having studied eukaryotic and prokaryotic cell structure in Unit 2 (AS Level), Unit 6, The diversity of life, is a straightforward introduction to the A Level syllabus. This
covers knowledge and understanding that is useful for Unit 7, Genetics, population genetics and evolutionary processes. Unit 8, Molecular biology and gene
technology, allows learners to use some of the concepts covered in Unit 7. Unit 11 can be taught at any time throughout the course if carrying out practical work is
dependent on seasonal timing: if taught before Units 9 and 10, the idea of control and coordination and chemiosmosis should be covered. Units 9 and 11 are best
taught with a gap in between to avoid confusion for learners when studying the biochemical processes of respiration and photosynthesis.
Teacher support
Teacher Support (http://teachers.cie.org.uk) is a secure online resource bank and community forum for Cambridge teachers, where you can download specimen and
past question papers, mark schemes and other resources. We also offer online and face-to-face training; details of forthcoming training opportunities are posted online.
This scheme of work is available as PDF and an editable version in Microsoft Word format; both are available on Teacher Support at http://teachers.cie.org.uk. If you
are unable to use Microsoft Word you can download Open Office free of charge from www.openoffice.org.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
8
Resources
The resources for this syllabus, including textbooks endorsed by Cambridge, can be found at www.cie.org.uk and Teacher Support http://teachers.cie.org.uk.
Endorsed textbooks have been written to be closely aligned to the syllabus they support, and have been through a detailed quality assurance process. As such, all
textbooks endorsed by Cambridge for this syllabus are the ideal resource to be used alongside this scheme of work as they cover each learning objective.
Where other textbooks have shown to be useful for some learning objectives they are referred to by the first author. These include:
King T, Reiss M, Roberts M. Practical Advanced Biology. Nelson Thornes, 2nd Edition 2001. ISBN: 9780174483083
Siddiqui S. Comprehensive Practical Biology for A Level. Ferozsons, 1999. ISBN 9690015729
Bio Factsheets. Curriculum Press www.curriculum-press.co.uk
These cover a wide range of topics and are also useful for revision and extension work. Individual factsheets can be obtained, as can a complete CD-ROM.
Biological Nomenclature, published by the Society of Biology (formerly the Institute of Biology).
This publication can be ordered by emailing the Education Department at the Society of Biology https://www.societyofbiology.org. The symbols, signs and
abbreviations used in examination papers follow these recommendations.
CD-ROM
Bioscope. Cambridge University Press. ISBN: 9781845650261
A simulation of a real microscope that includes a large number of botanical and zoological microscope slides at a range of magnifications, accompanied by paperbased tasks. It can be used for whole class teaching via a whiteboard or data projector, or by individual students on PCs.
Websites:
This scheme of work includes website links providing direct access to internet resources. Cambridge International Examinations is not responsible for the accuracy or
content of information contained in these sites. The inclusion of a link to an external website should not be understood to be an endorsement of that website or the
site's owners (or their products/services).
The particular website pages in the learning resource column of this scheme of work were selected when the scheme of work was produced. Other aspects of the sites
were not checked and only the particular resources are recommended.
Websites in this scheme of work, and some other useful websites, include:
http://www.ncbe.reading.ac.uk/
http://www.saps.org.uk/
The National Centre for Biotechnology Education: protocols and useful information
Science and Plants for Schools: protocols
http://www.biology4all.com/resources_library/index.asp
http://www.s-cool.co.uk/alevel/biology.html
http://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookTOC.html
http://www.rothamsted.ac.uk/notebook/index.php?area=&page=
Biology 4all: wide range of resources and links to other useful sites
S-cool: revision website
The Online Biology Book, hosted by Estrella Mountain Community College
The Molecular Biology Notebook
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
9
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/
http://www.cellsalive.com/
http://www.worldofteaching.com/A-ZBiologypowerpoints.html
http://www.ase.org.uk/resources/
http://www.nuffieldfoundation.org/practical-biology
http://www.nationalstemcentre.org.uk/sciencepracticals
http://www.biology-resources.com
http://www.biologyjunction.com/ap_biology_animations.htm
http://www.rsc.org/Education/Teachers/Resources/cfb/index.htm
https://www.societyofbiology.org/
v2.1 5Y02
Kimball’s Biology Pages (especially useful for teacher reference)
Cells Alive: covers a range of topics with straightforward animations
PowerPoint presentations donated by teachers
Association for Science Education: educational resources
Practical Biology: ideas and lesson plans
The National Stem Centre provides many resources including ideas for practical work
For learners to revisit IGCSE topics
Links to websites with animations - many different topics
Royal Society of chemistry: Chemistry for biologists
The Society of biology
Cambridge International AS & A Level Biology (9700) – from 2016
10
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 1: Biological molecules
Recommended prior knowledge
Learners will need some background knowledge in chemistry before embarking on this unit. They should understand the terms atom, molecule, electron and ion. They
should also have a basic understanding of covalent and ionic bonding, and of molecular and structural formulae. They should be able to write and understand simple
chemical equations. Some knowledge of energy changes (potential energy and bond energy) would be helpful.
http://www.rsc.org/Education/Teachers/Resources/cfb/basicchemistry.htm is a good starting point for learners to revise their knowledge of chemistry.
http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page1.html this also covers basic chemistry for biologists.
Context
This unit provides essential reference material for learners when studying all future units in their Cambridge International AS and A Level course. Knowledge of how the
structure and properties of biological molecules are related to their functions in cells and in organisms is fundamental to an understanding of many areas of biology.
The molecule of heredity, DNA, is a key concept. Cells can be visualised as structural units requiring biological molecules and as dynamic units carrying out
biochemical processes. Cells carry out biochemical processes, a key concept, and enzymes catalyse biological reactions. A thorough understanding of enzyme
function can be applied to studying processes such as:
DNA replication and protein synthesis in Unit 3, The role of DNA in the mitotic cell cycle;
the carriage of carbon dioxide in Unit 4, Transport and gas exchange;
gene technology in Unit 8, Molecular biology and gene technology;
respiration in Unit 9, Respiration;
photosynthesis in Unit 11, Plant physiology and biochemistry.
As part of biotechnology, enzymes are used commercially in a range of applications, with many of these using immobilised enzymes for a more efficient process.
Outline
This unit introduces learners to the biological molecules that are required by cells for both structural purposes and physiological processes. The main groups of organic
biochemicals, carbohydrates, lipids, proteins and nucleic acids, are studied. For carbohydrates, lipids and proteins, there is an emphasis on the relationship between
molecular structure, properties and functions in living organisms. Learners study the structure of nucleic acids and discuss DNA as the ideal molecule of inheritance in
preparation for Unit 3, The role of DNA in the mitotic cell cycle. Learning objective 2.3.d introduces the concepts of hydrogen bonding and solubility and considers the
roles of water in living organisms. This unit builds on knowledge of protein structure in describing and explaining enzyme activity. The mode of action of enzymes and
factors that affect enzyme action, including inhibitors, is covered. Learners are introduced to some basic enzyme kinetics. There are many opportunities to carry out
practical work, where learning can be reinforced and individual and class results can be analysed. The last section of the unit considers the differences between
enzymes free in solution and immobilised enzymes.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
11
Learning objectives
Suggested teaching activities
Learning resources
2.3.d
explain how hydrogen bonding occurs
between water molecules and relate
the properties of water to its roles in
living organisms (limited to solvent
action, specific heat capacity and
latent heat of vapourisation)
Discussion / brainstorm: the importance of water to the life of a cell, including
hydrogen bonding and as a solvent in biological systems (e.g. blood, phloem sap,
cytosol/cytoplasm). (I) (Basic).
Learners make notes, including the following:
o Draw and describe hydrogen bonding between water molecules. (I) (Basic)
o Make links between hydrogen bonding and the cohesive nature of water
molecules. (I) (Basic)
o Explain the link between hydrogen bonding and
the high specific heat capacity of water
the high latent heat of vapourisation of water. (I) (Challenging)
o Research examples to show the relationship between the properties of water
and its roles in organisms. (I) (Challenging)
Discuss the concept of polar / non-polar and the solubility or otherwise of the
biological molecules in this unit. (W) (Basic)
Online
http://faculty.fmcc.edu/mcdarby/majors
101book/chapter_03-chemistry/03Water_Properties.htm
http://www.rsc.org/Education/Teachers
/Resources/cfb/water.htm
http://www.worldofmolecules.com/solv
ents/water.htm
Key concepts
Cells as the units of life,
Biochemical processes,
Organisms in their environment
Textbooks/Publications
Bio Factsheet 30: The biological
importance of water.
Bio Factsheet 78: Chemical bonding in
biological molecules
Note
Ensure learners can use the following terms (see Unit 2):
hydrophilic
hydrophobic
polar
non-polar
charged / ionic
uncharged / non-ionic
water soluble
water-insoluble
lipid insoluble
lipid soluble
2.2.b
define the terms monomer, polymer,
macromolecule, monosaccharide,
disaccharide and polysaccharide
Key concepts
Biochemical processes,
DNA, the molecule of heredity
v2.1 5Y02
Learners write definitions for macromolecule, monomer and polymer and
consolidate. (W) (Basic)
o Match the terms with relevant examples (include an introduction of DNA and
RNA nucleotides).
o Discuss why lipids do not have monomers.
o Construct a simple table (complete bond names later).
polymer
name of bond
type of organic monomer
macromolecule
carbohydrate
monosaccharide polysaccharide
protein
amino acid
polypeptide
nucleic acid
DNA nucleotide
polynucleotide
RNA nucleotide
lipid
-
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.rsc.org/Education/Teachers
/Resources/cfb/carbohydrates.htm
Textbooks/Publications
Bio Factsheet 78: Chemical bonding in
biological molecules
12
Learning objectives
Suggested teaching activities
Learning resources
Further discussion (W) (Basic)
o The macromolecules are based on a skeleton of carbon atoms (‘life is based on
carbon'), which can form strong bonds with other atoms.
o Of the wide range of organic compounds formed, some provide energy for the
cell.
Introduce the terms condensation and hydrolysis by discussing the synthesis and
breakdown of polymers. (W) (Basic)
Brainstorm some carbohydrates and agree whether monosaccharide, disaccharide
or polysaccharide (W) (Basic)
o Learners make notes on: monosaccharides, using the terms triose, pentose and
hexose (glucose, galactose and fructose as e.g. of hexoses); disaccharides
(lactose, maltose, sucrose and cellobiose), giving their constituent
monosaccharides). (I) (Basic)
Note
Useful terms for later:
o pentose - nucleotide and nucleic acid structure in this unit,
o hexose for respiration (Unit 9 ) and photosynthesis (Unit 11).
2.2.a
describe the ring forms of -glucose
and glucose
Key concepts
Biochemical processes
2.2.c
describe the formation of a glycosidic
bond by condensation, with reference
both to polysaccharides and to
v2.1 5Y02
Provide details of the molecular structure of glucose (see 2.2.b) which, in solution, is
mainly in ring form (W) (Basic)
o Show learners how to use a logical sequence to build up the ring form of the
glucose molecule and number the carbon atoms. Learners practise then draw
the molecule from memory. (I) (Challenging)
o Learners complete a range of incomplete diagrams prepared by you, e.g. by
adding the -OH and -H groups. (F)
o Progress learners to be able to identify and draw a glucose molecule. (I)
(Basic)
Learners make molecular models of and forms of glucose using plastic sphere /
bond models or drinking straw models. (P) (Challenging)
Explain that knowledge of the and forms of glucose will help understanding of
disaccharide and polysaccharide structures and properties. (W) (Basic)
Online
http://www.biologie.uni-hamburg.de/bonline/e17/17.htm
http://www.rsc.org/Education/Teachers
/Resources/cfb/carbohydrates.htm#2
Outline how a glycosidic bond is formed to produce a disaccharide by a
condensation reaction (no details yet of molecular structure). (W) (Basic)
Learners draw the formation of an , 1-4 glycosidic bond and add the name of the
bond to their table from 2.2.b. (I) (Challenging)
Past Papers
Paper 22, Nov 2011, Q4 (b)
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 22, Nov 2011, Q4 (a)
Textbooks/Publications
13
Learning objectives
Suggested teaching activities
Learning resources
disaccharides, including sucrose
Work through the formation of a , 1-4 glycosidic bond (to form cellobiose). (W)
(Challenging)
Tell learners that the glucose monomer of sucrose is -glucose and ask them to use
a molecular diagram of a sucrose molecule to work out the structure of a fructose
molecule (no need to memorise this). (W) (Challenging)
Learners use the -glucose models previously constructed to form a glycosidic
bond. (P) (I) (Basic)
o Produce a section of a polysaccharide, e.g. from an amylose or cellulose
molecule. (G) (P) (I) (Challenging)
Bio Factsheet 78: Chemical bonding in
biological molecules
Key concepts
Biochemical processes
Note
Maltose is formed in nature from degradation reactions (i.e. breakdown) of starch, so
focus the activity on the concept of a condensation reaction to build up a
macromolecule and the formation of a glycosidic bond. The ‘formation’ of maltose
illustrates the principle of glycosidic bond formation by a condensation reaction.
2.1.a (i)
carry out tests for reducing sugars
and non-reducing sugars, the iodine
in potassium iodide solution test for
starch, the emulsion test for lipids and
the biuret test for proteins to identify
the contents of solutions
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Only the first part of this learning objective is included here: carry out tests for reducing
sugars and non-reducing sugars, and the iodine in potassium iodide solution test for
starch to identify the contents of solutions
Discuss the tests and explain they are useful to identify biochemicals in a range of
plant and animal material. (W) (Basic)
o Learners should describe the biochemical tests (‘food tests’ is a less helpful
term) and the results obtained, giving conclusions. (W) (Basic)
Practical work: carrying out the Benedict's test for reducing sugars.
o Explain that a negative test does not mean an absence of carbohydrate. (I)
(Basic)
o Learners test substances that will give positive results (e.g. glucose/fructose/
maltose/lactose solution) and negative results (e.g. sucrose solution, water,
protein/starch suspension, vegetable oil). (I) (Basic)
o Learners test natural liquefied biological materials (e.g. fruits, tubers) and
liquefied foods from the diet. (I) (Basic) (Challenging)
o Learners test a thin section of fruit placed on a microscope slide (add a few
drops of Benedict’s and heat over a spirit burner – use forceps): use a
microscope to observe colour changes. (P) (I) (Challenging)
Discuss the negative result for reducing sugar with sucrose and explain that hot acid
is used to hydrolyse sucrose, but neutralisation is required before adding Benedict’s.
(W) (Basic)
Practical work carrying out the test for a non-reducing sugar, where learners use
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
Textbooks/Publications
King p.19-22
Siddiqui p.56-60
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
14
Learning objectives
Suggested teaching activities
Learning resources
fresh samples of each of the substances that gave ‘negative’ results for the reducing
sugar test. (I) (Basic)
Practical work to consolidate reducing sugars and non-reducing sugar tests.
o Learners identify which unmarked solution is: glucose; sucrose; a mixture of both
glucose and sucrose. (I) (Basic)
o Extend this (excess of Benedict’s solution) to filtering the precipitates for
comparison and using a colorimeter (if available) to compare filtrates. (P) (I)
(Challenging)
Practical work to test for starch in a range of different types of starch (suspensions)
and food substances using iodine in potassium iodide solution. Learners see a range
of blue-black colours obtained (owing to the differing proportions of amylose to
amylopectin). (I) (Basic)
Practical booklet 2 can be carried out after this stage. See the Teacher’s practical
notes regarding the development of certain skills for Paper 3.
Note
Remind learners to control variables.
AR (analytical reagent) sucrose is preferred to LR (laboratory reagent) sucrose
(preferred to cane sugar) for the non-reducing sugar test (if cane sugar is used,
explain that it will contain impurities and may give a slight positive Benedict’s test
results).
2.1.b
carry out a semi-quantitative
Benedict’s test on a reducing sugar
using dilution, standardising the test
and using the results (colour standards
or time to first colour change) to
estimate the concentration
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Practical work: learners practise, and get a visual impression of, diluting a coloured
liquid, using water, to set concentrations. (I) (Basic)
Practical work: learners prepare glucose solutions of known concentration and then
carry out the Benedict's test, recording the time taken for the first indication of colour
change and to obtain colour standards. (I) (Basic)
o Follow-up with a semi-quantitative analysis, comparing time taken and
colour/colour depth to determine the approximate concentration of an unknown
solution. (I) (Challenging)
o Evaluate the test with learners and ask for ideas of other semi-quantitative tests
(e.g. allow precipitate to settle, dry and weigh). (W) (Challenging)
Practical booklet 2 can be carried out after this stage. See the Teacher’s practical
notes regarding the development of certain skills for Paper 3.
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 2
Online
http://www.saps.org.uk/secondary/teac
hing-resources/103-estimatingglucose-concentration-in-solution
15
Learning objectives
Suggested teaching activities
Learning resources
2.2.d
describe the breakage of glycosidic
bonds in polysaccharides and
disaccharides by hydrolysis, with
reference to the non-reducing sugar
test
Explain how a glycosidic bond can be broken by hydrolysis, referring to monomers
and monosaccharides. (W) (Basic)
Learners draw diagrams of the breakage of glycosidic bonds (by hydrolysis) of
maltose and sucrose. (I) (Challenging)
o Add annotations to explain the ideas behind the non-reducing sugar test. (I)
(Basic)
o Use the models of disaccharides previously constructed to demonstrate the
breakage of a glycosidic bond. (P) (I) (Basic)
o Extension activity: using molecular diagrams of galactose, lactose and
cellobiose, learners draw diagrams or construct models to show the breakdown
of lactose and cellobiose. (P) (I) (Challenging)
Online
http://www.rsc.org/Education/Teachers
/Resources/cfb/carbohydrates.htm#2
Key concepts
Biochemical processes,
Observation and experiment
Note
Learners should describe the breakage of the glycosidic bond in sucrose when
explaining non-reducing sugar test results (see 2.1.a)
2.2.e
describe the molecular structure of
polysaccharides including starch
(amylose and amylopectin), glycogen
and cellulose and relate these
structures to their functions in living
organisms
Key concepts
Cells as the units of life,
Biochemical processes
2.2.f
v2.1 5Y02
Use the molecular models to show short sections of amylose and amylopectin (or
strings of beads on wire) and discuss glycogen structure. (G) (Basic)
Learners describe the difference between the structures (include bonds formed) and
highlight the idea of ‘structure to function ‘.
o More compact structures for storage linked to the coiling effect (amylose) and
branching (amylopectin).
o Branching of amylopectin and glycogen provides large number of ‘ends’ to
attach /detach glucose units. (I) (Basic)
Demonstrate (molecular model / animation) how a straight chain is produced when
forming polysaccharides with alternate -glucose residues that rotate by 180°.(W)
(Basic)
Emphasise the structure to function of cellulose is different to that of the cell wall.
(W) (Basic)
Discuss the role of cellulose, then learners produce explanatory notes with diagrams
of how straight parallel chains are useful for structural purposes and how hydrogen
bonding (2.3.d) allows parallel cellulose molecules to form fibrils (links to cell wall
structure in Unit 2). (I) (Challenging)
Learners complete a gap-filling worksheet prepared by you to serve as a summary
of the main learning points for carbohydrates. (F)
Draw the general formula for a fatty acid.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.rpi.edu/dept/bcbp/molbioch
em/MBWeb/mb1/part2/sugar.htm
http://www.calfnotes.com/pdffiles/CN1
02.pdf
Textbooks/Publications
Bio Factsheet 39: Carbohydrates:
revision summary
Bio Factsheet 174: The structure and
function of polysaccharides
Past Papers
Paper 21, June 2011, Q5
Paper 22, Nov 2012, Q1 (d)
Online
16
Learning objectives
Suggested teaching activities
Learning resources
describe the molecular structure of a
triglyceride with reference to the
formation of ester bonds and relate the
structure of triglycerides to their
functions in living organisms
o Explain that it is a carboxylic acid and outline -COOH as the carboxyl group.
o Explain R is a hydrocarbon chain, and extend this to explain saturated or
unsaturated fatty acids. (W) (Basic)
Draw the molecular structure of glycerol and state that a triglyceride is produced with
the attachment of three fatty acids in condensation reactions. (W) (Basic)
o With prompting, learners work out how ester bonds form and add the name of
the bond to their table of 2.2.b. (I) (Challenging)
Learners make simple paper cut-out models of triglycerides to illustrate the absence
of polar groups and show the non-polar exposed fatty acids (so not soluble when in
contact with watery liquids). (W) (Basic)
Learners describe evidence that makes triglycerides good energy stores (many C-C
bonds; highly reduced so energy can be released by oxidation; insoluble in water so
can be localised in the organism). (G) (P) (I) (Challenging)
http://www.biotopics.co.uk/as/lipidcond
ensation.html
http://www.chemguide.co.uk/organicpr
ops/esters/background.html
Key concepts
Cells as the units of life,
Biochemical processes
Textbooks/Publications
Bio Factsheet 42: The structure and
function of lipids.
Bio Factsheet 74: The structure and
biological functions of lipids.
Bio Factsheet 78: Chemical bonding in
biological molecules
Past Papers
Paper 21, June 2011, Q5
Paper 22, June 2011, Q5 (a)(b)(i)
Paper 22, Nov 2011, Q4 (b)
2.2.g
describe the structure of a
phospholipid and relate the structure of
phospholipids to their functions in living
organisms
Key concepts
Cells as the units of life,
Biochemical processes
Learners label a printed diagram showing the structure of a phospholipid molecule
and discuss how the presence of polar groups relates to phospholipid behaviour
when in contact with watery liquids. (W) (Basic)
Discuss the function of phospholipids in forming the bulk of structure of cell
membranes, forming bilayers (link to Unit 2). (W) (Basic)
Learners do research to find out that: there are many different fatty acids and
phospholipids; some phospholipids have a nitrogen-containing (choline) portion. (H)
(Basic) (Challenging)
2.1.a (ii)
carry out tests for reducing sugars
and non-reducing sugars, the iodine in
potassium iodide solution test for
starch, the emulsion test for lipids
and the biuret test for proteins to
identify the contents of solutions
Only the second part of this learning objective is included here: carry out tests
emulsion test for lipids to identify the contents of solutions
Practical work, testing for lipids using the (ethanol) emulsion test.
o Test vegetable oil and yellow-dyed water. (I) (Basic)
o Test crushed fruits and seeds. (I) (Basic)
Practical booklet 2 is designed to be carried out after learners have used the
emulsion test as described above.
Key concepts
Note
Ensure learners understand that lipids include triglycerides (fats and oils).
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 152: Phospholipids
Past Papers
Paper 21, June 2011, Q5
Paper 22, June 2011, Q5 (a)(b)(i)(ii)
(c)(d)
Paper 22, Nov 2011, Q4 (b)
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
17
Learning objectives
Suggested teaching activities
Biochemical processes,
Observation and experiment
2.1.a (iii)
carry out tests for reducing sugars
and non-reducing sugars, the iodine in
potassium iodide solution test for
starch, the emulsion test for lipids and
the biuret test for proteins to
identify the contents of solutions
Key concepts
Biochemical processes,
Observation and experiment
2.3.a
describe the structure of an amino acid
and the formation and breakage of a
peptide bond
Key concepts
Biochemical processes
v2.1 5Y02
Learning resources
Textbooks/Publications
King p.19-22
Siddiqui p.56-60
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
Only the third part of this learning objective is included here: carry out tests biuret test
for proteins to identify the contents of solutions.
Practical work, testing for proteins using the biuret test on a solution of egg white,
skimmed milk, chicken or tofu and water. (I) (Basic)
Extension practical using a semi-quantitative biuret test: learners prepare a set of
standard solutions and compare the intensity of colour obtained of an unknown with
the standards (control variables). (P) (I) (Challenging)
Practical booklet 2 is designed to be carried out after learners have used the biuret
test as described above.
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
Textbooks/Publications
King p.19-22
Siddiqui p.56-60
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
Familiarise learners with the names of the 20 amino acids (encoded by the genetic
code – see Unit 3) and their three-letter shortened version from labelled diagrams.
Learners write out the general formula of an amino acid, and on the diagrams use a
colour code to identify the: R group; part common to them all; amine group;
carboxylic acid group. (W) (I) (Challenging)
o Learners make notes to show understanding that the ‘side-chain’ or R (residual)
group can take different forms and that the amino acids can be grouped
according to the properties of their R-group. (I) (Basic)
Learners draw simple diagrams of: peptide bond formation (choose two amino acids
from their diagram sheet) by condensation (add the name of the bond to their table
of 2.3.b); hydrolysis of the dipeptide. (I) (Challenging)
Discuss how a series of condensation reactions leads to the formation of a
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biotopics.co.uk/as/aa.html
http://www.worldofmolecules.com/life/
Textbooks/Publications
Bio Factsheet 78: Chemical bonding in
biological molecules
Bio Factsheet 80: Structure and
biological functions of proteins
Past Papers
Paper 21, June 2011, Q5
18
Learning objectives
Suggested teaching activities
polypeptide. (W) (Basic)
Learning resources
Paper 22, Nov 2011, Q4 (b)
Note
The names and structures of the amino acids are not required learning.
Learners could be introduced to the one-letter abbreviations (useful for Unit 8).
2.3.b
explain the meaning of the terms
primary structure, secondary structure,
tertiary structure and quaternary
structure of proteins and describe the
types of bonding (hydrogen, ionic,
disulfide and hydrophobic interactions)
that hold these molecules in shape
Key concepts
Biochemical processes
Learners write down their own polypeptide, 25 amino acids long (choose from the
sheet of 2.3.a) using encircled three-letter abbreviations and share with the rest of
the group to highlight how an enormous number of different polypeptides can be
obtained. Discuss the term primary structure. (W) (I) (Basic)
Make links forward to Unit 2 to the roles of cell structures in protein synthesis to fold
/ further modify the polypeptide chain. (W) (Basic)
Expand knowledge of hydrogen bonding (from 2.3.d) and 2.2.e) with an explanation
of secondary structure. (W) (Basic)
Learners suggest what will hold the chain in place to form a specific 3-D structure
before discussing tertiary structure. (W) (Basic) (Challenging)
o Include interactions between R groups and the different types of bonding. (W)
(Basic)
o Give a simple definition of quaternary structure. (W) (Basic)
o Discuss how the loss of tertiary (and quaternary where it exists) results in the
loss of function of the protein. (W) (Basic)
o Learners make notes on levels of organisation to highlight the relationship
between the structures and role of bonding in determining shape /stability. (I)
(Challenging)
Online
http://www.pdb.org/pdb/home/home.do
http://www.biology.arizona.edu/bioche
mistry/tutorials/chemistry/page2.html
Past Papers
Paper 21, Nov 2011, Q3 (a)
Note
For quaternary structure learners should know that this is a protein composed of
more than one polypeptide chain – details of the association between chains is not
required.
Do not allow learners to think that proteins with quaternary structure must be
composed of four polypeptides.
2.3.c
describe the molecular structure of
haemoglobin as an example of a
globular protein, and of collagen as an
example of a fibrous protein and relate
these structures to their functions (The
v2.1 5Y02
Show diagrams/images of globular and fibrous proteins to learners for them to
describe, and then discuss their features (include solubility) and overall roles (e.g.
mainly metabolically active versus mainly structural). Discuss the fact that many
fibrous proteins show little or no tertiary structure. (W) (G) (P) (I) (Basic)
(Challenging)
Display a diagram / image of haemoglobin for learners to identify the features of a
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://en.wikipedia.org/wiki/Hemoglobin
http://www.pdb.org/pdb/101/motm.do?
momID=4&evtc=Suggest&evta=Mole
culeof%20the%20Month&evtl=TopBa
r
19
Learning objectives
Suggested teaching activities
importance of iron in the haemoglobin
molecule should be emphasised. A
haemoglobin molecule is composed of
two alpha () chains and two beta ()
chains, although when describing the
chains the terms -globin and -globin
may be used. There should be a
distinction between collagen molecules
and collagen fibres)
globular protein and consolidate knowledge of levels of protein structure. (W)
(Basic) (Challenging)
o Give details of haem and explain the idea of a prosthetic group. (W) (Basic).
o Notes made or construct a spider diagram / concept map relating haemoglobin
structure to function. (I) (Challenging)
With textbook/internet research, learners make bullet-pointed notes on collagen
structure (include the difference between a molecule and a fibre), linking to its
function (including role in blood vessel structure – link to Unit 4). (W) (I) (Basic)
Learners construct a comparison table showing the similarities and differences
between haemoglobin and collagen. (F)
Compile a set of multiple choice questions from past papers for learners to
complete. (F)
Key concepts
Cells as the units of life,
Biochemical processes
2.1.a
carry out tests for reducing sugars and
non-reducing sugars, the iodine in
potassium iodide solution test for
starch, the emulsion test for lipids and
the biuret test for proteins to identify
the contents of solutions
v2.1 5Y02
Textbooks/Publications
Bio Factsheet 175: Haemoglobin:
structure & function
Past Papers
Paper 22, June 2011, Q3 (c)
Paper 21, Nov 2011, Q3 (c)
Note
Mention that haemoglobin has a role in the carriage of carbon dioxide (for Unit 4).
Practical investigation, without using instructions, to analyse the biochemicals in a
range of unknown solutions or liquefied solid foods. (F)
Practical booklet 2 is a suitable protocol (designed to develop skills for Paper 3).
Key concepts
Biochemical processes,
Observation and experiment
6.1.a
describe the structure of nucleotides,
including the phosphorylated
nucleotide ATP (structural formulae
are not required)
Learning resources
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
Textbooks/Publications
King p.19-22
Siddiqui p.56-60,
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
Draw a labelled diagram of a nucleotide to show the three components: phosphate,
pentose sugar and nitrogenous organic base (e.g. using a circle, pentagon and
rectangle) for learners to reproduce without help. (W) (I) (Basic)
Give out images of the structural formulae of the four RNA and four DNA
nucleotides, ensuring learners know the names of the bases and explaining carbon
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://hyperphysics.phyastr.gsu.edu/hbase/biology/atp.html
http://www.accessexcellence.org/RC/V
L/GG/basePair1.php
20
Learning objectives
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Suggested teaching activities
atom numbering. (W) (Basic)
o In a small group, learners interpret how the diagram of a nucleotide has been
derived and identify similarities and differences between the DNA and RNA
nucleotides. (G) (Basic) (Challenging)
o Learners draw a labelled generalised RNA and a DNA nucleotide, naming the
different pentose sugars and indicating the four different bases for each. (I)
(Basic)
Discuss briefly an image of the structural formula of ATP and agree it is a
phosphorylated nucleotide before learners draw a simple diagrammatic, annotated
version. Include the concept that on removal of a phosphate, energy is released
(links with 1.2.c and idea of activated nucleotides for 6.1.c and 6.2.d). (W) (I) (Basic)
Introduce DNA base-pairing for 6.1.b by showing learners structural /skeletal
formulae and diagrammatic forms. (W) (Basic)
o Allow learners to volunteer that in the diagrams: A and G are the same ‘length’
and are ‘longer’ than T and C (also the same length) as they are double ring
structures; the end where the pairs meet shows a complementary nature (e.g. A
pointed, T ‘V’ shaped; G convex, C concave).
o Introduce the concept of complementary base pairing and hydrogen bonding
between base pairs (mention also RNA/DNA base-pairing).
Learning resources
Textbooks/Publications
Bio Factsheet 129: ATP – what it is,
what it does.
Past Papers
Paper 23, Nov 2011, Q5 (a)
Note
Base names must be spelt correctly, e.g. thymine not thiamine, and learners must
be clear about the difference between adenine and adenosine.
Emphasise that the structural/skeletal formulae of the bases is not required.
6.1.b
describe the structure of RNA and
DNA and explain the importance of
base pairing and the different
hydrogen bonding between bases
(include reference to adenine and
guanine as purines and to cytosine,
thymine and uracil as pyrimidines.
Structural formulae for bases are not
required but the recognition that
purines have a double ring structure
and pyrimidines have a single ring
structure should be included)
v2.1 5Y02
Discuss phosphodiester bond (strong, covalent) formation by condensation reactions
to produce a polynucleotide (learners add the bond name to their table of 2.2.b). (I)
(Basic)
Learners prepare cut-out nucleotides and, with verbal prompts, build up a short
polynucleotide strand, learning about the sugar-phosphate backbone and noting the
variation in sequences among the class (different ‘information’). (P) (I) (H) (Basic)
Explain the concept of ‘direction’ of the strand (5′ to 3′) before learners build up the
anti-parallel complementary strand (see final activity 6.1.a). (P) (I) (Challenging)
o Point out how base pairing allows the strands to be parallel and the strength of
having many hydrogen bonds (from single weak H bonds). (W) (Basic)
Groups of learners can join together their sections to give the idea of a (short!) gene
and the class can see each gene carries different information to code for different
proteins. (W) (G) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.dnaftb.org
http://www.hhmi.org/biointeractive/dna/
index.html
http://accessexcellence.org/AB/GG/
http://www.ncbe.reading.ac.uk/ncbe/P
ROTOCOLS/DNA/extracting.html
http://learn.genetics.utah.edu/content/l
abs/extraction/
http://www.nature.com/nature/dna50/ar
chive.html
Past Papers
21
Learning objectives
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Suggested teaching activities
Learning resources
Learners fully label and annotate pre-existing diagrams of DNA. (I) (Basic)
Extension activity (see website recommended): learners read about the discovery of
DNA. (I) (Challenging)
Progress to RNA structure, giving an outline of the three types of RNA before
learners make notes, including diagrams. (W) (I) (Basic)
Learners construct a summary table of the similarities and differences between DNA
and RNA. (F)
Summary discussions (small group and class) about requirements of the ideal
molecule of inheritance, resulting in a large poster. (W) (G) (Basic) (Challenging)
o Carrying information to allow proteins to be synthesised (sequence of
nucleotides).
o Expression to obtain the proteins (transcription and translation, learned later).
o Stability (strong sugar-phosphate backbone, many H bonds).
o Faithful replication to pass on information to daughter cells (complementary
nature of the strands).
o Ability to provide variation (mutations, learned later).
Paper 21, June 2011, Q3
Paper 21, June 2012, Q6 (a)
Note
Save the nucleotides for DNA replication in Unit 3.
3.1.a
explain that enzymes are globular
proteins that catalyse metabolic
reactions
Key concepts
Cells as the units of life,
Biochemical processes
Brainstorm or provide multiple choice questions to gauge learner knowledge,
including understanding of the terms globular, metabolic and catalyst. Emphasise
that previous studies will be extended and name some enzymes they will learn about
e.g. DNA polymerase and carbonic anhydrase. (W) (Basic)
State that most enzyme names end with ‘ase’ and discuss the role of enzymes, e.g.
synthesising macromolecules; transferring groups such as phosphates; rearranging
molecules to form different ones. (W) (Basic).
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/animation__how_enzy
mes_work.html
http://www.sumanasinc.com/webconte
nt/animations/content/enzymes/enzy
mes.html
Textbooks/Publications
Bio Factsheet 163: Answering
Questions: enzyme activity.
Past Papers
Paper 23, Nov 2013, Q6 (c)
3.1.b
state that enzymes function inside cells
v2.1 5Y02
Explain that enzymes are produced within cells. Learners volunteer the meanings of
‘intra-‘ and ‘extra- ‘and discuss these with respect to enzymes that remain to function
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 24: Human digestion.
22
Learning objectives
(intracellular enzymes) and outside
cells (extracellular enzymes)
Key concepts
Cells as the units of life,
Biochemical processes
3.1.c
explain the mode of action of enzymes
in terms of an active site,
enzyme/substrate complex, lowering of
activation energy and enzyme
specificity (the lock and key hypothesis
and the induced fit hypothesis should
be included)
Key concepts
Biochemical processes
Suggested teaching activities
Learning resources
intracellularly and others that are released to act extracellularly (e.g. digestive
enzymes) (this links later to role of the Golgi body). (W) (Basic)
Note
Learners will benefit if they know the meaning of prefixes e.g. intra, extra, poly, milli,
mono. Explain that some have the same meaning but Latin or Greek origins (e.g. uni
versus mono).
Learners make notes on the mode of action of enzymes (remind them of protein
structure), highlighting structure to function. (I) (Challenging)
o Describe and explain enzyme structure, including the active site.
o Include a set of annotated diagrams of the lock and key and induced fit
mechanisms (noting the role of the R groups of amino acids at the active site in
binding with the substrate).
o Explain that many/most reactions can be catalysed in both directions.
Learners use paper cut-out models to show how enzymes can break up substrates
into smaller molecules or can build up larger molecules from smaller ones. (P) (I)
(Basic)
Discuss the concept of lowering activation energy. (W) (Challenging)
o Learners annotate a ‘boulder analogy’ graph to highlight that, although the
energy content of substrate and products is not changed, the reaction pathway
follows a lower energy course. (H) (Basic)
o Learners summarise a discussion about the different ways activation energy can
be lowered by adding notes to their diagrams or the graph. (I) (Challenging)
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/animation__how_enzy
mes_work.html
http://www.sumanasinc.com/webconte
nt/animations/content/enzymes/enzy
mes.html
http://www.learnerstv.com/animation/a
nimation.php?ani=161&cat=Biology
Past Papers
Paper 23, Nov 2013, Q6 (c)
Note
Use the term ‘complementary’ to describe how the substrate fits into, and binds at,
the active site. ‘Matches’ is incorrect.
Check understanding of the term substrate - some may have used the term reactant.
3.1.d
investigate the progress of an enzymecatalysed reaction by measuring rates
of formation of products (for example,
using catalase) or rates of
disappearance of substrate (for
example, using amylase)
v2.1 5Y02
Explain that the course of an enzyme-catalysed reaction can be shown by substrate
disappearance or product formation over time. (W) (Basic)
Emphasise that a rate measurement is given per unit time and that there will be a
change in the rate during the course of the reaction. (W) (Basic)
Learners carry out practical work using catalase (e.g. from yeast, potato, celery,
lettuce) to investigate the rate of release of oxygen (product) from hydrogen
peroxide (substrate). (W) (G) (P) (I) (H) (Basic) (Challenging)
o A graph should be constructed of volume produced (or mass lost if using an
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklets 4, 5
Online
http://www.practicalbiology.org/areas/a
dvanced/bio-molecules/factorsaffecting-enzymeactivity/investigating-an-enzymecontrolled-reaction-catalase-and-
23
Learning objectives
Suggested teaching activities
Learning resources
Key concepts
Biochemical processes,
Observation and experiment
electronic balance) over time intervals.
o Use the graph to calculate initial rate and explain the initial steep release of
product, which then flattens out.
Practical booklet 5. Learners carry out practical work using amylase to time how
long it breaks down starch. Remind learners that using iodine (in potassium iodide)
solution on samples shows the loss of starch from the reaction mixture over time.
This practical is designed to develop practical skills (itemised in the Teacher’s
practical notes) assessed in Paper 3. (W) (G) (P) (I) (H) (Basic)
Extend practical using amylase if a colorimeter is available to get quantitative
results. Trials are required to ensure that the colour of resulting solutions is not too
intense for the colorimeter for a graph. (P) (I) (Challenging)
Practical booklet 4 (carry out after Practical booklet 5) is a modification of the
method described above using catalase.
hydrogen-peroxideconcentration,47,EXP.html
www.csub.edu/~kszick_miranda/Enzy
mes%20part2.doc
http://www.saps.org.uk/secondary/teac
hing-resources/293-learner-sheet-24microscale-investigations-withcatalase
Textbooks/Publications
Bio Factsheet 130: Investigating
catalase
Past Papers
Paper 21, Nov 2011, Q2 (a)
3.2.a
investigate and explain the effects of
the following factors on the rate of
enzyme-catalysed reactions:
Temperature
pH (using buffer solutions)
enzyme concentration
substrate concentration
inhibitor concentration
Key concepts
Organisms in their environment
v2.1 5Y02
With prompting, learners explain why measuring the time taken for complete
removal of substrate is unsuitable if trying to measure the effect of substrate
concentration (with more substrate the rate of reaction is faster, but it takes longer
for it all to disappear). (W) (I) (Challenging)
Discuss with learners why, ideally, initial rates should be calculated when comparing
enzyme activity under different conditions. (W) (Challenging)
Develop planning skills: learners design an investigation in which several variables
need to be controlled and carry this out (ensure that a range of plans is covered).
(W) (I) (Basic) (Challenging)
Learners carry out practical activities on factors affecting the rate of an enzymecatalysed reaction (examples below). (P) (I) (Basic) (Challenging)
o Effect of temperature: the catalase experiment in 3.1.d.
o Effect of pH: use trypsin to digest protein in a suspension of milk powder.
o Effect of enzyme concentration or substrate concentration: use amylase or
diastase to digest a starch suspension.
Then learners present their results and contribute to whole class discussion,
following up with a written explanation. Construct and annotate graphs showing:
o the impact of rate of collisions (temperature, substrate concentration, enzyme
concentration).
o the effect on hydrogen bonding, tertiary structure, shape of active site and
complementary fit of substrate (temperature, pH, inhibitors).
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 5
Online
http://www.ncbe.reading.ac.uk/NCBE/
PROTOCOLS/menu.html
http://www.ncbe.reading.ac.uk/NCBE/
PROTOCOLS/juice.html
http://www.saps.org.uk/secondary/teac
hing-resources/95-investigating-theeffect-of-competitive-and-noncompetitive-inhibitors-on-the-enzymess-galactosidase
http://www.southernbiological.com/
http://www.saps.org.uk/secondary/teac
hing-resources/261-the-inhibition-ofcatechol-oxidase-by-lead
http://www.saps.org.uk/secondary/teac
hing-resources/106-the-effect-of-endproduct-phosphate-on-the-enzymephosphatase
Textbooks/Publications
24
Learning objectives
3.2.b
explain that the maximum rate of
reaction (Vmax) is used to derive the
Michaelis-Menten constant (Km) which
is used to compare the affinity of
different enzymes for their substrates
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Suggested teaching activities
Learning resources
(W) (I) (Basic) (Challenging)
Possibly demonstrate a practical that uses inhibitors considered to be hazardous to
the environment (minimises the volumes used). Check your local authority
regulations concerning safe disposal.
King p.64-68
Siddiqui p.69-75.
Bio Factsheet 43: Factors affecting
enzyme activity
Note
Ensure learners can interpret correctly graphs with the same shaped curve, e.g.
course of an enzyme-catalysed reaction / the effect of increasing substrate
concentration on the rate of a reaction.
For inhibitor concentration, 3.2.b should be covered first or incorporate this part of
3.2.a with 3.2.b.
To show that an inhibitor is competitive is difficult as separate reaction mixtures with
different concentrations of the substrate need to be made up.
Past Papers
Paper 21, June 2011, Q4
Paper 32, June 2013, Q1
Explain Vmax and Km (great detail not required) before learners make notes. (W) (I)
(Basic)
o Show learners how to obtain Vmax and Km from a graph.
o Learners arrive at the idea that the enzyme is saturated with substrate at the
maximum rate of reaction, Vmax.
o Show learners how to obtain Km from a graph, the concentration of substrate that
enables the enzyme to achieve half the maximum rate of reaction, or half Vmax
Learners obtain (Vmax) and (Km) using one of the graphs constructed from their
practical work. (I) (Basic)
Extend learner understanding of Km by discussion or a worksheet providing some
information accompanied by questions. (W) (I) (Challenging)
o Explain that (Km) is the affinity of enzyme for its substrate.
o Allow learners to suggest that an enzyme with a low Km
has a high affinity for its substrate
needs a lower concentration of substrate to reach Vmax than an enzyme with
a high Km.
o Explain that an enzyme with a low Km is more likely to be saturated with
substrate in the normal conditions of substrate within a cell, so variations in
substrate will have less effect on the rate of formation of product.
o Ask learners to explain why an enzyme with a high Km is likely to vary its activity
more (i.e. the concentration of substrate becomes more important).
Learners sketch out two graphs to show the differences between an enzyme with a
high Km and an enzyme with a low Km
o Annotate graphs with explanations. (I) (Challenging)
Online
http://www.worthingtonbiochem.com/introbiochem/substrate
Conc.html
Cambridge International AS & A Level Biology (9700) – from 2016
25
Learning objectives
Suggested teaching activities
Learning resources
3.2.c
explain the effects of reversible
inhibitors, both competitive and noncompetitive, on the rate of enzyme
activity
Following class discussion, learners use resources to make notes and annotated
diagrams about enzyme inhibition. (I) (Challenging)
o Draw graphs of increasing substrate concentration with and without inhibitors.
Learners construct a summary table showing the differences between competitive
and non-competitive inhibition (include the different graphs). (I) (Challenging)
Extension activity: learners investigate and discuss the use of inhibitors as medicinal
drugs, including the different uses of competitive versus non-competitive inhibitors.
(G) (P) (I) (Challenging)
Online
http://www.wiley.com/college/boyer/04
70003790/animations/enzyme_inhibiti
on/enzyme_inhibition.htm
Key concepts
Biochemical processes
3.2.d
investigate and explain the effect of
immobilising an enzyme in alginate on
its activity as compared with its activity
when free in solution
Key concepts
Observation and experiment
Textbooks/Publications
Bio Factsheet 31: Enzyme control of
metabolic pathways.
Note
Irreversible inhibition and allosteric regulation could be worth mentioning briefly
when covering 3.2.c.
Past Papers
Paper 21, Nov 2011, Q2 (b)
Practical: ‘Better milk for cats’ or similar protocol using a different enzyme.
o Discuss how immobilised enzymes are used in everyday applications. (W)
(Basic)
o Introduce the use of dipsticks containing glucose oxidase (useful for 14.1.k). (W)
(Basic)
Demonstrate the same enzymatic reaction using the enzyme free in solution.
Learners suggest the advantages of immobilising the enzyme rather than using it
free (not immobilised) and summarise with a comparison table. (W) (Challenging)
Extension practical: learners use immobilised yeast cells to investigate the
effectiveness of their sucrase or catalase enzymes. (P) (I) (Challenging)
Learners complete a worksheet prepared by you to interpret and compare graphical
and tabulated data for immobilised enzymes with free enzymes.
o Data extraction to compare both for the following factors: temperature; pH;
substrate concentration; inhibitor presence.
o Learners consider explanations of the differences between free and immobilised
enzymes, e.g. protective and stabilising effect of the alginate matrix; degradation
over time; active sites of immobilised enzymes may not all be available; time
taken for diffusion to occur; possibility of slightly altered active site shape when
immobilised, amongst others. (I) (Challenging)
Online
http://www.rpi.edu/dept/chemeng/BiotechEnviron/IMMOB/Immob.htm
http://www.scienceinschool.org/reposit
ory/docs/issue10_catmilk.pdf
http://www1.lsbu.ac.uk/water/enztech/i
meconom.html
Textbooks/Publications
King p.69-73
Siddiqui p.72-73
Bio Factsheet 148: Industrial uses of
enzymes.
Past Papers
Paper 32, June 2012, Q1 (b)
Paper 43, June 2011, Q2
Paper 43, Nov 2011, Q2 (b)
Note
Experiment and observation, a key concept, has increasingly been used to develop
biotechnological applications – here learners can appreciate how biological systems
can be used to benefit humans in the everyday world.
Learners should know the method to prepare alginate beads.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
26
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 2: Cells as the basic units of life
Recommended prior knowledge
Little prior knowledge is required but a basic knowledge of cell structure and practical knowledge of the light microscope would be helpful. The ability to carry out simple
mathematical calculations is required. Learners should understand kinetic theory (http://www.chemguide.co.uk/physical/kt/basic.html is a good basic introduction). If
Unit 1, Biological molecules, is taught after this unit, some knowledge of lipids, proteins and carbohydrates is useful.
Context
Unit 1, Biological molecules, leads on to an understanding of the structure of cells and the functions of cell structures, including biological membranes. This unit deals
with topics that are fundamental to almost every area of study covered in the AS and A Level course. Cell structure, and the functions of the various organelles, will
reappear in numerous contexts. Learners should appreciate the key concept that cells are the basic unit of life and that all living organisms are composed of one or
more cells. Learners will need to be reminded, or taught, how to use a light microscope. An understanding of how substances are transported across membranes is
essential reference material for other topics in this syllabus, especially those covering plant and animal physiology.
Outline
Early on, learners are introduced to the use of the microscope in cell studies, including use of the graticule and micrometer to measure cells. Calculations of
magnification and actual sizes are included in this unit. This unit covers the two fundamental types of cell, eukaryotic and prokaryotic. Details of cell structure are
studied, including the functions of organelles. The fluid mosaic model of membrane structure highlights how membranes can fulfil their roles. The role of the membrane
in cell signalling is introduced. The unit also covers the different mechanisms that enable the movement of substances into and out of cells.
Teaching time
It is recommended that this unit should take approximately 9% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
27
Learning objectives
Suggested teaching activities
Learning resources
1.1.d
explain and distinguish between
resolution and magnification, with
reference to light microscopy and
electron microscopy
Show images of both microscope types and agree more detail can be obtained
about cells / cell structure using microscopes. (W) (Basic)
Agree the meaning of magnification – learners write a worded version and link this
later to the formula used in 1.1.c. Explain how the overall magnification is obtained
(eyepiece x objective lens). (W) (Basic)
Introduce resolution, explaining why the resolution of electron microscopes is much
higher than that of light microscopes (only enough detail of the workings of each to
help understanding of resolution). (W) (Basic) (Challenging)
o Explain that detail smaller than 200nm (approximately half the wavelength of
light) cannot be resolved by the light microscope. (W) (Challenging)
Explain that increasing magnification is only desirable up to the limit of resolution,
e.g. up to approx. x 1000 for the light microscope (electron microscopes vary
considerably).
Compare the TEM and SEM (no details of working required) and the micrographs
produced, so learners see the difference between, and usefulness of, both.
Learners suggest advantages and disadvantages of the two types of microscope.
(G) (Basic)
Learners observe a range of photomicrographs and electron micrographs and
explain which type of microscope was used to produce the image. If these have a
mixture of magnifications and scale bars on them, they can be used in 1.1.e. (G) (P)
(Basic)
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=10
http://www.vcbio.science.ru.nl/en/virtua
llessons/#fesemsimulatie
http://www.biology.arizona.edu/cell_bio
/tutorials/cells/cells2.html
http://zeisscampus.magnet.fsu.edu/articles/basic
s/index.html
Key concepts
Observation and experiment
1.1.a
compare the structure of typical animal
and plant cells by making temporary
preparations of live material and using
photomicrographs
Key concepts
Cells as the units of life,
Observation and experiment
Practical: learning how to use the light microscope. (I) (Basic) (Challenging)
Brainstorm knowledge of the plant cell structure and animal cell structure and
discuss cells as the units of life. (W) (Basic)
Learners construct a comparison table, generalised animal cell v generalised plant
cell, the first row containing simple labelled diagrams. (I) (Basic) (Challenging)
Practical: learners make a temporary preparation, check and give comments on
technique and slides made of peers. (I) (Basic) (Challenging)
Discuss the slides and compare with the constructed table (links to the ideas in
1.1.d). (W) (Basic)
Textbooks/Publications
King p.39-41
Bio Factsheet 75: Microscopes and
their uses in Biology
Past Papers
Paper 21, June 2012, Q2 (a)
Paper 22, June 2013, Q2 (b)
Paper 22, Nov 2012, Q1 (a)
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=10
Textbooks/Publications
Siddiqui p.28-29
Note
This may be combined with 1.1.c and 1.1.e.
Diagram-drawing skills may be introduced here.
1.1.c
v2.1 5Y02
Revise the units of length commonly used during the course (see 1.1.c) with the
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 1
28
Learning objectives
Suggested teaching activities
Learning resources
use an eyepiece graticule and stage
micrometer scale to measure cells and
be familiar with units (millimetre,
micrometre, nanometre) used in cell
studies
metre (meter US) as the SI unit of length.
o Learners to perform conversions between nm, m, mm and m. (W) (Basic)
Explain how to use a stage micrometer to calibrate an eyepiece graticule. (W)
(Challenging)
o Practical booklet 1 is designed to develop the skills required by learners (see
Teacher’s practical notes) when measuring using an eyepiece graticule and a
stage micrometer.
o If learners always use the same microscope, then they can calibrate once only
for each objective lens, and keep a record of it. (I) (Challenging)
o Learners use the Bioscope to learn the principles of use. (I) (Challenging)
Learners use their calibrated eyepieces to measure a range of microscopic
specimens, choosing one specimen to draw (see 1.1.a). (I) (Basic) (Challenging)
o Learners measure the actual length of a part of a specimen on the slide and by
measuring the length drawn on their diagram, they can calculate the linear
magnification of their drawing. (I) (Basic)
CD-ROM
Bioscope – teaching and learning tool
for the skills required to use a
graticule and stage micrometer
successfully.
Key concepts
Cells as the units of life,
Observation and experiment
Note
Discourage measuring in cm as many forget to multiply by 10 to convert to mm
before converting to m.
The eyepiece graticules can be fitted permanently into the eyepiece of the
microscope.
Inexpensive stage micrometer scale kits and eyepiece graticules can be obtained
from the Cambridge publications catalogue www.cie.org.uk/cambridgefor/teachers/order-publications
1.1.b
calculate the linear magnifications of
drawings, photomicrographs and
electron micrographs
Key concepts
Observation and experiment
v2.1 5Y02
Hold up an apple, then drawings of the apple: at the same size = magnification x 1;
double the size = x 2; half the size = x 0.5. Discuss the mental calculation learners
have made to get the right answer.
o magnification = image size / actual size. (Group) (Basic)
Explain how to use scale bars to calculate magnification, emphasising that learners
should measure the scale bar length and not the image. (W) (Challenging)
Learners complete a worksheet prepared by you with images of varying stated
length (nm to mm) and with scale bars only. Use copyright-free images to prepare
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/c
ells/scale/
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=10
http://www.vcbio.science.ru.nl/en/virtua
llessons/#fesemsimulatie
http://www.biology.arizona.edu/cell_bio
/tutorials/cells/cells2.html
http://zeisscampus.magnet.fsu.edu/articles/basic
s/index.html
Textbooks/Publications
King p.20-22
Siddiqui p.42-43
Past Papers
Paper 31, Nov 2012, Q2 (b)(c)
Paper 33, Nov 2012, Q2 (b)
Paper 35, Nov 2012, Q2 (b)
Paper 12, Nov 2011, Q5
Past Papers
Paper 22, June 2011, Q4 (b)
Paper 21, June 2011, Q1 (a)
Paper 23, Nov 2011, Q1 (a)
Paper 31, June 2011, Q2 (c)
29
Learning objectives
Suggested teaching activities
Learning resources
the worksheet (e.g. Wikipedia). (P) (I) (Basic) (Challenging)
1.1.e
calculate actual sizes of specimens
from drawings, photomicrographs and
electron micrographs
Key concepts
Observation and experiment
1.2.b
recognise the following cell structures
and outline their functions:
cell surface membrane
nucleus, nuclear envelope and
nucleolus
rough endoplasmic reticulum
smooth endoplasmic reticulum
Golgi body (Golgi apparatus or
Golgi complex)
mitochondria (including small
circular DNA)
ribosomes (80S in the cytoplasm
and 70S in chloroplasts and
mitochondria)
lysosomes
centrioles and microtubules
chloroplasts (including small circular
DNA)
cell wall
plasmodesmata
large permanent vacuole and
tonoplast of plant cells
Discuss how the actual sizes can be calculated using the rearranged formula to
calculate magnifications. (W) (Basic)
o Explain also how to use scale bars to calculate actual sizes. (W) (Basic)
o Learners calculate actual sizes from diagrams and the photomicrographs and
electron micrographs from 1.1.d using the given scale bar or magnification. (P)
(I) (Basic) (Challenging)
Learners tackle worksheets prepared by you with exam-style (differentiated)
questions to calculate actual sizes and magnifications (use past papers). (I) (H) (F)
(Basic) (Challenging)
Interactive session using diagrams and electron micrographs: agree descriptions of
the cell structures and discuss their functions.
o With reference to plant and animal cells, introduce the terms eukaryote and
eukaryotic, explaining the meaning of ‘true nucleus’. (W) (Basic)
Provide an overview of how different cell structures are linked, e.g. outline sequence
of events in protein production and secretion. (W) (Basic)
Learners identify particular cell structures and state their function using electron
micrographs and photomicrographs, at various magnifications. Include examples of
both plant and animal cells (names of cell types not required). (G) (P) (I) (Basic)
(Challenging)
Learners label the cell structures on diagrams drawn from electron micrographs of
both plant cell and animal cells, and annotate each with a function. (F)
Note
Learners should understand (no definition required) that an organelle is a structure
within a cell that has a function.
Discuss the idea of the advantages of cellular compartments.
For mitochondria and chloroplasts see also 1.2.c.
Online
http://www.cellsalive.com/howbig.htm
Past Papers
Paper 21, Nov 2011, Q5 (a)
Online
http://www.biologie.uni-hamburg.de/bonline/library/falk/CellStructure/cellStr
ucture.htm
http://publications.nigms.nih.gov/inside
thecell/chapter1.html
http://www.cellsalive.com/cells/cell_mo
del.htm
http://learn.genetics.utah.edu/content/c
ells/insideacell/
http://www.bscb.org/?url=softcell/index
http://cellpics.cimr.cam.ac.uk/
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM006.html
http://www.rothamsted.bbsrc.ac.uk/not
ebook/index.html
Textbooks/Publications
Bio Factsheet 4: Structure to function
in eukaryotic cells.
Past Papers
Paper 22, Nov 2011, Q6 (a)
Paper 21, June 2012, Q2 (b)(c)(e)
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
30
Learning objectives
Suggested teaching activities
Learning resources
Extend 1.2.b so learners know that ATP is produced: in chloroplasts as a result of
the absorption of light; in mitochondria in aerobic respiration. (W) (Basic)
Discuss why a cell needs energy and the need for energy transfers within a cell. (W)
(Basic)
o Explain that ATP is the molecule used for these transfers and is described as the
universal energy currency of the cell.
o Stress that ATP is not a form of energy but that energy is released when ATP is
hydrolysed and this energy can be used by the cell.
Online
http://www.biologyinmotion.com/atp/ind
ex.html
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity
1.2.c
state that ATP is produced in
mitochondria and chloroplasts and
outline the role of ATP in cells
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 129: ATP–what it is,
what it does.
Note
This sets the scene for other learning objectives, e.g. 4.2.a, 12.1.a, 12.1.b, 13.1.f,
13.1.h and 15.1e, so do not be tempted to give too many details at this stage.
1.2.a
describe and interpret electron
micrographs and drawings of typical
animal and plant cells as seen with the
electron microscope
Key concepts
Cells as the units of life
1.2.d
outline key structural features of typical
prokaryotic cells as seen in a typical
bacterium (including: unicellular, 1-
v2.1 5Y02
Emphasise that although cells are the basic unit of life, they can have different
structures depending on their function. (W) (Basic)
State that membranes range from approximately 5-9 nm thick and allow learners to
explain that the boundary of the cell /nucleus is only seen with the light microscope
because of the contrast (membranes are not visible). (W) (Challenging)
o Learners volunteer that detail such as membranes are visible using the electron
microscope. (W) (Basic)
From electron micrographs of different cell types, learners can identify:
o whether plant or animal, stating the features that enabled the choice,
o all the cell structures seen, adding labels and annotations.
(P) (I) (H) (F) (Basic) (Challenging)
Extension activity: learners compare electron micrograph images and drawings with
those obtained with the light microscope. (P) (I) (Basic) (Challenging)
o Learners construct a descriptive list of the additional features seen. (G) (P)
(Basic)
Online
http://micro.magnet.fsu.edu/primer/tec
hniques/contrast.html
http://www.unimainz.de/FB/Medizin/Anatomie/works
hop/EM/EMAtlas.html
http://learn.genetics.utah.edu/content/c
ells/insideacell/
Short answer test to revise plant and animal cell structural details. (F)
Linking to the key concept of cells as the units of life, explain to learners that there
are two fundamental types of cell: eukaryotic and prokaryotic.
o Explain how the term ‘prokaryotic’ arose.
Online
http://www.cellsalive.com/cells/bactcell
.htm
http://www.ucmp.berkeley.edu/bacteria
/bacteria.html
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 21, June 2012, Q2
Paper 22, Nov 2012, Q1 (b)
31
Learning objectives
5m diameter, peptidoglycan cell
walls, lack of organelles surrounded by
double membranes, naked circular
DNA, 70S ribosomes)
Key concept
Cells as the units of life
Suggested teaching activities
o Discuss how the single cell comprising a unicellular organism will exhibit all the
characteristics that define life. (W) (Basic)
Build up a typical bacterial cell (example of a prokaryote) by introducing each key
structural feature in turn (e.g. overhead transparency overlays/PowerPoint slides).
(W) (Basic)
From 1.2.b, learners suggest functions of prokaryotic structures. (I) (Challenging)
Learners label a diagram, or draw a labelled diagram, of a typical bacterium /
prokaryote. (I) (Basic) (Challenging)
Annotate the diagram with an outline function. (H) (Basic)
Learning resources
Textbooks/Publications
Bio Factsheet 73: The prokaryotic cell
Past Papers
Paper 22, June 2011, Q4
Paper 23, Nov 2011, Q1
Note
Reference could be made to the bacteria responsible for cholera and TB (see Unit
5).
Archaea as prokaryotes are covered in Unit 7.
You could mention (to prepare for Unit 7), the kingdom Prokaryotae and the four
eukaryotic kingdoms, Fungi, Protoctista, Plantae and Animalia.
1.2.e
compare and contrast the structure of
typical prokaryotic cells with typical
eukaryotic cells (reference to
mesosomes should not be included)
Learners examine photomicrographs, electron micrographs and diagrams of typical
prokaryotic and eukaryotic cells. (G) (Basic)
o Learners discuss the major differences between the two cell types. (G) (Basic)
o Learners give a bullet-point list of similarities and construct a table of differences.
(I) (Challenging)
Key concepts
Cells as the units of life
Note
Mention to learners that mesosomes (in many textbooks) are now considered to be
artefacts from preparation for electron microscopy.
1.2.f
outline the key features of viruses as
non-cellular structures (limited to
protein coat and DNA/RNA)
Key concepts
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity
v2.1 5Y02
Outlining the key features of viruses for learners to produce annotated diagrams.
(W) (I) (Basic)
Learners investigate a range of viruses. (H)
o A follow-up discussion/debate about viruses as complex entities that do not fit
the cell theory of life (also applies understanding of the key concept of cells as
the units of life – are viruses living organisms?). (W) (Challenging)
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=52
Textbooks/Publications
Bio Factsheet 107: Answering exam
questions – cells
Past Papers
Paper 23, Nov 2011, Q1 (b)
Past Papers
Paper 21, June 2012, Q6 (c)
Note
Mention that some viruses have an additional outer envelope similar in nature to a
cell surface membrane (preparation for HIV in Unit 5).
Cambridge International AS & A Level Biology (9700) – from 2016
32
Learning objectives
Suggested teaching activities
Learning resources
4.1.a
describe and explain the fluid mosaic
model of membrane structure,
including an outline of the roles of
phospholipids, cholesterol, glycolipids,
proteins and glycoproteins
Learners make protein, cholesterol and phospholipid (mix of fatty acid tails – both,
saturated and unsaturated or one of each) cut-outs from templates provided by you.
(H) (Basic)
Learners complete a short test to recall knowledge of phospholipids, proteins and
carbohydrates. Go through this and make links to membrane structure. (F)
(Challenging)
o For a phospholipid, use a symbolised or molecular model to point out the
hydrophilic phosphate ‘head’ portion and the two hydrophobic hydrocarbon tails
(fatty acid residues).
o Relate protein structure to the main membrane protein types e.g. enzymes
(globular); channel (lining of amino acids with hydrophilic R groups), etc.
o Describe carbohydrate portions of glycolipids and glycoproteins as chains of
sugar molecules.
Discuss the basic model to describe the structure of membranes, explaining that the
physical boundary is based on phospholipids. (W) (Challenging)
o Draw a line indicating a water/air boundary and a diagram of a symbolised
phospholipid. Learners suggest how phospholipids would behave if they were
spread as monolayer (tails in the air, heads in water).
o Discuss the behaviour of phospholipids immersed in water (spheres, heads out,
tails to centre, natural self-assembly).
o Highlight the idea of a ‘fluid’ phospholipid bilayer forming a compartment (e.g.
cell/membranous organelle) and discuss which substances could cross the
hydrophobic core.
o Discuss the scattered (hence ‘mosaic’) proteins and their various overall roles,
e.g. enzymes, receptors for binding ligands, and the transport of polar molecules
and ions.
o Mention interspersed cholesterol molecules (lipids).
Learners use their cut-outs to build a section of a membrane, noting the larger gaps
when phospholipids with unsaturated fatty acid tails occur within the bilayer. (P) (I)
(Basic)
Discuss and explain factors affecting membrane fluidity, including: the role of
unsaturated and saturated fatty acids; how cholesterol acts to regulate; temperature.
(W) (Challenging)
Learners label the different membrane components on a range of different diagrams
(prepared by you) of the fluid-mosaic model. (I) (Basic).
Learners make notes to explain why the fluid mosaic model is an appropriate term to
use. (I) (Basic)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/754-using-beetroot-inthe-lab
www.ultranet.com/~jkimball/BiologyPa
ges/C/CellMembranes.html
http://www.wisconline.com/objects/ViewObject.aspx?
ID=ap1101
http://www.stolaf.edu/people/giannini/fl
ashanimat/lipids/membrane%20fluidit
y.swf
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 8: The cell surface
membrane.
Past Papers
Paper 21, Nov 2011, Q1 (a)
Paper 22, Nov 2012, Q2 (a)
33
Learning objectives
Suggested teaching activities
Learning resources
Link the presence of glycolipids and glycoproteins to the cell surface membrane and
outline their roles. (W) (Basic)
Learners practise drawing a labelled diagram of a section of a membrane that can
be completed under exam conditions in 3-4 minutes. (I) (F) (Challenging)
o Learners can annotate with the roles of the components. (F)
Note
Learners should know the terms given in the notes in 2.3.d (Unit 1) to explain
transport of substances across the phospholipid bilayer or using membrane proteins.
4.1.b
outline the roles of cell surface
membranes including references to
carrier proteins, channel proteins, cell
surface receptors and cell surface
antigens
Key concepts
Cells as the units of life,
Biochemical processes
4.1.c
outline the process of cell signalling
involving the release of chemicals that
combine with cell surface receptors on
target cells, leading to specific
responses
Learners suggest and list the desired features of cell surface membranes. Explain
that there are some specialised cells that can engulf e.g. bacteria to introduce
phagocytosis / endocytosis. (W) (I) (Basic)
Brainstorm a list of materials/substances entering and leaving cells. (W) (Basic)
Learners give a written explanation of the role of phospholipids and proteins in
controlling the passage of substances across the cell surface membrane, making
reference to its partially permeable nature. (I) (Challenging)
Learners research and note the differences between carrier and channel proteins
(how they act to transport solutes across the membrane), and explain how
aquaporins increase the membrane permeability to water. (I) (Basic)
Question and answer session revising protein structure, discussing cell surface
receptors for learners to make notes. (W) (Basic)
o Learners suggest / research examples of ligands, e.g. hormones,
neurotransmitters. (I) (Basic)
Outline how glycoproteins and glycolipids can act as antigens (also in Unit 5). (W)
(Basic)
Learners write out a summary of this learning objective. (F)
Online
http://www.biologymad.com/cells/cellm
embrane.htm
http://www.ncbi.nlm.nih.gov/books/NB
K9847/
A reminder of cell receptors introduces the idea of cell signalling. (W) (Basic)
Learners draw one or more annotated diagrams to show the general sequence of
events occurring in cell signalling. (I) (Challenging)
Extension work: learners apply knowledge to specific examples. (I) (Challenging)
Online
http://www.open.edu/openlearn/scienc
e-maths-technology/cellsignalling/content-section-0#
Past papers
Paper 22, June 2013, Q4 (c)
Key concepts
Cells as the units of life,
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
34
Learning objectives
Suggested teaching activities
Learning resources
Only the fifth part of this learning objective is included here: describe and explain the
processes of endocytosis and exocytosis
Learners refer to the list of substances that enter/leave cells (4.1.b)
o State that there is also ‘unwanted’ entry of, e.g. bacteria.
o Discuss how the nature of the substance and its size will direct which
mechanism of transport across the membrane is used.
o Learners place each item on the list into the correct group: through the
phospholipid bilayer; through membrane proteins; neither (too large/bulk
transport). (W) (I) (Challenging)
Learners recall membrane fluidity and read about bulk transport across membranes.
(I) (Challenging)
o Explain pinocytosis and phagocytosis (see 11.1.a in Unit 5) as forms of
endocytosis.
o Learners draw diagrams showing the sequence of events involved in
endocytosis and exocytosis (revise Golgi vesicle formation).
o Point out that endocytosis and exocytosis are active (energy-requiring)
mechanisms of movement of substances across membranes.
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
Biochemical processes
4.2.a (v)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Key concepts
Cells as the units of life,
Biochemical processes
4.2.c
calculate surface areas and volumes of
simple shapes (e.g. cubes) to illustrate
the principle that surface area to
volume ratios decrease with increasing
size
Key concepts
Observation and experiment
4.2.a (i)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
v2.1 5Y02
Learners use cubes to build 'organisms' of the same shape, with different numbers
of blocks, and calculate surface area to volume ratios. (I) (Basic)
o Discuss the discovery that SA:V decreases as size of organism (same shape)
increases.
o Highlight the relative distances from the outside to the inside.
Textbooks/Publications
Biological Nomenclature. Explains the
terminology that should be used
when teaching osmosis.
Bio Factsheet 54: Water potential
Bio Factsheet 116: Transport
Mechanisms in cells
Past Papers
Paper 21, Nov 2011, Q1 (b)
Paper 22, June 2012, Q1
Textbooks/Publications
Bio Factsheet 165: Surface Area and
Volume.
Note
This serves as an introductory exercise before considering diffusion (4.2.a (i)).
Only the first part of this learning objective is included here: describe and explain the
processes of diffusion
Explain that diffusion is a passive (thermodynamic) method of movement across
membranes. (W) (Basic)
Learners write a definition, make bullet-pointed notes to expand and draw simple
diagrams. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
35
Learning objectives
Suggested teaching activities
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Learning resources
Textbooks/Publications
Bio Factsheet 116: Transport
Mechanisms in cells
Key concepts
Cells as the units of life,
Biochemical processes
4.2.d
investigate the effect of changing
surface area to volume ratio on
diffusion using agar blocks of different
sizes
Key concepts
Observation and experiment
4.2.b
investigate simple diffusion using plant
tissue and non-living materials, such
as glucose solutions, Visking tubing
and agar
Key concepts
Cells as the units of life
4.2.a (ii)
describe and explain the processes
of diffusion, facilitated diffusion,
v2.1 5Y02
Practical: to represent ‘cubic’ organisms, learners cut different-sized agar (technical
agar better) or gelatine blocks, coloured using a pH indicator (e.g. cresol red or
phenolphthalein), then lower them carefully into dilute hydrochloric acid. Learners
time how long it takes for the cube to change colour to measure the effect of surface
area to volume ratio on diffusion. (P) (Basic)
Learners note the implications of a changing SA:V on the needs of multicellular
plants and animals (size too great; distances too far; diffusion too slow) and the
need for transport systems. (I) (Basic)
Discuss shapes that give a large surface area for the same volume (e.g. cube,
flattened to give a leaf lamina, with branching to give a plant shape). (W) (Basic)
o Explain how this means that in plants diffusion alone is sufficient for gases, so
no transport system is required (presence of stomata and lenticels mentioned).
(W) (Challenging)
Online
http://teachers.net/lessons/posts/2518.
html
http://www.neiljohan.com/projects/biolo
gy/sa-vol.htm
Practical: learners add glucose solution and/or starch suspension to lengths of
Visking tubing tied at one end, tie at the other end and place in water (and vice
versa) for a set time. The appearance of the tubing and the results of biochemical
tests on the internal and external solutions is recorded and results explained. (P) (I)
(Basic) (Challenging)
Practical: in agar (in Petri dishes) containing starch, learners cut out a central well,
add amylase solution (or use a soaked filter paper disc) and after incubation observe
the changes that occur when iodine (in potassium iodide) solution is added. (I)
(Basic)
Past Papers
Paper 35, Nov 2011, Q1
Only the second part of this learning objective is included here: describe and explain
the processes of facilitated diffusion
Emphasise that facilitated diffusion is also a passive method of movement across
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
Cambridge International AS & A Level Biology (9700) – from 2016
36
Learning objectives
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Suggested teaching activities
membranes and that it is diffusion through a channel or carrier protein. Learners
make notes and use textbooks/internet. (W) (Challenging)
Key concepts
Cells as the units of life,
Biochemical processes
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
Textbooks/Publications
Bio Factsheet 54: Water potential.
Bio Factsheet 116: Transport
Mechanisms in cells
Key concepts
Cells as the units of life,
Biochemical processes
4.2.a (iii)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Learning resources
Past Papers
Paper 22, June 2012, Q1
Only the third part of this learning objective is included here: describe and explain the
processes of osmosis (no calculations involving water potential will be set)
Remind learners that movement of water molecules by crossing the bilayer or via
aquaporins is passive. (W) (Basic)
Explain water potential. (W) (Challenging)
Learners define osmosis, make bullet-point notes and draw simple diagrams. (I)
(Basic)
Learners write a paragraph stating the similarities and differences between osmosis
and (passive) diffusion. (F)
Note
Terminology to use: partially permeable; water potential; solute potential; pressure
potential. Learners should ignore other terms that they come across such as
hypotonic and hypertonic, osmotic potential, etc.
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
Textbooks/Publications
Biological Nomenclature. Explains the
terminology that should be used
when teaching osmosis.
Bio Factsheet 54: Water potential.
Bio Factsheet 116: Transport
Mechanisms in cells
Past Papers
Paper 22, June 2012, Q1
4.2.f
explain the movement of water
between cells and solutions with
different water potentials and explain
the different effects on plant and
animal cells
v2.1 5Y02
Recall the different permeabilities of the cell surface membrane, partially permeable
and cell wall, (freely- or fully-) permeable. (W) (Basic)
Discuss the terms that can be used to describe cells: plasmolysis / plasmolysed,
flaccid, turgid / turgidity and lysis / haemolysis.
Learners describe what happens when animal and plant cells are placed into
different external solutions at the same, lower and higher water potential than that of
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 3
Online
http://www.kscience.co.uk/animations/
plasmolysis.htm
http://www.biotopics.co.uk/life/osmdia.
37
Learning objectives
Key concepts
Cells as the units of life,
Observation and experiment
Suggested teaching activities
Learning resources
the cells. Diagrams drawn and explanation given in terms of osmosis and water
potential.
Learners complete a worksheet (prepared by you) with the cellular environment and
the external solutions identified only with values of water potential. (I) (Basic)
(Challenging)
Practical: learners use water and different concentrations of salt solutions to observe
onion cells and make high power drawings. (I) (Challenging)
Extension practical: as above, learners observe changes in red blood cells (use a
safe, acceptable source). Making estimates of cell numbers makes this a semiquantitative investigation. (I) (Challenging)
html
http://www.s-cool.co.uk/alevel/biology/cells-andorganelles/revise-it/movement
http://www.neosci.com/demos/101041_cell%20processes/Presentation
.html
http://www.biologymad.com/resources/
ch%202%20%20getting%20in%20and%20out%2
0of%20cells.pdf
Past papers
Paper 52, June 2011, Q1
4.2.e
investigate the effects of immersing
plant tissues in solutions of different
water potential, using the results to
estimate the water potential of the
tissues
Learners immerse pieces of root or stem (e.g. potato tuber tissue) in sucrose
solutions of different concentrations. The water potential of the solution in which
there is no change in length or mass is the estimate of water potential of the tissue.
(I) (Basic)
Practical booklet 3 develops skills for Paper 3 (see Teacher’s practical notes),
followed up by Q1 in Paper 52, June 2011 (data interpretation).
Key concepts
Cells as the units of life,
Observation and experiment
Practical booklet 3
Online
http://www.biotopics.co.uk/life/carrot.ht
ml#top
http://www.saps.org.uk/secondary/teac
hing-resources/286-measuring-thewater-potential-of-a-potato-cell
Textbooks/Publications
King p.60-63
Siddiqui p.38, 40-43.
Past papers
Paper 52, June 2011, Q1
4.2.a (iv)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport,
endocytosis and exocytosis (no
calculations involving water potential
v2.1 5Y02
Only the fourth part of this learning objective is included here: describe and explain the
processes of active transport
Discuss examples of active transport to show why it is necessary to transport
substances against the concentration gradient. (W) (Basic)
Learners make notes on active transport, including the role of membrane (carrier)
proteins. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
38
Learning objectives
Suggested teaching activities
Learning resources
will be set) describe and explain the
processes of diffusion, facilitated
diffusion, osmosis, active transport,
endocytosis and exocytosis (no
calculations involving water potential
will be set)
Learners write a paragraph stating the similarities and differences between
facilitated diffusion and active transport. (I) (Challenging)
Learners construct a summary chart with main points (see below), and then add
details. (H) (F) (Challenging)
Textbooks/Publications
Bio Factsheet 116: Transport
Mechanisms in cells
Past Papers
Paper 22, June 2012, Q1
transport mechanism
Key concepts
Cells as the units of life,
Biochemical processes
active
passive
passive
diffusion
facilitated
diffusion
bulk
transport
endocytosis
phagocytosis
v2.1 5Y02
active
transport
exocytosis
pinocytosis
Cambridge International AS & A Level Biology (9700) – from 2016
39
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 3: DNA and the mitotic cell cycle
Recommended prior knowledge
Learners should have covered cell structure in Unit 2. Building on the key concept of cells as the basic unit of life, they should be familiar with the terms unicellular and
multicellular and know the definition of a tissue. Knowledge of the cell structures involved in protein synthesis and in mitotic cell division is essential so that learners
understand where and when the biological processes described in this unit occur. The role of enzymes in biological processes should be appreciated.
Context
This unit brings together important ideas from Units 1 and 2. Eukaryotic cells can divide by mitosis and meiosis. Cells arising as a result of mitosis are genetically
identical to each other and their parent cell, owing to faithful DNA replication during the cell cycle. DNA transcription and translation occurs during the cell cycle and
results in protein synthesis. Learners will have studied the structure of nucleic acids and proteins and will know the cell structures involved in protein synthesis. DNA as
the molecule of heredity, a key concept, contains coded information for the synthesis of proteins. The central dogma describes the flow of genetic information in a cell
and is a concept that works at a molecular level to help explain the more general statement that “the nucleus controls the cell’s activities”. Mitotic division by stem cells
allows multicellular organisms to develop and to maintain their programmed structure and organisation. Malfunctioning of cells may cause uncontrolled growth and
division and lead to tumours, or could cause the early death of cells. An understanding of the processes involved in the cell cycle will underpin later studies of genetic
control and detailed knowledge of mitotic division will facilitate understanding of the events occurring in meiotic division, studied later in the scheme of work.
Outline
This unit covers the mitotic cell cycle and begins with detail of the structure of chromosomes. After gaining an overview of the cell cycle, DNA replication by the semiconservative mechanism is tackled as part of late interphase of the cell cycle and then consideration is given to the importance of mitosis to unicellular and multicellular
organisms. Stem cells are introduced and an explanation of how uncontrolled division can lead to tumours is given. To aid understanding of the events occurring during
mitosis, especially of chromosome behaviour, learners also have the opportunity to study cells in stages of mitosis in prepared or temporary slides. The unit finishes
with a molecular definition of a gene and a gene mutation, and provides detail of DNA transcription and translation, which gives learners further insight into processes
occurring during interphase of the mitotic cell cycle.
Teaching time
It is recommended that this unit should take approximately 7% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
40
Learning objectives
Suggested teaching activities
Learning resources
5.1.a
describe the structure of a
chromosome, limited to DNA, histone
proteins, chromatids, centromere and
telomeres
State that the structure of chromatin alters during the cell cycle and explain that in a
non-dividing cell, chromatin is in its least condensed state. (W) (Basic)
o Learners describe a chromosome in a non-dividing cell or a cell in interphase as
a molecule of DNA complexed with histone protein.
o Remind/explain that the length of DNA in a chromosome is organised into
functional units, genes.
Learners draw and annotate a chromosome at prophase/metaphase to include two
sister chromatids, the centromere and telomeres
o Learners write a paragraph to explain that an identical sister chromatid is formed
before cell division. (W) (I) (Basic)
Extension: learners find out more about euchromatin and heterochromatin. (I)
(Challenging)
Online
http://www.dnalc.org/resources/3d/07how-dna-is-packaged-basic.html
http://ghr.nlm.nih.gov/handbook/basics
/chromosome
Explain that only some cells carry out mitotic cell division (most remain in the
interphase state) and one mitotic cell cycle results in two cells, following a nuclear
division (mitosis) and a cell division. (W) (Basic)
Learners research and produce an outline, annotated diagram of a cell cycle. (I)
(Challenging)
o Include the two main phases, interphase and a mitotic phase and note that the
timing of cell division is controlled by a number of genes.
o Indicate that DNA replication takes place in late interphase and that protein
synthesis occurs throughout interphase.
o Indicate that cell growth occurs in interphase.
o Include for the mitotic phase (mitosis) the main stages: prophase, metaphase,
anaphase, telophase and also indicate cytokinesis following telophase.
Add background information, e.g. cytokinesis only takes place if new cells are to be
formed (without cytokinesis a multinucleate cell is formed); notes on the G1, S and
G2 phases (use a key to indicate background information only).
Learners label incomplete diagrams (prepared by you). (F)
Introduce and give a general outline of stem cells (for 5.1.e), explaining that they
divide to become more stem cells and cells that differentiate.
o Discuss the location of stem cells in the bone marrow and within epithelial tissue
(describe this as lining or surface tissue).
o For plants, use the terms ‘meristem’, ‘meristematic’ and ‘cambium’ and discuss
locations within plants where this tissue occurs. (W) (Basic)
Online
http://www.cellsalive.com/cell_cycle.ht
m
Key concepts
Biochemical processes,
DNA, the molecule of heredity
5.1.c
outline the cell cycle, including
interphase (growth and DNA
replication), mitosis and cytokinesis
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
6.1.c
v2.1 5Y02
Revise 5.1.a and 5.1.c so learners understand the need for interphase
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 22, June 2011, Q1
Paper 23, June 2011, Q1 (c)
Online
41
Learning objectives
describe the semi-conservative
replication of DNA during interphase
Suggested teaching activities
Key concepts
Biochemical processes,
DNA, the molecule of heredity
chromosomes (and hence DNA) to replicate before mitosis occurs. (W) (Basic)
Learners match events/descriptions (printed on strips of card) to unlabelled
diagrams of semi-conservative replication to correctly describe the sequence of
events that occur in the process (you’ll need to prepare this in advance). (P) (I)
(Challenging)
o Ensure learners are clear about the role of DNA polymerase and DNA ligase and
the concept of activated nucleotides.
o Include a description pointing out that replication occurs in opposite directions for
each strand.
Learners explain what is meant by (define) semi-conservative replication. (I) (Basic)
Learners use their cut-outs of DNA nucleotides to simulate DNA replication.
o Use very short sections of double strands, separate them to show the template
strands and build up the two complementary strands. (P) (I) (Basic)
o Extension: simulate as it occurs – one strand built-up in one direction as a
continuous process and the other in Okazaki fragments (not required
knowledge). (P) (I) (Challenging)
Discuss how this process allows for faithful replication to produce identical DNA
molecules and hence genetically identical sister chromatids, ready for mitotic cell
division. (W) (Basic)
Learning resources
http://www.wiley.com/college/pratt/047
1393878/student/animations/dna_repl
ication/index.html
http://highered.mcgrawhill.com/sites/dl/free/0072437316/120
076/bio23.swf
http://www.accessexcellence.org/AB/G
G/dna_replicating.html
Textbooks/Publications
Bio Factsheet 207: How science
works: Meselson and Stahl’s classic
experiment.
Past Papers
Paper 22, Nov 2011, Q4 (c)(d)
Paper 23, Nov 2011, Q5 (b)
Note
The Meselsohn and Stahl investigation is not required learning but learners could be
given the information to test application of knowledge and understanding.
The poster (from Unit 1, DNA as the ideal molecule of inheritance) should remain
visible as this unit is covered.
5.1.d
outline the significance of telomeres in
permitting continued replication and
preventing the loss of genes
Key concepts
DNA, the molecule of heredity
v2.1 5Y02
Explain that DNA replication results in loss of a short section of the ends of the
chromosome and that telomeres are made from repeating sequences of nucleotides.
(W) (Basic)
Learners suggest how telomeres are useful, with a follow-up outline of their role
discussed and notes made: (W) (I) (Challenging)
o Telomeres serve to prevent the ends of chromosomes from being degraded.
o Without telomeres the ends would appear damaged to the cell’s repair
machinery so they prevent the ends from being joined to the ends of other
chromosomes.
o Telomeres protect genes and the integrity of the genetic material and allow
continued replication.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/c
hromosomes/telomeres/
42
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners investigate the shortening of telomeres with age and the role of
telomerase. (I) (Challenging)
5.1.b
explain the importance of mitosis in the
production of genetically identical cells,
growth, cell replacement, repair of
tissues and asexual reproduction
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
5.1.e
outline the significance of mitosis in
cell replacement and tissue repair by
stem cells and state that uncontrolled
cell division can result in the formation
of a tumour
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
v2.1 5Y02
Ensure that learners know the definition of a tissue. (W) (Basic)
Discuss with learners how their own growth occurs and how damaged tissue is
repaired. Remind them that replacement of cells can occur when cells are old/die
thorough programmed cell death.
Refer to the poster (DNA as the ideal molecule of inheritance) and agree that it is
essential that each daughter cell contains the same complete set of instructions and
the same number of chromosomes as the parent (i.e. genetically identical). (W)
(Basic)
Discuss how cells could be rejected (attack by the immune system) if the daughter
cells were genetically different and not recognised as ‘self’ (link to antigens in Unit 2
and see Unit 5). (W) (Challenging)
Learners investigate simple examples where mitosis is involved in reproduction e.g.
Hydra, or a plant that reproduces asexually. (H) (Basic)
Discuss briefly the terms clone and vegetative propagation. (W) (Basic)
Learners make brief notes summarising the discussions. (H) (F)
Online
http://www.nature.com/scitable/topicpa
ge/replication-and-distribution-of-dnaduring-mitosis-6524841
http://www.ncbi.nlm.nih.gov/pmc/article
s/PMC256985/pdf/03-10043_p214.pdf
http://sciencecases.lib.buffalo.edu/cs/c
ollection/
Learners research examples, e.g. the repair of damage to intestinal epithelial cells,
replacement of old cells in the gas exchange system. (I) (Basic)
o Extend learning to discuss how cells that are structurally and functionally the
same need to be genetically identical. (W) (Basic)
o Remind learners that all cells in the body have the same set of instructions and
explain that control of cell function is by the organised ‘switching on’ of relevant
genes. (W) (Challenging)
Explain (see 5.1.c) that the timing of cell division is under genetic control; an
alteration in a gene could lead to the cell dividing uncontrollably to form a tumour –
an example of how a cell malfunctioning upsets the delicate balance. (W)
(Challenging)
Learners sequence a set of diagrams (prepared by you) showing changes that occur
to result in a tumour (should include an abnormal mass from which two arrows
emerge to a benign growth and a cancerous (malignant) growth (see Unit 5). (I)
(Basic).
o Following research, learners add brief annotations to the diagrams. (H)
(Challenging)
o Extension: learners research differences between the two types of tumour. (I)
Online
http://stemcells.nih.gov/info/basics/pag
es/basics4.aspx
http://www.medicalnewstoday.com/info
/stem_cell/
http://science.education.nih.gov/supple
ments/nih1/cancer/guide/guide_toc.ht
m
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 23, June 2011, Q1 (b)
Past Papers
Paper 21, Nov 2011, Q4 (b)
43
Learning objectives
Suggested teaching activities
Learning resources
(Challenging)
Extend 5.1.c to discuss the statement: "Stem cells allow multicellular organisms to
develop and to maintain their programmed structure and organisation”. (W) (G)
(Challenging)
Extension: learners investigate biotechnological applications, e.g. the use of adult
stem cells in research and therapy. (I) (Challenging)
5.2.a
describe, with the aid of
photomicrographs and diagrams, the
behaviour of chromosomes in plant
and animal cells during the mitotic cell
cycle and the associated behaviour of
the nuclear envelope, cell surface
membrane and the spindle (names of
the main stages of mitosis are
expected)
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
5.2.b
observe and draw the mitotic stages
visible in temporary root tip squash
preparations and in prepared slides of
root tips of species such as those of
v2.1 5Y02
Demonstrate using a model of a cell (2n=4) (2 short and 2 long pipe cleaners =
chromosomes; cell surface membrane and nuclear envelope = string). (W) (Basic)
o Model the events as a continuous process.
o Model replication by attaching a second pipe cleaner to the first. Simulate
nuclear envelope disassembly by cutting the string into smaller lengths.
o Cytokinesis should be described for both animal and plant cells.
o Learners describe and make suggestions as to why various events occur. (W)
(Basic) (Challenging)
From a list (prepared by you), learners match an event that occurs in relation to the
spindle fibres and spindle (centrioles in animal cells only) to the behaviour of the
chromosomes during the mitotic cell cycle. (W) (Basic)
Learners work with their own models and talk through each stage. (P) (Challenging)
Learners make annotated diagrams of stages in mitosis. (I) (Challenging)
Learners practise identification of the stages and description of events using a range
of photomicrographs and diagrams of both plant and animal cells. (I) (Basic)
(Challenging)
Learners sequence images of a cell at various stages during the cycle, naming the
stages and noting chromosome behaviour. (F)
CD-ROM
Bioscope – has material which covers
this
Online
http://www.rothamsted.bbsrc.ac.uk/not
ebook/courses/guide/movie/mitosis.ht
m
http://faculty.nl.edu/jste/mitosis.htm
http://www.biology.arizona.edu/cell_bio
/tutorials/cell_cycle/main.html
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/animation__control_of_
the_cell_cycle.html
Textbooks/Publications
Bio Factsheet 76: The eukaryotic cell
cycle and mitosis
Note
Condensation/coiling of DNA to form the prophase chromosome can be simulated
by taking a very long piece of thin wire that is then wrapped round a pencil (which is
removed) to make a coiled, string-like structure that is now much shorter, fatter and
more visible.
Past Papers
Paper 21, June 2011, Q1 (c)
Paper 23, June 2011, Q1 (a)
Paper 21, Nov 2011, Q4 (c)
Learners draw from a prepared slide a plan diagram of a root tip to indicate: the root
cap; meristematic area (zone of cell division); zone of elongation (expansion); and
zone of differentiation. (I) (Basic)
Learners identify, draw and annotate cells (high power) in all stages of mitosis. (I)
(Challenging)
Online
http://www.microscopyuk.org.uk/micropolitan/index.html
http://www.saps.org.uk/secondary/teac
hing-resources/552-floating-garlic-
Cambridge International AS & A Level Biology (9700) – from 2016
44
Learning objectives
Suggested teaching activities
Learning resources
Vicia faba and Allium cepa
Learners prepare a root tip squash (e.g. garlic or onion root tips with acetic orcein or
toluidine blue) and examine their slide and those of others for stages of mitosis. (G)
(I) (Basic)
Learners use the eyepiece graticule by measuring the relative length and width of
chromosomes and cells. (I) (Challenging)
o Learners use the calibrated eyepiece graticule to measure the size of
chromosomes in m. (I) (Challenging)
Extension: learners investigate why each step of the procedure in the root tip squash
preparation is necessary. (I) (Challenging)
growing-rootshttp://www.saps.org.uk/secondary/teac
hing-resources/288-investigatingmitosis-in-allium-root-tip-squash
http://www.saps.org.uk/secondary/teac
hing-resources/109-staining-a-roottip-and-calculating-its-mitotic-index
Learners recall primary structure and a polypeptide (Unit 1) and suggest a definition
of a gene from previous learning objectives.
o Refer to the ‘DNA as the ideal molecule’ poster and ensure learners understand
the idea of the term ‘coded’ (see 6.2.c, 6.2.d). (W) (Basic)
o Discuss the fact that the sequence of nucleotides comprising a gene codes for
the amino acid sequence in a polypeptide chain. (W) (Basic)
Background discussion/extension research about the human genome project. (W) (I)
(Basic) (Challenging)
Online
http://evolutionlist.blogspot.co.uk/2006/
10/new-definitions-of-gene.html
http://www.sanger.ac.uk/
http://www.yourgenome.org/
Key concepts
Cells as the units of life
6.2.a
state that a polypeptide is coded for by
a gene and that a gene is a sequence
of nucleotides that forms part of a DNA
molecule
Key concepts
Biochemical processes,
DNA, the molecule of heredity
6.2.b
state that a gene mutation is a change
in the sequence of nucleotides that
may result in an altered polypeptide
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
v2.1 5Y02
Textbooks/Publications
King p.236, 207, 209
Siddiqui p.79-81.
Note
If learners query the origin of RNA, explain that there are genes that code for tRNAs
and rRNAs and that mRNA is an intermediate molecule in producing the
polypeptide. (W) (Basic).
For A Level, learners should understand that these proteins, including enzymes, will
ultimately allow development and control of cells and hence organisms (i.e. they
determine the nature of organisms).
After learners write this definition, use question and answer to recall (from Unit 1)
that primary structure determines secondary and tertiary structure, which then
determine the shape and shape of, e.g. active site, specific channel, receptor site.
This determines the function of the protein. (W) (Basic)
Stress to learners that the gene is responsible for a particular feature, trait or
characteristic and that a mutation is just an alternative form of the gene, an allele.
(W) (Basic)
Online
http://ghr.nlm.nih.gov/handbook/mutati
onsanddisorders/genemutation
http://www.yourgenome.org/dgg/gener
al/var/var_3.shtml
Note
Cambridge International AS & A Level Biology (9700) – from 2016
45
Learning objectives
Suggested teaching activities
Learning resources
Online resources may be best understood after learning about the genetic code and
transcription and translation
Learners do not need to define an allele at this point, see 16.2.a.
6.2.c
describe the way in which the
nucleotide sequence codes for the
amino acid sequence in a polypeptide
with reference to the nucleotide
sequence for HbA (normal) and HbS
(sickle cell) alleles of the gene for the
-globin polypeptide
Key concepts
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
Learners write out definitions of a gene and a gene mutation. (F)
Learners suggest why DNA needs to remain in the nucleus (large size, less prone to
degradation).
o Lead the discussion to explain that a ‘messenger’ molecule needs to be formed,
in transcription, to take the information to the ribosomes. (W) (Basic)
Discuss the concepts involved in the central dogma
(http://en.wikipedia.org/wiki/Central_dogma_of_molecular_biology overlap with ideas
in 6.2.d). (W) (Basic)
o Learners produce an annotated flow chart representing the flow of information,
beginning with DNA and ending in a functioning protein.
o Learners identify the point at which the nucleotide sequence becomes an amino
acid sequence.
o State that the process is termed translation (details in 6.2.d).
Learners study a DNA genetic dictionary/ DNA triplet table to work out, from specific
nucleotide base sequences, specific amino acid sequences. (P) (I) (Basic)
(Challenging)
o Explain this is the sequence on the strand (the template strand) that is used to
produce the polypeptide
o Include the sections where the nucleotide sequences of normal and sickle-cell
alleles differ.
Online
http://www.yourgenome.org/dgg/gener
al/proteins/proteins_2.shtml
http://www.kumc.edu/gec/
http://www.youtube.com/watch?v=J3H
VVi2k2No
Past Papers
Paper 23, June 2011, Q2 (b)(c)
Paper 21, Nov 2011, Q3 (b)
Paper 21, Nov 2013, Q5
Note
Learners should also be able to use the sequence on the non-template strand to
work out the amino acid sequence (using the DNA triplet table)
The sickle cell -globin polypeptide and sickle cell anaemia also occur in Units 5 and
7.
It is a common error for learners to state that DNA is a chain of amino acids. When
learners guess or are given incorrect matches, many will learn the incorrect match,
so only reinforce the correct relationship between nucleotides and DNA / RNA, and
between amino acids and protein.
6.2.d
describe how the information in DNA is
v2.1 5Y02
Previous learning objectives have included enough additional information to prepare
learners for the details of transcription and translation.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/
46
Learning objectives
Suggested teaching activities
Learning resources
used during transcription and
translation to construct polypeptides,
including the role of messenger RNA
(mRNA), transfer RNA (tRNA) and the
ribosomes
Learners sequence a set of events to describe and explain the process of
transcription. (P) (I) (Basic) (Challenging)
o Ensure learners realise that mRNA transcripts pass out through the nuclear
pores to the ribosomes. (W) (Basic)
o Explain post-transcriptional modification: sections not required, introns (now
known to have a role, not ‘genetic junk’ as previously believed), may be cut out
of the initial transcript and the ‘meaningful’ sections, exons, re-sealed to give
shorter mRNA transcripts. (W) (Challenging)
Formalise knowledge of the genetic code (universal, non-overlapping, degenerate,
sequential), by introducing the mRNA genetic dictionary / mRNA codon table.
For translation, provide learners with a set of diagrams (prepared by you) that can
be annotated and discussed.
Learners research the different ways the polypeptide formed can be modified in
post-translational modification. (I) (Challenging)
Learners write a paragraph on each of mRNA, tRNA and the ribosomes, explaining
their roles in transcription and translation. (H) (F) (Challenging)
Find the DNA nucleotide sequences of sections of proteins (choose from the
syllabus) to produce a worksheet (and mark scheme).
o Learners use the genetic code and one or more pieces of information to work out
missing information. Completed worksheets show the tRNA molecules involved
and the sequences of template and non-template DNA strands, mRNA and
amino acids. (H) (F) (Basic) (Challenging)
o Extension: learners explain why a DNA nucleotide sequence worked out only
using an amino acid sequence may not represent the actual DNA. (I)
(Challenging)
Learners produce a large annotated diagram to show transcription and translation in
relation to the different locations within the cell. (H) (Challenging)
Extension: learners research how post-transcriptional modification (removal of
introns and resealing of exons) allows one gene to be able to produce variations of
the protein product. (I) (Challenging)
molecules/transcribe/
http://www.brookscole.com/chemistry_
d/templates/student_resources/share
d_resources/animations/protein_synt
hesis/protein_synthesis.html
http://www.pbs.org/wgbh/aso/tryit/dna/
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Textbooks/Publications
Bio Factsheet 22: Protein synthesis I –
nucleic acids
Bio Factsheet 49: Protein synthesis II –
mechanisms
Past Papers
Paper 21, June 2011, Q3 (c)
Paper 23, June 2011, Q2 (d)
Paper 23, Nov 2011, Q5 (c)
Paper 22, Nov 2011, Q4 (b)
Paper 22, Nov 2011, Q4 (c)(d)
Note
TransCription comes before transLation alphabetically as well as in protein
synthesis.
With website animations, check the level of detail before recommending to learners.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
47
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 4: Transport and gas exchange
Recommended prior knowledge
Knowledge of cell structure, as covered in Unit 2, will enable learners to apply knowledge to cells involved in transport and gas exchange. An understanding of
diffusion, osmosis and active transport from Unit 2 is required, including confidence in understanding the movement of water in terms of differences in water potential.
Learners will need to have an understanding of haemoglobin structure and of hydrogen bonding between water molecules from Unit 1. It will be helpful if learners have
acquired basic knowledge of the mammalian circulatory system in previous studies.
Context
This unit extends the key concept of cells as the units of life by looking at the way in which cells and tissues of plants and mammals, multicellular organisms, are
provided with their requirements and how humans, as multicellular organisms, exchange gases in the lungs. The unit builds on learner knowledge of cell structure and
movement into and out of cells and highlights the importance of water as a transport medium. The work on blood in this unit leads into the immunity section in Unit 5.
Much of this unit lays the foundations for further work on physiology at A Level. In Unit 9, learners will study the way in which oxygen is used by cells for the
biochemical process of aerobic respiration, and how carbon dioxide is produced as a result of this process.
Outline
The topic of transport in plants is introduced by improving learner knowledge of plant anatomy and histology and their understanding of the relation between the
structure and function of transport tissues. Details of transport of water and minerals are covered, including a consideration of the factors affecting the rate of
transpiration, which gives learners the opportunity to carry out investigative practical work. Adaptations of organisms to their environment are exemplified by reference
to xerophytes. The transport of assimilates by phloem tissue is also covered. The topic of mammalian transport is introduced by considering the meaning of a closed
double circulation and then progresses to structure and function of the blood vessels, blood and heart. A comparison of blood, tissue fluid and lymph is made. The
carriage of respiratory gases is covered, which includes revisiting the structure and function of haemoglobin from Unit 1. Detail of gas exchange at the alveolus is
covered. The gross and fine structure of the human gas exchange system will allow learners to see the link between structure and function. Learners will make
comparisons in this unit, for example between xylem and phloem tissue, between an artery and vein, between blood, tissue fluid and lymph, and between the two sides
and upper and lower chambers of the heart .There are many good opportunities within this unit for learners to improve their microscope handling, observational and
diagram-drawing skills, and to develop manipulative and dissection skills if they choose to dissect a mammalian heart.
Teaching time
It is recommended that this unit should take approximately 14% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
48
Learning objectives
Suggested teaching activities
Learning resources
7.1.a
draw and label from prepared slides
plan diagrams of transverse sections
of stems, roots and leaves of
herbaceous dicotyledonous plants
using an eyepiece graticule to show
tissues in correct proportions
(see 1.1.c)
Revise a simple diagram of a plant: leaves and petioles, stem, (soil level), root(s)
and piliferous / root hair region. (W) (Basic)
o Explain the difference between: tissue and organ; transverse and longitudinal
sections (TS and LS).
o Explain what is meant by a herbaceous (i.e. non-woody) dicotyledon.
Discuss tissue distribution in leaves, roots and stem sections by projecting an
electronic image onto a screen. (W) (Basic)
o Learners see what they should observe later using the microscope (revise use).
o Describe how to draw the image as a plan diagram.
Learners identify tissues (especially the distribution of the vascular tissue) and make
plan diagrams (low power) from slides of TS of a leaf, stem or root (dicotyledonous
plants e.g. Ranunculus and Ligustrum), using the eyepiece graticule to gauge the
correct proportions. (I) (Challenging)
Learners draw labelled diagrams of stem and leaf sections and construct a table
comparing the two; similarities run across the columns, differences in separate
columns. (I) (Challenging)
CD-ROM
Bioscope
Key concepts
Cells as the units of life,
Observation and experiment
Note
Learners should be able to recognise: epidermis, endodermis, mesophyll, xylem,
phloem, cambium, cortex, pith.
High quality microscope slides are available to order, including those used in
previous practical examinations from the Cambridge publications catalogue
www.cie.org.uk/cambridge-for/teachers/order-publications
7.1.b
draw and label from prepared slides
the cells in the different tissues in
roots, stems and leaves of herbaceous
dicotyledonous plants using transverse
and longitudinal sections
Key concepts
Cells as the units of life,
Observation and experiment
Learners observe slides showing LS. An eyepiece graticule and stage micrometer
can be used for measurement. (I) (Challenging)
Learners draw and label individual cells under high power (from TS and LS slides).
(I) (Challenging)
Extension: learners practise using the eyepiece graticule and stage micrometer to
estimate actual dimensions of the cells. (I) (Challenging)
Background: discuss briefly differences between monocotyledons and dicotyledons.
(W) (Basic)
An extension discussion: outlining the anatomical transition in the area where the
root becomes the stem.
Note
High quality microscope slides are available to order, including those used in
previous practical examinations from the Cambridge publications catalogue
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Online
University biology department and
microscope manufacturer websites,
e.g.:
http://micro.magnet.fsu.edu/index.html
http://images.botany.org
Textbooks/Publications
Siddiqui p.5-7, 112, 115-124, 135-139
Past Papers
Paper 23, June 2011, Q3
Paper 35, June 2011, Q2
Paper 31, June 2011, Q2
Paper 34, June 2011, Q2
Paper 33, June 2013, Q2
CD-ROM
Bioscope – Superb slides and learning
tasks, including chloroplasts in
Elodea, a variety of leaf sections,
including sun and shade leaves.
Online
University biology department and
microscope manufacturer websites,
e.g.
http://www.vcbio.science.ru.nl/en/virtua
llessons/leaf/
http://www.mhhe.com/biosci/pae/botan
y/histology/html/ptmodov.htm
49
Learning objectives
Suggested teaching activities
www.cie.org.uk/cambridge-for/teachers/order-publications
Learning resources
http://leavingbio.net/FLOWERING%20
PLANTS.htm
http://images.botany.org/
Textbooks/Publications
Siddiqui p.5-7, 112, 115-124, 135-139
Bio Factsheet 19: Plant tissues
Past Papers
Paper 23, Nov 2011, Q3 (a)
7.1.c
draw and label from prepared slides
the structure of xylem vessel elements,
phloem sieve tube elements and
companion cells and be able to
recognise these using the light
microscope
Use photomicrographs and diagrams to illustrate and discuss, with teacher prompts,
the structure of xylem vessel elements, phloem sieve tube elements and companion
cells. (G) (I) (Challenging)
Learners add annotations to labelled diagrams of these three cell types. (F)
Key concepts
Cells as the units of life,
Observation and experiment
CD-ROM
Bioscope – useful for this section.
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/P/PlantTissues.html
http://leavingbio.net/FLOWERING%20
PLANTS.htm
http://www.mhhe.com/biosci/pae/botan
y/histology/html/ptmodov.htm
Textbooks/Publications
Siddiqui p.5-7, 112, 115-124, 135-139
Bio Factsheet 19: Plant tissues
Bio Factsheet 146: Tracheids, vessels
and sieve tubes
Bio Factsheet 132: Phloem
7.2.a
explain the movement of water
between plant cells, and between them
and their environment, in terms of
water potential (see 4.2. No
calculations involving water potential
will be set)
v2.1 5Y02
Provide learners with an overview diagram of the movement of water down a water
potential gradient from soil to air. (W) (Basic)
o Learners add given numerical values of water potential to the different locations,
for comparison, and annotate the diagram. (I) (Challenging)
Learners recall osmosis and the concept of water potential.
o Learners complete a worksheet (prepared by you) containing examples of
adjacent cells / cells and their environment with water potential values. Learners
work out and explain which way water will flow. (H) (F) (Basic) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologymad.com/resources/
transpiration.swf
Textbooks/Publications
Bio Factsheet 225: Synoptic biology:
water potential.
50
Learning objectives
Suggested teaching activities
Learning resources
From a diagram, learners suggest how a root hair cell is adapted for water and
mineral ion uptake (e.g. large surface area, lack of cuticle, thin cell walls, membrane
transport proteins, mitochondria). (W) (G) (Challenging)
Learners suggest how mineral ions are taken up by the root hair cell. (W) (Basic)
Learners research the most important mineral ions that are required, giving reasons.
(H)
Ensure that learners know the difference between the apoplastic pathway and
symplastic pathway (include the vacuolar pathway).
o Agree that osmosis is not involved in the apoplast pathway (no membranes).
o Use a model to explain why water has to take a symplastic pathway at the
endodermis (suberised Casparian strip).
o Learners use arrows and labels to show the different pathways on diagrams and
annotate, using the terms water potential and water potential gradient. (W) (I)
(Basic) (Challenging)
Learners stand small plants (intact root systems, soil washed off) in dye (e.g. eosin)
for 10-30 minutes, then cut thin sections to investigate the distribution of the dye and
show the position and continuous nature of xylem vessels (the dye collects in the
leaf as water is lost by transpiration). (I) (Challenging)
Learners use cut petioles of variegated leaves to make sections and observe xylem
tissue. (P) (I) (Basic)
Discuss briefly the concept of root pressure (outline only). (W) (Basic)
Online
http://www.microscopyuk.org.uk/mag/artmar00/watermvt.ht
ml
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/X/Xylem.html
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::600::480::/sites/dl/free/007353224
x/788092/Water_Uptake.swf::Water%
20Uptake
Key concepts
Cells as the units of life,
Organisms in their environment
7.2.c
describe the pathways and explain the
mechanisms by which water and
mineral ions are transported from soil
to xylem and from roots to leaves
(include reference to the symplastic
pathway and apoplastic pathway and
Casparian strip)
Key concepts
Cells as the units of life,
Biochemical processes
Textbooks/Publications
Bio Factsheet 82: Transport in
flowering plants
Bio Factsheet 108: Water movement
across the root
Past Papers
Paper 23, June 2011, Q3 (a)
Note
Root hairs can be seen clearly on newly-germinated seedlings, such as mung
beans, if these are grown on damp filter paper or cotton wool.
Do not discuss the concept of capillarity.
Learners are better to explain water movement in terms of water potential gradients
to avoid confusion with mass flow in phloem.
7.2.b
explain how hydrogen bonding of
water molecules is involved with
movement in the xylem by cohesion-
v2.1 5Y02
Tackle cohesion-tension first: use a question and answer session to help learners
make the link between hydrogen bonding of water molecules (cohesive forces) and
the concept of transpiration pull. (W) (Basic)
Discuss the concept of adhesion. Remind learners that the attraction of water
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://chemwiki.ucdavis.edu/Physical_
Chemistry/Physical_Properties_of_M
atter/Atomic_and_Molecular_Properti
51
Learning objectives
Suggested teaching activities
Learning resources
tension in transpiration pull and
adhesion to cellulose cell walls
molecules to the secondary cell wall of xylem vessel elements is mainly as a result
of hydrophilic cellulose (which is impregnated with lignin). (W) (Basic)
Learners write a paragraph explaining the difference between cohesion and
adhesion in the movement of water up the xylem. (F)
Learners research what is meant by a transpiration stream. (H) (Basic)
es/Intermolecular_Forces/Cohesive_
And_Adhesive_Forces
http://www.microscopyuk.org.uk/mag/artmar00/watermvt.ht
ml
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/X/Xylem.html.
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::600::480::/sites/dl/free/007353224
x/788092/Water_Uptake.swf::Water%
20Uptake
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 82: Transport in
flowering plants
Bio Factsheet 108: Water movement
across the root
Past Papers
Paper 23, June 2011, Q3 (a)
7.2.d
define the term transpiration and
explain that it is an inevitable
consequence of gas exchange in
plants
Key concepts
Cells as the units of life
v2.1 5Y02
Learners write a definition of transpiration. (I) (Basic)
Learners draw a large diagram of a vertical section through part of a leaf, adding
numbered annotations to show the pathway of water (beginning with water leaving
xylem vessels) and the sequence of events occurring, using correct water potential
terminology. (I) (Challenging)
o Emphasise the need to refer to water evaporated from the moist cell walls of the
spongy mesophyll cells as water vapour.
Discuss the association between transpiration (reduces the water potential at the top
of the plant) and tension (of cohesion-tension). (W) (Basic)
Learners explain the differences between transpiration and evaporation. (F)
Discuss cuticular transpiration (links to 7.2.f, leaves of xerophytes). (W) (Basic)
Learners study a graph showing how the rate of transpiration varies during a 24-hour
day and interpret using a word list (stomata, open, closed, photosynthesis, oxygen,
carbon dioxide, gas exchange, transpiration). (I) (Basic)
Extension: take climate into account and interpret a graph (prepared by you) with
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/T/Transpiration.html
Textbooks/Publications
Bio Factsheet 64: Transpiration
Bio Factsheet 81: Gas exchange in
plants
Past Papers
Paper 23, Nov 2011, Q3 (b)
Paper 22, Nov 2013, Q3 (a)
52
Learning objectives
Suggested teaching activities
Learning resources
transpiration varying over a few days. (I) (Challenging)
Learners research the advantages of transpiration and produce a list. (H) (Basic)
7.2.e
investigate experimentally and explain
the factors that affect transpiration rate
using simple potometers, leaf
impressions, epidermal peels, and
grids for determining surface area
Key concepts
Observation and experiment
Demonstrate the use (or show diagrams) of a standard commercial potometer to
measure water uptake (e.g. Thoday). (W) (Basic)
o Discuss the reasons for: a slanting cut across the leafy shoot; submerging in
water; use of petroleum jelly round the joint; drying leaves. (W) (Challenging)
Practical: learners make a simple potometer using a long piece of capillary tubing
that has a short length of rubber tubing attached at one end. The whole apparatus
can be supported vertically.
o Learners record the height of the air/water meniscus at suitable time intervals.
(P) (I) (Basic)
o Discuss how to make results quantitative, e.g. using grids to determine the
surface area of leaves; using the volume of a cylinder to calculate the volume of
water taken up. (W) (Basic)
Extension practical: learners enclose part of a plant inside a plastic bag and use
data-logging equipment and a humidity-recording sensor to investigate the effect of
transpiration on humidity. (P) (I) (Challenging)
Learners plan and/or carry out a controlled investigation into the effect of wind
speed, temperature or light on the rate of transpiration.
o Learners present results (or are given results) in graphical form and give
explanations for the shape of the graph. (P) (I) (Challenging)
Learners make temporary slides of epidermal strips from leaves of different species
(use nail varnish or ‘new skin’ liquid plaster and peel off when dry). (I) (Basic)
Practical booklet 6 is designed to develop some of the practical skills (listed in the
Teacher’s practical notes) assessed in paper 3.
Practical booklet 6
Online
http://www.mhhe.com/biosci/genbio/virt
ual_labs/BL_10/BL_10.html
http://www.saps.org.uk/secondary/teac
hing-resources/115-potometermeasuring-transpiration-rates
http://www.mikecurtis.org.uk/Potomete
r/potometer.html
http://www.saps.org.uk/secondary/teac
hing-resources/299-measuringstomatal-densityTextbooks/Publications
King p.142-146
Siddiqui p. 140-144, 146-147
Note
Remind learners that potometers measure rates of water uptake only and that a cut
end of a stem is not the same as uptake via root hairs.
If a potometer is placed on a balance sensitive to small changes in mass, then it is
possible to measure water uptake and transpiration.
7.2.f
make annotated drawings, using
prepared slides of cross-sections, to
show how leaves of xerophytic plants
v2.1 5Y02
Explain the terms mesophyte, hydrophyte and xerophyte and discuss ways in which
plants can reduce their water loss. (W) (Basic)
Learners consider the mesophyte leaf and give comparative descriptions (e.g.
thicker waxy cuticle, fewer stomata per unit area of leaf, etc.) using diagrams of
Cambridge International AS & A Level Biology (9700) – from 2016
CD-ROM
Bioscope – has suitable images.
Online
53
Learning objectives
Suggested teaching activities
Learning resources
are adapted to reduce water loss by
transpiration
leaves from a range of xerophytes. (P) (I) (Basic)
Learners use prepared slides of cross-sections of leaves of xerophytes to make
annotated plan diagrams and detailed drawings. (I) (Basic)
o Learners describe features and explain how each helps to reduce water loss. (I)
(Challenging)
o Extend this to a circus of activities with, e.g. living examples; photographs and
photomicrographs; Bioscope; microscope slides; electron micrographs. (P) (I)
(Challenging)
Learners make temporary slides of epidermal strips from leaves of mesophytes and
xerophytes and estimate the number of stomata per unit area to make quantitative
comparisons. (I) (Challenging)
o Extension: some may know how to use the t-test to see if differences are
significant (not required at AS Level). (P) (I) (Challenging)
www.worldofteaching.com/powerpoints
/biology/Xerophytes.ppt
Key concepts
Natural selection,
Organisms in their environment
7.2.g
state that assimilates, such as sucrose
and amino acids, move between
sources (e.g. leaves and storage
organs) and sinks (e.g. buds, flowers,
fruits, roots and storage organs) in
phloem sieve tubes
Key concepts
Cells as the units of life,
Biochemical processes
7.2.h
explain how sucrose is loaded into
phloem sieve tubes by companion
cells using proton pumping and the cotransporter mechanism in their cell
surface membranes
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Explain the term assimilates and discuss examples. (W) (Basic)
Introduce translocation as the movement of assimilates from the source (area where
they are produced) to the sink (area where they are used / stored).
o As an example, state that sucrose is loaded into phloem at the source, and then
removed at the sink.
o Learners suggest source and sink locations within the plant. (W) (Basic)
Note
Learners should also be familiar with the term photosynthates.
Use learner knowledge of membranes and transport mechanisms to describe and
explain the events that occur. (W) (Challenging)
Learners write out a set of cards containing relevant points and practise re-ordering
them to give a sequential account.
o These could range from main points to a detailed account (see table for
examples). (P) (I) (Basic) (Challenging)
o Learners write an account from memory. (F)
H+ actively pumped out of companion
cells
concentration of H+ builds up outside
Textbooks/Publications
Bio Factsheet 29: Plant and animal
adaptations to dry habitats
Bio Factsheet 84: Xerophytes and
hydrophytes
Online
http://leavingbio.net/FLOWERING%20
PLANTS.htm
Textbook/Publications
King p.146-147
Siddiqui p.135-136
Past Papers
Paper 23, June 2011, Q5 (b)(ii)
Online
http://www.uic.edu/classes/bios/bios10
0/lectf03am/sucrosepump.jpg
Past Papers
Paper 23, June 2011, Q5 (c)
Paper 21, Nov 2011, Q5 (b)
Paper 22, Nov 2011, Q6 (b)
ATP required
membrane impermeable to H+ so
Cambridge International AS & A Level Biology (9700) – from 2016
54
Learning objectives
Suggested teaching activities
the membrane
H+ diffuses back in via a membrane
carrier protein
cotransport of sucrose occurs
sucrose diffuses into phloem sieve
tube element
Learning resources
they cannot diffuse back in
down the electrochemical gradient
H+ and sucrose bind to the protein
(conformational change occurs)
via plasmodesmata
Note
Emphasise that the entry of sucrose into the phloem sieve tube is passive but the
whole process is sometimes described as ‘active loading’.
7.2.i
explain mass flow in phloem sap down
a hydrostatic pressure gradient from
source to sink
Key concepts
Cells as the units of life
Learners sort out cards (prepared by you) containing details such as below before
making notes. (P) (I) (Basic)
at the source, sucrose enters the phloem sieve tube
this lowers the water potential
this draws (extra) water into the sieve tube by osmosis
this increases the hydrostatic pressure
at the sink, sucrose leaves the phloem sieve tube
water follows osmotically
the hydrostatic pressure at the source is higher than at the sink
fluid / phloem sap moves from source to sink
down this pressure gradient
by mass flow
Online
http://highered.mcgrawhill.com/sites/9834092339/student_vi
ew0/chapter38/animation__phloem_loading.html
Textbook/Publications
Bio Factsheet 132: Phloem.
Past Papers
Paper 23, June 2011, Q5 (c)
Paper 21, Nov 2011, Q5 (b)
Note
Learners should understand that phloem translocates soluble organic compounds.
7.1.d
relate the structure of xylem vessel
elements, phloem sieve tube elements
and companion cells to their functions
Key concepts
v2.1 5Y02
For xylem vessel elements, use diagrams to aid a ‘structure to function’ discussion.
Recall the role of xylem in the transport of water and mineral ions and introduce the
need for lignification (see also 7.2.a) because of the tension created by the
transpiration pull.
o Learners suggest other functions of lignin and continue to provide other
examples of structure to function. (W) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
CD-ROM
Bioscope – useful for this section.
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/P/PlantTissues.html
55
Learning objectives
Suggested teaching activities
Learning resources
Cells as the units of life
o Learners match statements about structure to statements about function. The
activity could be divided into the main points and additional points. (P) (I) (Basic)
(Challenging)
Learners use resources (see also 7.1.c) to label diagrams of phloem sieve tube
elements and companion cells. (I) (Basic)
o Learners point out the relationship between structure and function for these two
cell types. (W) (Basic)
o Learners make bullet-pointed notes, using one colour for a structural detail and a
different colour for a link to a function. (I) (Challenging)
http://leavingbio.net/FLOWERING%20
PLANTS.htm
http://www.mhhe.com/biosci/pae/botan
y/histology/html/ptmodov.htm
Note
It is now believed that protein strands are not present in living, functioning phloem
tissue.
8.1.a
state that the mammalian circulatory
system is a closed double circulation
consisting of a heart, blood vessels
and blood
Key concepts
Cells as the units of life
v2.1 5Y02
Display an image giving an overview of the whole circulatory system and check that
learners can describe what is meant by pulmonary and systemic circulations. (W)
(Basic)
Use a question and answer session to determine that arteries carry blood away from
the heart and veins towards the heart. (W) (Basic)
Extension (useful for later studies): discuss names given to blood vessels serving
organs e.g. pulmonary + lungs; coronary + heart, hepatic + liver; renal + kidney. (W)
(Basic)
Learners make brief written notes explaining closed circulation and double
circulation. (I) (Basic)
Learners label diagrams of double circulation, including the heart chambers, the two
types of circulation and the names of the main blood vessels. (I) (Basic)
Learners describe the journey made by a red blood cell in one complete circuit of the
mammalian blood system. (H) (F) (Basic)
Extension: learners research and contrast the mammalian circulatory system with
organisms organised differently, e.g. insect, squid, fish and amphibians. Search
online for images of diagrams of insect, fish, amphibians and squid circulatory
systems. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 19: Plant tissues
Bio Factsheet 146: Tracheids, vessels
and sieve tubes
Bio Factsheet 132: Phloem
Past Papers
Paper 23, June 2011, Q5 (a)
Paper 22, June 2013, Q2 (a)
Online
http://www.bbc.co.uk/schools/gcsebite
size/pe/appliedanatomy/0_anatomy_
circulatorysys_rev1.shtml
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/AnimalHearts.html
56
Learning objectives
Suggested teaching activities
Learning resources
8.1.b
observe and make plan diagrams of
the structure of arteries, veins and
capillaries using prepared slides and
be able to recognise these vessels
using the light microscope
Gauge learner knowledge of the basic structure of arteries, veins and capillaries with
a brainstorming session before providing labelled diagrams. (W) (Basic)
Learners study photomicrographs of (muscular) arteries and veins (TS), and an
electron micrograph of capillaries. Learners label the layers and, with prompting,
annotate with details. (W) (I) (Basic)
Learners observe prepared TS slides, and draw labelled plan diagrams. Practise
measurement using an eyepiece graticule. (I) (Basic) (Challenging)
Extension: learners investigate the elasticity of blood vessels by suspending weights
on sections of arteries and veins. (P) (Challenging)
Learners carry out research into other types of blood vessels, including elastic
arteries, arterioles and venules (stress this is not required learning). (H)
(Challenging)
Learners sort out statements (prepared by you) into three columns for each of the
three blood vessel types. (F)
CD-ROM
Bioscope – has appropriate slides.
Key concepts
Cells as the units of life,
Observation and experiment
Online
http://sln.fi.edu/biosci/vessels/vessels.
html
http://www.histology.leeds.ac.uk/circul
atory/arteries.php
http://www.nuffieldfoundation.org/practi
cal-biology/elastic-recoil-arteries-andveins
http://library.med.utah.edu/WebPath/C
VHTML/CVIDX.html
Textbooks/Publications
Siddiqui p.175-177
8.1.c
explain the relationship between the
structure and function of arteries, veins
and capillaries
Learners construct a table showing the relationship between structure to function for
each of the three blood vessel types. (I) (Challenging)
Learners label the layers on diagrams of an artery, vein and capillary in TS, and then
annotate to link structure to function. (F)
Online
http://nsb.wikidot.com/2-2-3-comparethe-structure-of-arteries-capillariesand-vein
Key concepts
Cells as the units of life
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
57
Learning objectives
Suggested teaching activities
Learning resources
8.1.d
observe and draw the structure of red
blood cells, monocytes, neutrophils
and lymphocytes using prepared slides
and photomicrographs
Learners observe blood cells using the light microscope or use other images. (I)
(Basic)
o Learners draw labelled diagrams of the different cell types and make tables to
compare: red blood cells with white blood cells; monocytes with neutrophils. (I)
(Challenging)
Learners use resources to explain how the structural features of a red blood cell are
related to the function of oxygen transport. (I) (Challenging)
CD-ROM
Bioscope – has appropriate images.
Key concepts
Cells as the units of life,
Observation and experiment
Note
The terms erythrocyte and leucocyte should also be mentioned (not required
learning).
The function of the white blood cells and details of B-lymphocytes compared to Tlymphocytes are covered in Unit 5.
To help later understanding, explain that monocytes take on a different appearance
when they mature to become macrophages, and that these cells are usually in
locations other than blood tissue.
Online
http://micro.magnet.fsu.edu/index.html
http://education.vetmed.vt.edu/Curricul
um/VM8054/Labs/Lab6/Lab6.htm
Textbooks/Publications
King p.120-122, 164-165
Siddiqui p. 179-182
Bio Factsheet 62: Animal tissues I –
epithelia and blood
Bio Factsheet 36: Structure and
function of blood and lymph
Past Papers
Paper 22, June 2011, Q3 (a)(b)
8.1.e
state and explain the differences
between blood, tissue fluid and lymph
Key concepts
Cells as the units of life
Brainstorm the composition of blood and discuss the need for exchange with cells.
(W) (Basic)
o Discuss how and why the concentrations of substances in blood, such as
oxygen, carbon dioxide and dissolved glucose, can vary. (W) (Challenging)
Explain how pressure changes from the arterial to the venous end of the capillary
network. Ask for suggestions, with reasons, as to which of the components would be
able to leave the network. (W) (Challenging)
Learners use resources to label and annotate a diagram of a capillary network,
including explanations of how tissue fluid and lymph are formed and arrows to show
direction of blood flow, formation of tissue fluid and formation of lymph. (I)
(Challenging)
o Learners add arrows of different colours or styles (use a key) to represent the
movement of substances such as dissolved glucose and amino acids, oxygen
and carbon dioxide. (I) (Basic)
Learners construct a comparative table of differences between blood, tissue fluid
and lymph. (H) (F)
Textbooks/Publications
Bio Factsheet 36: Structure and
function of blood and lymph
Bio Factsheet 89: Tissue fluid
Bio Factsheet 171: Answering exam
questions: the formation and
drainage of lymph
Past Papers
Paper 21, June 2011, Q2 (b)
Note
Highlight the difference between blood and blood plasma.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
58
Learning objectives
Suggested teaching activities
Learning resources
8.2.a
describe the external and internal
structure of the mammalian heart
Learners check their knowledge of the internal structure of the heart by adding as
many labels as possible to a diagram. Go through this, allowing learners to add any
missing e.g. tendinous cords and papillary muscles, sinoatrial node, atrioventricular
node and Purkyne tissue. (I) (Basic)
Show learners images of the external structure of the heart and agree labels. (W)
(Basic)
Learners match up a set of labels with a set of descriptions. (I) (Basic)
Learners practise adding labels, with descriptive features, to a range of internal and
external diagrams of the heart. (H) (F) (Basic) (Challenging)
Learners study models of the heart or dissect a heart (or observe) obtained from
butchers, abattoirs or suppliers. (G) (P) (I) (Basic) (Challenging)
o Heart models are useful for learners to get a 3-D understanding if dissection is
not carried out.
Online
http://www.learnerstv.com/animation/a
nimation.php?ani=321&cat=biology
http://www.nhlbi.nih.gov/health/dci/Dis
eases/hhw/hhw_anatomy.html
http://www.sciencelearn.org.nz/Context
s/See-through-Body/SciMedia/Animations-andInteractives/Label-the-heart
http://library.med.utah.edu/WebPath/C
VHTML/CVIDX.html
Key concepts
Cells as the units of life
Note
Hearts obtained for dissection have often lost their blood vessels and some or all of
their atria. Obtaining heart and lungs may provide a more complete heart (useful for
the gross structure of the gas exchange system, studied later).
8.2.b
explain the differences in the thickness
of the walls of the different chambers
in terms of their functions with
reference to resistance to flow
Key concepts
Cells as the units of life
Learners complete a short test or sort statements into the correct order to remind
them about the pathway of blood in one complete circuit of the body. (F)
Explain that the differences in pressure between the left and right ventricles are
related to the ability to overcome resistance to flow by the blood vessels as blood
travels to the body tissues.
o Learners volunteer that there is a far lower resistance to flow in the pulmonary
circulation than in the systemic.
o Remind learners that the thicker the wall of a heart chamber, the more cardiac
muscle there is to generate force when it contracts.
Relate the thinner atrial walls (compared to the thicker ventricle walls) to the much
lower resistance that blood has to overcome to travel the short distance to the
ventricles. (W) (Basic)
Textbooks/Publications
King p.128-130
Siddiqui p.173-174
Bio Factsheet 35: Structure and
function of the mammalian heart
Online
http://www.physiologymodels.info/cardi
ovascular/arterioles.htm
Past Papers
Paper 22, June 2013, Q6 (b)
Note
Pulmonary capillaries are very delicate (very small diameter) so an increase from
normal pressure of blood leaving the right ventricle increases the likelihood of damage.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
59
Learning objectives
Suggested teaching activities
Learning resources
8.2.c
describe the cardiac cycle (including
blood pressure changes during systole
and diastole)
A discussion should switch the focus from a description of one complete circuit of
the body to one cardiac cycle.
o Remind learners that a decrease in volume of a heart chamber when the cardiac
muscle contracts means an increase in blood pressure within the chamber. (W)
(Basic)
o Associate the events occurring during one cardiac cycle to changes in blood
pressure , explaining that valves are pushed open and shut by differences in
pressure on either side. (W) (Challenging)
Learners produce a table describing the sequence of events (including the status
of the valves) occurring in one cardiac cycle and highlighting that both sides of the
heart contract and relax in unison: (I) (Challenging)
Online
http://www.pbs.org/wgbh/nova/eheart/h
uman.html
http://library.med.utah.edu/kw/pharm/h
yper_heart1.html
Key concepts
Cells as the units of life
right side of heart
Past Papers
Paper 23, Nov 2011, Q2 (b)
left side of heart
Learners annotate a set of diagrams (prepared by you) showing the heart during one
cardiac cycle. (F)
Use OHP overlays / PowerPoint presentation to build up a graph showing the
pressure and volume changes on one side of the heart (left side is most commonly
shown).
o Add heart diagrams below the x-axis in the different stages of the cycle,
corresponding to the correct times on the graph.
o Learners volunteer explanations throughout. (W) (Challenging)
Learners annotate a pressure change graph describing the event in the cardiac
cycle that correlates to the change shown on the graph (including points at which
named valves open and shut). (I) (Challenging)
Learners practise extracting information and interpreting questions based on
pressure change graphs (prepared by you). (I) (F) (Basic) (Challenging)
Note
ECGs (not required learning), accompanied by explanations, may be given as stimulus
material in a question.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
60
Learning objectives
Suggested teaching activities
Learning resources
8.2.d
explain how heart action is initiated
and controlled (reference should be
made to the sinoatrial node, the
atrioventricular node and the Purkyne
tissue, but not to nervous and
hormonal control)
Use explanations, interspersed with questions requiring thoughtful suggestions, to
present the following ideas:
o The heart is myogenic (initiates heart beat without receiving nerve impulses from
outside).
o The sinoatrial node (SAN - primary pacemaker) initiates muscle cell
depolarisation and atrial systole.
The insulating ring of non-conducting (connective) tissue (fibrous ring): prevents the
atria and ventricles from contracting at the same time; forces the wave of
depolarisation to pass through the atrioventricular node (AVN), delaying its passage
so the atria complete systole before ventricular systole begins.
The Purkyne tissue passes the depolarisation down to the apex of the heart so that
the ventricles contract from the bottom up, squeezing blood out up the arteries. (W)
(Challenging)
In the correct locations on a diagram of the heart, learners number the events
occurring in sequence, making notes underneath for each number. (I) (Basic)
Learners place in sequence statements of each of the events occurring, starting with
the SAN. (P) (I) (Basic)
o Create a second column so that statements of cardiac cycle events correspond
with the timing. (P) (I) (Challenging)
Online
http://hyperphysics.phyastr.gsu.edu/hbase/biology/sanode.ht
ml
http://www.nhlbi.nih.gov/health/healthtopics/topics/hhw/
Key concepts
Cells as the units of life
Textbooks/Publications
Bio Factsheet 139: Answering exam
questions on the heart
Bio Factsheet 7: Comparing transport
in plants and animals.
Past Papers
Paper 23, Nov 2011, Q2 (a)
Note
‘Wave of excitation’ or ‘impulses’ are acceptable terms, not signal, wave, pulse,
message or nerve impulse.
Learners should understand that the wave of depolarisation spreads across the
network of cardiac muscle fibres to bring about systole, and that the fibres do not
fatigue (no other details of cardiac muscle required).
9.1.a
describe the gross structure of the
human gas exchange system.
Key concepts
Cells as the units of life
v2.1 5Y02
Agree that the mammalian transport system carries the respiratory gases, oxygen
and carbon dioxide and contrast this with plant vascular tissue (not involved with gas
transport). Explain that the gas exchange system facilitates exchange with the
external environment. (W) (Basic)
Learners revise previous knowledge by labelling familiar structures on a diagram of
the human gas exchange system, using resources to complete labelling and add
annotations. (I) (Basic)
o Ensure learners know that the specialised gas exchange surface is the alveolus.
(I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Siddiqui p.183
61
Learning objectives
Suggested teaching activities
Learning resources
9.1.b
observe and draw plan diagrams of the
structure of the walls of the trachea,
bronchi, bronchioles and alveoli
indicating the distribution of cartilage,
ciliated epithelium, goblet cells, smooth
muscle, squamous epithelium and
blood vessels
Project images or show photomicrographs of the named structures and give
guidance as to how to identify the named structures and learn about the distribution
of the named features. (W) (Basic)
Learners observe, interpret, and draw plan diagrams of prepared slides. (I)
(Challenging)
o Learners also identify cilia, mucous glands and elastic fibres to prepare for 9.1.c.
(I) (Challenging)
o Learners complete a table (tick = present, cross = absent) such as below. (I)
(Challenging)
o Learners compare their diagrams and table with textbook versions. (I) (Basic)
Online
http://www.meddean.luc.edu/lumen/Me
dEd/Histo/frames/Histo15.html
http://micro.magnet.fsu.edu/index.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM040.html
Key concepts
Cells as the units of life
structure
cartilage
ciliated
epithelium
goblet cells
smooth
muscle
squamous
epithelium
Textbooks/Publications
King p.89-91
Siddiqui p.184-185
blood
vessels
trachea
bronchus
bronchiole
alveoli
Learners label diagrams of sections through the trachea, bronchus and bronchiole
and complete blank tables as above. (F)
Note
Learners should know the singular and plural: bronchus and bronchi; alveolus and
alveoli.
Explain that there are only a few goblet cells in the bronchiole (some textbooks may
state none are present) and discuss the reason for this, i.e. avoiding mucus
hindering gas exchange in the alveoli.
9.1.c
describe the functions of cartilage,
cilia, goblet cells, mucous glands,
smooth muscle and elastic fibres and
recognise these cells and tissues in
prepared slides, photomicrographs and
electron micrographs of the gas
exchange system
Discuss the reasons for the distribution of the various features within the gas
exchange system by explaining their functions. (W) (Basic)
Learners match statements: features with correct functions. (I) (Basic)
Reinforce learning by providing photomicrographs and electron micrographs for
learners to identify the features. (P) (I) (Challenging)
Learners give written explanations linking the presence / location of the features in
the different areas of the gas exchange system to their function. (F)
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.meddean.luc.edu/lumen/Me
dEd/Histo/frames/Histo15.html
http://micro.magnet.fsu.edu/index.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM040.html
Textbooks/Publications
King p.89-91
Siddiqui p.184-185
62
Learning objectives
Suggested teaching activities
Learning resources
Cells as the units of life
Past Papers
Paper 21, June 2011, Q1
Paper 22, Nov 2011, Q1
9.1.d
describe the process of gas exchange
between air in the alveoli and the
blood
Key concepts
Cells as the units of life
Discuss the roles of blood flow and ventilation in maintaining diffusion gradients for
oxygen and carbon dioxide between the alveoli and blood.
o Incorporate a question and answer session so learners can apply knowledge of
the function of haemoglobin (Unit 1). (W) (Basic)
Learners draw and annotate diagrams with key features of the process, adding
arrows to indicate the direction of exchange of oxygen and carbon dioxide. (I)
(Challenging)
Learners write a short account of how concentration gradients are maximised for
efficient gas exchange. (I) (Basic)
Learners produce a written description explaining gas exchange in terms of the
structure of the alveolus and capillary and diffusion across cell surface membranes.
(I) (Challenging)
o The account should make clear the difference between diffusion across alveolar
and capillary walls and diffusion across membranes.
Using a diagram of an alveolus and associated capillaries, learners give an account
of how the structure of the gas exchange surface is adapted for its function. (F)
Online
http://www.johnwiley.net.au/highered/in
teractions/media/Respiration/content/
Respiration/resp1a/frameset.htm
http://www.johnwiley.net.au/highered/in
teractions/media/Respiration/content/
Respiration/resp2a/bot.htm
Textbooks/Publications
Bio Factsheet 26: Gas exchange in
animals
Note
A common written error in examinations is to state that diffusion occurs across
‘epithelial cell walls’ or ‘the cell walls of the capillary’.
It is not sufficient to state that red blood cells take up oxygen: learners should refer
to oxygen uptake by haemoglobin in red blood cells.
8.1.f
describe the role of haemoglobin in
carrying oxygen and carbon dioxide
with reference to the role of carbonic
anhydrase, the formation of
haemoglobinic acid and
carbaminohaemoglobin (details of the
chloride shift are not required)
Use a question and answer session to revise haemoglobin structure (Unit 1) before
providing further details of oxygen binding and carriage and oxygen release. (W)
(Challenging)
With teacher prompting, learners construct a diagram summarising the carriage of
carbon dioxide by haemoglobin at the respiring tissue (ensure they understand that
the reverse happens in the lung tissue). (I) (Challenging)
o The labelled diagram to include the red blood cell, the endothelium with pores,
and the body cells.
o Discuss in stages, with learners adding information, the sequence of events
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=8
http://www.mrothery.co.uk/circulation/ci
rculationotes.htm#BLOOD
Textbooks/Publications
Bio Factsheet 175: Haemoglobin:
structure & function
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
63
Learning objectives
Suggested teaching activities
Learning resources
Cells as the units of life,
Biochemical processes
occurring.
Discuss the importance of carbonic anhydrase (recall enzyme knowledge), also
highlighting that haemoglobin is not the only protein found in red blood cells. (W)
(Basic)
Learners produce a written explanation of the events occurring in the: respiring
tissues, using a diagram as stimulus material; in the lungs. (H) (F) (Challenging)
Learners explain the roles of haemoglobin in the carriage of carbon dioxide in
buffering hydrogen ions and transporting carbon dioxide directly as
carbaminohaemoglobin. (I) (Challenging)
Past Papers
Paper 21, June 2011, Q2 (a)(c)
Paper 22, June 2011, Q3 (d)(e)
Note
Learners should not describe oxygen binding to haemoglobin as ‘bonding’.
8.1.g
describe and explain the significance
of the oxygen dissociation curves of
adult oxyhaemoglobin at different
carbon dioxide concentrations (the
Bohr effect)
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Introduce the oxygen dissociation curve step-by-step (a difficult concept to grasp),
returning to previous steps if necessary.
o Introduce partial pressure as a measure of concentration and ‘availability’ of
oxygen and the percentage saturation of haemoglobin as ‘affinity’ for oxygen.
o Explain that the oxygen dissociation curve is constructed from results of
experimental measurements.
o Explain the loading of oxygen in the lung (see 8.1.f).
o Explain the release of oxygen (i.e. oxyhaemoglobin dissociation) as a result of
the lower partial pressure in other body tissue (resting). (W) (Challenging)
Learners annotate their own diagrams of the oxygen dissociation curve of adult
haemoglobin. (I) (Challenging)
Learners suggest why the steep part of the curve is important and beneficial
(efficient unloading in partial pressures common in respiring tissues). (W)
(Challenging)
Explain the Bohr shift in relation to carbon dioxide carriage by haemoglobin, using a
summary diagram from 8.1.f.
o Explain that haemoglobin dissociates to a greater extent in working tissue as the
presence of increased carbon dioxide concentrations facilitates the unloading of
‘more’ oxygen by haemoglobin.
o Ask learners to suggest the significance of the greater dissociation (greater need
of tissues for oxygen as they are more actively respiring). (W) (Challenging)
Learners complete worksheets involving data extraction and interpretation of the
curve. (P) (I) (F) (Challenging)
Extension: learners research (using textbooks/internet), consider and explain the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=8
http://www.mrothery.co.uk/circulation/ci
rculationotes.htm#BLOOD
http://www.wiley.com/college/fob/anim/
http://www.wiley.com/college/fob/quiz/
quiz07/7-7.html
http://www.wiley.com/college/fob/quiz/
quiz07/7-12.html
Textbooks/Publications
Bio Factsheet 175: Haemoglobin:
structure & function
Bio Factsheet 9: Oxygen dissociation
curves
Past Papers
Paper 21, June 2011, Q2 (a)(c)
Paper 22, June 2011, Q3 (d)(e)
Paper 21, June 2011, Q2 (d)
Paper 23, June 2011, Q4
64
Learning objectives
Suggested teaching activities
Learning resources
oxygen dissociation curves of myoglobin and foetal haemoglobin. (H) (Challenging)
8.1.h
describe and explain the significance
of the increase in the red blood cell
count of humans at high altitude
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Learners make bullet-point notes after discussing how an increase in red blood cell
count is linked to an increase in haemoglobin, and how this compensates for the
lower saturation that occurs at high altitudes (hence ensuring that body tissues
receive sufficient oxygen). (W) (I) (Basic)
Learners complete a worksheet (prepared by you) to make comparisons of red blood
cell counts at different altitudes, including giving percentage changes. (H) (Basic)
(Challenging)
Extension: learners research the benefits to athletes of training at high altitude, or
investigate if communities who have always lived at high altitude are different to
others. (I) (H) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.sportsci.org/traintech/altitud
e/wgh.html
Textbooks/Publications
Bio Factsheet 149: High altitude
biology
65
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 5: Disease and protection against disease
Recommended prior knowledge
Some introductory knowledge of sickle cell anaemia would be useful, which may have arisen from additional information acquired when learning about sickle cell
haemoglobin in Unit 1, or about mutations in Unit 3. Also from Unit 1, an appreciation of protein structure to function will help when studying antibody structure and
function. Learners should have a good understanding of cell structure, the role of cell surface membrane receptors and the mechanism of endocytosis from Unit 2. They
should appreciate the difference between eukaryotes, prokaryotes and viruses. An understanding of how uncontrolled cell division may result in a tumour, studied in
Unit 3, is required. From Unit 4, learners should be familiar with the histology of the gas exchange system and have knowledge of white blood cells.
Context
Previous units have looked at living organisms on the molecular and cellular scale, before moving on to organs and systems. Disease is an outcome of the
malfunctioning of cells through altered biochemical processes. Infectious diseases show how humans interact with pathogens. These interactions are one component
of the key concept Organisms in their environment. A multicellular organism must organise, control and coordinate activities so that they have defence mechanisms
and can develop immunity from disease. A link is provided to another key concept, Natural selection, with a consideration of the development of antibiotic resistance by
bacteria. Learners are also introduced to monoclonal antibodies, one important aspect of biotechnology. Monoclonal antibodies are the result of observation and
experiment, which is a key concept.
Outline
An understanding is gained of what is meant by disease and what the differences are between infectious and non-infectious diseases. Learners are provided with
examples of non-infectious disease by learning more about sickle cell anaemia and considering how tobacco smoking affects the gas exchange and cardiovascular
systems. Five infectious diseases of global importance are studied in some detail: cause; transmission; prevention and control, including the use of antibiotics. The unit
continues with a consideration of the factors that influence the global patters of TB, malaria and HIV/AIDS. Smallpox is introduced as an infectious disease so that
learners can appreciate how vaccination programmes have helped to eradicate the disease. Penicillin is studied as an example of an antibiotic and learners then
progress to study antibiotic resistance and consider the steps taken to alleviate this problem. There are good opportunities within this unit for learners to develop their
skills in data analysis, particularly with respect to disease statistics. Natural and artificial immunity is studied, including the structure and function of antibodies. Learners
will be provided with more detail about phagocytes and the way in which they function to protect against disease. The events occurring during a specific immune
response are covered. A brief consideration is given to the outcome to the body when the immune system fails to work correctly, using myasthenia gravis as an
example. An account of the production of monoclonal antibodies and how they are used in the diagnosis of disease and treatment of disease is included. The unit
concludes with a study of vaccination and a comparison of the effectiveness of vaccination programmes in the prevention and control of the infectious diseases studied.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
66
Learning objectives
Suggested teaching activities
Learning resources
10.1.a
define the term disease and explain
the difference between an infectious
disease and non-infectious disease
(limited to sickle cell anaemia and lung
cancer)
Ask learners for their ideas for the definition of disease (see examples below).
o An abnormal condition affecting an organism, which reduces the effectiveness of
its function.
o An absence of one or more of physical, social and mental well-being. (W)
(Basic)
Learners name common infectious diseases and suggest the type of causative
organism, the pathogen (use both terms).
o Add examples to cover bacteria, viruses and fungi.
o Introduce protoctists as pathogens (causative pathogen of malaria) using simple
ideas (e.g. eukaryotes, many are unicellular, organisms not fitting into other
groups / kingdoms). (W) (Basic)
Learners give examples of non-infectious diseases.
o Ensure they include diseases of the gas exchange system (linked with tobacco
smoking) and sickle cell anaemia.
o Discuss the cause of sickle cell anaemia (see 6.2.c), Unit 3)). (W) (Basic)
Learners explain why lung cancer and sickle cell anaemia are not considered to be
infectious diseases.
Learners summarise discussions in a comparison table or in comparative sentences.
(I) (Basic)
Extension: learners research the term pathogen, e.g. ‘a biological agent (e.g. a virus,
bacterium, fungus or protoctist) that causes disease and has proteins (foreign/nonself antigens) as part of its structure that are different from those of the human host’.
Online
http://edis.ifas.ufl.edu/in722
Key concepts
Cells as the units of life,
Biochemical processes,
Natural selection
Textbooks/Publications
Bio Factsheet 40: Disease and
defence
Past Papers
Paper 21, Nov 2011, Q4 (b)
Paper 22, Nov 2011, Q2 (b)(i)
Note
‘Germs’ as an alternative to ‘pathogens’ is not acceptable.
A common error is to use the term disease rather than pathogen, e.g. “the disease
enters cells” or to name the disease instead of the pathogen e.g. “malaria enters red
blood cells”.
9.2.a
describe the effects of tar and
carcinogens in tobacco smoke on the
gas exchange system with reference to
lung cancer and chronic obstructive
pulmonary disease (COPD)
Key concepts
Cells as the units of life,
v2.1 5Y02
In a question and answer session, learners explain why chronic bronchitis and
emphysema are also non-infectious diseases (in addition to lung cancer). (W)
(Basic)
Check learner knowledge of the terms carcinogen and carcinogenic. (W) (Basic)
Learners volunteer examples before projecting/showing the long list of carcinogens
in tobacco smoke. (W) (Basic)
o Explain that lung cancer may happen naturally, but the risk is increased by a
range of different environmental factors, identifying tar as a main causative
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.lung.ca/diseasesmaladies/index_e.php
http://library.med.utah.edu/WebPath/L
UNGHTML/LUNGIDX.html
http://www.ash.org.uk/information/facts
-and-stats
http://www.insidecancer.org/
http://www.cancer.org/cancer/cancerca
67
Learning objectives
DNA, the molecule of heredity,
Observation and experiment
Suggested teaching activities
agent. (W) (Basic)
Relate back to Unit 3 and ask learners to write out an outline sequence of
consequential events leading to a tumour and the development of cancer. (W) (I)
(Basic)
Discuss the imprecision in the statement: “Cigarettes cause lung cancer” and ask
learners to suggest improvements, e.g. “There is a correlation between tobacco
smoking and the development of lung cancer”, “Tar in tobacco smoke is known to be
a cause of lung cancer”. (W) (Challenging)
Learners investigate how carcinogens can promote the mutation of two important
types of genes involved in the control of cell division, proto-oncogenes (form
oncogenes, associated with the development of cancer) and tumour suppressor
genes (may mutate so that they can no longer act as a control). (W) (I) (H)
(Challenging)
Name chronic bronchitis and emphysema as the two diseases of COPD. (W)
(Basic)
o For each, learners make short notes summarising the changes that occur in the
gas exchange system that lead to the symptoms of disease. (I) (Challenging)
Extension: learners use data from the WHO website to practise data handling and
investigate the occurrence of deaths from cancers. (P) (I) (Basic) (Challenging)
Learners collect, display and analyse data about a smoking-related disease of the
gas exchange system and give a short presentation to the class. (W) (H)
(Challenging)
Learning resources
uses/geneticsandcancer/oncogenesa
ndtumorsuppressorgenes/oncogenes
-tumor-suppressor-genes-andcancer-mutations-and-cancer
http://www.who.int/en/
http://www.sanger.ac.uk/genetics/CGP
/Census/
http://info.cancerresearchuk.org/cancer
stats/causes/genes/cancergenes/inde
x.htm
http://www.parliament.the-stationeryoffice.co.uk/pa/cm199900/cmselect/c
mhealth/27/9120907.htm
Textbooks/Publications
Bio Factsheet 104: Biological basis of
cancer.
Past Papers
Paper 22, Nov 2011, Q1 (c)(d)(e)
Note
Explain the difference between a mutagen (an agent that increases the mutation rate
of DNA) and a carcinogen (an agent that can cause cancer).
To help make links to changes that occur in the gas exchange system, learners will
benefit from an outline of the signs and symptoms that the diseases share in
common and those that are characteristic for each disease.
9.2.b
describe the short-term effects of
nicotine and carbon monoxide on the
cardiovascular system
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Explain what is meant by the term cardiovascular. (W) (Basic)
Introduce carbon monoxide and nicotine as two components of smoke that can
easily pass across the alveolar wall to the bloodstream.
o Discuss how the presence of these components can cause short-term effects,
which may lead to other short-term effects (consequential outcomes) and to
long-term effects. (W) (Basic)
Explain the affinity of haemoglobin to carbon monoxide (links to Unit 4) and the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.ash.org.uk/files/documents/
ASH_111.pdf
http://www.bhf.org.uk/
http://library.med.utah.edu/WebPath/A
THHTML/ATHIDX.html
http://library.med.utah.edu/WebPath/C
VHTML/CV005.html
68
Learning objectives
Suggested teaching activities
permanency of this association. (W) (Basic)
o Learners discuss the consequences of this with respect to: uptake of oxygen;
delivery to tissues (especially the extremities); effect on heart rate. (W) (G)
(Basic)
State that carbon monoxide can also cause damage to the endothelial lining, which
is a starting point for vascular disease (atheroma/atherosclerosis). (W) (Basic)
Learners make bullet-point notes about the effects of carbon monoxide. (F)
Learners research the short-term effects of nicotine and produce a concept map or
spider diagram (with links to consequential effects).
o Examples: damage to endothelial lining, which can cause turbulent blood flow
and increase risk of clotting (thrombosis); increase in blood pressure owing to
release of adrenaline (can also damage the endothelial lining); making platelets
‘sticky’(increasing platelet aggregation), so increasing thrombosis risk; increased
heart rate; vasoconstriction, which can reduce blood flow to extremities; increase
in LDLs (low-density lipoprotein). The summary could be in the form of a concept
map/spider diagram. (P) (I) (Challenging)
Extension: learners research how the short-term effects can lead to longer term
effects (e.g. atheroma and atherosclerosis, peripheral arterial disease). (H)
(Challenging)
Learning resources
Textbooks/Publications
Bio Factsheet 218: Biology of risk
factors 1: Smoking
Bio Factsheet 37: Ischaemic
(coronary) heart disease (for
extension work)
Past Papers
Paper 22, June 2011, Q6
Paper 22, Nov 2013, Q6 (b)
Note
The addictive effects of nicotine are not related to the cardiovascular system, so are
not required.
10.1.b
state the name and type of causative
organism (pathogen) of each of the
following diseases: cholera, malaria,
tuberculosis (TB), HIV/AIDS, smallpox
and measles (detailed knowledge of
structure is not required. For smallpox
(Variola) and measles (Morbillivirus)
only the name of genus is needed)
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Explain the convention for naming the organisms: upper case (capital) letter for the
first letter of the generic name, lower case letter for the specific epithet. (W) (Basic)
You may wish to concentrate on one disease and work through 10.1.b to 10.1.e
before moving onto the next disease. Alternatively two to four learners work together
(lesson and homework), to research information about one disease and prepare a
presentation for the class, sharing notes. (G) (H) (Challenging)
o Learners then make learning notes on each of the five diseases. (I) (H) (Basic)
Learners research the required information and complete the first two columns of a
large summary headed table. (I) (H) (Basic)
Learners carry out a mix and match card exercise (prepared by you) with the name
of disease, type of causative organism/pathogen, name of causative organism /
pathogen. (F)
Online
http://textbookofbacteriology.net/tuberc
ulosis.html
http://textbookofbacteriology.net/choler
a.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM018.html
Past Papers
Paper 22, Nov 2012, Q4 (a)
Note
Cambridge International AS & A Level Biology (9700) – from 2016
69
Learning objectives
Suggested teaching activities
Learning resources
In their own handwriting learners should underline the species name, in print they
are in italics.
A brief discussion of the term species will help understanding (defined in Unit 6).
Learners should spell species names correctly.
For malaria, parasite will be seen in addition to pathogen.
10.1.c
explain how cholera, measles, malaria,
TB and HIV/AIDS are transmitted
Key concepts
Cells as the units of life,
Organisms in their environment
See 10.1.b for group work.
Discuss what is meant by a transmission cycle, noting that the causative organism is
transmitted when a disease spreads.
o Learners suggest reasons for some diseases spreading more rapidly than
others.
o Summarise on a poster learner suggestions as to main modes of transmission.
o Learners assign a mode of transmission to each named disease and write a
paragraph for each. (W) (Basic)
Learners add key points to their summary table. (I) (Challenging)
Online
http://www.who.int/en/
http://www.who.int/research/en/
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=36
Note
Ensure learners know the difference between the causative organism of malaria, the
protoctist Plasmodium, and the mosquito vector, Anopheles.
10.1.d
discuss the biological, social and
economic factors that need to be
considered in the prevention and
control of cholera, measles, malaria,
TB and HIV/AIDS (a detailed study of
the life cycle of the malarial parasite is
not required)
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
v2.1 5Y02
See 10.1.b for group work.
Begin with a general discussion, learners suggesting what is meant by ‘social’
factors (relating to human society and interdependence - the idea of benefit to all as
a result of cooperation).
o Discuss the distinction between prevention and control. (W) (Basic)
Learners study information (provided by you), including statistics, about a recent
outbreak of one of the named diseases. (G) (Basic)
o Discuss the availability of vaccines and treatments (including drugs) for the
disease. (W) (Basic)
Outline what antibiotics are and when they are useful in the treatment of disease.
(W) (Basic)
Learners use information sheets to suggest ways of breaking the transmission cycle
for each disease, and the difficulties in making this happen.
o Learners consider biological, social and economic factors in relation to
prevention and control. (G) (P) (Challenging)
Learners research where these diseases are currently prevalent and how this affects
people in different parts of the world. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.who.int/en/
http://www.who.int/research/en/
http://www.cdc.gov/
Past Papers
Paper 23, Nov 2011, Q4
70
Learning objectives
Suggested teaching activities
Learning resources
Note
Learners should be aware that antibiotics can be antifungal.
10.1.e
discuss the factors that influence the
global patterns of distribution of
malaria, TB and HIV/AIDS and assess
the importance of these diseases
worldwide
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
See 10.1.b for group work.
From 10.1.d, learners give reasons why some countries are better able to prevent
and control a particular disease. (I) (Basic)
Learners choose one of the named diseases to research and produce a short report.
(H) (Challenging)
o Learners contribute from their report to a group discussion. (W) (Basic)
o Point out how there is often a correlation in disease pattern, e.g. high incidence
of TB in people with HIV/AIDS. (W) (Basic)
o Learners make summary learning notes on each disease. (I) (Basic)
Learners fill in details on a partially completed table summarising all the main points
for 10.1.b to 10.1.e (see Note). (F)
Online
http://www.cdc.gov/malaria/malaria_wo
rldwide/impact.html
http://www.ncbi.nlm.nih.gov/pubmed/2
1728152
http://www.who.int/hiv/mediacentre/ne
ws60/en/
Note
Display world maps showing the areas most affected by each disease.
10.2.a
outline how penicillin acts on bacteria
and why antibiotics do not affect
viruses
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Outline the difference between bacteriostatic and bactericidal antibiotics. (W)
(Basic)
Explain that the penicillin group of antibiotics are also known as beta lactams
(describes their structure). (W) (Basic)
Review learner knowledge of bacterial cell wall structure and use a question and
answer session to build up the action of penicillin.
o Explain that transpeptidase enzymes (glycoprotein peptidases) catalyse
formation of peptide cross links between peptidoglycan chains, which complete
the strength of the cell wall.
o Prompt learners to recall knowledge of enzyme inhibition before they suggest
how penicillin acts to inhibit transpeptidases.
o Learners suggest why penicillin is only active against growing bacteria that are
laying down new cell wall components. (W) (Challenging)
Display key terms and key points for learners to write a summary of the discussion.
(F)
Extension: learners research the other main ways in which antibiotics act and
explain why penicillin and other antibiotics do not harm human cells. (I)
(Challenging)
Microbiology practical: learners place filter paper discs impregnated with different
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.cellsalive.com/pen.htm
http://www.biology.ed.ac.uk/research/g
roups/jdeacon/microbes/penicill.htm
http://pathmicro.med.sc.edu/fox/antibio
tics1.htm
http://textbookofbacteriology.net/antimi
crobial.html
Textbooks/Publications
King p.172-173
Siddiqui p.52
Past Papers
Paper 22, June 2013, Q3 (b)
71
Learning objectives
Suggested teaching activities
Learning resources
antibiotics (e.g. Mast rings), or different concentrations of the same antibiotic, onto a
Petri dish with nutrient agar inoculated with non-hazardous bacteria (e.g. Bacillus
subtilis).
o Learners measure zones of inhibition created around the discs on the lawn of
bacteria and compare to determine the efficacy of each antibiotic (or antibiotic
concentration). (P) (I) (Challenging)
Learners write a paragraph explaining why antibiotics do not affect viruses (see Unit
2, viral structure), extending this to use HIV as an example. (I) (Challenging)
o Remind learners that there are anti-viral drugs effective against HIV. (W) (Basic)
10.2.b
explain in outline how bacteria become
resistant to antibiotics with reference to
mutation and selection
Key concepts
DNA, the molecule of heredity,
Natural selection,
Organisms in their environment
10.2.c
discuss the consequences of antibiotic
resistance and the steps that can be
taken to reduce its impact
v2.1 5Y02
Learners suggest changes in bacteria that could lead to the ‘inactivation’ of penicillin.
(W) (Challenging)
o Ensure the discussion covers: mutations in genes lead to new proteins; the new
protein can be an enzyme; the enzyme can breakdown penicillin; hence
antibiotic resistance.
o Introduce beta lactamase (formerly penicillinase) as the enzyme.
o Mention that plasmids often carry genes for antibiotic resistance.
Learners suggest how new proteins could act in other ways to provide resistance,
e.g. membrane proteins pumping out antibiotics (efflux pumps) or inactivating them.
(W) (Challenging)
Learners recall why it is important to complete a course of antibiotics in the
treatment of TB.
o Discuss how the presence of antibiotic acts as a selection pressure, so resistant
bacteria (with a mutation) are selected for, and those that are killed are selected
against.
o Explain the different ways (vertical and horizontal transmission) that resistance
can be passed. (W) (Challenging)
Learners write a summary of the discussions. (F)
Online
http://www.hpa.org.uk/Topics/Infectiou
sDiseases/InfectionsAZ/Antimicrobial
Resistance/
http://www.tufts.edu/med/apua/index.s
html
http://www.antibioticresistance.org.uk/
http://www.s-cool.co.uk/alevel/biology/evolution/reviseit/evolution-in-action
http://textbookofbacteriology.net/resant
imicrobial.html
Textbooks/Publications
Bio Factsheet 100: Antibiotics and
antibiotic resistance
Bio Factsheet 71: The control of
bacteria.
Note
Two common errors: stating that resistance to the antibiotic develops in people, not
in bacteria; confusing resistance with immunity.
Past Papers
Paper 22, June 2011, Q4 (c)(d)
Learners cover this learning objective by researching a chosen bacterium that shows
multiple drug resistance and present their findings to the rest of the group.
o Points to consider in reducing impact: dosage; length of treatment; use of narrow
spectrum antibiotics; identify correctly the causative organism; hygiene and
aseptic conditions in areas such as hospitals; measures to reduce the impact of
Online
http://www.bbsrc.ac.uk/web/FILES/Pub
lications/bioscience_behind_superbu
gs.pdf
Cambridge International AS & A Level Biology (9700) – from 2016
72
Learning objectives
Key concepts
Natural selection,
Organisms in their environment,
Observation and experiment
11.1.d
explain the meaning of the term
immune response, making reference to
the terms antigen, self and non-self
Key concepts
Cells as the units of life
11.1.a
state that phagocytes (macrophages
and neutrophils) have their origin in
bone marrow and describe their mode
of action
Key concepts
Cells as the units of life
v2.1 5Y02
Suggested teaching activities
Learning resources
antibiotic therapy with farm animals. (W) (I) (H) (Challenging)
Learners suggest mechanisms considered as ‘first line of defence’ (e.g. skin,
stomach acid).
o Explain that the next defence will be responses to invasion of body tissue.
o Discuss how the body can distinguish between non-self and self and recall
previous work on antigens. (W) (Basic)
Learners write a definition of antigen, referring to self and non-self, the production of
specific antibody to form an antigen-antibody complex and including examples (e.g.
a molecule on the outside of a bacterium, virus, parasite, allergen or tumour cell). (I)
(Basic)
Discuss the meaning of immune response (a complex series of reactions of the
body, involving white blood cells, to a non-self antigen) before learners make notes.
(W) (I) (Challenging)
o Ensure learners understand that the non-specific (innate) response involves
phagocytes and the specific (adaptive) response involves lymphocytes, and that
the responses interact.
o Explain that the reactions result in destruction of the foreign invader and prepare
the body for a faster response to a second invasion (so the person will have few
or no symptoms).
Past Papers
Paper 21, Nov 2011, Q6 (c)
Remind learners that all blood cells have their origin in the bone marrow (Unit 3,
5.1.c): stem cells) and that some mature elsewhere in the body.
o Learners recall that monocytes mature into macrophages, which are phagocytes
(see Note 8.1.d, Unit 4). (W) (Basic)
Learners draw annotated labelled diagrams of a neutrophil, a monocyte, and a
macrophage (arrow pointing from monocyte). Learners include a label to (Fc)
receptors that can bind to antibodies. (I) (Basic)
Explain that phagocytes can respond to isolated pathogens or to antibodies bound
to antigens of pathogens. (W) (Basic)
Learners sequence and label diagrams (provided by you) showing events occurring
during phagocytosis, recalling studies on endocytosis, the role of receptors and
function of lysosomes.
o Learners should know the term antigen presenting cell (APC). (I) (Basic)
CD-ROM
Bioscope – has relevant images.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://education.vetmed.vt.edu/Curricul
um/VM8054/Labs/Lab6/Lab6.htm
http://micro.magnet.fsu.edu/index.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM001.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM002.html
http://highered.mcgrawhill.com/sites/0072507470/student_vi
73
Learning objectives
Suggested teaching activities
(Challenging)
Learners match cards of descriptive text (provided by you) to diagrams of stages. (F)
Learners compare and contrast phagocytes and lymphocytes on microscope slides.
(I) (Basic)
Learning resources
ew0/chapter3/animation__phagocyto
sis.html
Textbooks/Publications
King p.164-165
Siddiqui p.181-182
Past Papers
Paper 21, Nov 2011, Q6
Paper 22, Nov 2011, Q2 (a)
11.1.b
describe the modes of action of Blymphocytes and T-lymphocytes
Key concepts
Cells as the units of life
v2.1 5Y02
Discuss how the non-specific response of phagocytes to infection differs from the
specific response of B-lymphocytes and T-lymphocytes, which each have different
modes of action. (W) (Basic)
Using a step-by-step teacher-prompted approach or by individual research, learners
draw an annotated flow diagram to show how specific B-lymphocytes respond
(humoral response):
o Recognition and binding of specific antigen.
o Activation/sensitisation followed by clonal expansion (mitotic division).
o Differentiation to produce (i) plasma cells that make antibodies in a primary
immune response and (ii) memory cells (see 11.1.e).
o There are important interactions with the T-lymphocytes response. (I)
(Challenging)
Discuss the similarity of the T-lymphocyte response (cell-mediated immunity) to the
humoral response, before outlining other key points.
o T-helper cells activation produces a clone of cells that release cytokines, which
stimulate and strengthen both the humoral response and macrophage response.
o T-killer (cytotoxic) cells activation produces a clone of cells that can directly kill,
for example, infected cells.
o Both types produce memory cells. (W) (Basic)
Learners choose to show the information in a flow diagram or with written notes. (I)
(Challenging)
Distinguish between receptors of B-lymphocytes and T-lymphocytes that bind nonself antigen: for B-lymphocytes the receptor is immunoglobulin (slightly different to a
secreted antibody); the T-receptor recognises antigens displayed on the surface of
APCs (see T-helper cells) or infected or foreign cells (see T-killer cells). (W)
(Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/B/B_and_Tcells.html
http://www.merckmanuals.com/home/i
mmune_disorders/biology_of_the_im
mune_system/acquired_immunity.ht
ml?qt=immune%20response&alt=sh
http://www.accessexcellence.org/AB/G
G/antibodies.html
http://www.cellsalive.com/antibody.htm
http://library.med.utah.edu/WebPath/H
EMEHTML/HEMEIDX.html
http://www.bu.edu/histology/p/21001oo
a.htm
Past Papers
Paper 23, Nov 2013, Q.1 (b)
Paper 21, Nov 2011, Q6 (c)
74
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners research the effect of active HIV in human T-lymphocytes (also
attacks phagocytes) and see the consequences of a reduction in numbers of white
blood cells (helps to explain why people with HIV/AIDS are prone to opportunistic
infections). (I) (Challenging)
Note
Refer to humoral and cell-mediated responses (not required knowledge) as learners
will see these terms in resources used.
11.1.e can be incorporated into this learning objective.
11.1.e
explain the role of memory cells in
long-term immunity
Key concepts
Cells as the units of life
Discuss why the presence of memory cells means that a secondary immune
response will be faster and stronger than a primary response. (W) (Basic)
Learners suggest meanings for the term immunity and write out an agreed
explanation of immunity and long-term immunity.
Learners could draw and annotate a sketch graph showing antibody concentrations
against time during an immune response. (I) (Basic)
o Learners reproduce this graph at a later date, with more detailed annotations. (F)
Online
http://www.biology.arizona.edu/immun
ology/tutorials/immunology/09t.html
Note
Encourage use of scientific terminology and explanations: phrases such as
‘remembers the disease’ and ‘fights the disease’ are unacceptable.
11.1.c
describe and explain the significance
of the increase in white blood cell
count in humans with infectious
diseases and leukaemias
Provide learners with information about leukaemias. Learners write an account
explaining the difference between an increase in white blood cell count
accompanying infectious diseases with that of leukaemias. (F)
Learners explain why people with leukaemia are susceptible to infections. (I) (Basic)
Extension: learners research the difference between acute and chronic leukaemias.
(H) (Challenging)
Key concepts
Cells as the units of life
11.1.f
explain, with reference to myasthenia
gravis, that the immune system
sometimes fails to distinguish between
self and non-self
Online
http://www.lls.org/diseaseinformation/
managingyourcancer/newlydiagnose
d/understandingdiagnosis/labimaging
tests/bloodtests/bloodcounts/
Textbooks/Publications
Siddiqui p.182-183
Use myasthenia gravis as an example to explain what is meant by autoimmune
disease, provide learners with a straightforward information sheet from which they
can make their own bullet-pointed notes. (I) (Basic)
Extension: learners research other auto immune diseases to highlight the range of
immune dysfunctions that can exist. (H)
Online
http://www.nlm.nih.gov/medlineplus/en
cy/article/000816.htm
https://www.mgacharity.org/information-mg
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
75
Learning objectives
Suggested teaching activities
Learning resources
Revise protein structure with a short written test. (F)
Discuss the basic structure of an immunoglobulin (e.g. IgG) and how these
molecules interact with antigens. (W) (Basic)
Explain that the variable regions in different antibodies have different sequences of
amino acids and ask for suggestions as to how this related to the specificity of
antibodies. (W) (Basic)
Learners use, for example, a ribbon diagram of IgG to explain how primary,
secondary, tertiary and quaternary structures of proteins are shown. (P) (I)
(Challenging)
Learners draw a labelled, annotated diagram linking the structure of an antibody to
its function, reproducing this diagram at a later stage. (I) (F) (Challenging)
Online
http://www.accessexcellence.org/RC/V
L/GG/ecb/antibody_molecule.php
http://www.biology.arizona.edu/immun
ology/tutorials/antibody/structure.html
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/AntigenReceptors.
html
Cells as the units of life
11.2.a
relate the molecular structure of
antibodies to their functions (see 2.3.b)
Key concepts
Biochemical processes
Past Papers
Paper 21, June 2013, Q2
Paper 23, Nov 2013, Q1
Note
Learners may be interested to know that antibodies are glycoproteins.
Mention the different antibody classes and refer to the term antitoxins (not required
learning) for interest.
There is potential confusion between antibodies and antibiotics – apply error-free
learning.
11.2.b
outline the hybridoma method for the
production of monoclonal antibodies
Key concepts
DNA, the molecule of heredity,
Observation and experiment
Learners review antigens, antibodies, specificity, B-lymphocytes, plasma cells and
cancer cells with a brainstorming session. (W) (Basic) (Challenging)
With guidance, learners work through the hybridoma method and produce either a
summary flow diagram, set of notes, or completed table. Learners highlight the main
stages of the process and the steps that occur within each stage are described and
explained. (I) (Challenging)
Ask learners to state the desirable features which are contributed by each cell that
become incorporated into the hybridoma cell (this contains the genetic material of
both cells). (W) (Basic)
Learners describe the distinction between the hybridoma cell and the monoclonal
antibody (see Note). (W) (Challenging)
Learners could make a list of all the cells involved in the production and state the
role of each. (I) (Basic)
Discuss why there has been a move to produce humanised antibody rather than
mouse antibody. (W) (Challenging)
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/M/Monoclonals.html
http://www.bio.davidson.edu/Courses/
molbio/MolLearners/01rakarnik/mab.
html
http://www.nap.edu/openbook.php?rec
ord_id=9450&page=8
Past papers
Paper 41, June 2012, Q2
Note
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
76
Learning objectives
Suggested teaching activities
Learning resources
Ensure learners understand that:
o a clone (group of genetically identical cells formed from one original ‘ancestor’
cell) of hybridoma cells produces one type of specific antibody, monoclonal
antibody;
o the ‘ancestor’ cell forms from the fusion of a specific plasma cell (B-lymphocyte)
and a myeloma cell.
In this rapidly-developing area of biotechnology, learners need to apply biological
principles and concepts to new situations.
11.2.c
outline the use of monoclonal
antibodies in the diagnosis of disease
and in the treatment of disease
Key concepts
Observation and experiment
Explain that a sample of fluid taken from a person with an infectious disease could
contain both pathogen (with non-self antigens) and specific antibody. (W) (Basic)
Learners study a set of diagrams showing the steps occurring in a direct enzymelinked immunosorbent test (ELISA) and answer a set of questions that require
application of the principles of immune response and knowledge of monoclonal
antibody. (I) (Challenging)
o Extension: learners describe what is occurring in an indirect ELISA test for the
presence of circulating specific antibody. (I) (Challenging)
Learners research one example of the use of monoclonal antibody in the treatment
of disease and present their findings to the class. (H) (W) (Basic) (Challenging)
Note
Learners do not need to know the term ELISA or the details of the test.
Online
http://www.mayoclinic.com/health/mon
oclonalantibody/CA00082
http://www.hhmi.org/biointeractive/imm
unology/vlab.html.
http://web.archive.org/web/200803290
02645/http://www.molecular-plantbiotechnology.info/hybridoma-andmonoclonal-antibodies-mabs/uses-ofmonoclonal-antibodies.htm
http://www.sumanasinc.com/webconte
nt/animations/content/pregtest.html
Textbooks/Publications
Bio Factsheet 112: Monoclonal
antibodies
Bio Factsheet 219: Monoclonal
antibodies: An update
Past papers
Paper 41, June 2012, Q2 (b)(c)
11.2.d
distinguish between active and
passive, natural and artificial immunity
and explain how vaccination can
control disease
v2.1 5Y02
Discuss the principles behind passive immunity before learners produce an account
explaining why (i) passive immunity is immediate but short-lived and active immunity
is delayed but longer-term, and (ii) passive immunity does not produce memory
cells whereas active immunity does. (W) (I) (Basic) (Challenging)
Learners draw an annotated version of the immune response curve to show how
vaccines act to give immunity. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.spmsd.co.uk/cat.asp?catid=
9
http://www.polioeradication.org/
http://www.who.int/features/factfiles/pol
io/en/
77
Learning objectives
Suggested teaching activities
Learning resources
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
Learners construct a summary chart, leaving enough room to add features and
examples to show the differences between the categories, or, the chart of immunity
is divided into active and passive, each divided into natural and artificial. (I) (Basic)
Immunity
Natural
Active
Passive
Artificial
Active
Textbooks/Publications
Bio Factsheet 99: Vaccines
Bio Factsheet 71: The control of
bacteria.
Past Papers
Paper 21, June 2011, Q6
Passive
Discuss briefly how vaccination can provide immunity to avoid the spread of disease.
Include the term herd immunity. (W) (Basic)
Extension (highly relevant): learners access current information on the programme
to eradicate polio.
11.2.e
discuss the reasons why vaccination
programmes have eradicated
smallpox, but not measles,
tuberculosis (TB), malaria or cholera
Key concepts
Cells as the units of life,
Organisms in their environment
Discuss the features that contributed to the success of the smallpox vaccination
programme, which was considered the main factor in the eradication of the disease.
(W) (Basic)
o Learners contribute information about the progress of vaccination programmes
for the other diseases. (W) (Basic)
Working in groups of four, each member researches one of the four named
diseases, making comparisons with the smallpox vaccination programme.
o Provide a list of terms to be incorporated into the group study, e.g. antigenic
concealment, antigenic drift, boosters, long/short-term, etc. (G) (Challenging)
Online
http://www.who.int/features/2010/small
pox/en/
http://en.wikipedia.org/wiki/Ali_Maow_
Maalin
http://www.who.int/topics/vaccines/en/
http://www.s-cool.co.uk/alevel/biology/immunity/reviseit/problems-with-vaccines
http://www.who.int/immunization/en/
http://www.iavi.org/Pages/default.aspx
Past Papers
Paper 22, Nov 2011, Q2 (b)(ii)(iii)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
78
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 6: The diversity of life
Recommended prior knowledge
Learners should have a good understanding of the difference between plant and animal cells and of the difference between prokaryotes and eukaryotes from Unit 2.
Also from Unit 2, learners should know the basic structure of viruses. They should also be familiar with ecological concepts, such as: the meaning of the terms
population and community; the flow of energy through the different trophic levels of the ecosystem; and interactions between organisms.
Context
This unit, above all the others, belongs to the learner. This is their opportunity to get to know the local environment, with opportunities for fieldwork and for research into
local conservation issues and local conservation projects, allowing a practical application of the key concepts of organisms in their environment and of observation and
experiment. Stimulating an interest in biodiversity will lead appropriately to the next unit, Unit 7, Genetics, population genetics and evolutionary processes.
Outline
The unit begins with a discussion of the meaning of the terms species, ecosystem and niche so that learners will have a good grounding for later ecological studies,
and then continues with a more detailed study of classification and taxonomy. Biodiversity is considered at three different levels, and species biodiversity is further
explored by fieldwork opportunities in a local area. Spearman’s rank correlation and Pearson’s linear correlation, together with Simpson’s diversity of index are
introduced as analytical tools for the data collected from fieldwork. The unit also covers the threats to the maintenance of biodiversity and discusses both issues
concerning conservation and practical ways to conserve endangered species and restore degraded habitats. One aspect of the key concept of organisms in their
environment is how humans can interact with their environment in ways that can have a great impact on ecosystems. Here, consideration is given to the part humans
may play in the extinction of species.
Teaching time
It is recommended that this unit should take approximately 6% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
79
Learning objectives
Suggested teaching activities
Learning resources
18.1.a
define the terms species, ecosystem
and niche
Carry out a brainstorming exercise to indicate how much learners can recall of each
term. (W) (Basic)
Discuss the species concept (and difficulties in defining the term – there are over 20
definitions) before learners make notes.
o Expand ideas of: reproductively isolated; production of fertile offspring; members
have the same (very similar) features in morphology, anatomy, physiology,
behaviour and biochemistry; occupy the same niche; defined by same (very
similar) DNA. (W) (I) (Basic)
Extension: learners explore difficulties in defining species in terms of fertile offspring
by researching examples, e.g. between plant species or between mammalian
species (polar bear and brown bear - rare; canid hybrids - common). (H)
(Challenging)
Extension: learners consider how the species concept works for asexually
reproducing organisms and for interspecific plasmid transfer between bacteria. (H)
(Challenging)
Learners write a definition of an ecosystem, incorporating the following ideas and the
same (or equivalent) terminology: (I) (Basic)
o a self-sustaining unit consisting of abiotic and biotic factors interacting together
o includes all organisms of all populations (in a given area)
o energy flows through and cycling of minerals occur.
Learners make notes on (ecological) niche, the functional role of a species, to
include: a description of its habitat; how it is adapted to its environment; interactions
with other organisms; features of its life-cycle. (I) (Basic)
Learners visit an ecosystem to place into context these terms and concepts,
describing in terms of: energy flow / trophic levels; interactions between organisms;
interactions between organisms and the physical environment. Examples of species
and of niche are described. (G) (P) (Basic) (Challenging)
Explain that an ecosystem can vary in size and could be temporary or permanent.
(W) (Basic)
Online
http://purchon.com/ecology/
http://www.ecologydictionary.org/
Key concepts
Natural selection,
Organisms in their environment
Textbooks/Publications
Bio Factsheet 131: Ecological niche
Past Papers
Paper 22, June 2011, Q2
Paper 41, June 2012, Q1 (a)
Note
A niche is often described in terms of an organism or a population.
A field trip should be considered before covering 18.1.c) to 18.1.f). If a trip is not
possible, visiting any suitable area populated by plants and animals, within or near to
school, will be a rewarding experience for learners.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
80
Learning objectives
Suggested teaching activities
Learning resources
18.2.a
describe the classification of species
into the taxonomic hierarchy of
domain, kingdom, phylum, class,
order, family, genus and species
Learners suggest a method to sort all the different organisms in the world and then
share ideas. (W) (G) (Basic)
Introduce the idea of sorting as ‘classification’ and agree that a hierarchical
approach is sensible.
o State that levels in the hierarchy are termed taxonomic ranks, with each example
of a rank known as a taxon (plural: taxa).
o Explain that the members of a group share common (homologous) features
based on phylogenetic / evolutionary patterns (more details in Unit 7). (W)
(Basic)
Display a ‘tree of life’ with the three domains and briefly outline the other taxonomic
ranks, asking for suggestions why the species taxon is considered to be the only
natural classification group.
o Outline the classification of humans, with learners contributing their ideas. (W)
(Basic)
Learners note down the taxonomic ranks listed and decide a good mnemonic to help
remember the hierarchical order. (P) (I) (Basic)
Extension: choose one or more organisms to classify from domain through to the
species, for example, organisms encountered during fieldwork. (H) (Basic)
(Challenging)
Extension: learners research classification systems based on analogous features. (I)
(Basic)
Online
http://www.microscopyuk.org.uk/mag/indexmag.html?http://
www.microscopyuk.org.uk/mag/artmay98/classif.html
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Class
ification/classification.htm
Learners complete a short written test (produced by you, with mark scheme) about
prokaryotes and eukaryotes. (F)
Explain that the Archaea and Bacteria are both prokaryotic but have quite different
features, reflecting their evolutionary history.
o State some features of the Archaea that contrast with Bacteria: e.g. different cell
wall structure, which can be quite varied (not murein); different types of
membrane lipids (not phospholipids); differences in tRNA and ribosomes.
o Discuss the specialised habitats of some members of the Archaea: high
temperatures, extreme saline, and anaerobic environments. (W) (Basic)
Learners use resources (textbooks, internet, etc.) to produce a list of the main
features of each domain. (I) (Basic)
Online
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Evolution/index.htm
http://www.ucmp.berkeley.edu/alllife/th
reedomains.html
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
18.2.b
outline the characteristic features of
the three domains Archaea, Bacteria
and Eukarya
Key concepts
Cells as the units of life,
DNA, the molecule of heredity,
Organisms in their environment
Textbooks/Publications
Bio Factsheet 91: Taxonomy and
classification.
Bio Factsheet 170: Answering Exam
Questions: Classification and Keys
Note
For this syllabus learners should use ‘Bacteria’ and not ‘Monera’.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
81
Learning objectives
Suggested teaching activities
Learning resources
18.2.c
outline the characteristic features of
the kingdoms Protoctista, Fungi,
Plantae and Animalia
Learners brainstorm the names of the kingdoms. Write down all ideas so any
incorrect can be put into context (i.e. see 18.2.a).
o Agree the kingdoms and discuss criteria used for classification into Fungi,
Animalia or Plantae kingdom, e.g. animals are eukaryotic, multicellular, feed as
heterotrophs. Point out that absent features also helps confirm the classification,
e.g. no cells with cell walls, don’t photosynthesise.
o Discuss the Protoctista as the kingdom that contains organisms that do not quite
fit into the other kingdoms.
o Learners make notes using resources. (W) (Basic)
Learners make up an imaginary ‘named’ organism and produce a sticky note or label
with enough of a description for it to be classified into a kingdom. The notes could be
stuck around the class for a class activity, learners revealing their answers at the
end of the activity. (W) (I) (Basic) (Challenging).
Online
http://www.ucmp.berkeley.edu/plants/p
lantae.html
Key concepts
Cells as the units of life,
DNA, the molecule of heredity,
Organisms in their environment
18.2.d
explain why viruses are not included in
the three domain classification and
outline how they are classified, limited
to type of nucleic acid (RNA or DNA)
and whether these are single stranded
or double stranded
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
18.1.b
explain that biodiversity is considered
at three different levels:
variation in ecosystems or habitats
the number of species and their
relative abundance
genetic variation within each
species
Key concepts
v2.1 5Y02
Textbooks/Publications
Bio Factsheet 91: Taxonomy and
classification
Bio Factsheet 170: Answering Exam
Questions: Classification and Keys
Past Papers
Paper 43, June 2011, Q1 (c)
Paper 43, Nov 2011, Q1 (c)
Paper 41, Nov 2012, Q11 (a)
Check learner knowledge of the main features of viruses (1.2.f) with a question and
answer session.
o Add more information about the genetic material: either single or doublestranded RNA or single or double-stranded DNA, but never both RNA and DNA.
o Learners produce a generalised diagram that is annotated. (W) (I) (Basic)
Learners suggest why viruses are not included in the three domain classification.
o Remind learners of the Unit 2 discussion (viruses do not fit the key concept of
cells as the basic units of life) and see if they have any other points to contribute.
(W) (Basic)
Online
http://www.eoearth.org/view/article/51c
bef267896bb431f69cb9a/?topic=51cb
fc78f702fc2ba8129e70
http://www.johnkyrk.com/virus.html
A discussion about the term biodiversity will highlight that a simple definition may be
difficult. Introduce the idea of three different ‘levels’ of biodiversity, ecosystem,
species, and genetic. (W) (Challenging)
o Point out the transition from an ecological to a molecular biological approach.
o Explain that ecosystem biodiversity is more difficult to measure, as ecosystems
may merge at their ‘boundaries’ (so not easy to define) and vary greatly in size.
Explain that biodiversity can be considered at a local, national and global level. (W)
(Basic)
Give a definition of a habitat, for reference only, e.g. the particular location and type
of local environment occupied by a population or organism, characterised by its
Online
http://www.eoearth.org/topics/view/494
80/
http://www.bbsrc.ac.uk/web/FILES/Exh
ibitions/pod2-factsheet.pdf
http://www.geography.learnontheintern
et.co.uk/topics/ecosystem.html
http://wwf.panda.org/about_our_earth/
biodiversity/what_is_biodiversity/
http://www.iucn.org/iyb/about/?gclid=C
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 32: Viruses made
simple.
82
Learning objectives
DNA, the molecule of heredity,
Organisms in their environment
Suggested teaching activities
physical features or by its dominant producers. (W) (Basic)
Learners volunteer the different types of medium-scale (meso) ecosystems in their
region: e.g. wood/forest, lake/river, field, rocky shore (ecosystem biodiversity).
o To understand how biodiversity can be reduced, learners suggest an occurrence
for each ecosystem that would lead to its loss. (W) (Basic)
In groups, volunteer states a habitat within one of the named ecosystems, choosing
the next person to give another habitat and so on. (G) (Basic) (Challenging)
Reinforce, using examples, learner understanding of the differences between
ecosystem and habitat, e.g. the habitat of a catfish is a freshwater stream versus the
catfish is part of the freshwater ecosystem; removal of boulders from the stream bed
reduces the variety/number of different habitats in the ecosystem. (W) (Basic)
Learners consider species biodiversity within a community.
o Give a definition of community (reference only), e.g. all of the populations of all
of the different species within a specified area at a particular time.
o Explain, using examples, the difference between number of species (count of
how many species exist within a particular community), and relative abundance
of species (count how many members of each species there are - the population
size).
o Expand the discussion to consider species diversity on a global scale. (W)
(Challenging)
For genetic biodiversity, explain that a genome is the sum total of all the hereditary
information in an organism, and discuss how, although each species can be
identified by a characteristic genome, there will still be variation (link to Unit 7).
o Learners recall from Unit 3, the different nucleotide sequences for HbA (normal)
and HbS (sickle cell) alleles and their definition of a mutation (6.2.b).
o Explain that genetic biodiversity (variation) can be within a population or
between populations. (W) (Basic)
Learners summarise discussions with their own notes, using examples to help their
explanation. (F)
Extension: learners consider further examples of how ecosystem biodiversity can be
affected by different factors: trophic levels, food chains/webs and energy flow; the
cycling of nutrients; interactions. (H) (Challenging)
Learning resources
J7n2a2576QCFQsGbAodI3nz1A
Note
When tackling variation in ecosystems or habitats, reference to some of the issues in
18.3.a and 18.3.h will help for later studies.
18.1.c
v2.1 5Y02
Random sampling is best demonstrated by holding up one page from a large
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 11
83
Learning objectives
explain the importance of random
sampling in determining the
biodiversity of an area
Key concepts
Organisms in their environment,
Observation and experiment
Suggested teaching activities
newspaper that contains words of different sized fonts, images and blank areas.
o Explain that this simulates a field, which has no more than 26 species living
there, each species represented by a letter of the alphabet. (W) (Basic)
o Learners discuss a method to determine how many different species and how
many individuals of each species there are (and only 30 minutes to carry out the
task). (G) (Challenging)
o Discuss a suitable strategy, highlighting the importance of: having to sample;
taking a number of samples (the sample may be unrepresentative, e.g. a
photograph could represent a bare rock, so no individuals would be found);
choosing the correct size/area of each sample; random sampling (biased
sampling - any measurements can only apply to the sample, not to the whole
area). (W) (Basic)
Learning resources
Online
http://www.countrysideinfo.co.uk/howto
.htm
http://fua.field-studiescouncil.org/media/59629/how_to_carr
y_out_a_random_sample.pdf
Note
Learning objectives 18.1.c to 18.1.f are best understood, and could be carried out, in
the context of fieldwork. Practical booklet 11 may provide suitable protocols and
should be consulted first.
18.1.d
use suitable methods, such as frame
quadrats, line transects, belt transects
and mark-release-recapture, to assess
the distribution and abundance of
organisms in a local area
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
See Note for 18.1.c.
Learners use resources to note the difference between distribution and abundance.
(I) (Basic)
Discuss different techniques for estimating, e.g. counting numbers of each of the
different species within the quadrat; ‘by eye’ estimation of percentage of quadrat
covered by each particular plant species; using an abundance scale (e.g. ACFOR).
o Learners suggest what to do with their data in order to make calculations of
estimates of population size. (W) (Basic)
Discuss how quadrats of a known area can be used for random sampling and the
importance of: choosing the right size of frame quadrat (e.g. size of organisms, area
to cover; reducing edge effects); when to use a quadrat with a grid. (W) (Basic)
Explain line and belt transects for systematic sampling.
o Learners suggest advantages and disadvantages of belt versus line transects.
o Explain the difference between interrupted belt transects (quadrats placed at
regular intervals) or continuous belt transects (quadrats laid side by side). (W)
(Basic)
Learners consider different (theoretical) fieldwork tasks and choose whether frame
quadrats randomly placed, line transects, interrupted belt transects or continuous
belt transects would be most the appropriate, justifying their answers. (H) (F) (Basic)
(Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 11
Online
http://www.countrysideinfo.co.uk/howto
.htm
http://fua.field-studiescouncil.org/media/59629/how_to_carr
y_out_a_random_sample.pdf
http://fua.field-studiescouncil.org/teaching-equipment-andmethods.aspx
http://www.biologymad.com/resources/
RevisionM5Ch4.pdf
http://www.nuffieldfoundation.org/appli
ed-science/distribution-andabundance-species
Textbooks/Publications
King Chapter 11
Siddiqui, Chapter 7
84
Learning objectives
18.1.e
use Spearman’s rank correlation and
Pearson’s linear correlation to analyse
the relationships between the
distribution and abundance of species
and abiotic or biotic factors
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Suggested teaching activities
Learning resources
Discuss the concept behind the mark-release-recapture technique and situations
where mark-release-recapture would be appropriate. Show the formula to use:
number in the first sample x number in second sample
number marked in second sample
o Explain the problem if there is a low rate of recapture, e.g. 20 animals caught
and marked, 1 marked in 10 captured the second time, estimate of total number
=200/1 = 200, but 2 marked individuals recaptured makes the estimate only 100.
(W) (Basic)
o Learners practise this using a container of beans or beads. Remove a small
handful to be marked for the first sample, add them back to the container (shake
them up), remove a second sample for the ‘recapture’ (closed eyes) and record
results, obtaining the estimate using the formula. (P) (I) (Basic)
Learners obtain estimates of population size from several different sets of data using
the mark-release-recapture formula. (I) (Basic)
o Learners extract the required numerical data from paragraphs of prose to
estimate the population size (no formula provided). (F)
Learners make notes on the mark-release-recapture technique, annotating the
formula to use and explaining some of the assumptions made: marked animals
returned to the population mix randomly; the marking had no effect (e.g. non-toxic,
more visible to predators); the marking remained on individuals; equal chance of
capturing marked and unmarked individuals; no immigration or emigration during the
sampling. (I) (Challenging)
Learners carry out fieldwork, using each of the methods listed to assess the
distribution and abundance of organisms. (G) (P) (Basic) (Challenging)
Bio Factsheet 5: An idiot’s guide to
populations.
Bio Factsheet 68: Fieldwork
techniques
Bio Factsheet 184: Investigating sand
dunes.
See Note for 18.1.c.
Discuss instances in fieldwork where differences in species abundance or
distribution occurred (or provide examples). Explain that the next step is to find out if
these correlate with some factor, either biotic or abiotic (see 18.1.a).
o Explain the measure of association between two variables ranges from
completely negatively correlated, -1, to completely positively correlated, +1; the
closer to these values, the stronger the relationship.
o Explain that a statistical test cannot confirm a relationship between the two, but
can lends support to it. (W) (Basic)
Discuss situations when Pearson’s linear coefficient calculation is carried out: when
there is interval (quantitative) data that shows a linear relationship and a statistical
assessment of the strength of the correlation is required (e.g. data plotted on a
Practical booklet 11
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.statstutor.ac.uk/topics/corre
lation/pearsons-correlationcoefficient/
http://www.statstutor.ac.uk/topics/corre
lation/spearmans-correlationcoefficient/
http://www.heckgrammar.co.uk/index.p
hp?p=10310
85
Learning objectives
Suggested teaching activities
Learning resources
scattergraph; a ‘by-eye’ judgment of correlation is not always reliable). (W)
(Challenging)
o Learners work through an example, with guidance, starting with a null hypothesis
statement before using the formula to calculate the Pearson product moment
correlation. Learners use a table of critical values to reject or accept the null
hypothesis and make a statistically valid statement about the strength of the
correlation and its significance. (W) (I) (Basic) (Challenging)
Explain that if one variable increases and the other increases (or decreases) then
Spearman’s rank correlation can be carried out, even if the relationship is non-linear,
and that ordinal data can also be used with this test. (W) (Challenging)
o Work through examples with learners, as with Pearson’s test, and discuss how
to use Spearman’s table. (W) (I) (Basic) (Challenging)
Learners analyse relationships by practising a number of different examples using
either Spearman’s rank correlation or Pearson’s linear correlation.
o Learners then work with calculated values to analyse the data and make
judgements about the strength of the relationship. (I) (Basic) (Challenging)
Discuss how correlation does not imply causation, e.g. abundance of a plant species
appears to decrease with increasing altitude. Applying caution with cause and effect
would consider other factors that change with altitude (oxygen concentration,
temperature, soil nutrients etc.). (W) (Basic)
Textbooks/Publications
Bio Factsheet 144: Spearman’s rank
correlation coefficient.
Note
Learners should work through examples themselves before using other resources
available to them.
Learners could use spreadsheet software to enter the relevant figures and obtain a
scattergraph and the final calculated value, and then explain what the results are
showing. You could set up spreadsheets of data for learners to access (see learning
resources).
Practical booklet 11 includes the chi-squared test for association. This is another
use in addition to the ‘goodness of fit’ test (see 16.2.d).
18.1.f
use Simpson’s Index of Diversity (D) to
calculate the biodiversity of a habitat,
using the formula D = 1–(Σ(n/N)2) and
state the significance of different
values of D
v2.1 5Y02
See Note for 18.1.c.
Explain that Simpson’s Index of Diversity gives an overall measure of diversity by
taking into account the number of different species in a sample and the abundance
of each species.
o Explain that a high D value represents high biodiversity, indicating a high
number of species, evenly spread for abundance. The value of D goes down if
there are fewer species, or if, for example, one or a few species are very
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 11
Online
http://www.countrysideinfo.co.uk/simps
ons.htm
http://www.nuffieldfoundation.org/appli
ed-science/ecology-and-simpsons-
86
Learning objectives
Suggested teaching activities
Key concepts
Organisms in their environment,
Observation and experiment
abundant and others are very rare.
o Discuss how this can be used to compare biodiversity over time in any one area.
(W) (Basic)
Learners use their fieldwork data (or be given data) to calculate a biodiversity value
and state its significance. (I) (Challenging)
18.3.a
discuss the threats to the biodiversity
of aquatic and terrestrial ecosystems
(see 18.1 b)
Key concepts
Organisms in their environment,
Observation and experiment
To check understanding of the terms, learners give examples of specific local
terrestrial and aquatic ecosystems. (W) (Basic)
Discuss the global food and energy demands (from increasing population size,
developing nations and increasing industrialisation) that may affect ecosystems (also
to a lesser extent, demand for ‘living’ space). (W) (Basic)
o Learners consider these factors on a local basis, suggest ways to satisfy these
demands and consider the consequential effects of this action on one chosen
local terrestrial or aquatic ecosystem. (P) (Challenging)
o Point out that global effects, such as climate change and global warming can still
affect at a local level. (W) (Basic)
o Learners add their ideas to master sheets headed, ‘demand for food’, ‘demand
for energy’ and ‘demand for living space’ (each sheet divided vertically into
‘terrestrial ecosystems’ and ‘aquatic ecosystems’) and follow up with a class
discussion. It is highly likely that their ideas will reflect what is happening
globally. (W) (Basic)
Learners produce a general list, using local and global examples to help explain
each point. (H) (Challenging)
Note
The effect of introducing alien species into an ecosystem is also an important
feature, covered in 18.3.f (you may prefer to teach 18.3.f with 18.3.a).
17.3.e
explain why organisms become
extinct, with reference to climate
change, competition, habitat loss and
killing by humans
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
Discuss what is meant by extinction, pointing out that it is a natural process and part
of the theory of evolution by natural selection (see Unit 7).
o Explain that there is a threshold number below which extinction is inevitable.
o Learners suggest why species become extinct (check that those referenced in
17.3.e are covered). (W) (Basic)
Learners find examples (relevant to them) of plant and animal species that have
become extinct or are near extinction for the reasons listed in 17.3.e and produce
poster displays. (G) (P) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
diversity-index
Textbooks/Publications
Bio Factsheet 34: Species diversity
Online
http://evolution.berkeley.edu/evolibrary
/news/120301_chipmunks
http://www.wri.org/resources/maps
http://www.iucnredlist.org/initiatives/fre
shwater/panafrica/threats
http://www.biodiv.be/biodiversity/threat
s
http://environment.nationalgeographic.
co.uk/environment/
Textbooks/Publications
Bio Factsheet 27: Biological effect of
deforestation
Bio Factsheet 203: Climate change
and ecological decoupling
Bio Factsheet 197: Biology of coral
reef ecosystems
Past Papers
Paper 41, June 2011, Q8 (a)(b)
Online
http://www.bbc.co.uk/lastchancetosee/
sites/about/extinction.shtml
http://www.iucnredlist.org/
Past Papers
Paper 43, June 2011, Q1 (a)
87
Learning objectives
Suggested teaching activities
Learning resources
18.3.b
discuss the reasons for the need to
maintain biodiversity
Learners research the reasons to maintain biodiversity. (H) (Basic)
o In a follow-up discussion include the following ideas: maintenance of gene pools;
preservation of genetic diversity; applications of the use of gene technology (see
Unit 8); current and new uses of organisms; discovery of new species (may have
use in the future); aesthetic and spiritual benefits; practical value of animals (e.g.
dolphins helping autistic children); the awe of the vast range of organisms, their
attractive or unusual appearances and different methods of survival. (W) (Basic)
Agree some main categories, e.g. genetic, future uses, current uses, spiritual /
aesthetic, etc. (W) (Basic)
o Learners place each idea on the list in the correct category, with an
accompanying explanation. (I) (Challenging)
Online
http://www.nationalgeographic.com/xp
editions/lessons/08/g68/preserve.htm
l
http://www.davidsuzuki.org/search/?q=
biodiversity&x=0&y=0
http://wwf.panda.org/about_our_earth/
biodiversity/biodiversity/
Key concepts
Organisms in their environment,
Observation and experiment
Textbooks/Publications
Bio Factsheet 224: Why we need
biodiversity
Past Papers
Paper 41, June 2012, Q6 (b)(ii)
Paper 41, June 2013, Q9 (a)
Paper 43, Nov 2013, Q5 (a)(iii)
Online
http://wwf.panda.org/
http://www.cites.org/
Key concepts
Organisms in their environment,
Observation and experiment
Learners suggest what is meant by ‘NGOs’. Discuss the advantages of nongovernmental organisations, such as greater cooperation between nations,
international agreements that can be reached sooner than inter-governmental
agreements.
o Introduce WWF and CITES.
o Learners are shown or browse CITES Appendices I, II and III. (W) (Basic)
Learners check the websites or read summary print-out sheets to become familiar
with a variety of NGOs active in conservation.
o Agree a definition for the term ‘conservation’. (W) (Basic)
o Learners write a short account summarising the role of the WWF and CITES and
the benefits of NGOs in general. They could also add details of a local
conservation group. (H) (Basic)
18.3.c
discuss methods of protecting
endangered species, including the
roles of zoos, botanic gardens,
conserved areas (national parks and
marine parks), ‘frozen zoos’ and seed
Introduce the International Union for Conservation of Nature (IUCN). Discuss what is
meant by the term ‘endangered’ (refer learners to work on biodiversity).
o Discuss (or display the IUCN web page) the criteria used to classify an organism
as endangered. (W) (Basic)
o Learners write a definition of the term ‘endangered’, researching a named
example and include the species name and the reasons for it being endangered.
Online
http://www.iucn.org/knowledge/tools/
http://www.iucnredlist.org/
https://worldwildlife.org/species/directo
ry?direction=desc&sort=extinction_st
atus
18.3.g
discuss the roles of non-governmental
organisations, such as the World Wide
Fund for Nature (WWF) and the
Convention on International Trade in
Endangered Species of Wild Fauna
and Flora (CITES), in local and global
conservation
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
88
Learning objectives
Suggested teaching activities
banks
Key concepts
Organisms in their environment,
Observation and experiment
(H) (Basic)
o Learners findings are shared in a class presentation. (W) (Basic)
Learners refer to the species identified in their fieldwork for 18.1.d and use the IUCN
Red List to determine their category. (I) (Basic)
Discuss what is meant by a frozen zoo and a seed bank. (W) (Basic)
o Learners research the variety of methods employed to help protect endangered
species in one of: zoos, botanic gardens, national parks, marine parks. Include
any advantages or disadvantages of each method. (G) (Basic) (Challenging)
o Learners produce a summary sheet of their research to share with the class. (W)
(G) (Challenging)
o Produce one card for each member of the group. On each card write one of the
categories listed (zoo, national park etc.). Give out the cards randomly. Learners
give a written outline of methods used to protect endangered species. (F)
Learners research local and national efforts to protect endangered named species.
(H) (Basic)
With reference to genetic improvement and the maintenance of the gene pool,
learners research examples of wild relatives of crop plants, landraces of crop plants
and rare breeds of livestock. (H) (Basic)
A visit to a national park, nature reserve, zoo or botanic garden will enable learners
to see the work that is being done locally or nationally.
Note
Point out that the IUCN list does not cover all groups of organisms.
Learning resources
http://www.endangeredspecie.com/
http://www.kew.org/index.htm
http://www.zsl.org/conservation/
http://www.petermaas.nl/extinct/index.
html
http://www.eoearth.org/topics/view/495
13/
http://www.bbsrc.ac.uk/society/schools
/secondary/extinct.aspx
http://www.satavic.org/biodiversity.htm
http://www.jic.ac.uk/corporate/about/pu
blications/substainable.pdf
http://www.sandiegozooglobal.org/wha
t_we_do_banking_genetic_resources
/frozen_zoo/
http://animals.nationalgeographic.co.uk
/animals/conservation/
Textbooks/Publications
Bio Factsheet 65: Conservation
Bio Factsheet 208: Captive breeding
and the role of zoos
Past Papers
Paper 43, Nov 2011, Q1 (a)(b)
Paper 42, June 2012, Q6 (a)
18.3.d
discuss methods of assisted
reproduction, including IVF, embryo
transfer and surrogacy, used in the
conservation of endangered mammals
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Explain that humans can assist reproduction in endangered mammals and, with
learner input, discuss the techniques involved.
o Learners suggest the considerations when deciding that assisted reproduction
should be used, such as: research to decide on appropriate method (not always
easy to study reproduction in rare mammals); modify technique to be specific to
the mammal; evaluating success. (W) (Basic)
Learners make notes, using resources, outlining the main stages and the main
principles involved. (I) (Challenging)
o Learners apply the principles to examples they have been given or have
researched. (H) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.cvmbs.colostate.edu/bms/P
DF/640_RM_endangsld.pdf
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/S/Sexual_Reproduct
ion.html#ART
http://www.eplantscience.com/index/bi
otechnology/animal_biotechnology/m
anipulation_of_reproduction_and_tra
nsgenic_animals/biotech_in_vitro_fert
ilization_technology.php
89
Learning objectives
Suggested teaching activities
Learning resources
Learners could be asked to sort statements, some irrelevant to be discarded, to end
up with a set of notes that could be used as a summary of assisted reproduction. (I)
(Basic)
http://nationalzoo.si.edu/SCBI/reprodu
ctivescience/consendangeredcats/
Note
Learners may have included ideas from this in their research for 18.3.c.
Although this learning objective is about endangered mammals, not about assisted
reproduction for humans, the techniques are similar and learners may gain useful
information by researching them.
18.3.e
discuss the use of culling and
contraceptive methods to prevent
overpopulation of protected and nonprotected species
Key concepts
Organisms in their environment,
Observation and experiment
18.3.f
use examples to explain the reasons
for controlling alien species
Key concepts
Organisms in their environment,
Observation and experiment
Past Papers
Paper 41, June 2011, Q3 (a)
Paper 42, June 2013, Q5
Ensure learners know what is meant by the two terms, and then explain that there
are frequently debates about the issue, including deciding when a population is
considered to be ‘over-populated’. (W) (Basic)
Learners research examples meaningful to them, including the different reasons
given to either culling or use of contraceptive methods, and explaining why one
method was favoured. (I) (Basic)
Provide new examples: learners write a short article weighing up the advantages
and disadvantages of culling versus contraceptive methods. (F)
Organise a mini debate. (W) (H) (Basic) (Challenging)
Online
http://www.tams.act.gov.au/parksrecreation/plants_and_animals/urban
_wildlife/local_wildlife/kangaroos/kan
garoo_population_control_methods
http://www.egzac.org/whyusecontrace
ption.aspx
http://www.ceru.up.ac.za/elephant/faqs
.php
Note
Stress that learners will need to develop the ability to apply principles to new
situations
Textbooks/Publications
Bio Factsheet 65: Conservation.
Discuss how, in many ecosystems throughout the world, the introduction of alien
species has had harmful economic or ecological effects (termed ‘alien-invasive’
species). Balance this with a discussion of how some alien species have been of
benefit. (W) (Basic)
Learners research examples of alien species (local, national and global) that are
now considered unwelcome, and for each explain the reasons for controlling them.
(H) (Basic)
Online
http://www.birdlife.org/worldwide/progr
ammes/invasive-alien-species
http://eol.org/info/460
http://www.galapagos.org/conservation
/invasive-species/
Note
This may have been discussed with 18.3.a.
Some agencies give ‘alien’ and ‘exotic’ slightly different meanings, others use them
interchangeably. Also seen are ‘non-indigenous’, ‘non-native’ and ‘introduced’.
v2.1 5Y02
Textbooks/Publications
Bio Factsheet 105: Manipulation and
control of reproduction.
Some parts of this are relevant.
Cambridge International AS & A Level Biology (9700) – from 2016
Past papers
Paper 41, June 2011, Q8 (a)(b)
90
Learning objectives
Suggested teaching activities
Learning resources
18.3.h
outline how degraded habitats may be
restored with reference to local or
regional examples
Discuss the concept of restoration ecology and the need for scientific planning and
understanding when restoring degraded habitats or ecosystems. (W) (Basic)
Learners research one example and present their findings to the group. (W) (I)
(Challenging). Points to consider:
o A description of the habitat before degradation.
o Reasons for the degradation and what may happen if degradation continues.
o What could be / is being carried, with overall aims, e.g. re-establishing what was,
improving by addition of species or physical factors, modifying to create a new
habitat.
o The benefits to the community of restoration.
Online
http://en.wikipedia.org/wiki/Restoration
_ecology
http://www.ser.org/
http://www.nature.com/scitable/knowle
dge/library/restoration-ecology13339059
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
91
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 7: Genetics, population genetics and evolutionary processes
Recommended prior knowledge
Learners should have a good knowledge and understanding of the mitotic cell cycle from Unit 3. They should be able to describe the structure of DNA and the events
occurring in DNA replication, in transcription and in translation from Unit 3, including an understanding of the genetic code. Learners should have a good understanding
of what is meant by a gene, an allele and a gene mutation. An appreciation of the diversity of life, from Unit 6, will stimulate interest in how diversity has come about.
Context
This unit builds on AS Level work, especially Unit 3, DNA and the mitotic cell cycle. It leads on from Unit 6, The diversity of life, so that learners are provided with an
explanation of how the mechanisms of natural selection and isolation can lead to the formation of new species. This unit strongly incorporates the key concepts of cells
as the basic units of life, biochemical processes, DNA, the molecule of heredity and observation and experiment. Knowledge and understanding gained in this unit will
be particularly useful for Unit 8, Molecular biology and gene technology.
Outline
The unit begins with an introduction to ideas and terms that will be needed. The mechanism and significance of meiosis is dealt with, showing how genetic information
passes from parent to offspring. A link is made to gamete formation in animals and plants. Genetic crosses are practised and the chi-squared test is used. The nature of
genes and alleles and their role in determining the phenotype is discussed, including human conditions that result from gene mutations. Once an understanding of basic
genetics is gained, the unit leads to a consideration how the passage of information from parent to offspring is translated to population genetics. Variation, and its
importance for the mechanism of natural selection, is studied before considering the role of natural selection in evolution and speciation. Natural selection is a key
concept in biology, with mutation acting as the raw material for evolution. The unit considers how selection pressures allow successful individuals to survive to pass on
genes to the next generation and how changes in the genetic make-up of the population, coinciding with isolation, can lead to speciation. The key concept of
observation and experiment is exemplified by studying the improvement of the milk yield of dairy cattle and the improvement of crop plants by humans. Humans can
apply the principles of natural selection to artificial selection and speed up the process of biological change.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
92
Learning objectives
Suggested teaching activities
Learning resources
16.1.a
explain what is meant by homologous
pairs of chromosomes
Introduce the topic explaining that a fertilised egg cell will have a set of
chromosomes from the mother and a set from the father, to give pairs of
chromosomes in cells. (W) (Basic)
Discuss the features of homologous chromosomes. (W) (Basic)
o Learners list the similarities and differences between a pair of homologous
chromosomes and note the differences between the X and Y chromosomes. (I)
(Basic)
Online
http://www.nature.com/nature/journal/v
423/n6942/fig_tab/423810a_F1.html
Key concepts
DNA, the molecule of heredity
Note
Avoid using 46 chromosomes and 23 pairs of chromosomes in explanations (also for
16.1.b): a common error is stating these when answering questions about other
organisms.
The term bivalent is the same as one pair of homologous chromosomes.
16.1.b
explain the meanings of the terms
haploid and diploid and the need for a
reduction division (meiosis) prior to
fertilisation in sexual reproduction
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
From 16.1.a, explain that cells with one set of chromosomes are termed haploid (n),
and a particular species has a specific haploid number. Extend this to explain the
term diploid (2n). (W) (Basic)
o Discuss why a diploid organism needs a reduction division (meiosis) to produce
haploid cells. Use phrases such as ‘restore the diploid number on fertilisation’,
‘to avoid doubling the number of chromosomes’. (W) (I) (Basic)
Extension: learners outline the differences between asexual and sexual reproduction
and between asexual reproduction in eukaryotes and asexual reproduction in
prokaryotes (background information - refer to binary fission). (H) (Challenging)
Online
http://www.accessexcellence.org/RC/V
L/GG/ecb/haploiddiploid_sexual_reproduction.php
Note
Do not go into details of meiosis for this learning objective.
Mention that some organisms only have one set of chromosomes, while others have
one set for some part of their life cycle
16.2.a (i)
explain the terms gene, locus, allele,
dominant, recessive, codominant,
linkage, test cross, F1 and F2,
phenotype, genotype, homozygous
and heterozygous
Key concepts
Biochemical processes,
v2.1 5Y02
Only part of this learning objective is included here: explain the terms gene, locus,
allele, dominant, recessive, phenotype, genotype, homozygous and heterozygous
Learners recall previous studies:
gene 6.2.a definition
allele 6.2.b concept of new alleles forming by mutation
6.2.c HbA and HbS alleles.
Use pipe cleaner or string models, with sticky labels for alleles, to help explain gene,
allele, locus, dominant, recessive, heterozygous, homozygous, genotype, then
discuss the meaning of phenotype. (W) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biology.arizona.edu/vocabul
ary/mendelian_genetics/mendelian_g
enetics.html
http://www.genome.gov/glossary/index
.cfm?id=8
Textbooks/Publications
Bio Factsheet 156: Dominant and
93
Learning objectives
Suggested teaching activities
Learning resources
DNA, the molecule of heredity
Learners write definitions for the terms and draw diagrams of homologous
chromosomes to annotate locus and allele and, using examples, draw homologous
chromosomes with different genotypes (homozygous alleles and heterozygous
alleles; dominant and recessive), indicating the phenotype. (I) (Challenging)
Learners match a set of cards with terms to a second set with definitions. (F)
Recessive Alleles.
Bio Factsheet 45: Gene expression
Past Papers
Paper 41, Nov 2011, Q9 (a)
Note
It is useful to introduce the term early so learners can correlate the behaviour of
chromosomes in meiosis and the formation of gametes with allele behaviour (and
enhance understanding of genetic crosses).
16.1.c
outline the role of meiosis in
gametogenesis in humans and in the
formation of pollen grains and embryo
sacs in flowering plants
Key concepts
Cells as the units of life
State that meiosis involves two divisions to produce four cells. Explain what is meant
by the term ‘gamete’. Highlight the role of meiosis in terms of a reduction division
and the production of genetically different cells. (W) (Basic)
Using resources, learners write out a definition and give an outline of
gametogenesis, naming the ovary and testis as the organs involved and including
the role of meiosis. (I) (Challenging)
Learners draw a fully labelled human life cycle. (I) (Basic)
Using resources and teacher input, learners produce annotated diagrams to outline
the formation of pollen grains and embryo sacs.
o Diploid pollen mother cells in pollen sacs (in the anther) divide by meiosis to
form 4 haploid microspores. These mature to become pollen grains (details of
mitosis not required.
o In the ovule the megaspore mother cell divides by meiosis to form 4 haploid
megaspores: one survives to divide by mitosis to produce an eight-nucleate
embryo sac. (I) (Challenging)
Learners compare the main similarities and differences between gametogenesis in
humans with pollen grain and embryo sac formation in plants.
o Include a flow chart diagram to highlight the stages where meiosis and mitosis
occur. (H) (Challenging)
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter28/animation__unique_fe
atures_of_meiosis.html
http://wps.prenhall.com/esm_freeman_
biosci_1/0,6452,501052-,00.html
http://highered.mcgrawhill.com/sites/0072495855/learner_vi
ew0/chapter28/animation__spermato
genesis__quiz_1_.html
Textbooks/Publications
Bio Factsheet 168: Gamete Formation
in Animals
Note
Details of ovary and testis histology are not required.
Learners should be familiar with the terms oogenesis and spermatogenesis.
16.1.d
describe, with the aid of
photomicrographs and diagrams, the
v2.1 5Y02
With a short written test (prepared by you, with mark scheme), assess learner recall
of mitosis. (F)
Show learners diagrams or photographs of an ordered haploid chromosome set
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologymad.com/CellDivisio
n/CellDivision.htm
94
Learning objectives
behaviour of chromosomes in plant
and animal cells during meiosis, and
the associated behaviour of the
nuclear envelope, cell surface
membrane and the spindle (names of
the main stages are expected, but not
the sub-divisions of prophase)
Suggested teaching activities
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
16.1.e
explain how crossing over and random
assortment of homologous
chromosomes during meiosis and
random fusion of gametes at
fertilisation lead to genetic variation
including the expression of rare,
recessive alleles
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
v2.1 5Y02
(karyotype), e.g. human sperm and egg to review knowledge of homologous
chromosomes, haploid, diploid, sex chromosomes. (W) (Basic)
Learners model meiosis with teacher guidance. Use pipe cleaners (or string or wool)
to demonstrate the behaviour of 4 chromosomes. Explain the use of e.g. one
homologous pair (i.e. maternal and paternal) = 2 (sister chromatids) light blue and 2
dark blue pipe cleaners; the second homologous pair use a different colour, light and
dark.
o Learners model late interphase (DNA replication means 1 pipe cleaner becomes
2 identical) before moving onto the stages of meiosis. Learners suggest ‘what
happens next’ and explain why each stage occurs.
o At the appropriate points explain the concepts of chiasmata formation, crossing
over and independent assortment. (P) (I) (Basic) (Challenging)
o Learners model meiosis (no help, noting the comparisons with mitosis (correct
spellings). (P) (I) (Challenging)
Learners study prepared slides, photomicrographs and diagrams. (I) (Basic)
Learners draw a series of annotated diagrams, or annotate prepared diagrams. (I)
(Basic)
Learners construct a table of differences between mitosis and meiosis or sort a set
of statements into comparative statements, into two columns. (I) (Basic)
(Challenging)
Learners recall their understanding of a gene and an allele. Emphasise the
importance of using the terms in the correct context. (W) (Basic)
Use the pipe cleaner models of a homologous pair (label ‘A’ on each chromatid of
one homologue and label ‘a’ on each chromatid of the other) to explain how
reduction division separates the two alleles of a gene.
o Mention how this creates variation when gametes fuse randomly at fertilisation.
o Discuss how this allows rare recessive alleles to come together. (W) (Basic)
Choose two different organisms, e.g. fruit fly (n=4) and humans. Using 2n, learners
work out how many different types of gamete could be formed with two homologous
pairs assorting randomly and independently at metaphase I of meiosis. (I)
(Challenging)
Make a pipe cleaner / string model for a second homologous pair using ‘B’s and ‘b’s.
Learners show how random assortment in one cell can produce AB and ab gametes,
and in another Ab and aB gametes.
o Using this example, learners explain how random fusion contributes to variation.
o Learners draw annotated diagrams to illustrate the concepts. (W) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
www.biology.arizona.edu/cell_bio/tutori
als/meiosis/page3.html
http://www.biologyinmotion.com/cell_di
vision/index.html
http://www.sumanasinc.com/webconte
nt/animations/content/meiosis.html
http://www.cellsalive.com/meiosis.htm
Textbooks/Publications
Bio Factsheet 50: Sources of genetic
variation.
Past Papers
Paper 43, June 2011, Q7 (a)
Online
http://www.biologymad.com/CellDivisio
n/CellDivision.htm
www.biology.arizona.edu/cell_bio/tutori
als/meiosis/page3.html
http://www.biologyinmotion.com/cell_di
vision/index.html
http://www.sumanasinc.com/webconte
nt/animations/content/meiosis.html
http://www.cellsalive.com/meiosis.htm
http://www.biozone.co.uk/biolinks/GEN
ETICS.html#Inheritance
http://www.contexo.info/DNA_Basics/M
eiosis.htm
http://www.sumanasinc.com/webconte
nt/animations/content/independentas
95
Learning objectives
Suggested teaching activities
Add labels (‘alleles’) ‘D’ to the homologue with ‘A’ genes, and ‘d’ to the homologue
with ‘a’ genes. Explain that if the genes are on the same chromosome, they are said
to be linked.
o Demonstrate crossing over to show how this can lead to even more variation in
the gametes (AD, ad = parental: Ad, aD = recombinant).
o Explain that the longer the chromosome pair, the greater the number of possible
crossovers.
o Learners draw annotated diagrams to illustrate the concept. (W) (Challenging)
Learners give written and diagrammatic descriptions of random assortment, crossing
over and random fusion, explaining how each of these leads to genetic variation. (F)
Learning resources
sortment.html
Past Papers
Paper 43, June 2011, Q7 (b)
Note
Explain that homologous pairs assort randomly at metaphase I and this means they
are assorting independently of other homologous pairs.
16.2.a (ii)
explain the terms gene, locus, allele,
dominant, recessive, codominant,
linkage, test cross, F1 and F2,
phenotype, genotype, homozygous
and heterozygous
Key concepts
Biochemical processes,
DNA, the molecule of heredity
v2.1 5Y02
Only part of this learning objective is included here: explain the terms codominant,
linkage, test cross, F1 and F2
Using the pipe cleaner / string models, discuss the meaning of the term codominant.
(W) (Basic)
Remind learners of a simple monohybrid cross from previous studies and using the
terms already discussed show what is meant by F1 and F2. Briefly explain a test
cross for learners to define. (W) (I) (Basic)
Learners match a set of cards with terms from 16.2.a to a second set with all the
definitions. (F)
Note
These definitions are best understood when tackling 16.2.b.
A full explanation of test cross should be reserved for later.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biology.arizona.edu/vocabul
ary/mendelian_genetics/mendelian_g
enetics.html
http://www.genome.gov/glossary/index
.cfm?id=8
Textbooks/Publications
Bio Factsheet 156: Dominant and
Recessive Alleles.
Bio Factsheet 45: Gene expression
96
Learning objectives
Suggested teaching activities
Learning resources
16.2.b
use genetic diagrams to solve
problems involving monohybrid and
dihybrid crosses, including those
involving autosomal linkage, sex
linkage, codominance, multiple alleles
and gene interactions (the term
epistasis does not need to be used;
knowledge of the expected ratio for
various types of epistasis is not
required. The focus is on problem
solving)
Using resources, learners write out what is meant by a monohybrid cross and a
dihybrid cross, and explain what is meant by true (or pure) breeding, multiple alleles,
pedigree diagrams, autosomal chromosome and sex chromosome. (I) (Basic)
Monohybrid cross: using a visual (photographs/drawings) simple example (e.g.
purple and white flowers in pea plants), demonstrate how to set out a genetic
diagram (circles should be drawn around the gametes).
o Learners explain why they can be certain of the genotype if a pea plant has
white flowers.
o Explain test crosses. (W) (Basic)
o Learners work though one problem themselves and peer-check the quality of the
genetic diagrams. (I) (Basic)
Learners construct genetic diagrams, working through monohybrid cross problems,
including pedigree diagrams. Learners also performing test crosses. (P) (I) (F)
(Basic) (Challenging)
Codominance: describe an example of codominance and the convention to
represent this (alleles as superscripts). Many examples involve a ‘colour’ gene:
ensure learners know that C is for colour, not codominance.
o Go through the different ratios obtained and ask learners to explain why no test
cross is required. (W) (Basic)
o Learners work through some codominance problems (monohybrid crosses). (I)
(Basic) (Challenging)
Multiple alleles: as an example, discuss the inheritance of human blood groups
(ABO system) to illustrate multiple alleles, dominance, recessiveness and
codominance before learners work through problems. (W) (I) (Challenging) (Basic)
Sex linkage: describe the largely non-homologous X and Y chromosomes to explain
why the male genotype has only one allele for genes located on sex chromosomes.
o Using an example of a sex-linked trait, e.g. eye colour in Drosophila, explain how
to annotate the allele symbol as a superscript by the X (Y- shows that the allele
is absent in the Y chromosome). (W) (Basic)
o Learners write down the possible genotypes for this trait, then tackle a
monohybrid cross problem, covering the reciprocal cross. (I) (Basic)
o Emphasise that not all problems indicating numbers of individuals of each sex,
or stating ‘female crossed with male’ will be sex-linked inheritance. (W) (Basic)
o Learners state and explain the pattern of inheritance associated with sex-linkage
and then practise questions. (I) (Challenging)
Learners model using pipe cleaners / string, or draw diagrams, to show how a
written genetic cross correlates to events occurring at meiosis and fertilisation. (P) (I)
Online
http://learn.genetics.utah.edu/content/i
nheritance/
http://www.dnaftb.org
http://www.biology.arizona.edu/mendel
ian_genetics/mendelian_genetics.htm
l
http://faculty.baruch.cuny.edu/jwahlert/
bio1003/genetics.html
http://www.utilitypoultry.co.uk/sexlinkag
e.shtml
http://udel.edu/~mcdonald/mythintro.ht
ml
http://www.pc.maricopa.edu/Biology/rc
otter/BIO%20181/Lab/181Labpdf/10
MendelianGenetics.pdf
http://www.mendelmuseum.com/eng/1online/experiment
.htm
http://www.sumanasinc.com/webconte
nt/animations/content/mendel/mendel
.html
http://www.learnerstv.com/animation/a
nimation.php?ani=2&cat=Biology
Key concepts
DNA, the molecule of heredity,
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 23: Genetics made
simple: I
Bio Factsheet 97: A guide to sex
linkage
Bio Factsheet 93: The ABO Blood
Group System
Bio Factsheet 183: Variations from
expected Mendelian Monohybrid
Ratios.
Bio Factsheet 115: Answering
Examination Questions: Genetics
97
Learning objectives
Suggested teaching activities
Learning resources
(Challenging)
Dihybrid cross: explain that these involve two genes located on non-homologous
chromosomes (unlinked / separate linkage groups). Work through a dihybrid cross,
e.g. Mendel’s pea plants, showing how to write out genotypes e.g. AaBb and not
ABab. (W) (Basic)
o Learners work out the possible gametes from crossing the double
heterozygotes. Guide learners how to construct a Punnett square and complete
it correctly before they work out the phenotypic ratio (explain that 9:3:3:1 still fits
the 3:1 monohybrid crosses ratio: each gene shows a 12:4 ratio). Learners work
through a test cross. (W) (I) (Challenging)
Linkage: remind learners of the concept of linkage and of crossing over (16.1.e)):
two linked genes involve only one homologous chromosome pair. Using a model or
diagrams, explain how linked genes could result in both parental and recombinant
types in the gametes and offspring, but not in the standard Mendelian ratios.
o Discuss why genes close together will produce few, if any, recombinant types
(the further apart the greater proportion of recombinant to parental types). (W)
(Challenging)
Learners tackle a range of differentiated questions involving two genes. (I) (F)
(Basic) (Challenging)
Past Papers
Paper 43, June 2011, Q9 (b)
Paper 41, June 2012, Q7
Note
The terms backcross and incomplete dominance are no longer used.
There are two approaches: (i) cover the theory of the learning objective, then
learners work on genetics problems or (ii) have a set of problems prepared for each
type of cross and learners practise these as they are taught.
Some human genetic traits used as examples in schools are now known to be more
complex than at first thought, Learners should be discouraged from analysing
patterns of inheritance in their family.
16.2.c
use genetic diagrams to solve
problems involving test crosses
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
This learning objective is covered in 16.2.b.
Consolidate by agreeing that a test cross should be performed to find out the
genotype of an organism that is known to have a dominant trait but could be
homozygous dominant or heterozygous. (W) (Basic)
Note
Learners should appreciate the advantage of carrying out test crosses in terms of the
ratios between the phenotypic classes when compared to a cross involving two
heterozygotes.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/i
nheritance/
http://www.dnaftb.org
http://www.mendelmuseum.com/eng/1online/experiment
.htm
98
Learning objectives
Suggested teaching activities
Learning resources
16.2.d
use the chi-squared test to test the
significance of differences between
observed and expected results (the
formula for the chi-squared test will be
provided) (see Mathematical
requirements)
Revise different ratios obtained with the different types of genetic cross,
emphasising that these are theoretical (based on probability) ratios.
o Learners mentally calculate expected numbers from totals e.g. with 40 offspring,
how many of each if expecting a 3:1 ratio? (W) (Basic)
Approach the concept using observed results: learners suggest and justify the type
of genetic cross when given actual genotype numbers, e.g. codominance, for a ratio
of 32 red, 26 pink, 10 white flowers (ratio approximating 1:2:1). (W) (Basic)
o Learners debate a result of: 15 red, 20 pink, 13 white. Agree that a statistical test
is needed to compare the observed ratio to the expected: near enough for
differences to be due to chance effects or so different that other factors should
be considered. (W) (Challenging)
Practical booklet 11. Work through, with guidance (if not covered in 18.1.e, in the
context of field study), examples of the use of the chi-squared test. (I) (Basic)
Learners use a calculated chi-squared value to:
o State the critical value at a stated probability level.
o State where the chi-squared value fits in the range of probabilities.
o Make a conclusion, referring to a null hypothesis and significance level. (I)
(Basic) (Challenging)
Learners use results from a genetic cross (increasing difficulty)to:
o Practise the calculations involved in the chi-squared test
o Interpret the results to write a valid conclusion about the nature of the genetic
cross. (I) (Basic) (Challenging)
Note
See also the syllabus section, Mathematical requirements.
Learners should be able to:
o Identify the situations where the use of the test is applicable
o Use the table of critical values and state the probability of obtaining their results
by chance.
Learners should consider :
o The use of stating the actual probability value (p), which they can calculate using
software
o The probabilities of 0.05 and 0.01 (often used to report results).
Online
http://www.blc.arizona.edu/courses/mc
b422/MendelStarFolder/merChiSquar
e.html
Explain that biological variation describes the variation within a population (members
of the same species).
o Learners suggest examples of variation that is: inherited / genetic; not inherited /
environmental; likely to be due to both genetic and environmental sources.
Online
http://www.nature.com/scitable/knowle
dge/library/mutations-are-the-rawmaterials-of-evolution-17395346
Key concepts
Observation and experiment
17.1.a
describe the differences between
continuous and discontinuous variation
and explain the genetic basis of
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 79: The chi-squared test
for goodness of fit.
Past papers
Paper 43, Nov 2013, Q1
Paper 51, Nov 2011, Q2
Paper 53, Nov 2011, Q2
99
Learning objectives
Suggested teaching activities
Learning resources
continuous (many, additive genes
control a characteristic) and
discontinuous variation (one or few
genes control a characteristic)
(examples from 16.2.f) may be used to
illustrate discontinuous variation;
height and mass may be used as
examples of continuous variation)
o Explain the equation Vp = Vg +Ve, (no need to learn) and use an example (e.g.
blood groups) to show Ve = 0 when a trait is due only to genetic effects.
o Discuss the use of monozygotic twins, (Vg = 0), to study the effects of the
environment on variation. (W) (Basic)
Learners produce a list of causes of genetic variation for sexually reproducing
organisms and for asexually reproducing organisms (i.e. only mutation), as well as
causes of environmental variation (disease, edaphic factors, climate, water
availability, etc.). (I) (Challenging)
Using resources, learners define discontinuous variation (include a bar chart) and
continuous variation (include a histogram), and give examples. (I) (Basic)
o Learners consider a trait that has a genetic basis and describe what is likely to
be occurring to if the variation is (i) discontinuous (one/two genes), and (ii)
continuous (polygenic, environmental effects may also contribute). (I)
(Challenging)
http://www.nature.com/scitable/topicpa
ge/genomics-enables-scientists-tostudy-genetic-variability-6526364
http://www.bbc.co.uk/schools/gcsebite
size/science/edexcel_pre_2011/gene
s/genesrev1.shtml
Explain the situations where the t-test would be applicable and work through an
example. (W) (Basic)
Learners work through a number of examples, stating a null hypothesis and using a
table of critical values to state the probability of obtaining the result. (W) (I) (Basic)
(Challenging)
Learners choose from a list of outlines of investigations those for which the t-test
could be used. (F)
Practical booklet 10
Key concepts
DNA, the molecule of heredity,
Natural selection,
Organisms in their environment
17.1.c
use the t-test to compare the variation
of two different populations (see
Mathematical requirements)
Key concepts
Observation and experiment
Note
There is information about this test in the syllabus (Mathematical requirements
section).
Practical booklet 10 gives learners the opportunity to use the t-test on data that
they have collected themselves
Textbooks/Publications
Bio Factsheet 50: Sources of genetic
variation
Online
http://www.theseashore.org.uk/theseas
hore/Stats%20for%20twits/T%20Test
.html
http://archive.bio.ed.ac.uk/jdeacon/stati
stics/tress4a.html
Textbooks/Publications
Bio Factsheet 3: Which stats test
should I use?
Past papers
Paper 51, June 2012, Q1
Paper 52, June 2011, Q2
17.1.b
explain, with examples, how the
environment may affect the phenotype
of plants and animals
v2.1 5Y02
Learners recall the difference between genotype and phenotype and describe the
flow of information from DNA to the phenotype. (W) (Basic)
Explain that the term ‘environment’ encompasses everything that is not considered
genetic. (W) (Basic)
Learners research examples that they are given and provide explanations for the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.flowersbulbs.com/ql_hydran
gea_color.htm
http://www.nature.com/scitable/topicpa
ge/environmental-influences-on-
100
Learning objectives
Suggested teaching activities
Learning resources
Key concepts
DNA, the molecule of heredity,
Organisms in their environment
observations. (I) (Basic) (Challenging)
Learners research further examples and report back to the class. (H) (Basic)
gene-expression-536
http://www.nature.com/scitable/topicpa
ge/phenotypic-range-of-geneexpression-environmental-influence581
http://www.nature.com/scitable/content
/gene-environment-interactions-fromepidemiological-studies-33011
http://www.newscientist.com/article/dn
1520-iq-is-inherited-suggests-twinstudy.html
http://www.nature.com/scitable/topicpa
ge/the-collective-set-of-alleles-in-a6385985
16.2.e
explain that gene mutation occurs by
substitution, deletion and insertion of
base pairs in DNA and outline how
such mutations may affect the
phenotype
Use questioning to gauge knowledge of DNA structure, the definition of a gene
mutation, protein synthesis and protein structure. (W) (Basic)
Outline the changes that occur to give base substitution, deletion and insertion
mutations. Point out how frameshift mutations arise. Learners can produce summary
notes. (W) (Basic)
o Learners research and give an account of how a base substitution in the Hb A
allele to produce the Hb S allele leads to the altered amino acid in sickle cell
anaemia. (W) (Challenging)
o Learners work out the new amino acid sequences for examples of insertion and
deletion mutations and suggest how this could affect the protein synthesised
(include examples leading to premature stop codons). (I) (Challenging)
Discuss how it is possible that some changes in DNA nucleotide sequences have no
(e.g. same amino acid specified), or little (e.g. non-structural amino acid replaced)
consequential effects while others have profound effects. (W) (Challenging)
Extension: learners research examples of gene mutations resulting in cystic fibrosis
(differing severities). (W) (Challenging)
Online
http://www.dnaftb.org/dnaftb/27/conce
pt/index.html
http://www.who.int/genomics/public/ge
neticdiseases/en/index2.html
http://chroma.gs.washington.edu/outre
ach/genetics/sickle/
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/M/Mutations.html
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
Note
Focus on gene mutation, but alert learners to the existence of chromosomal
mutations (sections of chromosomes/many genes and chromosome number).
16.2.f
outline the effects of mutant alleles on
v2.1 5Y02
Learners construct a flow chart to show how a gene mutation can lead to symptoms
of sickle cell anaemia. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 94: Gene Mutations
Bio Factsheet 179: Answering Exam
Questions: Mutation
Past Papers
Paper 43, June 2011, Q9 (a)
Online
http://www.s-cool.co.uk/a-
101
Learning objectives
Suggested teaching activities
Learning resources
the phenotype in the following human
conditions: albinism, sickle cell
anaemia, haemophilia and
Huntington’s disease
Learners research one other condition from the list then work with others (that have
covered the same condition) to produce an information sheet to present to the class
to use as notes. (W) (G) (H) (Basic) (Challenging)
level/biology/evolution/reviseit/evolution-in-action
Notes on sickle cell anaemia.
Textbooks/Publications
Bio Factsheet 110: Genetic Disease in
Humans.
Key concepts
DNA, the molecule of heredity,
Organisms in their environment
16.2.g
explain the relationship between
genes, enzymes and phenotype with
respect to the gene for tyrosinase that
is involved with the production of
melanin
Provide information about the role of tyrosinase. Learners produce an annotated
flow diagram to illustrate the relationship between the gene, the enzyme and the
phenotype. (I) (Challenging)
Online
http://ghr.nlm.nih.gov/gene/TYR
Discuss how named examples of animals, plants and bacteria with different
genotypes and hence phenotypes (e.g. bacteria and antibiotic resistance) may differ
in their chances of survival or in their reproductive capacity. (W) (Basic)
Learners suggest why ‘more likely to survive to reproduce’ is more important for the
species than ‘more likely to survive’ (idea of passing on genetic information. (W)
(Basic)
Learners debate the advantages and disadvantages of asexual and sexual
reproduction. (G) (Basic)
Online
http://learn.genetics.utah.edu/content/v
ariation/sources/
http://darwiniana.org/evolution.htm
http://www.eoearth.org/article/Genetic_
variation
http://www.wellcometreeoflife.org/
Key concepts
Biochemical processes,
DNA, the molecule of heredity
17.1.d
explain why genetic variation is
important in selection
Key concepts
Natural selection
Note
Learners should have an outline of selection – covered in detail later.
17.2.a
explain that natural selection occurs as
populations have the capacity to
produce many offspring that compete
for resources; in the ‘struggle for
existence’ only the individuals that are
v2.1 5Y02
Introduce the idea that organisms have high reproductive potential and given ideal
conditions, exponential or explosive population growth occurs (starting with a few
individuals).
o Describe examples of ideal conditions and for each ask learners to suggest
phenotypes (and hence genotypes) that are more likely to survive (introduce the
term differential survival) if ideal conditions are not maintained.
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 43, Nov 2013, Q2 (c)
Online
http://www.bbsrc.ac.uk/web/FILES/Exh
ibitions/pod1-factsheet.pdf
http://www.biologycorner.com/workshe
ets/peppermoth_paper.html
http://www.accessexcellence.org/AE/A
102
Learning objectives
Suggested teaching activities
best adapted survive to breed and
pass on their alleles to the next
generation
Key concepts
Natural selection
o Remind learners of variation within a population and explain that some
organisms are better adapted to survive when selection pressures act to control
population size (most populations oscillate about a mean size).
o Explain that individuals that are better adapted to survive are said to be fitter
than those who do not have the adaptations. (W) (Basic)
Learners list examples of selection pressures and describe phenotypes that are
selected for and those selected against. (I) (Basic)
Learners summarise discussions with bullet-point notes and complete the idea of
natural selection with the following points:
o Individuals selected for pass on their alleles to their offspring when they
reproduce (differential reproduction)
o The frequency of the allele in the population increases. (I) (Challenging)
Explain that a gene pool describes the sum of all alleles for all the genes in a
population. (W) (Basic)
Explain that most mutations are not beneficial. Learners complete a worksheet
(prepared by you) describing and explaining changes to allele frequencies / the gene
pool following mutation: (a) if the mutation is not beneficial and is a (i) dominant
allele and (ii) recessive allele; (b) if environmental factors change and the mutation
becomes beneficial. (F)
Learners research examples of natural selection and produce a summary table:
example, different phenotypes involved, selection pressure(s) involved, adaptation
possessed, and additional notes.
o Suggestions: warfarin resistance in rats; melanism in peppered moths;
cyanogenic clover; antibiotic resistance in bacteria; resistance in insects to
insecticides. (H) (Challenging)
Learners choose one example from the summary table and write a sequential
account to explain how allele frequencies within a population can change. (F)
Learning resources
EPC/WWC/1995/camouflage.html
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/P/Populations2.html
http://www.eoearth.org/article/Populati
on_ecology
http://www.pbs.org/wgbh/evolution/libr
ary/01/2/l_012_02.html
www.biologyinmotion.com/evol/
http://anthro.palomar.edu/synthetic/syn
th_4.htm
Past Papers
Paper 43, June 2011, Q8
Note
Avoid using the phrase ‘survival of the fittest’ (different phenotypes can be equally
fit).
Background: take some time to discuss the work of Charles Darwin and Alfred
Russel Wallace.
An understanding of abiotic and biotic limiting factors and of density-dependent and
density-independent factors will be beneficial.
17.2.b
v2.1 5Y02
Explain that in most cases the environment remains relatively stable and so the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
103
Learning objectives
explain, with examples, how
environmental factors can act as
stabilising, disruptive and directional
forces of natural selection
Suggested teaching activities
same phenotype has a selective advantage in each generation.
Discuss how the environment acts as a stabilising force of natural selection, so that
selection pressures act to remove the extremes of the phenotype (e.g. birth weight in
human babies).
Discuss the other two modes of selection: directional, where allele frequencies
change in one direction (e.g. drug resistance in bacteria) and disruptive, where the
extremes of the phenotype are favoured (e.g. size of male Pacific salmon). (W)
(Basic)
Learners draw annotated graphs for each of stabilising, directional and disruptive
selection to show the frequency of phenotypes ‘before’, ‘during’ and ‘after’ a period
of time when selection occurred. (I) (Basic)
Learners research and describe one further example for each of the three types. (H)
(Challenging)
http://www.eoearth.org/article/Evolutio
n?topic=49508
http://www.blackwellpublishing.com/ridl
ey/a-z/Stabilizing_selection.asp
http://www.nature.com/nature/journal/v
313/n5997/abs/313047a0.html
Learners should consider how natural selection can affect the level of genetic
variation for any one heritable trait.
o Use an example (e.g. melanism in Biston betularia) to discuss how a different
set of selection pressures in a different environment affects allele frequencies
and leads to different outcomes for the population. (W) (Basic)
Learners research the link between sickle cell anaemia and malaria to describe and
explain the differences in allele frequencies between areas free of malaria and areas
where malaria is endemic. (H) (Challenging)
Learners use beads to model the effect on allele frequency in a population by
differential survival of two different genotypes for one gene.
o Place a large (known) number of beads of two different colours (alleles) in a
container (the population). Decide on a percentage survival rate for the
homozygous recessive genotype, e.g. 60%.
o Pick out pairs of beads at random, discarding four out of every ten pairs of
recessive beads. When all beads have been used, only replace the ones which
'survived' (not discarded) and repeat for the next generation.
o Record numbers of each genotype in each generation and construct graphs to
show the effect of selection over time. (G) (Challenging)
Introduce Darwin’s finches and outline the main points of the founder effect for
learners to summarise. (W) (I) (Challenging)
Explain that genetic drift involves chance effects, known as sampling errors, where
the allele frequencies of a small founding (ancestor) group are unlikely to be
Online
http://www.pbs.org/wgbh/evolution/libr
ary/06/3/l_063_03.html
http://www.nature.com/scitable/knowle
dge/library/natural-selection-geneticdrift-and-gene-flow-15186648
http://biology4.wustl.edu/cloverproject/
Assets/White%20Clover%20Backgro
und%20for%20Teachers.pdf
http://evolutiontextbook.org/content/free/notes/ch18
_WN18Dc.html
http://sickle.bwh.harvard.edu/malaria_s
ickle.html
http://wps.prenhall.com/esm_freeman_
evol_3/0,8018,849374-,00.html
http://evolution.berkeley.edu/evolibrary
/home.php
Key concepts
Natural selection,
Organisms in their environment
17.2.c
explain how selection, the founder
effect and genetic drift may affect allele
frequencies in populations
Key concepts
Natural selection
v2.1 5Y02
Learning resources
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 44: Evolution.
Also useful for 17.3c).
Past Papers
Paper 42, June 2012, Q1 (a)
Paper 42, June 2013, Q8 (b)
Textbooks/Publications
Bio Factsheet 191: What have we
learned from Darwin’s finches?
104
Learning objectives
Suggested teaching activities
Learning resources
representative of the larger main population (the smaller the population the greater
the likely effect).
o Exemplify the concept using Darwin’s finches. (W) (Basic)
Learners suggest the similarities and differences between natural selection and
genetic drift and then engage in class discussion. (W) (P) (Basic) (Challenging)
o Similarities: both involve changes in allele frequency and can contribute to
change (evolution).
o Differences: natural selection is a directed process, genetic drift is not; only
natural selection involves adaptations; with natural selection the frequency of the
‘advantageous’ allele increases whereas with genetic drift, allele frequencies
change by chance/sampling error (the frequency of a ‘disadvantageous’ allele
could increase). (W) (G) (Challenging)
17.2.d
use the Hardy-Weinberg principle to
calculate allele, genotype and
phenotype frequencies in populations
and explain situations when this
principle does not apply
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
Explain that Hardy and Weinberg considered the behaviour of genes in idealised
populations.
o Work through an example to show how allele frequencies can be used to
calculate genotype frequencies and how genotype frequencies can be used to
calculate allele frequencies. (W) (Basic)
o Learners work through simple examples using the Hardy-Weinberg equation and
make notes. (I) (Basic)
Learners use an example where the number of individuals with the recessive trait is
known to calculate the proportion, and hence number of, heterozygotes in a
population. (W) (Challenging)
Learners make notes to:
o Explain the differences between allele frequencies, genotype frequencies and
phenotype frequencies.
o Explain the conditions that need to be met for the Hardy-Weinberg principle to
apply. (I) (Challenging)
Learners suggest reasons why an unchanging allele frequency from one generation
to the next is rarely encountered in nature (non-random breeding; not all individuals
produce offspring; not a static population as there is emigration/immigration;
selection occurs; mutation occurs).
o Discuss how these frequencies would change if mutations occurred (e.g. harmful
recessive mutations; heterozygote advantage etc.), so that learners appreciate
the potential for change by evolution. (W) (Basic)
Explain to learners that the Hardy-Weinberg equations can be used to determine
frequencies for ‘at this moment in time’ occurrences.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://anthro.palomar.edu/synthetic/syn
th_2.htm
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/H/Hardy_Weinberg.
html
http://highered.mcgrawhill.com/sites/0767424263/student_vi
ew0/chapter4/the_hardyweinberg_equilibrium.html#
http://www.wwnorton.com/college/biolo
gy/discoverbio3/core/content/ch17/an
imations.asp
http://www.perinatology.com/calculator
s/Hardy-Weinberg.htm
Textbooks/Publications
Bio Factsheet 211: Hardy Weinberg
and population genetics.
105
Learning objectives
Suggested teaching activities
Learning resources
o Learners use an example, e.g. the incidence of cystic fibrosis to calculate the
allele frequencies and work out the carrier frequency (the heterozygotes) in the
population. (I) (Challenging)
17.3.a
state the general theory of evolution
that organisms have changed over
time
Key concepts
Natural selection
17.3.b
discuss the molecular evidence that
reveals similarities between closely
related organisms with reference to
mitochondrial DNA and protein
sequence data
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
17.3.c) includes the idea that species have formed from pre-existing species.
Discuss the ideas of ‘change over time’ and of common descent - there is
overwhelming evidence to suggest that all life is related. (W) (Basic)
Learners research examples of evolution to outline how change over time has
occurred. (H) (Challenging)
o A class discussion will help learners appreciate that the pace of change can be
different for different examples.
Learners suggest the type of evidence used to determine whether organisms were
closely related (i.e. comparative morphology and anatomy, fossils, classification and
embryology). (W) (Basic)
o Explain how the continually improving techniques to obtain DNA base/nucleotide
sequences and protein amino acid sequences (e.g. rapid sequencing) has
provided databases to improve understanding of relationships. (W)
(Challenging)
Explain that evolutionary related proteins that belong in a group (protein family) can
be most usefully compared between organisms. (W) (Basic)
Introduce the use of a single letter code for the amino acids before learners analyse
(in terms of closely related organisms) sequence data of a number of organisms
(e.g. for cytochrome C). (I) (Challenging)
With prompting, learners suggest how mitochondrial DNA differs from nuclear DNA
(inherited only from the mother; doesn’t swap genetic material with paternal
mitochondrial DNA and higher mutation rate).
o Discuss the usefulness, in terms of close relationships, of databases for
comparing mitochondrial DNA sequences of different organisms. (W) (I)
(Challenging)
Online
http://evolution.berkeley.edu/evolibrary
/article/evo_47
Textbooks/Publications
Jones, Fosbery, Taylor, Gregory,
pages
253-254 (2007), or pages 374-375
(2013), includes the Darwin-Wallace
theory and a discussion about
speciation.
Online
http://evolution.berkeley.edu/evolibrary
/news/100501_xwoman
http://www.wiley.com/college/pratt/047
1393878/instructor/activities/phylogen
etic_trees/index.html
http://www.indiana.edu/~ensiweb/lesso
ns/molb.ws.pdf
Past papers
Paper 43, Nov 2013, Q2
Note
This has close links to 19.2.a) and bioinformatics.
Learners should understand that there are freely accessible databases available to
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
106
Learning objectives
Suggested teaching activities
Learning resources
researchers.
17.3.c
explain how speciation may occur as a
result of geographical separation
(allopatric speciation), and ecological
and behavioural separation (sympatric
speciation)
Key concepts
Natural selection,
Observation and experiment
17.3.d
explain the role of pre-zygotic and
v2.1 5Y02
Review learner understanding of the terms species and gene pool by a question and
answer session. (W) (Basic)
Define speciation.
o Discuss the importance in speciation of (i) reproductive isolation and (ii) natural
selection acting within a population in different ways on different groups. (W)
(Basic)
Give examples (e.g. separating land masses millions of years ago and road laying
dividing up forests) illustrating ways that sub-populations are formed by geographical
separation and brainstorm other examples. (W) (Basic)
o Discuss how the different abilities of organisms to move from one area to
another are an important factor in the formation of new species.
o Remind learners that the process of allopatric speciation requires that the
populations remain separated and interbreeding is prevented. (W) (Basic)
Learners research one or two examples and use these to explain what is meant by
allopatric speciation. (I) (Basic)
Extension: learners research how the observations made of the four species of
mockingbirds in the Galapagos Islands are believed to have had a large influence on
Darwin’s development of the concept of natural selection. (H) (Challenging)
Introduce the idea of sympatric speciation: occurring within the same geographic
area by reducing gene flow between groups of the same population.
o State that two of the many ways to do this is by ecological separation and by
behavioural separation and ask learners to suggest what this means or to
volunteer examples. (W) (Basic)
o Learners research one example of each to explain the principles involved and
share their findings with the group. (W) (I) (Challenging)
Learners research the evolution of cichlid fish in the great lakes of Africa, e.g. Lake
Victoria, and present arguments as to whether speciation has occurred by allopatric
speciation, sympatric speciation, or both. (I) (Challenging)
Learners continue their work on Darwin’s finches and the founder effect to explain
how speciation has occurred by both allopatric and sympatric speciation. (I)
(Challenging)
Learners write a paragraph comparing allopatric and sympatric speciation. (F)
Remind learners that isolating mechanisms provide a barrier to gene flow and when
successful interbreeding no longer occurs a new species is considered to have been
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://people.rit.edu/rhrsbi/GalapagosP
ages/DarwinFinch.html
http://www98.homepage.villanova.edu/
robert.curry/Nesomimus/index.html
http://www.sciencedaily.com/releases/
2011/10/111003080523.htm
http://www.thescientist.com/?articles.view/articleNo/
23704/title/Evidence-for-sympatricspeciation/
http://www.nature.com/scitable/topicpa
ge/polyploidy-1552814
http://www.evolutionsbiologie.unikonstanz.de/pdf1-182/P089.pdf
http://evolution.berkeley.edu/evolibrary
/news/090301_cichlidspeciation
Textbooks/Publications
Bio Factsheet 142: Modern Examples
of Evolution in Action
Bio Factsheet 92: Isolation
Mechanisms
Past Papers
Paper 41, June 2011, Q8 (c)
Paper 41, June 2012, Q1
Online
http://www.biologyaspoetry.com/terms/
107
Learning objectives
Suggested teaching activities
post-zygotic isolating mechanisms in
the evolution of new species
Key concepts
Natural selection
17.2.e
describe how selective breeding
(artificial selection) has been used to
improve the milk yield of dairy cattle
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
formed. (W) (Basic)
Learners write out definitions of the two types of reproductive isolating mechanisms
and then decide whether the examples from 17.3.c are pre-zygotic or post-zygotic.
(I) (Basic)
Post-zygotic isolating mechanisms may need further discussion and summary with
individual notes.
o Discuss what is meant by a hybrid (hybridisation from 17.2.f is a different
context). Explain that generally a hybrid dies as an embryo or is sterile if it
survives, so a sub-population on the verge of becoming a separate species is
unlikely with interbreeding to incorporate back into the main population – the
gene pools are sufficiently different.
o Explain that hybrids that manage to produce fertile offspring tend to be less fit
than others and with natural selection will die out. (W) (I) (Challenging)
Provide descriptive examples of speciation on separate cards for learners to
produce two piles, pre-zygotic or post-zygotic and then compare with a partner. (P)
(I) (Basic)
Learners produce a written outline of the overall role of isolating mechanisms in
speciation and then describe, using examples, the contribution of pre-zygotic and
post-zygotic isolating mechanisms.
o The account should highlight the differences between the two. A word list or a
hints sheet could be provided. (F)
Explain that in selective breeding, humans have applied knowledge of natural
selection to make ‘improvements’. (W) (Basic)
Discuss why selective breeding to improve the milk yield of dairy cattle must take
place over several generations. (W) (Basic)
o Learners suggest main stages involved in the selective breeding programme,
before presenting ideas to the group. (W) (G) (Basic)
o Learners research details, guided by prompts such as: ‘Explain whether one or
many genes are involved’; ‘State what needs to be considered for improved milk
yield’; ‘Describe other desirable features for the cattle involved’. (H)
(Challenging)
Learners describe (e.g. in a table) the similarities and differences between selective
breeding and natural selection. (F)
Learners use data for milk yield of different generations in a selective breeding
programme to carry out a statistical comparison (t-test). (I) (Challenging)
Learners discuss the balance between improving features and maintaining genetic
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
postzygotic_barrier.html
http://wps.pearsoncustom.com/wps/me
dia/objects/5697/5834441/ebook/htm/
0cc6e.htm?14.03
Textbooks/Publications
Bio Factsheet 92: Isolation
Mechanisms
Past papers
Paper 43, Nov 2013, Q2 (c)
Online
http://www.embryoplus.com/cattle_ayr
shire.html
http://www.ilri.org/InfoServ/Webpub/full
docs/SmHDairy/chap5.html#Dairy%2
0cattle
http://rstb.royalsocietypublishing.org/co
ntent/360/1459/1479.full#abstract-1
http://babcock.wisc.edu/node/182
http://www.petermaas.nl/extinct/articles
/selectivebreeding.htm
Textbooks/Publications
Bio Factsheet 187: Selective Breeding
of Cattle
108
Learning objectives
Suggested teaching activities
Learning resources
diversity. (G) (Challenging)
Past Papers
Paper 43, Nov 2011, Q8
17.2.f
outline the following examples of crop
improvement by selective breeding:
the introduction of disease
resistance to varieties of wheat and
rice
the incorporation of mutant alleles
for gibberellin synthesis into dwarf
varieties so increasing yield by
having a greater proportion of
energy put into grain
inbreeding and hybridisation to
produce vigorous, uniform varieties
of maize
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
Continue the theme of 17.2.e with a discussion about the need to supply an
increasing global population and the improvement of crop plants.
o Learners suggest the most important crop plants grown (the three most
important are maize wheat and rice – grain crops).
o Outline the difference between crop improvement by conventional means,
selective breeding, and improvement by genetic modification. (W) (Basic)
Learners may be able to name a disease to which wheat (e.g. stem rust) and rice
(e.g. sheath blight) are susceptible; discuss the need to breed crop plants resistant
to disease (e.g. disease lowers yield and some can leave harmful toxins in the crop).
o Learners recall the steps involved in selective breeding and suggest desirable
features, e.g. resistant to infection, maintaining resistance for a long time,
localising infection to one area of the plant, resistance to toxin accumulation,
seed (kernel) resistance, able to produce a high yield when infected. (W)
(Challenging)
o Learners research the steps involved in introducing disease resistance into
wheat or rice (cover one crop each and share notes). (P) (Basic)
State that the presence of gibberellins leads to stem elongation and explanations will
be covered in Unit 11 (15.2.d, 16.3.d).
o Explain that the sd-1 gene encodes an enzyme (GA20-oxidase) involved in the
later stages of gibberellin biosynthesis.
o Learners suggest an outcome if mutations in this gene occur (very low levels of
gibberellins resulting in dwarf varieties).
o Explain that some varieties of crops such as rice and barley have these semidwarf / dwarf varieties. (W) (Challenging)
Learners write definitions of inbreeding and hybridisation and explain what is meant
by inbreeding depression, outbreeding, and hybrid vigour. (I) (Basic)
o Discuss the difficulties in maize in achieving the balance between homozygosity
and heterozygosity. (W) (Basic)
o Learners list the advantages and disadvantages of inbreeding and outbreeding
in maize. (I) (Challenging)
o Learners explain how selective breeding has produced homozygous maize
plants that can be crossed with other homozygous plants, to produce hybrids
with combinations of desirable features. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://archaeology.about.com/od/dome
stications/qt/wheat.htm
http://www.dupont.com/corporatefunctions/our-approach/globalchallenges/food.html
http://irri.org/our-work/research/betterrice-varieties/disease-and-pestresistant-rice
http://www.lsuagcenter.com/en/crops_l
ivestock/crops/rice/Diseases/
http://www.agprofessional.com/resourc
e-centers/wheat/disease/news/Dodisease-resistant-wheat-varietiespay-a-price-in-yield-229754951.html
http://www.businessinsider.com/10crops-that-feed-the-world-20119?op=1
http://5e.plantphys.net/article.php?ch=
20&id=355
Past Papers
Paper 43, June 2011, Q4 (a)
Paper 41, Nov 2013, Q5
109
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners research the ‘Green Revolution’ and debate the advantages and
disadvantages of this. (W) (Basic)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
110
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 8: Molecular biology and gene technology
Recommended prior knowledge
The structure of proteins and the structure of DNA from Unit 1 should be well understood. In addition, from Unit 3, learners should be familiar with semi-conservative
replication of DNA and understand the principles of transcription, the genetic code and translation in the synthesis of proteins. Knowledge from Unit 7 of gene
expression, including an understanding of how some mutations affect gene expression is also required.
Context
This unit provides learners with the opportunity to consider some of the latest developments in biology and appreciate the key concept of observation and experiment.
In this unit, learners will see how humans can make use of living systems and organisms to benefit themselves, such as in the development of genetically modified
plants and in improvements in genetic screening, in the treatment of genetic disorders and advancements in forensic science. Knowledge and understanding of
biological facts, principles and concepts from previous units will help their understanding of the techniques applied.
Outline
The lac operon is studied as an example of gene regulation and control in eukaryotes is touched upon with a discussion of the role of transcription factors. The study of
gene expression with the use of microarrays is covered. Recombinant DNA is explained and steps involved in genetic engineering are covered, including the use of
enzymes, plasmids, markers and control sequences, including promoters. Two main applications of genetic engineering, the production of proteins of medical
importance and the production of genetically modified crops and livestock are studied. Gel electrophoresis and the amplification of DNA by the polymerase chain
reaction are two techniques that are described and an application of these is considered with an outline of the technique associated with genetic fingerprinting.
Learners see that the pace of development of genetic technology can be partly attributed to bioinformatics. Other aspects of genetic technology that are covered are
the sequencing of genomes, screening for genetic conditions and gene therapy. The unit also includes a discussion on the social and ethical issues and implications of
genetic technology.
Teaching time
It is recommended that this unit should take approximately 9% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
111
Learning objectives
Suggested teaching activities
Learning resources
16.3.b
explain genetic control of protein
production in a prokaryote using the
lac operon
Learners complete a short written test (prepared by you, with mark scheme) to
remind them of previous knowledge and help understanding of this unit.
o Include relevant questions on: prokaryote structure (including plasmids and
genes for antibiotic resistance); definition of a gene; DNA structure and
replication; protein synthesis. (F)
o Go through the answers before proceeding. (W) (Basic)
Explain that in protein synthesis, gene expression describes the whole process
where DNA is transcribed to produce mRNA, which is translated to produce
polypeptides (that form proteins).
o Discuss the need to control gene expression, as all genes cannot be switched
on at any one time. (W) (Basic)
Explain the concept of an operon, then display a diagram of the arrangement in the
lac operon and describe the gene products of gene Z and gene Y.
o Discuss the roles of lactose permease and -galactosidase in lactose uptake
and metabolism, encouraging learners to contribute using AS Level knowledge.
(W) (Challenging)
Learners participate in a group demonstration using a large model set-up.
o Sheets of coloured paper stuck together represent the operon (promoter,
operator, genes Z, Y and A); the operator gene has a shape cut out,
complementary to the shape of the repressor protein; a separate sheet of paper
represents the regulatory gene (located elsewhere on the genome); use different
shapes for each of glucose, lactose, RNA polymerase and repressor protein.
o Discuss each gene and then place on top of them cards with their labels
(remove to test learners).
o Involve learners to describe the state of the operon when: no lactose is present
and glucose is present; when no glucose is present and lactose is present. (W)
(Challenging)
o Repeat, but this time allow learners to take charge and share out the
demonstration. (W) (I) (Challenging)
Learners annotate a set of diagrams and give explanations. (I) (Challenging)
Learners complete a gap-filling exercise that serves as their notes. (I) (Basic)
Learners sort out a set of statements to show the sequence of events occurring (F)
Online
http://www.sumanasinc.com/webconte
nt/animations/content/lacoperon.html
http://pathmicro.med.sc.edu/mayer/gen
eticreg.htm
http://highered.mcgrawhill.com/sites/0072556781/student_vi
ew0/chapter12/animation_quiz_4.htm
l
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/L/LacOperon.html
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Textbooks/Publications
Bio Factsheet 45: Gene Expression
Note
The lac operon of Escherichia coli was the first example of genetic control
discovered and investigated.
Details of cAMP and the catabolite activator protein are not required.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
112
Learning objectives
Suggested teaching activities
Learning resources
16.3.a
distinguish between structural and
regulatory genes and between
repressible and inducible enzymes
Learners make notes on the differences between: structural and regulatory genes;
repressible and inducible enzymes. (I) (Basic)
o Learners also explain that a repressor protein is the product of a regulatory
gene.
o Learners determine whether the enzyme products of the lac operon structural
genes are repressible or inducible enzymes (they are inducible). (I) (Basic)
Online
http://textbookofbacteriology.net/regula
tion.html
http://www.sumanasinc.com/webconte
nt/animations/content/lacoperon.html
http://pathmicro.med.sc.edu/mayer/gen
eticreg.htm
http://highered.mcgrawhill.com/sites/0072556781/student_vi
ew0/chapter12/animation_quiz_4.htm
l
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/L/LacOperon.html
Explain that RNA polymerase in eukaryotic cells cannot initiate transcription alone:
binding of transcription factors (proteins) to the DNA and to each other allow RNA
polymerase to bind; others bind to the RNA polymerase (the whole complex is
termed the transcription initiation complex). (W) (Basic)
o Learners draw annotated diagrams to visualise the function of transcription
factors. (I) (Basic)
Extension: learners investigate more detail of transcription factors, e.g. how inactive
transcription factors can be activated. (I) (Challenging)
Online
http://biotech.about.com/od/proteinengi
neering/f/transcriptfact.htm
http://bcs.whfre.d
eman.com/thelifewire/content/chp14/1
402002.html
Discuss how each cell of a multicellular organism contains the same genes, but
some will be inactive and there will be no gene expression (link back to 16.3.b).
o Learners suggest why detection of mRNA is carried out to measure gene
activity. (W) (Basic)
Explain, step-by-step, the principles behind the use of microarrays, with learners
making notes.
o Researchers can now access a database of nucleotide sequences (often called
‘gene sequences’) for different genes.
o Multiple copies of the sequences are placed by robotic machines (micro-scale
process) into separate areas on a solid surface, e.g. glass slide.
o Using reverse transcriptase, cDNA is synthesised using fluorescent nucleotides
from the mRNA collected, indirectly ‘labelling’ the genes that are most active.
o cDNA added to the microarray surface ‘hybridises’ (complementary copy) with
their particular gene sequence.
Online
http://www.bio.davidson.edu/courses/g
enomics/chip/chip.html
http://www.genome.gov/glossary/index
.cfm?id=125
http://www.webbooks.com/MoBio/Free/Chap9.htm
http://learn.genetics.utah.edu/content/l
abs/microarray/
Key concepts
Biochemical processes,
DNA, the molecule of heredity
16.3.c
explain the function of transcription
factors in gene expression in
eukaryotes
Key concepts
Biochemical processes,
DNA, the molecule of heredity
19.1.i
explain, in outline, how microarrays are
used in the analysis of genomes and in
detecting mRNA in studies of gene
expression
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
113
Learning objectives
Suggested teaching activities
Learning resources
o The intensity of the fluorescent-coloured areas can be detected using scanners
and the most active genes identified. (W) (Challenging)
Discuss a use of microarrays for learners to research further, e.g. comparing gene
activity of healthy and diseased cells.
o E.g. use red fluorescent nucleotides to ‘label’ the cDNA of a healthy cell, use
green for that of the tumour cell. A combined image of the two scans will show
red, green and yellow areas: red = genes from healthy cell expressed more than
tumour cell; green = genes from the tumour cell expressed more; yellow = both
cells expressing the genes equally. (W) (H) (Challenging)
19.1.a
define the term recombinant DNA
Key concepts
DNA, the molecule of heredity
v2.1 5Y02
Remind learners that, in Unit 7, ‘recombination’ and ‘recombinant’ are terms used in
the context of crossing over and the production of genetically different gametes and
offspring. (W) (Basic)
Explain that there are many definitions of recombinant DNA: learners need the idea
that novel DNA is formed by joining together DNA/genes from different sources.
o Explain that DNA can be added to plasmids, hence the term ‘recombinant
plasmid’, and transferred from one organism to another, hence ‘recombinant
host’. (W) (Basic)
Learners write a definition, qualifying with reference to recombinant plasmids and
recombinant hosts. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://higheredbcs.wiley.com/legacy/col
lege/voet/0470129301/animated_figs/
ch03/3-26.html
114
Learning objectives
Suggested teaching activities
Learning resources
19.1.b
explain that genetic engineering
involves the extraction of genes from
one organism, or the synthesis of
genes, in order to place them in
another organism (of the same or
another species) such that the
receiving organism expresses the
gene product
Remind learners that genes code for proteins and in genetic engineering the desired
product is a protein.
o Learners suggest why it is necessary to use another organism to produce the
protein. (W) (Basic)
Talk learners through the outline construction of a large flow diagram: brief
explanations for each step will help for 19.1.c, 19.1.e, 19.1.f, 19.1.g and 19.1.h,
when they can add further notes (see below). (W) (I) (Basic)
Online
http://www.learner.org/interactives/dna/
engineering.html
http://www.biology.arizona.edu/molecul
ar_bio/problem_sets/Recombinant_D
NA_Technology/recombinant_dna.ht
ml
Textbooks/Publications
Bio Factsheet 13: Genetic engineering
Key concepts
DNA, the molecule of heredity,
Observation and experiment
Past Papers
Paper 41, Nov 2011, Q7
Learners suggest why mRNA is sometimes used to obtain the gene (many more
copies of the mRNA in the cell than the genes; a host bacterial cell cannot cut out
introns from the RNA transcripts of eukaryotic DNA). (W) (Challenging)
Introduce the idea that DNA libraries are now available. (W) (Basic)
Explain that a vector (carrier) is frequently used (often a plasmid) to get the desired
gene into the host. (W) (Basic)
o Discuss when gene cloning occurs: producing many initial copies of the desired
gene and as the host cell replicates. (W) (Challenging)
Learners revise 17.2.a and give an account of the similarities and differences
between genetic engineering and selective breeding. (H) (Challenging)
Learners investigate what is meant by a cDNA library. (I) (Challenging)
Note
19.1.b can be amalgamated with 19.1.h.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
115
Learning objectives
Suggested teaching activities
Learning resources
19.1.h
explain the roles of restriction
endonucleases, reverse transcriptase
and ligases in genetic engineering
Outline the role of restriction endonucleases and DNA ligases.
o Explain how different endonucleases cleave at different, specific sequences to
obtain blunt or ‘sticky’ / overlapping ends.
o Learners add the enzymes to their main flow-chart from 19.1.b and annotate.
(W) (Basic)
Provide learners with details of different restriction endonucleases. On nucleotide
sequence diagrams, learners indicate the cleavage sites and state whether blunt or
sticky ends are produced and the number of fragments formed. (P) (I) (Challenging)
Outline the role of reverse transcriptase.
o Learners annotate their flow chart.
o Explain where DNA polymerase would be required (amplifies the gene). (W) (I)
(Basic)
Learners sequence a set of cards, each containing a single step involved in genetic
engineering. With a second set of cards containing more detail, allocate these to the
correct step. (F)
Learners produce a summary table of names of enzymes involved in genetic
engineering and details of the reactions they catalyse. (H) (Basic)
Extension: learners research the origins of these enzymes. (I) (Basic)
Online
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::535::535::/sites/dl/free/007243731
6/120078/bio37.swf::Restriction%20E
ndonucleases
http://www.geogene.com/genetic-engbasics.html
Discuss features of plasmids and ask learners to suggest advantages: found in
bacteria (will be taken up); small (easy to manipulate/easily taken up); replicate
semi-conservatively (identical copies); replicate independently within bacteria (so
gene cloning occurs); can be removed from one bacterial species and be taken up
by another (greater flexibility); can be cut at specific locations by restriction
endonucleases (for gene insertion). (W) (Challenging)
o Learners add annotations in the relevant steps of their flow chart of 19.1.b. (I)
(Basic)
Explain that once bacteria have taken up the plasmid, they are said to be
‘transformed’. (W) (Basic)
Background: explain that plasmids are more easily taken using, for example,
electroporation or by using calcium ions and heat shock (the bacteria are said to be
‘competent’). (W) (Basic)
Online
http://www.addgene.org/mol_bio_refer
ence/plasmid_background/
Key concepts
Biochemical processes,
Observation and experiment
19.1.e
describe the properties of plasmids
that allow them to be used in gene
cloning
Key concepts
Cells as the units of life,
DNA, the molecule of heredity,
Observation and experiment
Past Papers
Paper 42, June 2012, Q4 (a)(i)
Note
It is preferable to state that plasmids are taken up, rather than ‘placed in’ bacteria.
Learners should appreciate that other organisms, such as yeasts, are useful in
genetic engineering, as they can carry plasmids.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
116
Learning objectives
Suggested teaching activities
Learning resources
19.1.f
explain why promoters and other
control sequences may have to be
transferred as well as the desired gene
Learners recall (16.3.b) that a promoter is a nucleotide sequence on the DNA where
RNA polymerase attaches to initiate transcription.
o Explain that the transcription start point (the first nucleotide to be transcribed) is
within the sequence and the promoter allows the RNA polymerase to recognise
which DNA strand is the template.
o Remind learners of the involvement of transcription factors and that there are
genes coding for these, and that other control sequences exist (no detail
required). (W) (Basic)
With these discussed, learners suggest why, in genetic engineering, promoters and
other control sequences may need to be transferred with the desired gene. (W)
(Challenging)
Learners make brief annotations to their summary flow-chart from 19.1.b. (I) (Basic)
Learners write a short paragraph to explain the role of promoters and why they can
be said to control the expression of a gene. (F)
Extension: learners investigate how the early production of insulin by genetic
engineering used the machinery of the lac operon to control gene expression. (I)
(Challenging)
Online
http://www.addgene.org/mol_bio_refer
ence/promoter_background/
Key concepts
DNA, the molecule of heredity,
Observation and experiment
Past Papers
Paper 42, June 2012, Q4 (a)(ii)
Paper 41, June 2013, Q2 (c)(ii)
Note
In bacteria, RNA polymerase recognises and binds to the promoter with the aid of
one main protein transcription factor but in eukaryotes binding is enabled by a
complex of transcription factors.
19.1.g
explain the use of genes for
fluorescent or easily stained
substances as markers in gene
technology
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Learners recall the concepts involved in DNA uptake to produce recombinant hosts
(19.1.b).
o Explain that a cut plasmid may (with DNA ligase present) re-circularise and be
taken up by a host bacterial cell, or a bacterial cell may not be transformed (take
up the plasmid). These bacteria would not have the desired gene.
o Agree that some method to identify the recombinant bacteria is desirable
(‘screening for recombinants’) in order to avoid wasting money if all bacterial
forms were cultured together. (W) (Basic)
Use images to explain how the gene encoding GFP, green fluorescent protein (most
commonly used gene), is placed between the promoter and the desired gene.
Transcription of both genes occurs and GFP and the desired product result.
o Discuss how UV light enables selection of host cells for large scale culturing,
while non-recombinant bacteria will not fluoresce. (W) (Challenging)
o Learners add annotations to their flow-chart from 19.1.b about screening for
successful recombinants and write a paragraph of explanation. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.dnaftb.org/34/problem.html
http://www.chm.bris.ac.uk/motm/GFP/
GFPh.htm
http://www.conncoll.edu/ccacad/zimme
r/GFP-ww/GFP-1.htm
http://www.scholarpedia.org/article/Flu
orescent_proteins
http://www.microscopyu.com/articles/li
vecellimaging/fpintro.html
http://micro.magnet.fsu.edu/primer/tec
hniques/fluorescence/fluorescentprot
eins/fluorescentproteinshome.html
http://www.gmocompass.org/eng/safety/human_healt
117
Learning objectives
Suggested teaching activities
Learners research one example where genes for enzymes that produce fluorescent
or easily stained substances are now used as markers. Examples are presented to
the class. (W) (G) (P) (Basic)
Note
Background: provide learners with a brief historical perspective on the use of
antibiotic resistance markers to enable screening and explain why these are
becoming less favoured.
19.2.c
explain the advantages of producing
human proteins by recombinant DNA
techniques (reference should be made
to some suitable examples, such as
insulin, factor VIII for the treatment of
haemophilia and adenosine
deaminase for treating severe
combined immunodeficiency (SCID))
Key concepts
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Discuss the advantages of producing human proteins by genetic engineering /
recombinant DNA techniques (‘genetic manipulation’ is also a term used).
o Discuss how some of the diseases were not previously treatable with the natural
protein: could not be extracted or produced (e.g. adenosine deaminase);
expensive to produce and purify; required extraction from many blood donations
(e.g. factor VIII); problems with the protein used for treatment (e.g. insulin from
pigs or other mammals).
o Discuss additional benefits such as: fewer/no allergic responses from
contaminants; lower/no immune responses from non-self antigen detection; no
risk of disease from contaminating pathogens; ethically/religiously/morally more
acceptable.
o Include an outline of the benefits of using bacteria, yeast or mammalian cells in
tissue culture. (W) (Basic)
Learners research the genetically engineered protein products for treatment of
people with the conditions listed. Provide guidance.
o State whether the protein could be extracted for treatment before genetic
engineering techniques.
o State the function of the protein and if the protein is deficient or absent.
o State how successful the treatment is and whether there are alternative
treatment methods. (H) (Challenging)
Learners make outline notes following discussion on their research. Fill in any gaps
with further explanation.
o Explain that some people require the protein insulin to regulate their blood
glucose concentration (covered in Unit 10). (W) (Basic)
o Explain that factor VIII is a protein required in the cascade of reactions involved
in blood clotting and is used to treat haemophilia (16.2.f, Unit 7). (W) (Basic)
o For SCID, explain that mutations of the ADA gene result in a lack of adenosine
deaminase: a build-up of the substrate (deoxyadenosine) is toxic to immune
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
h/126.position_efsa_antibiotic_resista
nce_markers.html
http://www.medicalnewstoday.com/ar
ticles/31227.php
Past Papers
Paper 41, Nov 2012, Q3 (a)(ii)
Paper 41, June 2013, Q2 (b)
Online
http://www.diabetes.co.uk/insulin/huma
n-insulin.html
http://resources.schoolscience.co.uk/u
nilever/1618/proteins/Protch4pg3.html
http://ghr.nlm.nih.gov/condition/adenos
ine-deaminase-deficiency
Past Papers
Paper 43, Nov 2011, Q5 (b)
118
Learning objectives
Suggested teaching activities
Learning resources
system cells (background information: an autosomal recessive disorder). (W)
(Basic)
Learners list the benefits, giving relevant examples where relevant. (F)
Note
The benefits of using bacteria or yeast cells as hosts could be a useful extension
discussion.
19.3.a
explain the significance of genetic
engineering in improving the quality
and yield of crop plants and livestock
in solving the demand for food in the
world, e.g. Bt maize, vitamin A
enhanced rice (Golden riceTM) and GM
salmon
Key concepts
Observation and experiment
Learners recall selective breeding in cattle and in crop plants (17.2.f) and
discussions about the global demand for food (and energy).
o Learners suggest ways in which crops and livestock may be genetically modified
to benefit populations.
o Discuss why Golden riceTM providing vitamin A is considered an improvement in
the quality of a crop plant.
o Explore further ideas that crops may be modified to give a higher yield: two main
ways are making crops resistant to herbicides and resistant to pests (insects).
o Learners suggest why livestock improvements (far less common) are not as
universally approved. Discuss the idea of livestock such as sheep, cattle, hens
and goats growing faster, larger and being more resistant to disease.
o Debate the farming of GM salmon (not strictly ‘livestock’), which can grow to a
marketable size much quicker than non-GM salmon. (W) (Basic) (Challenging)
Learners write an account explaining why crops genetically modified for herbicide
and pest resistance would lead to increased yields. (I) (Basic)
Learners state ways in which livestock can be modified, giving examples to help
their answer. (I) (Basic)
Learners outline the advantages and disadvantages of crop improvement by
conventional breeding techniques compared to genetic modification. (F)
Extension: learners research examples of crop improvement by genetic modification
(such as frost resistance, ability to fix nitrogen, increased time for fruit spoilage,
drought resistance, etc.) and of livestock improvement. (H) (Challenging)
Online
http://www.cato.org/sites/cato.org/files/
serials/files/regulation/2003/4/v26n14.pdf
http://www.newscientist.com/article/dn
3364-gm-crops-boost-yields-more-inpoor-countries.html#.UvhpJ_s9BOo
http://www.europabio.org/do-gm-cropsreally-have-higher-yields
http://www.gmocompass.org/eng/agri_biotechnology/
breeding_aims/147.pest_resistant_cr
ops.html
http://www.efsa.europa.eu/en/topics/to
pic/gmanimals.htm
Textbooks/Publications
Bio Factsheet 13: Genetic engineering
Bio Factsheet 69: Genetic engineering
in agriculture
Bio Factsheet 192: Investigating
weeds and crop yield.
Past Papers
Paper 43, June 2011, Q5 (a)
Paper 42, June 2012, Q4 (a)
19.3.b
outline the way in which the production
of crops such as maize, cotton,
v2.1 5Y02
In groups, learners use resources to prepare annotated flow diagrams summarising
one example of crop improvement from the list in the learning objective.
o Copies of the summary diagrams are made and shared with the rest of the class.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.gmocompass.org/eng/grocery_shopping/c
119
Learning objectives
Suggested teaching activities
Learning resources
tobacco and oil seed rape, may be
increased by using varieties that are
genetically modified for herbicide
resistance and insect resistance
Learners research and produce summary notes about the use of Agrobacterium
tumefaciens as one of the most common vectors and other methods such as
electroporation and ‘gene guns’ to deliver genetic material into host plant cells.
Learners find, analyse and evaluate data that compares the yields of GM crops with
non-GM crops. (H) (Challenging)
rops/24.genetically_modified_rice.ht
ml
http://www.nature.com/scitable/knowle
dge/library/use-and-impact-of-btmaize-46975413
http://en.wikipedia.org/wiki/Golden_rice
http://www.goldenrice.org/
Key concepts
Observation and experiment
Textbooks/Publications
Bio Factsheet 13: Genetic engineering
Bio Factsheet 69: Genetic engineering
in agriculture
Bio Factsheet 192: Investigating
weeds and crop yield.
19.3.c
discuss the ethical and social
implications of using genetically
modified organisms (GMOs) in food
production
Key concepts
Observation and experiment
Learners use guidelines to research some ethical and social implications of using
GMOs, and then debate and discuss these points in class. (W) (H) (Basic)
Learners produce summary points about the topic. (I) (Challenging)
Note
Advise learners to look at the source of funding and editorial policy of websites to
gauge whether the information is objective and impartial.
Online
http://technyou.education.csiro.au/mod
ule/ethics-food-andagriculture/page/204/issues
http://www.i-sis.org.uk/GE-ethics.php
http://www.beep.ac.uk
http://www.salmonnation.com/fish/gefis
h.html
http://www.oceanconservancy.org/ourwork/aquaculture/aquaculturegenetically.html
Textbooks/Publications
Bio Factsheet 13: Genetic engineering.
Bio Factsheet 106: Ethical issues in Alevel Biology
Bio Factsheet 137: GM Farm Scale
Evaluation Trials.
Past Papers
Paper 43, June 2011, Q5 (b)(c)(d)
Paper 42, June 2012, Q4 (e)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
120
Learning objectives
Suggested teaching activities
Learning resources
19.1.c
describe the principles of the
polymerase chain reaction (PCR) to
clone and amplify DNA (the role of Taq
polymerase should be emphasised)
Use a question and answer session to agree that: the desired gene used in the
genetic engineering process needs to be cloned (19.1.b); DNA polymerase is
required to replicate DNA (Unit 3); the DNA strands are held together strongly by
many (individually) weak hydrogen bonds. (W) (Basic)
Explain that, outside the cell, heat (approximately 90°C) can be used to separate the
DNA strands.
o Learners explain why heat stable polymerase enzymes are required.
o Introduce Taq polymerase derived from the thermophilic bacterium Thermus
aquaticus, and discuss how this enzyme’s thermostable structure also allows it
to have a long shelf life.
o Explain what primers are before explaining their role in dictating the correct
section of DNA to be copied and enabling Taq polymerase attachment. (W)
(Challenging)
Using diagrams, provide an overview of PCR. Involve learners in explanations of the
benefits of Taq polymerase stability (heating and many cycles). (W) (Basic)
o Learners label the diagrams and produce a two-column table: main stage and
corresponding explanations. (I) (Challenging)
Learners match statements of the main stages with explanations of why they are
carried out, they then sequence them. (F)
Learners match statements of the components involved to their role in the process.
(F)
Online
http://www.genome.gov/Glossary/index
.cfm?id=159
http://www.webbooks.com/MoBio/Free/Ch9E.htm
http://www.saps.org.uk/secondary/teac
hing-resources/119-investigatingplant-evolution-amplifying-dna-usingpcr
http://www.rothamsted.ac.uk/notebook/
pcr.htm
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Observation and experiment
Textbooks/Publications
Bio Factsheet 67: Modern techniques
in biology: genetics.
Note
Explanation of a primer can be limited to the idea of a short nucleotide sequence
that binds to the DNA template strand at a specific sequence, so enabling chain
elongation.
T. aquaticus was discovered in 1969 in Yellowstone National Park in Wyoming,
USA, noted for its hot springs and geysers.
19.1.d
describe and explain how gel
electrophoresis is used to analyse
proteins and nucleic acids, and to
distinguish between the alleles of a
gene (limited to the separation of
polypeptides and the separation of
DNA fragments cut with restriction
endonucleases)
v2.1 5Y02
Show learners an electrophoresis kit (or a photograph of a kit), explaining the
principles and outlining the technique.
o Include discussion on: the composition of the gel (size of ‘pores’ formed by the
fibrous matrix); ability to alter the voltage applied and/or the ‘run’ time; methods
used e.g. stains or fluorescent dyes to ‘see’ separated bands (if not visible).
o Prompt learners to suggest and explain the factors affecting movement through
the gel. Ensure they appreciate that separation of a mixture will be based on:
size/length/mass; and charge (discuss resistance to flow). (W) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 12
Online
http://www.genome.gov/Glossary/?id=
56
http://www.life.uiuc.edu/molbio/geldige
st/electro.html#run
http://www.ncbe.reading.ac.uk/NCBE/
MATERIALS/menu.html
121
Learning objectives
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Suggested teaching activities
Learning resources
Learners explain why samples of DNA/RNA will move towards the anode
(phosphate groups give a negative charge), and how restriction enzymes (see
19.1.h) will give specific different-sized fragments.
o Explain that the solution containing the DNA fragments can be treated so the
charge is the same for all; hence they are separated by size/length (all
fragments same shape).
o Discuss how RNA molecules will be of different lengths and hence separation by
size will work. (W) (Basic)
Learners use kits (or simulations) to carry out gel electrophoresis of DNA. (I)
(Challenging)
Using resources, learners draw an annotated diagram that helps to outline the
principles behind the process, using nucleic acids as an example. (I) (Basic)
Learners recall protein molecular structure to realise that a mixture can be different
lengths, charges and shapes, hence requiring a different electrophoresis set-up to
DNA. (W) (Basic)
o Explain that a buffer can be used to provide a uniform negative charge and
unfold the proteins.
Learners research identification of a protein by protein blotting or antibody tagging.
(H) (Challenging)
Learners investigate the uses of gel electrophoresis in the analysis of proteins and
nucleic acids and a ‘class list’ made of each to display. (W) (H) (Basic)
Extension: learners research the advantages and disadvantages of the two main
gels, agarose and polyacrylamide. (I) (Challenging)
Learners discuss the differences that may exist between alleles of a gene.
o Discuss how alleles of only slightly different length can be detected with the
correct gel composition.
o Explain that if alleles are the same or similar, undetectable length, restriction
enzymes could be used to obtain fragments: different fragments with different
sequences can be detected. An alternative is using a DNA probe.
o Mention that there are DNA sequence ‘libraries’ to obtain known sequences to
act as markers.
o Use sickle cell anaemia to exemplify how differences between alleles can
sometimes be detected by sampling the protein products, e.g. the two types of
haemoglobin (confirms carrier status). (W) (Challenging
Practical booklet 12 is a protocol for separating dyes by gel electrophoresis that
demonstrates the principles involved in separating DNA.
http://www.bio-rad.com/
http://www.edvotek.com/
http://www.medicine.mcgill.ca/physio/vl
ab/Other_exps/endo/electrophoresis.
htm
http://www.bio-rad.com/enca/applications-technologies/proteinelectrophoresis
http://bcs.whfreeman.com/lehninger5e/
content/cat_020/0301_gel_electropho
resis.html?v=chapter&i=03020.01&s=
03000&n=00020&o=7
http://learn.genetics.utah.edu/content/l
abs/gel/
http://www.neosci.com/demos/101091_DNA/Labs_RestrictionEnzyme.
swf
http://www.biotechlearn.org.nz/themes/
dna_lab/gel_electrophoresis
www.ncbe.reading.ac.uk/ncbe/protocol
s/PDF/DiceSG.pdf
http://www.stanford.edu/group/hopes/c
gi-bin/wordpress/2011/03/genetictesting/
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 67: Modern techniques
in Biology: Genetics.
Past Papers
Paper 41, June 2012, Q3 (b)
Paper 42, June 2013, Q2 (b)
122
Learning objectives
Suggested teaching activities
Learning resources
Note
Generally, small agarose gels are used to separate DNA (lower voltage for
approximately 1-2 hours) whereas large polyacrylamide gels are required for
proteins (higher voltages for about 4 hours). Different electrophoresis tanks and
power packs are required.
Links to 19.2.d: genetic screening can involve gel electrophoresis, e.g. identifying
carriers. In some cases restriction enzymes are used, or probes to locate specific
base sequences.
o Cystic fibrosis: some mutant alleles have large deletions.
o Huntington’s disease: the mutant allele of the Huntington gene has tri-nucleotide
repeat sequences.
o Some cases of haemophilia: a mutant allele in the factor VIII gene has an
insertion that inactivates the gene.
19.2.g
outline the use of PCR and DNA
testing in forensic medicine and
criminal investigations
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Explain that pure DNA or DNA mixed with other biological materials (e.g. in a tissue
sample such as dried blood) is analysed and compared to existing profiles or known
markers.
o Explain what variable number tandem repeats (VNTRs) are and detail their
importance in an analysis, including: a particular VNTR occurs at a specific
locus; for a particular VNTR different individuals can have a different number of
repeats (so different lengths of the DNA section); VNTRs that are very variable
in different individuals can be used as markers. (W) (Challenging)
Learners suggest the role of PCR (amplify the quantity of each VNTR marker in the
sample). (W) (Basic)
Ensure learners understand that the chance that two individuals (except for identical
twins) have exactly matching DNA profiles (genetic fingerprints) for these selected
markers is virtually nil. (W) (Challenging)
Learners use resources to extract the main points of the technique of genetic
fingerprinting and list as bullet points. (I) (Challenging)
Learners carry out analyses of different results of genetic fingerprints or make up
their own worksheet containing simulated results from a crime scene to swap within
the class for another learner to analyse. (P) (I) (Basic)
Learners explain the role of PCR in DNA fingerprinting and outline the principles as
applied to VNTRs:
o Very small samples of DNA can be analysed.
o Millions of DNA copies can be produced (so can run many tests on the same
original DNA sample).
Cambridge International AS & A Level Biology (9700) – from 2016
Online
https://koshland-sciencemuseum.org/sites/all/exhibits/exhibitd
na/index.jsp
http://learn.genetics.utah.edu/content/l
abs/pcr/
http://technyou.education.csiro.au/mod
ule/dna-profiling/page/220/dnaprofiles-forensic-use
http://www.pbs.org/wgbh/nova/sheppar
d/analyze.html
Past Papers
Paper 41, June 2012, Q3 (a)
123
Learning objectives
Suggested teaching activities
Learning resources
o Longer VNTRs will be impeded more by the gel (move a shorter distance in the
same time than the shorter VNTRs). (I) (Challenging)
19.2.a
define the term bioinformatics
Key concepts
Observation and experiment
19.2.b
outline the role of bioinformatics
following the sequencing of genomes,
such as those of humans and
parasites, e.g. Plasmodium (details of
methods of DNA sequencing are not
required)
Key concepts
v2.1 5Y02
Learners work out what the term bioinformatics means: biology and data, computer
science and information technology merged into one (remind them about statistics).
(W) (G) (Basic)
Explain that there are linked databases holding freely available, continually updated,
information on: nucleotide sequences of genes (gene sequences); whole genome
sequences; mutation sequences; amino acid sequences of proteins; protein
structures; phenotypic data.
o Ideas for learners to consider: input, storage and retrieval of biological
information for analysis; data that can be searched is increasing exponentially.
o Learners define the term bioinformatics and list the principles involved. (W) (I)
(Challenging)
Demonstrate how to use BLAST (basic local alignment search tool), which compares
nucleotide or protein sequences to databases. When a match is found, the statistical
significance of the match is calculated.
o Show learners how a nucleotide sequence can be matched to an amino acid
sequence and how these may match up to known genes belonging to
organisms. (W) (Challenging)
Learners explore the world of bioinformatics for themselves if there is internet
access and report back findings. (W) (H) (Challenging)
Note
Suitable databases to explore are Ensembl (genome), GenBank (DNA sequence),
UniProt (protein sequence), PDB (protein structure) and COSMIC (somatic
mutations in cancer).
Online
http://www.yourgenome.org/downloads
/genomiclinks.pdf
http://www.bioinformatics.org/wiki/Bioin
formatics_FAQ
http://www.ploscompbiol.org/article/info
%3Adoi%2F10.1371%2Fjournal.pcbi.
1002789
http://www.biotnet.org/trainingmaterials/das-game
http://www.genecards.org/#
http://www.genome.gov/glossary/index
.cfm?id=17
http://www.malacards.org/
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/WTDV027167.htm
http://www.ebi.ac.uk/about
http://www.bioinformaticsatschool.eu/
http://www.nature.com/scitable/topicpa
ge/genomics-enables-scientists-tostudy-genetic-variability-6526364
Give an outline of the human genome project (HGP).
o With prompting, learners suggest the role of bioinformatics, such as in: targeting
drug design to the individual; investigating evolutionary links by comparing gene
and protein sequence data; searching for the functions of genes; identifying
mutations; identifying genetic risk factors; gene therapy. (W) (Challenging)
Revise Plasmodium and the control of malaria, including problems with finding a
vaccine (Unit 5). (W) (Basic)
o Then open up a discussion about the role of bioinformatics following the
sequencing of genomes of the species of Plasmodium.
Online
http://www.yourgenome.org/downloads
/genomiclinks.pdf
http://www.bioinformatics.org/wiki/Bioin
formatics_FAQ
http://www.genecards.org/#
http://www.genome.gov/glossary/index
.cfm?id=17
http://www.malacards.org/
Cambridge International AS & A Level Biology (9700) – from 2016
124
Learning objectives
Suggested teaching activities
Learning resources
Natural selection,
Observation and experiment
o Learners suggest the benefits in identifying the genes involved in antigenic
variation and in evading the immune response (information gained about how
some species are more invasive than others).
o Learners discuss how information could be used in the search for new drugs and
vaccines. (W) (G) (Challenging)
Learners write an account of the role of bioinformatics following the sequencing of
genomes, referring to the HGP and the Plasmodium genome and making relevant
links to other relevant learning objectives. (F)
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/WTDV027167.htm
http://www.ebi.ac.uk/about
http://www.bioinformaticsatschool.eu/
http://www.nature.com/scitable/topicpa
ge/genomics-enables-scientists-tostudy-genetic-variability-6526364
http://www.sanger.ac.uk/resources/do
wnloads/protozoa/plasmodiumfalciparum.html
http://www.nature.com/nature/journal/v
419/n6906/full/nature01097.html
http://web.ornl.gov/sci/techresources/H
uman_Genome/project/timeline.shtml
http://web.ornl.gov/sci/techresources/H
uman_Genome/project/info.shtml
http://web.ornl.gov/sci/techresources/H
uman_Genome/publicat/genegatewa
y/GeneGatewayHandout.pdf
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/T/Taxonomy.html
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/WTDV027173.htm
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/Videos-genomes-and-genetictesting/WTDV027199.htm
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
125
Learning objectives
Suggested teaching activities
Learning resources
19.2.d
outline the advantages of screening for
genetic conditions (reference may be
made to tests for specific genes such
as those for breast cancer, BRCA1
and BRCA2, and genes for
haemophilia, sickle cell anaemia,
Huntington’s disease and cystic
fibrosis)
Learners suggest what is involved in genetic screening (using family history and, if
the test is available, analysing tissue samples for DNA) and name conditions for
which genetic screening is available.
o Ensure the conditions listed are included and explained. (W)
Explain what is meant by genetic counselling. (W) (Basic)
Brainstorm advantages of screening for genetic conditions and complete the list if
necessary.
o Provides information about increased risk of having genetic conditions.
o Identifies carriers.
o Early diagnosis, including identification of disorders in embryos.
o Identifies conditions in foetuses (early treatment may be possible and allows
parents to prepare.
o Enables decisions to be made about having children or having follow-up
treatment. (W) (Challenging)
Learners research and make outline notes on the genetic conditions named, then
match up advantages from the brainstorm list to each condition. (I) (Basic)
Extension: learners suggest some of the disadvantages of screening. (I)
(Challenging)
Online
http://www.nlm.nih.gov/medlineplus/cy
sticfibrosis.html
http://ghr.nlm.nih.gov/gene/CFTR
http://www.ygyh.org/cf/whatisit.htm
http://resources.schoolscience.co.uk/B
BSRC/casestudies/cystic.pdf
http://learn.genetics.utah.edu/content/d
isorders/screening/
http://www.hdfoundation.org/html/hdsat
est.php
http://www.merck.com/mmhe/sec22/ch
256/ch256b.html
Key concepts
DNA, the molecule of heredity,
Natural selection,
Observation and experiment
Note
This topic needs careful handling.
Background: some genetic conditions are more common in certain groups as a
result of common ancestry (sharing similar genetic make-up), e.g. cystic fibrosis is
most common in Caucasians; sickle cell anaemia is common in West and East
African, African-American and Mediterranean populations; Huntington’s disease is
more common in Europe and countries with European links.
19.2.e
outline how genetic diseases can be
treated with gene therapy and discuss
the challenges in choosing appropriate
vectors, such as viruses, liposomes
and naked DNA (reference may be
made to SCID, inherited eye diseases
and cystic fibrosis)
Key concepts
DNA, the molecule of heredity,
v2.1 5Y02
Explain that in gene therapy, the aim is for affected cells to take up the normal, nonmutated gene and produce the normal, functioning protein product.
o Prompt learners to suggest methods of delivery of the normal gene, such as
viruses and liposomes (you may need to describe liposomes). (W) (Basic)
Learners discuss in groups why viruses may be ideal vectors, and then share ideas
with the class. Features: small; can be manipulated to incorporate the gene, be
harmless and not trigger an immune response; target particular cells and enter, or
inject the gene into the cell; have mechanisms to pass through the mucus lining
cells; can integrate their nucleic acid into the target cell genome.
o Explain that the ‘ideal’ virus is difficult to find as it will be almost impossible to fit
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 110: Genetic Disease in
Humans.
Bio Factsheet 134: Cystic Fibrosis
Bio Factsheet 215: Genetic Testing
and Screening
Online
http://www.nlm.nih.gov/medlineplus/cy
sticfibrosis.html
http://ghr.nlm.nih.gov/gene/CFTR
http://www.ygyh.org/cf/whatisit.htm
http://resources.schoolscience.co.uk/B
BSRC/casestudies/cystic.pdf
http://learn.genetics.utah.edu/content/d
isorders/screening/
http://www.hdfoundation.org/html/hdsat
est.php
126
Learning objectives
Observation and experiment
Suggested teaching activities
all the criteria. (W) (G) (Challenging)
Learners research the advantages of the type of virus used in the gene therapy for
eye disease and explain why the eye is a good candidate for gene therapy. (I)
(Challenging)
Learners research (also use knowledge of cell surface membrane structure) why
liposomes can be used as vectors.
o Learners explain how liposomes have been used in clinical trials for the
treatment of cystic fibrosis.
o Extension: learners include an account of the problems faced in treating this
condition. (I) (Challenging)
Explain that SCID has been a successful candidate for gene therapy: the gene for
adenosine deaminase is introduced into T-lymphocytes removed from children with
SCID. The lymphocytes are cultured in tissue culture with a viral vector and then the
cells injected back into the child. (W) (Basic)
Extension: learners research the historical work done by French-Anderson, Blaese
and Rosenburg on SCID gene therapy and explain how the therapy was carried out.
(H) (Basic)
Discuss any recent successes in naked DNA therapy. Explain that initial results
showed that direct injection into muscle has indicated some success in uptake; there
has also been uptake by liver cells. (W) (Basic)
Learning resources
http://www.merck.com/mmhe/sec22/ch
256/ch256b.html
http://learn.genetics.utah.edu/content/g
enetherapy
http://www.visionresearch.eu/index.php?id=696
http://www.newscientist.com/article/dn
24879-gene-therapy-restores-sightin-people-with-eye-disease.html
http://www.newscientist.com/article/mg
22029413.200-bubble-kid-successputs-gene-therapy-back-on-track.html
http://history.nih.gov/exhibits/genetics/
sect4.htm
http://www.genemedresearch.ox.ac.uk/
genetherapy/cfgt.html
http://www.extremetech.com/extreme/1
71873-naked-dna-gene-therapyused-to-non-invasively-cure-heartdisease
http://ghr.nlm.nih.gov/handbook/therap
y/procedures
Textbooks/Publications
Bio Factsheet 51: Gene therapy
Past Papers
Paper 41, Nov 2011, Q5
Paper 43, Nov 2013, Q10 (a)
19.2.f
discuss the social and ethical
considerations of using gene testing
and gene therapy in medicine
(reference should be made to genetic
conditions for which treatments exist
and where none exist, also to IVF,
embryo biopsy and preselection and to
v2.1 5Y02
Explain that there are social and ethical considerations (see Note) of using gene
testing and gene therapy.
o Agree that not all genetic conditions are treatable.
o Discuss issues arising from: gene testing embryos by performing an embryo
biopsy; couples deciding on IVF treatment for embryo testing and preselection
for implantation.
o If not discussed in 19.2.d, explain briefly what is meant by therapeutic abortion.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.medscape.com/viewarticle/
505222_4
http://ghr.nlm.nih.gov/handbook/therth
e/ethics
Textbooks/Publications
Bio Factsheet 51: Gene therapy
127
Learning objectives
Suggested teaching activities
therapeutic abortions)
(W) (Basic)
Learners write their ideas under four headings on pieces of paper ‘Gene testing –
social consideration’; ‘Gene testing – ethical consideration’; ‘Gene therapy - social
consideration’; Gene therapy - ethical consideration’.
o Learners justify their statements to a small group and, if agreed, add it to a
poster.
o Display the posters for learners to consider and make notes. (G) (I) (Basic)
(Challenging)
Key concepts
Observation and experiment
Learning resources
Past Papers
Paper 41, Nov 2011, Q5
Note
This needs to be treated with sensitivity.
Social = related to human society, e.g. interdependence, mutual relationships,
cooperation for all to benefit.
Ethics = set of agreed standards, determine what is acceptable, followed by a group
of individuals, regulated behaviour.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
128
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 9: Respiration
Recommended prior knowledge
Learners should be familiar with the concept of energy transfer and understand that energy contained within biological compounds can be released for use by the cell.
They should have a sound understanding of what a molecule is, and understand chemical formulae and equations. It would be helpful if they understood the concept of
oxidation and reduction, at least at a simple level.
Context
This unit considers the key concept of biochemical processes and focuses on how the energy contained within food molecules such as glucose is transferred into the
universal energy currency of ATP for use in the cell. All unicellular and multicellular organisms use the organic compound ATP to drive the energy-requiring processes
that occur in cells. There are many direct links to other areas of the syllabus, such as: the structure and role of glucose and lipids from Unit 1; mitochondrion structure
and function from Unit 2; the role of enzymes in metabolic reactions from Unit 2; and ATP from Units 1 and 3. The unit has close links with photosynthesis in Unit 11,
which also covers the concept of energy transfer and ATP synthesis. Throughout the syllabus there are examples of the use of ATP for biochemical processes.
Outline
This unit covers the need for energy in living organisms and the universal occurrence of ATP as energy currency. The four main stages of aerobic respiration,
glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation are described. A distinction is made between the synthesis of ATP by substrate-linked
reactions and by oxidative phosphorylation; the role of coenzymes in these stages is made clear. A comparison is made between aerobic and anaerobic respiration in
mammals and in yeast. An explanation of RQ is given and different respiratory substrates are considered. Learners use respirometers to make quantitative studies of
respiration and have an opportunity to improve planning and evaluative skills. This unit lends itself to sequential descriptions and the construction of flow diagrams to
illustrate the many different stages that occur within the overall process.
Teaching time
It is recommended that this unit should take approximately 7% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
129
Learning objectives
Suggested teaching activities
Learning resources
12.1.a
outline the need for energy in living
organisms, as illustrated by anabolic
reactions, such as DNA replication
and protein synthesis, active transport,
movement and the maintenance of
body temperature
Brainstorm ideas to construct a disorganised set of statements. Encourage learners
to include examples from prokaryotes and eukaryotes. (W) (Basic)
o Learners give headings for main uses of energy in organisms, accompanied by
bullet-point notes.
o Agree that some examples from the brainstorming session could be grouped,
e.g. under ‘movement’. Bullet points could include: bacteria and flagellar
movement (outline the difference between prokaryotic and eukaryotic flagella);
protoctists and amoeboid movement, synchronous rhythm of cilia and flagellar
movement; discharge of spores in fungi; muscle contraction in animals;
translocation of sugars or closure of flytrap (see 15.2.a) in plants.
o Learners recall Unit 1, Biological molecules, for relevant bullet points for
anabolic reactions. (I) (Basic)
Online
http://www.elmhurst.edu/~chm/vchem
book/592energy.html
http://www.rsc.org/Education/Teacher
s/Resources/cfb/index.htm
Key concepts
Cells as the units of life,
Biochemical processes
Note
Ensure that learners understand the meanings of the terms metabolism and
catabolism.
12.1.b
describe the features of ATP that
make it suitable as the universal
energy currency
Key concepts
Biochemical processes
Use questioning to remind learners of the structure of an ATP molecule. Ensure
learners realise that energy is released at each step of the complete hydrolysis of
ATP:
ATP ADP AMP
(W) (Basic)
Write out a list of features that make ATP suitable as the universal energy currency.
o Learners add brief notes to explain each feature, including a diagram showing
the one-step process of release of energy from ATP hydrolysis and synthesis of
ATP from ADP and Pi (inorganic phosphate). (I) (Basic)
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/ATP.html
http://staff.jccc.net/pdecell/metabolism
/entrans.html#atpadp
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBookATP.html
Textbooks/Publications
Bio Factsheet 129: ATP – what it is,
what it does
Past Papers
Paper 41, June 2011, Q7 (a)
12.2.a
list the four stages in aerobic
respiration (glycolysis, link reaction,
Krebs cycle and oxidative
phosphorylation) and state where
each occurs in eukaryotic cells
v2.1 5Y02
Learners recall an overall equation for aerobic respiration:
glucose + oxygen energy + water + carbon dioxide
o State that ATP should be substituted for ‘energy’.
o Learners write out a balanced equation using the correct chemical formulae (for
completeness, mention heat energy). (W) (Basic)
Learners write out the overall equation for aerobic respiration and produce a large
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://leavingbio.net/RESPIRATION%28ordinary%20level%29.htm
http://leavingbio.net/respiration%28higher%20level%29.htm
130
Learning objectives
Key concepts
Cells as the units of life,
Biochemical processes,
Natural selection
12.2.b
outline glycolysis as phosphorylation
of glucose and the subsequent
splitting of fructose 1,6-bisphosphate
(6C) into two triose phosphate
molecules, which are then further
oxidised to pyruvate with a small yield
of ATP and reduced NAD
Key concepts
Biochemical processes
Suggested teaching activities
diagram (full page) of a cell (cytoplasm labelled), containing a (not-to-scale) large
labelled mitochondrion with visible cristae (1.2.b, Unit 2).
o Learners write the heading of each of the four stages in the correct locations
and add to this later. (I) (Basic)
Learning resources
Past Papers
Paper 41, June 2011, Q7 (b)(iii)
Note
Glycolysis: can be shown later as glucose pyruvate.
Link reaction: pyruvate entering the mitochondrial matrix and the reaction with
coenzyme A, acetyl coenzyme A, enters the cycle.
Krebs cycle: main stages of the cycle only, showing involvement of FAD and NAD,
decarboxylation and ATP production.
Oxidative phosphorylation: NADH and FADH leaving the cycle to the crista, ATP
formation.
Highlight to learners the similar biochemistry in different species of organisms (link
to the evidence for evolution in Unit 7).
Build up the idea that: (i) respiration is a series of enzyme-controlled metabolic
reactions, (ii) it takes place in all living cells, and (iii) energy contained in molecules
such as glucose is used to make ATP molecules. (W) (Basic)
Explain that glycolysis occurs in the cytoplasm (in virtually every organism) in both
anaerobic and aerobic respiration. (W) (Basic)
Learners copy out a skeleton flow diagram of glycolysis, with glucose, the two
intermediates, and pyruvate shown (missing intermediate stages could be signified
by the correct number of arrows in between).
o With question and answer prompts, learners build up their flow charts with detail
and explanatory annotations. Ensure they understand that: coenzyme NAD is
required to act as an electron (hydrogen) carrier for the enzyme-catalysed
reaction (see 12.1.d); NADH has different fates, depending on whether or not
oxygen is available.
o Learners show clearly the tally of ATP use and production.
o The number of carbons for each of the molecules in the process is shown in
brackets. (W) (I) (Challenging)
Explain that in glycolysis ATP can be formed when another phosphorylated organic
compound transfers a phosphate to ADP: so ATP is synthesised as a product in a
substrate-linked reaction (see 12.1.c). (W) (Basic)
Online
http://glycolysis.co.uk/
www.science.smith.edu/departments/
Biology/Bio231/glycolysis.html
http://www.sumanasinc.com/webconte
nt/animations/content/cellularrespirati
on.html
http://www.johnkyrk.com/glycolysis.ht
ml
http://highered.mcgrawhill.com/sites/9834092339/student_vi
ew0/chapter7/how_glycolysis_works.
html
http://resources.teachnet.ie/foneill/res
pir.html
Past Papers
Paper 41, Nov 2011, Q6 (a)(b)
Note
If able learners are given a more complete picture, stress that the additional
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
131
Learning objectives
Suggested teaching activities
Learning resources
intermediate steps and compounds are not required learning.
Mention that ‘substrate-level phosphorylation’ is an alternative term to substratelinked ATP synthesis.
12.2.c
explain that, when oxygen is available,
pyruvate is converted into acetyl (2C)
coenzyme A in the link reaction
Key concepts
Biochemical processes,
Organisms in their environment
Explain that pyruvate travels from the cytosol through the inner and outer
mitochondrial membranes to enter the matrix where the link reaction occurs. (W)
(Basic)
Learners study and comment on the link reaction equation before making notes.
They should note that:
o Coenzyme A transfers an acetyl group to the Krebs cycle (see 12.1.d).
o Carbon dioxide is given off, hence decarboxylation* occurs.
o NAD acts as an electron (hydrogen) carrier, hence dehydrogenation* occurs.
o The reaction occurs twice for each original glucose molecule. (G) (I) (Basic)
(Challenging)
Note
See 12.2.e also.
12.2.d
outline the Krebs cycle, explaining that
oxaloacetate (a 4C compound) acts as
an acceptor of the 2C fragment from
acetyl coenzyme A to form citrate (a
6C compound), which is reconverted
to oxaloacetate in a series of small
steps
Key concepts
Biochemical processes
Build up the simple diagram showing the required steps in the Krebs cycle, including
the number of carbon atoms for the three named compounds.
o Emphasise: its cyclic nature; enzyme-controlled reactions (no names required);
more steps are involved than is shown. (W) (I) (Basic)
Explain that two carbon dioxide molecules are released for one turn of the cycle and
ask learners to decide where this is and add to the diagram.
o Tell learners where substrate-linked phosphorylation occurs (see 12.2.b and
12.1.c) so they can add ATP formation to their diagram (knowledge of GTP not
required).
o Learners volunteer the role of NAD and FAD, and then add the formation of
NADH and FADH to their cycle (see 12.2.d). (I) (Basic)
Learners state and explain how many turns of the cycle occur for each molecule of
glucose. (I) (Basic)
Allow learners a short time to look at their diagrams, and then talk through the steps
while they draw the cycle. (F)
Online
http://www.saps.org.uk/learners
http://www.wiley.com/legacy/college/b
oyer/0470003790/animations/tca/tca.
htm
http://www.science.smith.edu/departm
ents/Biology/Bio231/krebs.html
http://www.johnkyrk.com/krebs.html
http://highered.mcgrawhill.com/sites/0072507470/student_vi
ew0/chapter25/animation__how_the
_krebs_cycle_works__quiz_1_.html
Online
http://www.saps.org.uk/learners
http://www.wiley.com/legacy/college/b
oyer/0470003790/animations/tca/tca.
htm
http://www.science.smith.edu/departm
ents/Biology/Bio231/krebs.html
http://www.johnkyrk.com/krebs.html
Past Papers
Paper 43, June 2011, Q6 (a)(b)
Note
Learners should avoid websites that have far more detail than required.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
132
Learning objectives
Suggested teaching activities
12.2.e
explain that reactions in the Krebs
cycle involve decarboxylation and
dehydrogenation and the reduction of
NAD and FAD
Learners add annotations to the Krebs cycle:
o dehydrogenation occurs: the NADH and FADH contain hydrogen atoms protons
and electrons (from the respiratory substrate)
o decarboxylation of intermediates occurs: carbon dioxide is given off. (I) (Basic)
Give learners time to assimilate the information on their diagrams before testing
them. (I) (Challenging)
Key concepts
Biochemical processes
12.1.c
explain that ATP is synthesised in
substrate-linked reactions in glycolysis
and in the Krebs cycle
Learning resources
Note
Dehydrogenase and decarboxylase enzymes could be mentioned here (not required
learning).
Learners add an explanation of ATP synthesis by substrate-linked reactions to their
summary diagram of 12.2.a. (W) (Basic)
Online
http://sandwalk.blogspot.co.uk/2007/1
2/how-cells-make-atp-substratelevel.html
Learners label a basic diagram of the membrane carriers of the electron transport
chain (ETC) and the ATP synthase (synthetase) complex in the inner mitochondrial /
crista membrane (include labels for the mitochondrial matrix and the intermembrane space).
With prompting and guidance, learners show on their diagram the transfer of
hydrogen to the membrane from NADH and FADH and the release of the
coenzymes for re-use in the Krebs cycle. (W) (Basic)
Learners contribute to build up the rest of the diagram. For the electron transport
chain include:
o Hydrogen from NAD/FAD split into protons and electrons.
o Oxidation-reduction reactions are involved (hence ‘oxidative’) as electrons are
transported down the ETC (i.e. to lower energy levels).
o Energy provided by the electron transfer is used to pump protons from the
matrix into the intermembrane space.
o Oxygen (final electron acceptor) + electrons + protons produce water as a waste
product.
For chemiosmosis, use learner knowledge of AS Level to discuss:
o The relatively impermeability of the membrane to protons (so allowing a buildup).
Online
http://www.science.smith.edu/departm
ents/Biology/Bio231/etc.html
http://bcs.whfreeman.com/thelifewire/c
ontent/chp07/0702001.html
Key concepts
Biochemical processes
12.2.g
explain that during oxidative
phosphorylation:
energetic electrons release energy
as they pass through the electron
transport system
the released energy is used to
transfer protons across the inner
mitochondrial membrane
protons return to the mitochondrial
matrix by facilitated diffusion
through ATP synthase providing
energy for ATP synthesis (details of
ATP synthase are not required)
Key concepts
Biochemical processes
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 12: Respiration
Past Papers
Paper 42, June 2013, Q4 (a)(i)
133
Learning objectives
Suggested teaching activities
Learning resources
o Facilitated diffusion of protons through the enzyme complex down their
concentration (and electrical) gradient.
o The enzyme-catalysed synthesis of ATP from ADP and inorganic phosphate by
the movement of protons (proton-motive force). (W) (I) (Challenging)
Learners sort a set of statements into a correct sequence to outline oxidative
phosphorylation and then add an outline to their summary diagram of 12.2.a. (P) (I)
(Basic) (Challenging)
Learners write a sequential account of the process. (F)
12.2.f
outline the process of oxidative
phosphorylation including the role of
oxygen as final electron acceptor (no
details of the carriers are required)
Key concepts
Biochemical processes
Assess understanding of 12.2.g by agreeing an outline summary with learners.
o Oxidative phosphorylation is the last stage in the release of energy from the
initial respiratory substrate and oxygen is the final electron acceptor.
o The two linked parts to the process are the events involving the electron
transport chain and the events linked with a process known as chemiosmosis.
o The sources of the ‘energetic’ electrons are NADH and FADH from the Krebs
cycle and NADH from the link reaction.
o ATP formation by oxidative phosphorylation is a process involving oxidationreduction reactions, where the energy needed for ATP synthesis is from the
transfer of electrons from a higher energy electron donor to a lower energy
electron acceptor.
Learners add an outline of the link reaction, Krebs cycle and oxidative
phosphorylation to their summary diagram of 12.2.a. (I) (Basic)
Online
http://www.stolaf.edu/people/giannini/fl
ashanimat/metabolism/mido%20e%2
0transport.swf
Past Papers
Paper 43, June 2011, Q6 (c)
Note
Carriers do not need identifying but explain that these are membrane proteins.
Learners should be able tackle the concepts involved in 12.2.h if they have
mastered the outline of 12.2.g.
Chemiosmosis as a term is not specified in a learning objective, but learners should
be familiar with the term.
12.1.e (i)
explain that the synthesis of ATP is
associated with the electron
transport chain on the membranes
of mitochondria and chloroplasts
(see 12.2.g)
Only part of this learning objective is included here: explain that the synthesis of ATP is
associated with the electron transport chain on the membranes of mitochondria (see
12.2.g)
With a brief written test, confirm learner knowledge and understanding of this
learning objective (all details previously covered). (I) (Basic)
In preparation for Unit 11, explain that there is also an ETC located in the thylakoid
membranes of chloroplasts. (W) (I) (Basic)
Online
http://www.ncbi.nlm.nih.gov/books/NB
K21063/
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
134
Learning objectives
Suggested teaching activities
Learning resources
Explain that many enzymes require a non-protein (co-)factor, in their active site to
help in catalysis, and that organic cofactors that associate with the enzyme during
catalysis and then dissociate are known as coenzymes. (W) (Basic)
Ensure learners now understand that NAD and FAD are electron (hydrogen)
carriers, so become reduced and can give electrons to electron acceptors during
respiration (becoming oxidised again).
o Learners should be clear that the oxidation of NADH and FADH releases energy
that can be used to synthesise ATP. (W) (Basic)
Online
http://www.ebi.ac.uk/thorntonsrv/databases/CoFactor/index.php
From electron micrographs of mitochondria, learners identify the outer and inner
membrane, cristae and matrix.
o Learners check if 70S ribosomes and small circular DNA is visible. (P) (I)
(Basic)
Learners construct an annotated diagram summarising how the structure of a
mitochondrion is adapted for its functions. (I) (Challenging)
Online
http://www.johnkyrk.com/mitochondrio
n.html
Use flow diagrams to explain the lactate pathway in mammals and the ethanol
pathway in yeast, with learners providing the main outline of glycolysis (glucose to
pyruvate) and naming the location (cytoplasm). (W) (Basic)
Explain that these pathways occur when oxygen is not available, with pyruvate and
ethanol acting as the final electron acceptors to produce lactate and ethanol as
waste products. (W) (Basic)
Learners suggest why pyruvate needs to be processed further when no more ATP
is produced (the regeneration of NAD to allow glycolysis to continue - there is a very
limited quantity of NAD in each cell). (W) (Basic)
Learners add an outline to their summary diagram of 12.2.a after making their own
flow diagrams. (I) (Basic)
Learners begin with oxidative phosphorylation and work backwards through earlier
stages to write down a series of statements showing the consequences if oxygen is
not available. (F) (Challenging)
Learners research the concept of oxygen debt and write an explanation.
Online
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBookGlyc.html#An
aerobic
http://www.brianmac.demon.co.uk/oxd
ebit.htm
Cells as the units of life,
Biochemical processes
12.1.d
outline the roles of the coenzymes
NAD, FAD and coenzyme A in
respiration
Key concepts
Biochemical processes
12.2.i
describe the relationship between
structure and function of the
mitochondrion using diagrams and
electron micrographs
Key concepts
Cells as the units of life,
Biochemical processes
12.2.k
explain the production of a small yield
of ATP from respiration in anaerobic
conditions in yeast and in mammalian
muscle tissue, including the concept of
oxygen debt
Key concepts
Biochemical processes,
Natural selection
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 61: Chloroplasts and
mitochondria
Textbooks/Publications
King p.84
Siddiqui p.101
Past Papers
Paper 43, June 2013, Q4 (b)
135
Learning objectives
Suggested teaching activities
Learning resources
o Annotations can be added to the lactate pathway to show how, when oxygen
becomes available, lactate can be converted back to pyruvate, which can then
be converted to glucose and glycogen for storage, or enter the Krebs cycle. (H)
(Challenging)
Extension practical: learners investigate the effect of different concentrations of
ethanol on rates of respiration in yeast. (I) (Challenging)
Note
Mention to learners that anaerobic respiration in yeast is also known as alcoholic or
ethanol fermentation and that anaerobic respiration in mammalian tissues is also
known as lactic acid or lactate fermentation.
Explain to learners that the reduction of pyruvate to lactate is common in many
bacteria. Highlight that these reactions are similar in widely different species of
organism.
12.2.l
explain how rice is adapted to grow
with its roots submerged in water in
terms of tolerance to ethanol from
respiration in anaerobic conditions and
the presence of aerenchyma
Key concepts
Organisms in their environment
12.2.j
distinguish between respiration in
aerobic and anaerobic conditions in
mammalian tissue and in yeast cells,
contrasting the relative energy
released by each (a detailed account
v2.1 5Y02
Remind learners of xerophytes and adaptation to survival in arid conditions (7.2.f)
and introduce rice as a plant adapted to survive with its roots submerged in water,
which has little oxygen. (W) (Basic)
Explain that an ethanol build-up is toxic to yeast cells and that plant cells also
produce ethanol when in anaerobic conditions.
o Agree that continuous or prolonged anaerobic conditions as experienced by rice
when it is growing in flooded fields means that root cells need to be tolerant to
ethanol. (W) (Basic)
Check learner understanding of the terms used in the learning objective: submerged
and tolerance. (W) (Basic)
Learners use a light microscope to observe aerenchyma in root and stem sections
of prepared slides. (I) (Basic)
To summarise, learners list and explain the features that make rice adapted to grow
with roots that are submerged in water, and explain why most plants cannot survive
when their roots are submerged in water. (F)
Online
http://plantsinaction.science.uq.edu.au
/edition1/?q=content/18-1-2adaptive-responses-waterlogging
www.biologymad.com/resources/Crop
%20Plants.pps
Learners suggest what is meant by respiration: brainstorm ideas such as: the
release of energy from food; the production of ATP; ATP for use by the cell; the
process occurs in the cell.
o Expand the discussion to distinguish between aerobic respiration and
respiration in anaerobic conditions. (W) (Basic)
Emphasise that most of the ATP is synthesised as a result of oxidative
Textbooks/Publications
Jones, Fosbery, Taylor, Gregory, has
on page 205 (2007), or on page 277
(2013), a balance sheet of ATP use
and synthesis. This could be used to
give learners an idea of the
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 41, Nov 2011, Q4 (a)(b)
Paper 42, June 2013, Q10 (b)
136
Learning objectives
Suggested teaching activities
of the total yield of ATP from the
aerobic respiration of glucose is not
required)
phosphorylation, requiring the reduced coenzymes from the link reaction and Krebs
cycle (compare with the 2ATPs produced without oxygen). (W) (Basic)
Learners make notes comparing respiration in aerobic and anaerobic conditions.
(W) (Basic)
Key concepts
Biochemical processes
12.2.h
carry out investigations to determine
the effect of factors such as
temperature and substrate
concentration on the rate of respiration
of yeast using a redox indicator (e.g.
DCPIP or methylene blue)
Key concepts
Biochemical processes,
Organisms in their environment,
Observation and experiment
12.1.f
explain the relative energy values of
carbohydrate, lipid and protein as
respiratory substrates and explain why
lipids are particularly energy-rich
Key concepts
Biochemical processes
v2.1 5Y02
Note
‘Balance sheets’ are not required. There are different totals for ATP production in
aerobic respiration, varying from 32, to 36, to 38 in older text books. In more recent
texts, the estimate of ‘1NADH = 3ATP’ is now seen as approximately 1NADH =
2.5ATP (also 1FADH = 1.5ATP).
Learning resources
difference in relative energy
released.
Past Papers
Paper 41, June 2011, Q7 (b)(ii)
Paper 41, Nov 2011, Q6 (c)
Remind learners that yeast is not a plant but a fungus. Emphasise that yeast
respires aerobically and in anaerobic conditions. (W) (Basic)
Explain that redox dyes are used as indicators of hydrogen transfer and in
investigations can be used as artificial hydrogen acceptors to provide a visual check
on the rate of respiration (the reduction of NAD or FAD cannot be ‘seen’). (W)
(Basic)
o State that methylene blue is blue in the oxidised state (without hydrogens) and
turns colourless as hydrogens are accepted and it becomes reduced. (W)
(Basic)
o With this knowledge, small groups can be set the task of planning an
appropriate investigation to carry out. (G) (Challenging)
Note
These investigations are a good opportunity to develop planning skills.
Experiments with yeast and anaerobic respiration require the substrate solution
(e.g. glucose) to be boiled (to remove oxygen) and cooled.
Learners recall the overall equation for aerobic respiration and understand how it
balances. (W) (Basic)
Explain that many cells can use other respiratory substrates, such as other sugars,
lipids and proteins, and that different substrates have different energy values per
unit mass. (W) (Basic)
Reflect back to 12.1.e to remind learners about the importance of supplying
hydrogen to the ETC for electron flow and the release of energy for ATP production.
Learners consider ratios of C, H and O, to explain and note down the relative
energy values of proteins, carbohydrates and lipids, noting that lipids, with
proportionately more hydrogen per g of substrate, will yield more energy. (W) (I)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://mutuslab.cs.uwindsor.ca/schurk
o/animations/bombcal/animation4.ht
m
http://highered.mcgrawhill.com/sites/0073040541/learner_vi
ew0/chapter7/animation__bomb_cal
orimeter.html#
137
Learning objectives
Suggested teaching activities
Learning resources
(Basic)
Note
Knowledge of how the energy values are obtained is not required (see learning
resources / endorsed textbooks for background information).
12.1.g
define the term respiratory quotient
(RQ) and determine RQs from
equations for respiration
Key concepts
Biochemical processes,
Organisms in their environment
12.2.m
carry out investigations, using simple
respirometers, to measure the effect
of temperature on the respiration rate
of germinating seeds or small
invertebrates
Key concepts
Observation and experiment
Learners write out the definition of respiratory quotient and the formula to use when
calculating RQ values.
o Explain that volumes or moles or molecules can be used but for any one
calculation they should not be mixed.
o Learners calculate the RQ value for glucose. (W) (I) (Basic)
When provided with equations, learners calculate the RQs for named substrates.
(P) (I) (Basic) (Challenging)
o Learners construct a summary table for carbohydrates, proteins and lipids
(approximate values). (I) (Basic)
o Learner explain the link between high RQ values and anaerobic respiration. (I)
(Basic)
Learners try SAQ 15.8, in Jones, Fosbery, Taylor, Gregory (2007), to calculate an
RQ for a fatty acid. (I) (Challenging)
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Phot
osynResp/PhotosynResp.htm
Explain how to use a simple respirometer to determine the rate of oxygen uptake
and rate of carbon dioxide production. (W) (Basic)
Discuss the benefits of using thermostatically-controlled water baths to maintain a
constant temperature.
o Learners suggest other ways of maintaining a constant temperature, with peer
evaluation of the method. (P) (I)
Practical booklet 7 involves using a simple respirometer and provides opportunity
for data analysis and planning for Paper 5. Learners plan an investigation to find the
optimum temperature for respiration. Learners swap and carry out a partners plan
exactly as written, each to provide their partner with an evaluation of the plan. (P) (I)
(Challenging)
Practical booklet 7
Note
You may wish to save time and also carry out the requirement of 12.1.h.
Simple designs, using a single syringe and capillary tubing (as in Practical booklet
7) are far more sensitive to temperature and require minimal handling.
The simple respirometers are more reliable in yielding results than the modifications
of the Barcroft respirometer, usually given in practical guides.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
In Jones, Fosbery, Taylor, Gregory,
pages 208-209 (2007), or page 281
(2013), explains respiratory quotient
and has worked examples.
Past Papers
Paper 43, Nov 2012, Q8 (c)
Online
http://www.phschool.com/science/biol
ogy_place/labbench/lab5/features.ht
ml
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Phot
osynResp/PhotosynResp.htm
Textbooks/Publications
King p.80-83
Siddiqui p.101-103
138
Learning objectives
Suggested teaching activities
Learning resources
Temperature compensation by having two tubes linked by a manometer results in
well controlled experiments, but introduces potentially leaky joints.
A teacher demonstration of a temperature-compensated respirometer is advisable,
so learners see both types.
12.1.h
carry out investigations, using simple
respirometers, to determine the RQ of
germinating seeds or small
invertebrates (e.g. blowfly larvae)
Learners carry out an investigation to measure RQ using the simple respirometers
(planning skills may be developed here),
o e.g. learners measure carbon dioxide production and oxygen absorption by
germinating seeds, and calculate RQ. This has the potential to develop abilities
evaluating investigations. (I) (Challenging)
Key concepts
Observation and experiment
Practical booklet 7
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Phot
osynResp/PhotosynResp.htm
http://www.phschool.com/science/biol
ogy_place/labbench/lab5/features.ht
ml
Textbooks/Publications
King p.80-83
Siddiqui p.101-103
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
139
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 10: Mammalian physiology, control and coordination
Recommended prior knowledge
Learners should have a good understanding of cell structure and the structure of a cell surface membrane. They should have an appreciation of the role of the various
components, particularly the role of glycoproteins as receptors in cell signalling and of membrane transport proteins. They should understand the concept of water
potential and have good knowledge of transport mechanisms across membranes, including facilitated diffusion and active transport from Unit 2.
Context
This unit builds on the key concept of cells as the basic units of life to consider how mammals, as multicellular organisms, control and coordinate activities and how
homeostatic mechanisms enable a balance to be maintained. The maintenance of homeostatic mechanisms for healthy functioning, such as in controlling blood
glucose concentrations, extends learner understanding of non-infectious disease. Cell structure, cell membranes, transport across membranes and the mammalian
circulatory system are topics covered at AS Level that are an important foundation for the learning objectives studied in this unit. A study of dipsticks, biosensors and
the contraceptive pill highlights the dependence of humans on biotechnology: biotechnology results from observation, enquiry and experiment, a key concept. The
examples studied here extend learner knowledge from those already covered in Unit 8.
Outline
This unit begins by highlighting the importance of responding to external and internal stimuli with effective control and coordination by the nervous system and by the
endocrine system. The structure and function of the motor and sensory neurone is covered and there is a detailed study of the transmission of nerve impulses,
including transmission across the synapse and the neuromuscular junction, followed by a consideration of the sliding filament theory of muscle contraction. Learners
consider the involvement of the nervous and endocrine systems in homeostatic mechanisms and discuss the role of negative feedback. Thermoregulation,
osmoregulation and blood glucose regulation exemplify the importance of homeostasis in mammals. The production of urea and the role of the kidney in the excretion
of nitrogenous wastes are described. Detail of the control of blood glucose concentration and water content (by the kidney) illustrates the concept of homeostasis.
Biotechnological applications are included by considering the use of dipsticks and biosensors in the detection of glucose in the blood and urine, and of protein and
ketones in urine. The unit concludes with a study of the menstrual cycle and the role of hormones in the cycle, which leads to a description of the contraceptive pill.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
140
Learning objectives
Suggested teaching activities
Learning resources
15.1.a
compare the nervous and endocrine
systems as communication systems
that co-ordinate responses to changes
in the internal and external
environment (see 14.1.a) and 14.1.b)
Discuss the need for communication between organs in a multicellular organism and
how activities need to be controlled and coordinated. (W) (Basic)
Use a brainstorm session to gauge learner knowledge and to discuss the main
features of each. As individuals make suggestions and agree whether they are
referring to the nervous or endocrine system. (W) (Basic)
o Learners note down that the two systems are for control, coordination and
internal communication, and that they can interrelate and affect each other. (W)
(Basic)
Learners research and give definitions of the terms: stimulus, receptor, effector,
control centre and response. (I) (Basic)
Learners list the features of an endocrine gland (an organ or tissue), with teacher
guidance. (W) (I) (Basic)
o Learners sketch endocrine glands onto a cut-out / diagram of a body and name
the hormones that they secrete. Fill in any gaps in knowledge, mentioning those
particularly that are in this syllabus. (I) (Basic)
o Learners name the target cells / tissues of each hormone, consolidating
understanding of hormones acting at a distance from their origin and at particular
sites of action. (W) (Basic)
Focus on the nervous system and ask what the equivalent to the hormones would
be to enable coordination. Encourage learners to use the terms nerve impulses or
impulses. (W) (Basic)
Continue the discussion for learners to name the brain as the main control centre,
and muscles and glands, including endocrine glands, as effectors.
Divide the class into two. One half participates in a group discussion to suggest
examples of internal changes in organisms, stating for each one: the organs /
systems that are affected; receptor(s); communication method; effector(s); and
response(s). The other half suggests examples of changes in external environment.
The two groups come together to share ideas. (W) (G) (Basic).
CD-ROM
Bioscope – has images of nerves (LS
and TS).
Key concepts
Cells as the units of life,
Organisms in their environment
Online
http://www.udel.edu/Biology/Wags/hist
opage/colorpage/cp/cp.htm
http://www.s-cool.co.uk/alevel/biology/nervous-and-hormonalcontrol
Textbooks/Publications
Bio Factsheet 38: Animal hormones
and hormone action.
King p. 151-152
Siddiqui p.164-167, 171
Past Papers
Paper 41, June 2011, Q9 (a)
Note
It will be noted that both systems involve negative feedback – a verbal clarification of
this mechanism is sufficient as learners will define the term later.
Understanding of all terms will be consolidated as learners cover specific examples
within the unit.
15.1.b
describe the structure of a sensory
v2.1 5Y02
Explain that nerves are composed of many specialised nerve cells, neurones, held
by connective tissue. (W) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www2.estrellamountain.edu/facul
141
Learning objectives
Suggested teaching activities
Learning resources
neurone and a motor neurone
Learners draw, label and annotate a sensory and a motor neurone. (I) (Basic)
o Learners compare the diagrams with electron micrographs. (I) (Challenging)
Learners explain how the structure of the neurone is related to its function (or wait
until after 15.1.d has been covered). (H) (Basic)
Learners complete unlabelled and incomplete diagrams (the diagrams could lack
nuclei, myelin sheaths and synaptic knobs). (F)
ty/farabee/biobk/BioBookNERV.html#
The%20Neuron
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/N/Neurons.html
Explain the difference between a sensory receptor cell and a sense organ, e.g.
tongue = organ of taste; taste cells are chemoreceptors (sensory receptor cells)
found in clusters called taste buds. (W) (Basic)
Explain that the different forms of energy arriving at the sensory receptor get
converted (transduced) into electrical energy of the nerve impulse.
o State that all sensory receptors are transducers. (W) (Basic)
Learners research and list the different sensory receptors in humans and name the
forms of energy received by each receptor. (P) (I) (Basic)
Describe the sensory neurone with a resting potential and explain how a stimulus
leads to membrane depolarisation and impulse transmission.
o State that depolarisation causes an action potential to be generated and explain
that details are covered later. (W) (Challenging)
Choose for example, chemoreceptors as sensory receptors and state that they
detect specific molecules or classes of molecule.
o Learners suggest internal and external stimuli that are detected by
chemoreceptors and give examples of responses (e.g. the difference between
harmful / toxic substances taken into the mouth and food). (W) (Basic)
Show learners a diagram of a sensory receptor cell / chemoreceptor and explain that
a taste cell has contact with a sensory neurone.
o Explain that the binding of molecules to receptors on the cell surface membrane
(many microvilli) of the taste cell leads to depolarisation, which is passed onto
the sensory neurone and the control centre.
o Learners state the type of transduction that has occurred. (W) (Challenging)
Learners produce a diagram of a sensory receptor cell, showing synapses with
dendrites of a sensory neurone.
o Learners annotate the sequence of events occurring from the detection of a
stimulus to an impulse being transmitted along the sensory neurone. (I)
(Challenging)
Introduce the terms receptor potential and all-or-nothing law/rule, either by teacher-
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp44/4402001.html
http://faculty.washington.edu/chudler/t
wopt.html
http://www.answers.com/topic/tasteand-smell
Key concepts
Cells as the units of life
15.1.c
outline the roles of sensory receptor
cells in detecting stimuli and
stimulating the transmission of nerve
impulses in sensory neurones (a
suitable example is the chemoreceptor
cell found in human taste buds)
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 43, Nov 2011, Q9 (a)
Textbooks/Publications
King p.180-183
Past Papers
Paper 41, Nov 2011, Q11 (a)
142
Learning objectives
Suggested teaching activities
Learning resources
led discussion or by textbook/internet research. (W) (I) (Challenging)
Practical: learners carry out experiments to investigate touch, temperature and pain
receptors in the skin. (P) (I) (Basic)
Note
Explain to learners that some sensory receptors are also sensory neurones, while
others are specialist receptor cells that synapse with sensory neurones.
Learners should feel confident applying the principles of the process to other
examples of sensory receptor cells.
15.1.d
describe the functions of sensory, relay
and motor neurones in a reflex arc
Key concepts
Cells as the units of life
Explain that a reflex arc is the neural pathway behind a reflex action.
o Introduce the relay neurone before asking learners to draw and annotate a reflex
arc. (W) (I) (Basic)
Practical: learners look at prepared slides of cross-sections of the spinal cord to
identify features. (I) (Basic)
Practical: learners carry out an experiment on a particular reflex action.
o For each, learners draw a reflex arc and annotate to show the function of the
neurones. (F)
Learners research examples of reflexes using the spinal cord and the brain,
detailing: stimulus; receptor; effector; and response. (H) (Basic)
o Learners share examples with the class. (W) (Basic)
Online
http://www.sumanasinc.com/webconte
nt/animations/content/reflexarcs2.htm
l
http://www.sciencejoywagon.com/explr
sci/media/reflex.htm
http://www.intelligencetest.com/reflex/i
ndex.htm
Textbooks/Publications
Bio Factsheet 58: Reflex action
Note
Point out that some reflex actions (e.g. the pupil reflex) involve the brain rather than
the spinal cord.
15.1.e
describe and explain the transmission
of an action potential in a myelinated
neurone and its initiation from a resting
potential (the importance of sodium
and potassium ions in impulse
transmission should be emphasised)
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Describe an action potential as a rapid, temporary change in a membrane potential,
explaining that this acts as a ‘booster’ to ensure the impulse (see 15.1.a) travels the
distance. (W) (Basic)
Explain the potential difference across the neurone membrane (mention also the
presence of large anions inside the axon).
o Build on AS Level knowledge to discuss how the resting potential is maintained
(membrane polarised) by the sodium-potassium pump.
o Explain the presence of non-voltage gated channels and facilitated diffusion of
K+ outwards.
o Describe the voltage-gated channels (NaV and KV) specific to the two ions
(which are closed). (W) (Challenging)
Learners set the scene by drawing an annotated diagram of the axon at rest /
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp44/4402002.html
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=40
http://www.biologymad.com/NervousS
ystem/nerveimpulses.htm
http://outreach.mcb.harvard.edu/anima
tions/actionpotential_short.swf
Past Papers
Paper 41, Nov 2011, Q11 (a)
143
Learning objectives
Suggested teaching activities
v2.1 5Y02
Learning resources
polarised. (I) (Basic)
Revisit understanding of ‘partially permeable’ and discuss ‘relatively impermeable’
and ‘relatively permeable’.
o Explain that open voltage-gated channels will increase membrane permeability
to the ion concerned (Na+ or K+). (W) (Basic)
Display diagrams showing the outside and the inside of a neurone – one at a time or
project an animation – to explain what occurs when depolarisation in the previous
section increases the membrane voltage above a threshold value (relate back to allor-nothing from 15.1.c). Include diagrams for:
o Depolarisation: explain how the open NaV channels stimulate more channels to
open (further depolarisation = positive feedback); action potential = the large
change in membrane potential.
o Repolarisation: Describe the changes occurring to NaV and KV channels and
movement of ions.
o (Temporary) undershoot: explain that the membrane is more permeable to K+
than at rest, until their channels close.
o Refractory period: explain how closed voltage-gated channels and action of the
sodium-potassium pump restores the resting potential.
o At each stage, learners suggest permeability states to the different ions,
highlighting the slower-to-react KV channels and the importance of inactivity of
NaV channels. (W) (Challenging)
Learners prepare the axes on graph paper and sketch the changes to potential as
each stage is discussed. (I) (Basic)
o Learners annotate the graph, explaining what is occurring at different time
points: resting potential, rising and falling phases of action potential, undershoot,
refractory period. (F)
Discuss how Na+ entering the axon establishes a local circuit between this and the
negatively charged resting potential in the area ahead. (W) (Challenging)
o Learners suggest how current flow changes membrane permeability to Na+ to
cause self-propagation of the action potential, and how/why this is in one
direction only. (W) (Challenging)
Discuss the two phases of the refractory period. (W) (Challenging)
Learners draw four diagrams of the same section of axon (e.g. draw a simple
cylinder to show the outside and inside of the neurone), headed ‘resting potential’
‘depolarisation’ ‘repolarisation’ ‘refractory period’.
o Learners draw on the location or movement of Na+ and K+, giving a summary
under each diagram. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
144
Learning objectives
Suggested teaching activities
Learning resources
Learners explain the difference between the following: absolute refractory period and
relative refractory period; resting potential and action potential; polarised and
depolarised; impulse and action potential. (H) (Challenging)
Note
There are no action potentials in short neurones as current flow is sufficient to
ensure the impulse travels the short distance.
15.1.f
explain the importance of the myelin
sheath (saltatory conduction) in
determining the speed of nerve
impulses and the refractory period in
determining their frequency
Key concepts
Cells as the units of life
15.1.g
describe the structure of a cholinergic
synapse and explain how it functions,
including the role of calcium ions
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners use resources to draw a labelled, annotated diagram showing transmission
of an action potential in a myelinated axon.
o Learners add explanations to show how saltatory conduction is brought about,
noting the high concentration of voltage-gated channels at the nodes.
o Learners note how saltatory conduction has a great effect on speed of
transmission of impulses. (I) (Challenging)
Learners link the inactivated sodium voltage-gated channels during the falling phase
and part of the undershoot of the action potential (see 15.1.e), to an inability to
trigger another action potential immediately if a second depolarisation arrives.
o Learners annotate their action potential graph. (W) (I) (Challenging)
Learners interpret diagrams and electron micrographs of an axon with a myelin
sheath, identifying Schwann cells and nodes of Ranvier.
o Learners study electron micrographs of unmyelinated axons and make
comparisons. (I) (Basic)
Online
http://www.bu.edu/histology/m/t_electr.
htm
http://www.bu.edu/histology/p/21201lo
a.htm
http://www.unimainz.de/FB/Medizin/Anatomie/works
hop/EM/EMSchwannE.html
Learners copy out a definition of a synapse. Explain they will study a cholinergic
synapse, which is a chemical synapse. (W) (I) (Basic)
Learners draw and label a diagram of a synapse. (I) (Basic)
Learners compare electron micrographs and diagrams of synapses. (I) (Basic)
Remind learners of links with AS Level before outlining events in synaptic
transmission: for example, mitochondria, exocytosis, diffusion, membrane proteins,
hydrolysis catalysed by enzymes. (W) (Basic)
One learner makes the first statement in the sequence of events in synaptic
transmission and chooses another learner to describe the next event, and so on. (G)
(Basic)
A learner chooses a diagram in the sequence and a partner describes what is
occurring and what will happen next. (P) (Basic)
Learners rearrange a set of diagrams to arrive at the correct sequence of events in
synaptic transmission. (F) (Basic)
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp44/4402003.html
http://www.sumanasinc.com/webconte
nt/animations/content/synaptictransmi
ssion.html
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/D/Drugs.html
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 41, June 2011, Q6 (c)
Textbooks/Publications
Bio Factsheet 20: Nerves and
synapses
Bio Factsheet 155: Answering exam
questions on neurones and synapse
145
Learning objectives
Suggested teaching activities
Learning resources
o Learners add annotations to the sequenced diagrams and if necessary make
additional bullet points. (F) (Challenging)
Extension: discuss the effects of drugs on the transmission across the synapse and
show learners how to apply knowledge and understanding to new situations. (W)
(Basic)
Past Papers
Paper 43, Nov 2011, Q9 (b)
Note
Explain that there are other types of chemical synapses, and mention electrical
synapses.
15.1.h
outline the roles of synapses in the
nervous system in allowing
transmission in one direction and in
allowing connections between one
neurone and many others (summation,
facilitation and inhibitory synapses are
not required)
Key concepts
Cells as the units of life
15.1.i
describe the roles of neuromuscular
junctions, transverse system tubules
and sarcoplasmic reticulum in
stimulating contraction in striated
muscle
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners suggest and note down which features ensure one-way transmission of
impulses across a synapse (vesicles with transmitter substance only found in the
presynaptic neurone; specific receptor proteins only located on the postsynaptic
membrane). (W) (I) (Basic)
Discuss the fact that one neurone can have many synapses relating to it, thus
allowing interconnection of numerous nerve pathways. (W) (I) (Basic)
Background: discuss the benefits of interconnection (a stimulus can lead to a range
of responses; can collect more information; excitatory and inhibitory synapses
provide more flexibility in response, hence a wider range of behaviour. (W) (Basic)
Extension: learners carry out some simple investigations into learning that involves
synapses. (P) (I) (Challenging)
Online
http://www.skoool.ie/skoool/examcentr
e_sc.asp?id=2879
Learners study one or more labelled diagrams and establish that: striated muscle is
voluntary; skeletal muscle, the multinucleate cells are also known as muscle fibres
and contain a bundle of myofibrils.
o Learners note that the cell surface membrane of the muscle fibre is termed
sarcolemma, and the cytoplasm is sarcoplasm.
o Explain that the sarcoplasmic reticulum is in contact with the myofibrils and is
similar to SER (Unit 1) and that transverse system tubules are infoldings of the
cell surface membrane. (W) (Basic)
Learners label a diagram of a neuromuscular junction, adding labels using resources
and knowledge of synaptic transmission.
o Learners note that the neuromuscular junction is a form of synapse that is
necessary to allow the effector to respond. (I) (Basic)
Learners sort cards containing details of the sequence of events occurring following
depolarisation at the synaptic terminal of the motor neurone (end with calcium ion
release by the sarcoplasmic reticulum – see 15.1.k).
Online
http://www.bu.edu/histology/p/21501oo
a.htm
https://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter10/animation__function_
of_the_neuromuscular_junction__qui
z_3_.html
http://www.getbodysmart.com/ap/musc
letissue/fibers/sr/tutorial.html
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
King p.202-205.
Past Papers
Paper 41, Nov 2012, Q1 (b(i)
Textbooks/Publications
Bio Factsheet 190: Neuromuscular
junctions
146
Learning objectives
Suggested teaching activities
Learning resources
o Learners make notes, highlighting roles of the named items in the learning
objective. (P) (I) (Challenging)
Extension: learners research myasthenia gravis (Unit 11) and compare a normal and
a myasthenic neuromuscular junction. (H) (Challenging)
15.1.j
describe the ultrastructure of striated
muscle with particular reference to
sarcomere structure
Key concepts
Cells as the units of life
15.1.k
explain the sliding filament model of
muscular contraction including the
roles of troponin, tropomyosin, calcium
ions and ATP
Key concepts
Biochemical processes
14.1.a
discuss the importance of homeostasis
in mammals and explain the principles
of homeostasis in terms of internal and
external stimuli, receptors, central
control, co-ordination systems,
effectors (muscles and glands)
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Discuss the idea of a sarcomere (see 15.1.i diagrams) as the basic unit of
contraction, a repeating unit of a pattern made by thick and thin protein filaments.
(W) (Basic)
Learners label and annotate diagrams of the same sarcomere (i) relaxed, (ii)
contracting, and (iii) fully contracted, to prepare for 15.1.k.
o Learners compare electron micrographs with their diagram. (I) (Basic)
Online
http://www.bu.edu/histology/p/21601oo
a.htm
Explain the sliding filament model while learners add labels to prepared diagrams.
o Discuss the role of the released calcium ions in binding to sites on troponin and
shifting the position of tropomyosin to expose the myosin binding sites. (W)
(Basic)
Learners annotate their diagrams from 15.1.j. (I) (Challenging)
As a whole group, the first member states the first event occurring, ‘depolarisation of
the membrane of the synaptic terminal’ and then chooses the next member of the
group to continue the ‘story’. (W) (Challenging)
Learners produce a written account, or a flow chart diagram, summarising the
sequence of events occurring from the arrival of an action potential at the synaptic
terminal of the motor neurone to the contraction of the sarcomere. (F)
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp47/4702001.html
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Exercise-energy-andmovement/WTDV033020.htm
Learners write an explanation of what is meant by homeostasis.
o Explain that they should think of main ideas and use appropriate terminology
(e.g. give choice as below).
Maintenance of, an internal / a cellular, environment …
at a constant level / set point / norm / normal level / stable level or within
normal limits …
despite changes / fluctuations in the internal or external environment …
using negative feedback control mechanisms …
so that cells can function efficiently. (I) (Basic)
Learners suggest the different parameters or physiological factors that should be
kept at / around a set point (e.g. temperature, blood glucose concentration, blood pH
/ carbon dioxide concentration, water balance / water potential, metabolic wastes)
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Hom
eostasis/Homeostasis.htm
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 46: Muscles.
147
Learning objectives
Suggested teaching activities
Learning resources
and explain the importance of maintaining the balance.
o Encourage use of the terms negative feedback (defined in 14.1.b) receptors and
effectors. (W) (Basic)
Learners use separate cards (limit 10-12) to write out definitions and features of the
terms stimulus, receptor, effector, control centre, response.
o Learners swap with a partner, who can write down the relevant term that is being
described. (P) (I) (Challenging)
14.1.b
define the term negative feedback and
explain how it is involved in
homeostatic mechanisms
Key concepts
Cells as the units of life
Learners write out the simple definition using resources and then qualify further after
discussion:
o Physiological processes or a changing external environment can cause variation
from the set point.
o A mechanism brings the internal environment back to the set point, or small
oscillations about the set point.
o Negative feedback always involves a receptor and effector and often involves a
control centre. (W) (I) (Challenging)
Using a named example, learners draw a flow chart to summarise homeostatic
control and negative feedback, showing the named receptor(s), effector(s) and
control centre (if present). (H) (Basic)
Learners are provided with a paragraph describing a named example of homeostatic
control and construct an annotated diagram as a summary. (F)
14.1.c
outline the roles of the nervous system
and endocrine system in co-ordinating
homeostatic mechanisms, including
thermoregulation, osmoregulation and
the control of blood glucose
concentration
Learners write a paragraph explaining what the two systems have in common and
then construct a table of the differences. (I) (Challenging)
Learners to research the difference between: excretion and secretion; an endocrine
gland and an exocrine gland. (H) (Basic)
Using resources, learners outline the involvement of the nervous system and
endocrine system in each of the named mechanisms, including naming, and
describing the role of, any hormones. (I) (Basic)
Key concepts
Cells as the units of life,
Biochemical processes
Note
There are close links to 15.1.a.
The research on osmoregulation and blood glucose concentration is useful for later
studies.
14.1.d
describe the deamination of amino
Learners suggest the distinction between excretion and egestion. (W) (Basic)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologyonline.org/4/1_physiological_homeost
asis.htm
http://scienceaid.co.uk/biology/humans
/homeostasis.html
http://science.jrank.org/pages/3365/Ho
meostasis.html
Textbooks/Publications
Bio Factsheet 28: Feedback control
mechanisms
Bio Factsheet 161: Negative Feedback
Mechanisms
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp41/41020.html
http://www.abpischools.org.uk/page/m
odules/homeostasis_sugar/sugar2.cf
m
Online
http://www.ilng.in/pdf/mtg_bio_final.pdf
148
Learning objectives
Suggested teaching activities
Learning resources
acids and outline the formation of urea
in the urea cycle (biochemical detail of
the urea cycle is not required)
Describe how deamination removes the toxic part of an amino acid molecule,
forming highly toxic ammonia, and leaves a useful keto acid (chemical energy for
respiration or conversion for energy storage).
o Explain that in many terrestrial animals the ammonia is immediately converted to
the less toxic urea. (W) (Basic)
Learners annotate an outline diagram of deamination and the urea (ornithine) cycle
as you provide additional information, including: takes place in the liver; enzyme
controlled; ATP required; urea transported dissolved in the blood. (I) (Basic)
Extension: learners draw a molecule of urea highlighting that it is a small organic
compound (useful for later work on the kidney). (W) (Basic)
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/U/UreaCycle.html
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 59: Excretion.
Note
Explain that amino acids are not stored in the body.
14.1.e
describe the gross structure of the
kidney and the detailed structure of the
nephron with its associated blood
vessels using photomicrographs and
electron micrographs
Key concepts
Cells as the units of life
Agree with learners the location of their kidneys. (W) (Basic)
Show learners, on a whole kidney, what is meant by transverse and longitudinal
sections before learners identify structures from images.
o Learners hold up to the light the prepared slides of rat kidney to show the shape
of the entire kidney in LS or TS, and the areas of cortex and medulla. (W) (I)
(Challenging)
Learners dissect (e.g. from a sheep), or use images of, a whole kidney to make
annotated drawings of the external appearance and a section through the kidney. (I)
(Challenging)
Go through a diagram of nephron structure, including the associated blood vessels.
Refer also to the high blood pressure in the renal artery.
o Explain that the venous system does not begin immediately after the glomerulus,
and that there is a dense capillary network serving the nephrons. (W) (Basic)
o Learners label and annotate the diagram. (I) (Basic)
Note
If a kidney is dissected, learners can trace the renal artery, renal vein and ureter,
and follow the blood vessels into the cortex.
CD-ROM
Bioscope – has images of kidney
sections.
Online
http://www.histology.leeds.ac.uk/urinar
y/kidney.php
http://library.med.utah.edu/WebPath/R
ENAHTML/RENALIDX.html
http://www.cie.org.uk/cambridgefor/teachers/order-publications/
Textbooks/Publications
King p.155-156
Siddiqui p.191-194
Bio Factsheet 1: The kidney: excretion
and osmoregulation
Past Papers
Paper 32, June 2011, Q2
Paper 41, June 2012, Q10 (a)
14.1.f
describe how the processes of
v2.1 5Y02
For an overview, learners annotate a large diagram as you outline the processes
occurring in each region. (W) (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
149
Learning objectives
Suggested teaching activities
Learning resources
ultrafiltration and selective
reabsorption are involved with the
formation of urine in the nephron
Explain how sufficient pressure is present for ultrafiltration.
o Discuss how the presence of the plasma proteins remaining in the blood has
some effect on water potential and the filtration process. (W) (Basic)
Learners annotate diagrams to explain how the structure of the Bowman’s capsule
and glomerulus allows the process of ultrafiltration to occur.
o Explain the role of the basement membrane as the true dialysing filter. (I)
(Challenging)
Learners make a list of the components of glomerular filtrate and list the components
of blood that are too large for ultrafiltration. (I) (Basic)
Learners interpret tables showing the concentration of various substances in the
blood plasma and the glomerular filtrate to make comparisons. (I) (Basic)
Learners annotate diagrams of selective reabsorption in the proximal convoluted
tubule (PCT), with teacher-led prompts
o To consolidate, learners make bullet point notes using resources. (I)
(Challenging)
Learners produce a summary listing the mechanisms of transport used in selective
reabsorption and the substances that are transported. (I) (Basic)
Learners explain how the structure of the cuboidal epithelial cells of the PCT are
suited to their function. (H) (F) (Challenging)
Background: learners research the principles behind kidney dialysis. (I)
(Challenging)
et/BiologyPages/K/Kidney.html
www.biologyinmotion.com/nephron/ind
ex.html
http://www.biologymad.com/resources/
kidney.swf
http://www.sumanasinc.com/webconte
nt/animations/content/kidney.html
Key concepts
Cells as the units of life,
Biochemical processes
Textbooks/Publications
Bio Factsheet 1: The kidney: excretion
and osmoregulation
Bio Factsheet 59: Excretion
Bio Factsheet 150: Answering Exam
Questions on the Kidney
Past Papers
Paper 41, June 2012, Q10 (b)
Note
For the overview diagram, explain that in the loop of Henle most water is
reabsorbed, and that the outward movement of sodium (and chloride) ions into the
interstitial fluid occurs to create a very low water potential. No details of the
mechanism or the countercurrent multiplier are required.
14.1.g
describe the roles of the
hypothalamus, posterior pituitary, ADH
and collecting ducts in osmoregulation
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners recall from 14.1.c and AS Level why it is important to control the water
content of the blood (refer to water potential gradients and osmosis).
o Learners discuss the consequences and the conflict between maintaining a
constant volume of blood and maintaining constant water potential, e.g. when
someone has a meal high in salt. (W) (Basic)
Learners rearrange a set of linked, sequential statements to give a description of the
roles in osmoregulation of the hypothalamus, posterior pituitary; ADH and collecting
duct (CD). Include one statement to show the role of the distal convoluted tubule
(DCT).
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/K/Kidney.html
www.biologyinmotion.com/nephron/ind
ex.html
http://www.biologymad.com/resources/
kidney.swf
http://www.sumanasinc.com/webconte
nt/animations/content/kidney.html
150
Learning objectives
Suggested teaching activities
Learning resources
o Reminded learners that the surrounding (interstitial) fluid has a very low water
potential. (P) (I) (Challenging)
o Learners use the statements as the basis for their notes. (I) (Basic)
Learners are later given only a few of these statements to sequence and fill in the
missing details. (F)
Learners produce a flow chart to show the negative feedback control of water in the
blood. (H) (Basic)
As a summary, learners interpret data from tables or graphs to explain and relate
concentrations of different substances in each part of the nephron. (I)
(Challenging).
14.1.h
explain how the blood glucose
concentration is regulated by negative
feedback control mechanisms, with
reference to insulin and glucagon
Key concepts
Cells as the units of life,
Biochemical processes
Learners suggest (i) why it is important for blood glucose concentration to be kept
relatively constant, and (ii) why, in healthy people, oscillations around the norm
concentration is inevitable. (W) (Basic)
Using resources, learners construct a table similar to the incomplete table below. (I)
(Basic)
norm/set point of 90-120mg of glucose
100cm-3 blood
increases above
decreases below
stimulus detected by
beta () cells
alpha () cells
pancreas
pancreas
hormone released
insulin
glucagon
main target tissues of liver and muscles
liver
hormone
(+adipose tissue)
main effects of
stimulates uptake of
stimulates
hormone
glucose
breakdown of
………………..
glycogen to glucose
……………………
…………………….
final outcome
blood glucose
concentration
decreases
Textbooks/Publications
Bio Factsheet 1: The kidney: excretion
and osmoregulation
Bio Factsheet 59: Excretion
Bio Factsheet 150: Answering Exam
Questions on the Kidney
Online
http://www.biologyreference.com/BlCe/Blood-Sugar-Regulation.html
http://www.mydr.com.au/gastrointestin
al-health/pancreas-and-insulin
http://www.betacell.org/content/articlevi
ew/article_id/1/
Textbooks/Publications
Bio Factsheet 145: Blood sugar and its
control
Past Papers
Paper 43, Nov 2011, Q7
blood glucose
concentration
increases
Learners describe the sequence of events occurring in the body after having a
carbohydrate-rich meal (illustrating homeostasis). (H) (Basic)
Learners construct a flow chart to show negative feedback control of blood glucose
concentration involving insulin and glucagon.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
151
Learning objectives
Suggested teaching activities
Learning resources
o Learners add annotations or bullet points and include the terms homeostasis,
stimulus, receptor, effector and negative feedback. (F)
Extension: learners investigate the effect of diabetes mellitus on the control of blood
glucose concentration. Links: use of dipsticks, 14.1.k; insulin production by genetic
engineering, 19.2.c. (H) (Basic)
Note
Accurate spelling is important: both glucagon and glycogen are terms used in this
topic.
14.1.i
outline the role of cyclic AMP as a
second messenger with reference to
the stimulation of liver cells by
adrenaline and glucagon
Key concepts
Biochemical processes
Use a question and answer session to remind learners of membrane proteins that
function as receptors and enzymes.
o Explain that liver cells have different receptors to bind adrenaline and glucagon.
o Learners suggest why the hormones are unable to trigger directly reactions
within the cell (hydrophilic, do not enter cell).
o Use a diagram to outline how binding causes production in the cytoplasm of
cyclic AMP, which then stimulates the enzymatic conversion of glycogen to
glucose. (W) (Basic)
Learners write a paragraph to explain the difference between first and second
messengers. (F)
Online
http://courses.washington.edu/conj/gpr
otein/cyclicamp.htm
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::535::535::/sites/dl/free/007243731
6/120109/bio48.swf::Action%20of%2
0Epinephrine%20on%20a%20Liver%
20Cell
Note
Muscle cells have receptors for adrenaline but not for glucagon.
Names of the specific receptors are not required.
Notes are not necessary at this point as a summary of 14.1.j will suffice
14.1.j
describe the three main stages of cell
signalling in the control of blood
glucose by adrenaline as follows:
hormone-receptor interaction at the
cell surface (see 4.1c))
formation of cyclic AMP which binds
to kinase proteins
an enzyme cascade involving
activation of enzymes by
phosphorylation to amplify the signal
v2.1 5Y02
Discuss the role of adrenaline so learners understand the need for a higher-thannormal blood glucose concentration. (W) (Basic)
Discuss the sequential process using diagrams. (W) (Challenging)
Learners annotate copies of the diagrams, highlighting how one event triggers the
next:
o Binding of adrenaline and activation of G (membrane) protein.
o Enzyme-catalysed formation of cyclic AMP at the membrane and consequential
activation of kinase proteins.
o Phosphorylation of enzymes involved in carbohydrate and lipid metabolism, e.g.
for the breakdown of glycogen to glucose-1-phosphate. (I) (Challenging)
Learners re-order statements to show the sequential process (F)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::535::535::/sites/dl/free/007243731
6/120109/bio48.swf::Action%20of%2
0Epinephrine%20on%20a%20Liver%
20Cell
http://www2.estrellamountain.edu/facul
ty/farabee/BIOBK/biobookendocr.htm
l
http://courses.washington.edu/conj/gpr
otein/cyclicamp.htm
152
Learning objectives
Suggested teaching activities
Learning resources
Remind learners how a dipstick is used to detect glucose and then explain the
principles of operation before learners make notes.
o Learners write out a worded reaction and explain why a reaction catalysed by
glucose oxidase will confirm the presence of glucose (enzyme specificity,
Unit 1).
o Explain that peroxidases are used so that the hydrogen peroxide product reacts
with a chemical (chromogen) that produces a coloured product. (W) (I) (Basic)
Practical: if available, learners compare Clinistix to Diastix. (W) (Basic)
Outline the operation of the biosensor by incorporating questions to link to AS Level
topics: partially permeable membrane, diffusion of glucose molecules (from the
blood sample), immobilised enzymes and specificity.
o Discuss how the reaction needs to be detected, e.g. use of electrodes; a
decrease in oxygen; increase in hydrogen peroxide; production of gluconic acid.
o Learners explain how the digital read-out is proportional to the concentration of
glucose in the sample. (W) (Challenging)
Discuss how dipsticks and portable devices to detect glucose and measure
concentrations are considered great improvements for people with diabetes
(compared to times before glucose biosensors and the Benedict’s tests. (W) (Basic)
Learners compare the use of glucose dipsticks and glucose biosensors, explaining
advantages of each. (I) (Challenging)
Learners draw a diagram to show the main parts of a biosensor and annotate to
show the principles of operation. (F)
Online
http://www.southernbiological.com/kitsand-equipment/specialisedlaboratory-and-field-equipment/urinetesting/g10-41-diastix/
Key concepts
Cells as the units of life,
Biochemical processes
14.1.k
explain the principles of operation of
dip sticks containing glucose oxidase
and peroxidase enzymes, and
biosensors that can be used for
quantitative measurements of glucose
in blood and urine
Key concepts
Biochemical processes,
Observation and experiment
Textbooks/Publications
Bio Factsheet 157: Diabetes –
Management or Cure?
Bio Factsheet 167: Biosensors
Past Papers
Paper 41, Nov 2011, Q2 (b)
Note
Link with previous work on insulin (14.1.h) and a practical for immobilised enzymes
(3.2.d).
Note that some textbooks state that the oxidation of glucose produces,
gluconolactone, which is an intermediate of gluconic acid.
Discuss ideas and developments in the commercial production of glucose
biosensors, e.g. devices that can control and regulate insulin doses.
Learners should be able to use the principles of operation to apply to a design that
they may not have come across.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
153
Learning objectives
Suggested teaching activities
Learning resources
14.1.l
explain how urine analysis is used in
diagnosis with reference to glucose,
protein and ketones
Learners reflect back to14.1.f and explain why glucose and proteins would not
normally be found in urine in detectable levels.
Explain that ketones are products of carbohydrate, protein and lipid metabolism, but
high levels in urine may indicate ill health, such as in uncontrolled type I diabetes.
Explain that a urine analysis could indicate a condition: glycosuria and diabetes
mellitus; proteinuria / albuminuria / microalbuminuria and renal disease or damage
e.g. that may have been caused as a result of long-term type II diabetes. (W)
(Basic)
o Learners make outline notes on each of the three named urine compounds.
o Notes to include the diagnostic role of urine dipsticks (specific for each or
multiple combination strips testing for all three). (I) (Basic)
Online
http://www.patient.co.uk/doctor/urinedipstick-analysis
http://www.medicinenet.com/urine_test
s_for_diabetes/article.htm
Key concepts
Biochemical processes,
Observation and experiment
Past Papers
Paper 41, Nov 2011, Q2 (a)
Note
Very low concentrations are excreted by healthy people, levels detected by urine
dipsticks are indicative of possible health problems.
Details of other tests that can be performed on urine are not required.
15.1.l
explain the roles of the hormones FSH,
LH, oestrogen and progesterone in
controlling changes in the ovary and
uterus during the human menstrual
cycle
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners review the endocrine system and hormones with a short written test.
Discuss the different origins of the named hormones involved in the menstrual cycle,
explaining target tissues differ.
o Emphasise for later their importance in synchronising activities of the ovary and
uterus. (W) (Basic)
Use diagrams to describe the maturation of the follicle in the ovary, ovulation and the
formation of the corpus luteum.
o Describe the events occurring in the uterus. (W) (Basic)
Learners draw a large outline graph. The x-axis being time (to 28 days – explain that
cycles may be longer or shorter), y-axis being hormone concentration (arbitrary
units).
o Learners sketch diagrams of (i) the physical changes in the uterus over 28 days
(above the graph), and (ii) the changes occurring in the ovary (below the graph).
(I) (Basic)
o Using description and question and answers build up the graph to show the
changing concentrations of the hormones over the 28 days (use a method to
distinguish oestrogen and progesterone, the sex hormones, from FSH and LH,
the two pituitary hormones.
o Discuss the feedback mechanisms that occur to enable the cycle to be
controlled, learners annotate or add bullet point notes. (W) (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Horm
ones/Hormones.htm
http://highered.mcgrawhill.com/sites/0072495855/learner_vi
ew0/chapter28/animation__positive_
and_negative_feedback__quiz_1_.ht
ml
http://highered.mcgrawhill.com/sites/0072495855/learner_vi
ew0/chapter28/animation__maturatio
n_of_the_follicle_and_oocyte.html
Textbooks/Publications
Bio Factsheet 57: Oestrous cycles.
Includes the menstrual cycle
Past Papers
Paper 41, June 2012, Q5 (a)
Paper 42, Nov 2013, Q4
154
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners investigate the role of gonadotrophin releasing hormone (GnRH)
in the control of the menstrual cycle. (I) (Challenging)
Learners discuss the changes to the graph(s) for shorter / longer cycles, explaining
the reasons for their choices. (G) (Challenging)
Learners describe specific examples within the cycle of positive and negative
feedback mechanisms. (I) (Challenging)
Learners complete unlabelled diagrams and graphs showing the events in the
menstrual cycle. (F)
Note
It may be beneficial for learners to know the full names of FSH and LH: they are not
required learning.
15.1.m
outline the biological basis of
contraceptive pills containing
oestrogen and/or progesterone
Key concepts
Observation and experiment
v2.1 5Y02
Learners research how the combined oral contraceptive pill prevents pregnancy and
compare this with the progesterone /progestin-only pill. (H) (Basic)
Learners consider how concentrations of oestrogen and progesterone differ in
women who are taking the contraceptive pill.
o Learners explain the effects of these differences in terms of the feedback
mechanisms discussed in 15.1.l. (I) (Challenging)
Online
http://www.patient.co.uk/search.asp?s
earchTerm=contraceptive+pill&collect
ions=Condition_Leaflets
http://hcd2.bupa.co.uk/fact_sheets/htm
l/hormonal_contraception.html
Note
The role of oestrogen and/or progesterone in controlling fertility is an extension of
learners’ knowledge and understanding of the menstrual cycle.
Past Papers
Paper 43, June 2011, Q3 (b)
Cambridge International AS & A Level Biology (9700) – from 2016
155
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 11: Plant physiology and biochemistry
Recommended prior knowledge
As with respiration, learners should be familiar with the concept of energy transfer, for example from light energy to chemical energy. They should have a sound
understanding of what a molecule is, and understand chemical formulae and equations. It would be helpful if they understood the concept of oxidation and reduction, at
least at a simple level. Knowledge from AS Level of plant cell structure and of gene expression will help understanding of the role of gibberellin in cell elongation. It
would be helpful if learners had an appreciation of the importance of communication, control and coordination in multicellular organisms.
Context
This unit considers another aspect of the key concept of biological processes and studies the transfer of energy from light energy to the energy contained in organic
compounds in living organisms. It has close links to Unit 9, Respiration, and revisits the concepts involved in the synthesis of ATP by chemiosmosis. It builds on
material covered at AS Level: enzymes and biological molecules, especially glucose and starch, from Unit 1; plant cell structure and chloroplast structure and function
from Unit 2; and leaf structure, including stomata from Unit 4. Having considered mammalian physiology in Unit 10, the plant hormones abscisic acid and gibberellin are
used to exemplify communication, control and coordination in plants. Learners first come across gibberellin when studying selective breeding in Unit 7. This unit could
be taught before Unit 9, Respiration, if it is felt more logical to introduce learners first to the process involved with the initial input of energy into the ecosystem.
Outline
The unit begins with an overview of photosynthesis, highlighting the transfer of energy and the link between the light dependent and light independent stages. The light
absorbing pigments are introduced and linked to the concepts involved with absorption and action spectra: learners can also separate photosynthetic pigments by
chromatography. The light dependent and light independent stages of photosynthesis are described. The concept of limiting factors is introduced and learners have the
opportunity of investigating factors affecting the rate of photosynthesis. A consideration of how this knowledge can be applied to crop plants is included. More detail is
provided of the ways in which the structure of a chloroplast is suited to its functions. Learners also consider how some plants have evolved to cope with life in hot
environments. Response to an external stimulus is exemplified by a study of the Venus fly trap. Stomatal closure and opening, including the role of abscisic acid, the
role of auxin in cell elongation and the effect on gene activation of gibberellin is covered. There are numerous practical opportunities within this unit to develop skills
relating to planning, data analysis and the evaluation of investigations.
Teaching time
It is recommended that this unit should take approximately 8% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
156
Learning objectives
Suggested teaching activities
Learning resources
13.1.b
state the sites of the light dependent
and the light independent stages in the
chloroplast
Project or show an image or diagram of a chloroplast and check learner knowledge
from Unit 1 by a question and answer session.
o Learners explain why the thylakoid membranes are the location of ATP
synthesis (refer back to mitochondrial membranes: site of ATP synthase,
location for photosynthetic pigments).
o Learners suggest why the stroma is the site of the Calvin cycle (enzyme
reactions). (W) (Challenging)
Online
http://resources.teachnet.ie/foneill/phot
o.html
Key concepts
Cells as the units of life,
Biochemical processes
13.1.c
describe the role of chloroplast
pigments (chlorophyll a, chlorophyll b,
carotene and xanthophyll) in light
absorption in the grana
Key concepts
Cells as the units of life
Note
A review may be necessary of the anatomy of the leaf, so that learners can visualise
mesophyll tissue and mesophyll cells containing chloroplasts.
13.3.a may be taught first to give a visual overview of where the processes of
photosynthesis occur.
Allow learners to state the role of chlorophyll before raising the level of
understanding to explain that the light energy needs to be transferred. Explain that:
o Absorption occurs in areas of the thylakoid membrane that contain
photosystems.
o Chlorophyll a and chlorophyll b are two types of chlorophyll molecule in a typical
photosystem, along with other photosynthetic pigments, e.g. carotenes and
xanthophylls.
o Each type of pigment absorbs certain wavelengths of light and reflects others
(mention the antenna complex).
o Absorbed energy is passed on to a special pair of chlorophyll molecules that can
pass on energetic/excited electrons to electron acceptors. (W) (Challenging)
Learners label and annotate an unlabelled diagrammatic version of a photosystem
as you talk them through the various components.
o Learners note that: the special pair act as the reaction centre and the others as
accessory pigments; in Photosystem I (PI) the pair have a characteristic
absorption wavelength of 700 nm (P700), and in PII of 680 nm (P680).
o Refer to the higher energy state of the electrons as photoactivation of
chlorophyll. (I) (Challenging)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/283-photosynthesishow-does-chlorophyll-absorb-lightenergy
http://phototroph.blogspot.ca/
Textbook/Publications
Bio Factsheet 63: Pigments in plants
Note
Explain that xanthophylls and carotenes are carotenoids.
This overlaps with 13.1.f so details of the photosystems may be taught there.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
157
Learning objectives
Suggested teaching activities
Learning resources
13.1.d
interpret absorption and action spectra
of chloroplast pigments
Background practical to help understanding: learners follow, or have demonstrated
or described, a protocol to measure an absorption spectrum to see how the curve on
the graph is obtained.
o Explain that absorption is measured using a spectrophotometer). (W) (P) (I)
Learners study separate absorption graphs for each of the chloroplast pigments (i.e.
each has a characteristic absorption spectrum): check understanding with a
worksheet. (I) (Basic)
Provide learners with a ‘classic’ absorption spectrum graph (includes the main
pigments) and a set of questions assessing ability to extract data and show
understanding.
o Learners suggest the advantages to plants of having different pigments (extends
the range of light wavelengths absorbed). (F)
Explain how the graph for the action spectrum of photosynthesis is obtained. (W)
(Basic)
Show learners a ‘classic’ action spectrum with peaks in the red and blue regions and
sketch an absorption spectrum graph of pigment ‘X’ (actually chlorophyll a) and a
separate one for a pigment ‘Y’ (peaking in the green region).
o Learners suggest, with a reason, which is most likely to be involved in light
absorption for photosynthesis, so that the correlation between absorption and
action spectra is seen. (W) (Basic)
Explain that there are more pigments involved than those usually shown, so the
absorption spectrum graph is only similar to the action spectrum graph.
o Explain that there are different carotenes and xanthophylls and different plants
have a characteristic set of pigments. (W) (Basic)
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/ActionSpectrum.ht
ml
http://www.saps.org.uk/secondary/teac
hing-resources/130-the-effect-of-lightcolour-and-intensity-on-the-rate-ofphotosynthesis
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
Textbooks/Publication
Siddiqui p.91
Past papers
Paper 51, Nov 2011, Q1 (a)(b)
Note
Check that the absorption spectrum is well understood before moving onto the
action spectrum, ensuring that learners make the association between the two.
13.1.e
use chromatography to separate and
identify chloroplast pigments and carry
out an investigation to compare the
chloroplast pigments in different plants
(reference should be made to Rf values
in identification)
Practical: learners could carry out the separation for pigments of one plant, and
compare results with others that have used different plants.
o Learners make measurements and calculate Rf values, comparing with
published values to make identifications. (G) (I) (Basic)
Practical booklet 8 is a protocol for separating chloroplast pigments by paper
chromatography. Colours fade relatively quickly so measurements should be made
as soon as possible (or take photographs) after removing chromatograms from the
solvent.
Online
http://www.saps.org.uk/secondary/teac
hing-resources/181-learner-sheet-10thin-layer-chromatography-forphotosynthetic-pigments
Textbook/Publications
Key concepts
v2.1 5Y02
Practical booklet 8
Cambridge International AS & A Level Biology (9700) – from 2016
158
Learning objectives
Suggested teaching activities
Learning resources
King p.113-114
Siddiqui p.90-91
Observation and experiment
Past Papers
Paper 41, Nov 2011, Q10 (b)
Paper 51, Nov 2011, Q1 (c)(d)(e)
Paper 53, Nov 2011, Q1 (d)(ii)
13.1.f
describe the light dependent stage as
the photoactivation of chlorophyll
resulting in the photolysis of water and
the transfer of energy to ATP and
reduced NADP (cyclic and non-cyclic
photophosphorylation should be
described in outline only)
Key concepts
Biochemical processes
v2.1 5Y02
Use a diagram to ask learners questions about what happens in a photosystem
(13.1.c).
o Ensure learners know that excitation of energetic electrons results in a transfer
to an acceptor.
o Explain that the absorption of light energy in PII also triggers the photolysis of
water by an enzyme (termed the oxygen evolving complex, closely located to the
reaction centre). (W) (Basic)
With verbal prompts, learners build up the ‘Z-scheme’ to produce an outline of noncyclic photophosphorylation and include explanations.
o Sketch a ‘rising’ letter ‘N’, then add PII, then PI (represent energy
levels).
o Add circles for the electron transport chain carriers (or label ETC)
and add arrows to show the electron pathway.
o Add arrows to show the production of ATP as electrons flow down the ETC.
o Show the photolysis of water, with electrons replacing the gap in PII, oxygen
evolved.
o Show the electrons accepted by NADP to produced reduced NADP.
o Add the title non-cyclic photophosphorylation (noted for 13.1.a later). (I) (Basic)
Learners repeat the construction of the Z-scheme and add explanatory notes without
help. (F)
o Describe cyclic photophosphorylation.
o Learners suggest why only ATP can be synthesised.
o Learners add this in a different colour to their Z-scheme. (I) (Basic)
Learners revise work on chemiosmosis (Unit 9) to give an account of ATP synthesis
at the thylakoid membrane. A partially labelled diagram showing a section through
the thylakoid membrane with electron carriers of the ETC and the ATP synthase
complex can be used as stimulus. (H) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://cnx.org/content/m48011/latest/
http://www.life.illinois.edu/govindjee/tex
tzsch.htm
http://www.johnkyrk.com/photosynthesi
s.html
Textbook/Publications
Bio Factsheet 02: The essential guide
to photosynthesis.
Bio Factsheet 153: The Light
Dependent Stage of Photosynthesis
Past Papers
Paper 43, Nov 2013, Q7 (a)
159
Learning objectives
Suggested teaching activities
Learning resources
12.1.e (ii)
explain that the synthesis of ATP is
associated with the electron
transport chain on the membranes
of mitochondria and chloroplasts
(see 12.2.g)
Only part of this learning objective is included here: explain that the synthesis of ATP
is associated with the electron transport chain on the membranes of chloroplasts (see
12.2.g)
Learners complete a short written test to remind them of previous work
o Chloroplasts are cellular structures where ATP is formed.
o ATP is an energy transfer molecule.
o The initial energy input for chloroplasts is light energy and for mitochondria,
energy-containing organic compounds.
o The ETC involves thylakoid membrane proteins capable of accepting and
donating electrons. (F)
Online
http://www.ncbi.nlm.nih.gov/books/NB
K21063/
Key concepts
Cells as the units of life,
Biochemical processes
13.1.a
explain that energy transferred as ATP
and reduced NADP from the light
dependent stage is used during the
light independent stage (Calvin cycle)
of photosynthesis to produce complex
organic molecules
Key concepts
Biochemical processes,
Organisms in their environment
In groups learners construct a large, poster-sized concept map / spider diagram with
photosynthesis as a topic. (G) (Basic)
Discuss and agree as a class the main points and improve ideas to A Level
standard. Learners then make notes in diagrammatic or bullet-point form.
o An overall equation for photosynthesis (word equation changed to chemical
formulae, balanced).
o Two main stages, occurring in the chloroplasts of mesophyll cells and both
involving enzymes.
o In the light dependent stage, light energy is transferred to ATP and the reduced
coenzyme, NADP.
o Oxygen (waste product) from this stage can be used for aerobic respiration (in
plant or released into the atmosphere to other organisms).
o In the light independent stage (also termed the Calvin cycle), carbon dioxide,
ATP and NADPH are used for the production of complex organic molecules,
such as glucose and starch. (W) (I) (Challenging)
Note
Learners should understand the terms ‘autotroph’, ‘photoautotroph’ and ‘producer’.
Avoid using the terms ‘light reaction’ and ‘dark reaction’.
13.1.g
outline the three main stages of the
Calvin cycle:
fixation of carbon dioxide by
combination with ribulose
bisphosphate (RuBP), a 5C
v2.1 5Y02
Discuss why the light dependent stage of photosynthesis needs to occur when no
glucose has yet been made (allows the transfer of light energy to ATP and reduced
NADP).
o Learners write out the overall equation of photosynthesis to spot that carbon
dioxide has not yet been involved (sets the scene for the Calvin cycle). (W)
(Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbook/Publications
Bio Factsheet 153: The Light
Dependent Stage of Photosynthesis
Past papers
Paper 41, June 2013, Q10 (b)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/134-photosynthesisa-survival-guide-teaching-resources
http://photoscience.la.asu.edu/photosy
n/study.html
http://www.johnkyrk.com/photosynthesi
sdark.html
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/a2bio
logy.htm
http://staff.jccc.net/pdecell/photosyn/ph
otoframe.html
http://faculty.fmcc.suny.edu/mcdarby/A
nimals&PlantsBook/Plants/01Photosynthesis.htm
Past papers
Paper 43, Nov 2013, Q7 (b)
Online
http://www.science.smith.edu/departm
ents/Biology/Bio231/calvin.html
http://www.wiley.com/college/boyer/04
70003790/animations/photosynthesis
/photosynthesis.htm
160
Learning objectives
Suggested teaching activities
Learning resources
compound, to yield two molecules of
GP (PGA), a 3C compound
the reduction of GP to triose
phosphate (TP) involving ATP and
reduced NADP
the regeneration of ribulose
bisphosphate (RuBP) using ATP
Learners link together a set of statements, based around the ideas in the learning
objectives and including rubisco, to describe the Calvin cycle.
o Provide curved arrows, so that they can create a cycle with their statements. (P)
(I) (Challenging)
Discuss their cycles.
o Emphasise the roles of reduced NADP and ATP (include the concept of
recycling to the light dependent stage).
o Explain that the steps are catalysed by enzymes.
o Show how 6 carbon dioxide molecules are required to produce 1 glucose
molecule, so that the overall equation for photosynthesis makes sense.
o Learners then produce their own annotated Calvin cycle. (W) (I) (Challenging)
Background: learners investigate the experiments carried out by Calvin and his
colleagues using the ‘lollipop’ apparatus. (I) (Challenging)
Learners annotate fully a skeleton outline of the Calvin cycle (provide a variety so
that each contains different information – could be differentiated). (F) (Basic)
(Challenging)
http://nobelprize.org/nobel_prizes/che
mistry/laureates/1961/calvinlecture.pdf
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 02: The essential guide
to photosynthesis.
Bio Factsheet 227: RuBP carboxylase
– the most important enzyme on the
planet?
Past Papers
Paper 41, June 2011, Q10 (b)
Paper 43, June 2011, Q10 (b)
Note
For ‘error-free learning’, use only the syllabus names and abbreviations:
o GP (glycerate 3-phosphate) or PGA (3PG / 3-phosphoglycerate /
3-phosphoglyceric acid)
o TP (triose phosphate). Avoid other common names: glyceraldehyde 3-phosphate
(GALP); 3-phosphoglyceraldehyde (PGAL)
o Explain that other acceptable names are used.
No names of enzymes, other than rubisco, are required.
13.1.h
describe, in outline, the conversion of
Calvin cycle intermediates to
carbohydrates, lipids and amino acids
and their uses in the plant cell
Key concepts
Biochemical processes
v2.1 5Y02
Agree that GP is the raw material for producing carbohydrates, lipids and amino
acids (no details of pathways required).
o Learners add this information to their Calvin cycle. (I) (Basic)
Briefly discuss how two molecules of GP can produce a hexose sugar. (W) (Basic)
Discuss, using question and answer, the use of hexose sugars (glucose and
fructose, Unit 1), including:
o Immediate use to release energy as respiratory substrates.
o Synthesis of sucrose for transport to sinks (revise plant transport, Unit 4).
o Conversion to starch or lipid for energy storage.
o Production of structural compounds (cellulose).
o Learners suggest what else is required to synthesise amino acids for proteins
Cambridge International AS & A Level Biology (9700) – from 2016
161
Learning objectives
Suggested teaching activities
Learning resources
(uptake of nitrate and sulfate ions in the roots). (W) (Basic)
Learners produce an outline set of notes from the discussion. (I) (Basic)
13.3.a
describe the relationship between
structure and function in the
chloroplast using diagrams and
electron micrographs
Key concepts
Cells as the units of life,
Biochemical processes
Place the chloroplast into context as a summary.
o Learners identify: the photosynthetic organism (plant); the organ of
photosynthesis (leaf); the main photosynthetic tissue (palisade mesophyll); the
organelle of photosynthesis (chloroplast); the structures of the chloroplast. (W)
(Basic)
Learners draw a labelled diagram of a chloroplast, annotating (or write a summary)
to show how the chloroplast is adapted for photosynthesis.
o Note the requirement for membranes and intermembrane spaces to generate
ATP as electrons pass along a chain of electron carriers.
o Note the locations of the light dependent stage and the light independent stage.
(I) (Challenging)
Learners interpret photomicrographs and electron micrographs of chloroplasts,
drawing labelled diagrams. (I) (Basic)
Online
http://www.vcbio.science.ru.nl/en/imag
e-gallery/show/PL0130/
http://www.vcbio.science.ru.nl/en/fese
m/applets/chloroplast/
http://www.biologie.uni-hamburg.de/bonline/e05/r21.htm
http://faculty.uca.edu/johnc/Chloroplast
_and_microbodies.jpg
Textbook/Publications
Bio Factsheet 198: Chloroplasts –
structure and function
Bio Factsheet 61: Chloroplasts and
mitochondria
Past Papers
Paper 41, Nov 2011, Q10 (a)
13.2.a
explain the term limiting factor in
relation to photosynthesis
Key concepts
Biochemical processes,
Organisms in their environment
13.2.b
explain the effects of changes in light
intensity, carbon dioxide concentration
and temperature on the rate of
photosynthesis
Key concepts
v2.1 5Y02
Show learners a number of definitions of the term limiting factor. As a group produce
an explanation to note down that is in the context of photosynthesis. (W) (I) (Basic)
Learners draw a generalised graph showing the rate of photosynthesis on the y-axis
and the factor on the x-axis.
o Label the graph with the regions where the factor directly affects the rate of
photosynthesis and those where other factors become limiting. (I) (Basic)
Online
http://www.rsc.org/learnchemistry/content/filerepository/CMP/
00/001/068/Rate%20of%20photosynt
hesis%20limiting%20factors.pdf
Learners suggest the factors that may affect the rate of photosynthesis, and discuss
ways in which the rate could be measured. (W) (Basic)
Learners suggest the parts of the photosynthetic process that involve enzymes, and
hence affect photosynthetic rate.
o Light dependent stage: photolysis of water; synthesis of ATP (ATP synthase);
transfer of electrons to NADP for reduction.
o Light independent stage: each of the steps of the Calvin cycle (the bulk of
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=43
http://resources.teachnet.ie/foneill/exp
er.htm
http://www.assessnet.org.uk/elearning/
Cambridge International AS & A Level Biology (9700) – from 2016
162
Learning objectives
Suggested teaching activities
Learning resources
Biochemical processes,
Organisms in their environment,
Observation and experiment
enzyme-catalysed reactions occur here).
Learners use their notes on chloroplast pigments and the two stages of
photosynthesis to suggest how changes in carbon dioxide concentration and light
intensity will affect the rate of photosynthesis.
o Include an explanation as to why the light independent stage will not operate
when there is no light. (I) (Basic) (Challenging)
To link back to 13.2.a learners interpret graphs showing the effects of limiting
factors, explaining why the rate of photosynthesis changes and using extracted date
to support their answer. (I) (Challenging)
Textbook/Publications
King p.115-117, 149
Siddiqui p.86-89, 94
Bio Factsheet 136: Practical
Investigations for Photosynthesis
Bio Factsheet 25: Tackling data
interpretation questions II:
photosynthesis (limiting factors)
Past Papers
Paper 41, June 2012, Q8 (a)(b)
13.2.c
explain how an understanding of
limiting factors is used to increase crop
yields in protected environments, such
as glasshouses
Key concepts
Biochemical processes,
Observation and experiment
13.2.d
carry out an investigation to determine
the effect of light intensity or light
wavelength on the rate of
photosynthesis using a redox indicator
(e.g. DCPIP) and a suspension of
chloroplasts (the Hill reaction)
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Explain that knowledge of limiting factors can be used to control the growing
conditions of commercial crops, especially in protected environments. (W) (Basic)
Brainstorm ideas as to what growers can do to increase crop yields in glasshouses.
Include:
o Artificial light (photosynthesis for more hours of the day; increase light intensity
on days with little sunlight).
o Use of paraffin lamps (carbon dioxide and heat). (W) (Basic)
o Learners make notes and explain how these will improve yield. (F)
Online
http://www.bbc.co.uk/schools/gcsebite
size/science/add_aqa/photosynthesis
/photosynthesisrev3.shtml
http://www.omafra.gov.on.ca/english/cr
ops/facts/00-077.htm
From 13.2.b learners will know that the production of oxygen can be used to
measure the rate of photosynthesis.
o Learners suggest why the rate of production of NADP in the light dependent
stage correlates with the rate of photosynthesis.
o Explain that a way of measuring this could be to use a different electron
acceptor, DCPIP, which can be visualised (blue dye that becomes colourless
when reduced). (W) (Basic)
o Learners suggest how DCPIP can be used to measure rate. (W) (Challenging)
Learners carry out a version of the Hill reaction practical or watch it demonstrated
and then explain a set of results. Ensure that both investigations, light intensity and
light wavelength, are covered. (P) (I) (H) (Challenging)
Discuss the findings of the original investigation performed by Robin Hill: oxygen is
evolved in the absence of carbon dioxide; the electrons transferred to the electron
acceptor originate from water. (W) (Challenging)
Practical booklet 9
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.nuffieldfoundation.org/practi
cal-biology/investigating-lightdependent-reaction-photosynthesis
http://www.saps.org.uk/secondary/teac
hing-resources/157-measuring-therate-of-photosynthesis
http://www.hansatechinstruments.com/forum/uploads/david
_walker/whose.pdf
Textbook/Publications
163
Learning objectives
13.2.e
carry out investigations on the effects
of light intensity, carbon dioxide and
temperature on the rate of
photosynthesis using whole plants,
e.g. aquatic plants such as Elodea and
Cabomba
Key concepts
Observation and experiment
13.3.b
explain how the anatomy and
physiology of the leaves of C4 plants,
such as maize or sorghum, are
adapted for high rates of carbon
fixation at high temperatures in terms
of:
the spatial separation of initial
carbon fixation from the light
dependent stage (biochemical
details of the C4 pathway are
required in outline only)
the high optimum temperatures of
the enzymes involved
Key concepts
Biochemical processes,
Natural selection,
Organisms in their environment
v2.1 5Y02
Suggested teaching activities
Learning resources
Practical booklet 9 (Hill reaction) uses melting point tubes as reaction vessels and
does not use a centrifuge. Learners can investigate the effect of both light
wavelength and light intensity on the rate of photosynthesis. Pooled data for analysis
may be collected as preparation for Paper 5. Learners can also use the technique to
devise plans that can be peer reviewed (see 12.2.h and 12.2.m).
Siddiqui p.93-93
Practical: learners investigate the effect of light intensity, light wavelength, carbon
dioxide concentration and temperature on the rate of photosynthesis.
o Learners design and carry out at least one investigation of their own, once a
technique has been shown to them. (I) (Challenging)
o Learners explain how the plan can be modified to investigate the effect of limiting
factors. (I) (Challenging)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/190-using-pondweedto-experiment-with-photosynthesishttp://www.saps.org.uk/secondary/teac
hing-resources/284-investigatingphotosynthesis-with-leaf-discs
http://www.saps.org.uk/secondary/teac
hing-resources/285-learner-sheet-20starch-production-in-plants-duringphotosynthesis
Note
Carbon dioxide concentration can be varied by using an aquatic (water) plant in
varying concentrations of solutions containing sodium hydrogen carbonate (sodium
bicarbonate).
Learners review C3 photosynthesis by completing worksheets with gaps or by
rearranging cards describing stages and then suggest why the term C3 plant is
used. (W) (P) (I) (F) (Basic)
Explain that rubisco can also catalyse the oxygenation of RuBP.
o Use diagrams, and remind learners of enzyme inhibition (AS Level) to prompt
them to suggest why the reaction is favoured in high oxygen concentrations.
o Learners suggest the conditions when oxygen concentrations will be high (high
light intensity and high temperatures increase rate of light dependent stage). (W)
(Basic)
o Learners write an explanation of photorespiration. (I) (Basic) (Challenging)
Explain that C4 plants are traditionally from hotter environments. (W) (Basic)
Describe, using diagrams, the structural and functional features of maize or sorghum
as examples of C4 plants. (W) (Challenging)
o Learners suggest how the features adapt the plants to reduce the effects of
photorespiration and allow high rates of carbon fixation.
o Learners label and annotate a diagram of a section through the leaf of a C4
plant.
o Learners produce a comparison table of C3 (see 13.3.a) and C4 leaf structure.
(W) (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Past paper
Paper 53, Nov 2011, Q1 (a)(b)(c)
Online
http://www.icrisat.org/cropsorghum.htm
http://en.wikipedia.org/wiki/Sorghum
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/C/C4plants.html
http://www.marietta.edu/~biol/biomes/p
hotosynthesis.htm
www.biologymad.com/resources/Crop
%20Plants.pps
Past Papers
Paper 43, June 2011, Q4
164
Learning objectives
Suggested teaching activities
Learning resources
Discuss the effect of higher temperatures on C3 enzymes versus C4 enzymes. (W)
(Basic)
o Learners use their graph(s) from 13.2.b (temperature v rate of photosynthesis),
to sketch in a curve for a C4 plant. (I) (Basic)
Extension: learners consider the effects of global warming on the distribution of C4
plants. (I) (Challenging)
15.2.a
describe the rapid response of the
Venus fly trap to stimulation of hairs on
the lobes of modified leaves and
explain how the closure of the trap is
achieved
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Display photographs of the Venus fly trap plant and its modified leaves.
o Leaners brainstorm uses of nitrogen in plants.
o Discuss the need for a source of nitrogen in addition to the products of
photosynthesis.
o Explain that the plant requires supplemental nitrogen owing to low levels of
nitrogen in the bog habitats where it is found. (W) (Basic)
Explain to learners that the equivalent of an action potential occurs to cause the
snapping shut of the trap to catch insects.
o Briefly review learner understanding of stimulus, receptor and action potential
(Unit 10). (W) (Basic)
Learners sequence a set of statements as the basis to make notes. Ideas to include:
o Stimulus = insect movement (mechanical).
o Receptors = hair cells (upper leaf surface).
o Touching two times in succession, i.e. the presence of an insect, results in
depolarisation of the hair cell membrane (owing to an influx of positive ions).
o If the depolarisation is large enough, action potentials spread across from
receptor cells to reach cells on the outside surface.
o One possible mechanism of closure of the trap:
H+ is pumped out of cells on the outside surface into the cell walls
The low pH causes cell wall loosening and movement out of H+ leads to
influx of Ca2+
Water follows osmotically and the cells swell to snap the trap shut. (I)
(Challenging)
Background: learners investigate how carnivorous plants like the Venus flytrap
digest and absorb their insect catch. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://plantsinmotion.bio.indiana.edu/pl
antmotion/movements/nastic/nastic.ht
ml
http://www.botany.org/Carnivorous_Pla
nts/venus_flytrap.php
165
Learning objectives
Suggested teaching activities
Learning resources
14.2.a
explain that stomata have daily
rhythms of opening and closing and
also respond to changes in
environmental conditions to allow
diffusion of carbon dioxide and
regulate water loss by transpiration
Learners link stomatal opening and closure to transpiration (Unit 4) and
photosynthesis.
o Discuss the environmental stimuli for opening and closure (learners recall factors
affecting transpiration rate).
o Explain the ‘internal clock’ of guard cells and the daily rhythm of opening during
the day and closing during the night. (W) (Basic)
Provide graphs showing daily rhythms of opening and closing, with the effects of
changing environmental conditions on particular days.
o Learners describe and explain the graph, using this as the basis of their notes.
(I) (Challenging)
Online
http://www.tiem.utk.edu/~gross/bioed/
webmodules/circadianrhythm.html
Key concepts
Cells as the units of life,
Organisms in their environment
14.2.b
describe the structure and function of
guard cells and explain the mechanism
by which they open and close stomata
Key concepts
Cells as the units of life,
Biochemical processes
14.2.c
describe the role of abscisic acid in the
closure of stomata during times of
water stress (the role of calcium ions
as a second messenger should be
emphasised)
Key concepts
Biochemical processes,
v2.1 5Y02
Note
Mention the term circadian rhythm (not required learning).
Very high wind speeds may also cause stomatal closure – some books do not show
this on typical graphs.
Learners draw and label a diagram of guard cells, making a note of their function. (I)
(Basic)
Learners use an outline diagram of the events occurring for stomatal opening and
complete a worksheet to describe and explain the mechanism involved (uses much
knowledge from AS Level). (I) (Challenging)
Learners use knowledge of the mechanism of stomatal opening to write out and
explain the sequence of events occurring for stomatal closure. (F)
Learners use prepared slides (see 7.2.e, Unit 4) to observe guard cells and stomata.
(I) (Basic)
Learners observe stomatal opening and closure in temporary slides made of
epidermal strips in solutions of different water potential. (I) (Basic)
Online
http://www.phschool.com/science/biolo
gy_place/labbench/lab9/stomamov.ht
ml
http://www.saps.org.uk/secondary/teac
hing-resources/104-stomata-functionguard-cells-and-transpiration
Describe the role of abscisic acid (ABA) as a 'stress hormone' to help plants survive
difficult environmental conditions such as drought. (W) (Basic)
Explain to learners that calcium ions are important in plant cell signalling. (W)
(Basic)
Learners make summary bullet-point notes based on the following ideas:
o Guard cells have receptors for ABA: the presence of ABA results in high
concentrations of calcium ions within the cytoplasm.
o ABA can inhibit the proton pump used to pump out protons, preventing the
inward flux of potassium ions.
Online
http://labs.biology.ucsd.edu/schroeder/
clickablegc.html#figure1
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/ABA.html
http://www.planthormones.info/abscisicacid.htm
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
166
Learning objectives
Organisms in their environment
Suggested teaching activities
o The presence of both ABA and calcium ions leads to changes in the membrane
that causes the opening of potassium ion channels.
o The calcium ions, therefore, can be considered as a second messenger.
o Movement out of potassium ions from the cell will cause stomatal closure (see
14.2.b). (I) (Challenging)
Note
Not all the details of ABA and calcium ion involvement in stomatal closure are
known: it is worth checking for updates.
The changes in the membrane are depolarisation as a result of activation of anion
channels in the membrane (details not required).
As abscisic acid can enter cells, receptors could be membrane-bound or internally
located.
15.2.b
explain the role of auxin in elongation
growth by stimulating proton pumping
to acidify cell walls
Key concepts
Cells as the units of life,
Biochemical processes
Discuss how cell division and cell elongation will lead to plant growth and stem
elongation.
o Explain that auxin is a plant hormone involved in cell elongation. (W) (Basic)
Discuss details of cell wall structure before outlining the sequence of events that
occur (learners recall AS Level knowledge). Learners make notes to include:
o Auxin increases the activity of proton pumps (ATP required) and protons are
pumped out of the cell into the cell wall.
o The decrease in pH activates expansins (proteins) involved in loosening cell wall
structure.
o Water moves in by osmosis, increasing turgor and allowing cells to elongate. (W)
(I) (Challenging)
Learning resources
Bio Factsheet 48: Tackling exam
questions: plant growth substances
Bio Factsheet 111: Plant Growth
Substances
Past Papers
Paper 43, June 2011, Q11 (a)
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp38/3802003.html
http://croptechnology.unl.edu/pages/inf
ormationmodule.php?idinformationm
odule=998688536&topicorder=6&ma
xto=11&minto=1
http://home.earthlink.net/~dayvdanls/pl
ant_grow.htm
http://www.personal.psu.edu/fsl/ExpCe
ntral/
Note
Auxins are a class of hormones, rather than one particular plant hormone. At this
level the use of ‘auxin’ is acceptable. The same applies to gibberellins.
15.2.c
describe the role of gibberellin in the
germination of wheat or barley
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Introduce gibberellin as a hormone that promotes germination by breaking seed
dormancy.
o Agree what is meant by ‘germination’. (W) (Basic)
Learners annotate a diagram of a section through a wheat or barley grain, showing
the sequential events occurring once water is imbibed. Use questioning and include:
o Diffusion, e.g. of gibberellin from embryo to aleurone layer;
o Transcription and translation (in aleurone layer cells for production of digestive
hormones);
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 10
Online
http://www.indiana.edu/~oso/animation
s/barley.html
Textbooks/Publications
King p.240-241
167
Learning objectives
Suggested teaching activities
o Hydrolysis of starch and protein (by digestive enzymes) and use of products for
respiration and growth of seedling. (I) (Challenging)
Learners organise a set of statements to show the correct sequence of events in
seed germination. (F)
Practical booklet 10: learners carry out practical to investigate the effect of different
concentrations of gibberellic acid on stimulating amylase activity in germinating
seeds.
o The results can be analysed using the t-test (see 17.1.c). (P) (I) (Basic)
15.2.d
explain the role of gibberellin in stem
elongation including the role of the
dominant allele, Le, that codes for a
functioning enzyme in the gibberellin
synthesis pathway, and the recessive
allele, le, that codes for a nonfunctional enzyme
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
16.3.d
explain how gibberellin activates genes
by causing the breakdown of DELLA
protein repressors, which normally
inhibit factors that promote
transcription
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
v2.1 5Y02
Learning resources
Past Papers
Paper 43, June 2011, Q11 (b)
Paper 41, Nov 2013, Q9
Remind learners of 15.2.b and explain that in stem elongation, gibberellin causes
both cell division and cell elongation. (I) (Basic)
Learners recall basic points: the definition of an allele (Unit 3); genes code for
polypeptides / proteins; enzymes are proteins; the definitions of dominant and
recessive (alleles). (W) (Basic)
Explain that there is a gene responsible for expressing an enzyme that is important
in the synthesis of active gibberellin.
o State that there is a dominant allele for the functioning enzyme and a recessive
allele for a non-functioning enzyme. (W) (Basic)
Learners use knowledge of genetics and of the role of gibberellin to explain how
plants that are LeLe and Lele will have tall stems, whereas plants that are lele will
have short stems. (F)
Learners carry out practical work to investigate the effect of gibberellic acid on stem
(hypocotyl) elongation and on seed germination (barley) (see 15.2.c).
Online
http://www.tutorvista.com/content/biolo
gy/biology-iv/plant-growthmovements/gibberellins.php
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/G/Gibberellins.html
http://www.plant-hormones.info/
Note
This could be amalgamated with 16.3.d.
Past Papers
Paper 43, Nov 2012, Q10 (b)
Explain that DELLA proteins are regulators of growth: they bind to transcription
factors necessary for expression of genes coding for growth proteins.
o Learners explain how the DELLA proteins can be considered repressors. (W)
(Basic)
Explain that gibberellin can bind to intracellular receptor proteins (GID1) and that this
leads to a complex with DELLA proteins, making them susceptible to degradation by
the cell.
o Learners suggest the consequences of this breakdown. (W) (Challenging)
Learners describe the sequence of events that lead to an event such as stem
elongation in the presence of gibberellins. (I) (Challenging)
Practical booklet 10
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
King p.244
Bio Factsheet 118: Germination
Bio Factsheet 133: Comparing
Chemical Communication in Plants
and Animals
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/G/Gibberellins.html
168
Learning objectives
Observation and experiment
Suggested teaching activities
Learning resources
Note
Learners could be directed to use this information on the mode of action of
gibberellins in their interpretations of results from practical booklet 10 (see 15.2.c).
© Cambridge International Examinations 2014
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
169
Scheme of work
Cambridge International AS and A Level
Biology
9700
For examination from 2016
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Contents
Overview ........................................................................................................................................................................................................................................................... 3
Key concepts ............................................................................................................................................................................................................................................... 3
Practical work .............................................................................................................................................................................................................................................. 4
Suggested teaching order............................................................................................................................................................................................................................ 5
Teacher support........................................................................................................................................................................................................................................... 8
Unit 1: Biological molecules ............................................................................................................................................................................................................................ 11
Unit 2: Cells as the basic units of life .............................................................................................................................................................................................................. 27
Unit 3: DNA and the mitotic cell cycle ............................................................................................................................................................................................................. 40
Unit 4: Transport and gas exchange............................................................................................................................................................................................................... 48
Unit 5: Disease and protection against disease ............................................................................................................................................................................................. 66
Unit 6: The diversity of life .............................................................................................................................................................................................................................. 79
Unit 7: Genetics, population genetics and evolutionary processes ................................................................................................................................................................ 92
Unit 8: Molecular biology and gene technology ............................................................................................................................................................................................ 111
Unit 9: Respiration ........................................................................................................................................................................................................................................ 129
Unit 10: Mammalian physiology, control and coordination ........................................................................................................................................................................... 140
Unit 11: Plant physiology and biochemistry .................................................................................................................................................................................................. 156
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
2
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Overview
This staged teaching scheme of work provides ideas about how to construct and deliver a two-year course of study with all of the AS Level syllabus taught in Year 1
and the remainder of the A Level syllabus taught in Year 2. The syllabus has been broken down into teaching units, which incorporate one or more of the syllabus units,
with suggested teaching activities and learning resources to use in the classroom.
Recommended prior knowledge
Learners should have attained at least a grade C in IGCSE or O Level Biology, or the equivalent in another award such as Co-ordinated Science.
Outline
Whole class (W), group work (G), pair (P) and individual activities (I) are indicated, where appropriate, within this scheme of work. Suggestions for homework (H) and
formative assessment (F) are also included. The activities in the scheme of work are only suggestions and there are many other useful activities to be found in the
materials referred to in the learning resource list.
Opportunities for differentiation are indicated as basic and challenging; there is the potential for differentiation by resource, length, grouping, expected level of
outcome, and degree of support by the teacher, throughout the scheme of work. Length of time allocated to a task is another possible area for differentiation.
Where a learning objectives has been divided so that part of that learning objective content is taught at a different time to the rest of the learning objective, these are
identified by (i) or (ii), etc., and the specific part of the learning objective is in bold.
Key concepts
The key concepts on which the syllabus is built are set out below. These key concepts can help teachers think about how to approach each topic in order to encourage
learners to make links between topics and develop a deep overall understanding of the subject. As a teacher, you will refer to these concepts again and again to help
unify the subject and make sense of it. If mastered, learners can use the concepts to solve problems or to understand unfamiliar subject-related material.
Cells as the units of life
A cell is the basic unit of life and all organisms are composed of one or more cells. There are two fundamental types of cell: prokaryotic and eukaryotic.
Biochemical processes
Cells are dynamic: biochemistry and molecular biology help to explain how and why cells function as they do.
DNA, the molecule of heredity
Cells contain the molecule of heredity, DNA. Heredity is based on the inheritance of genes.
Natural selection
Natural selection is the major mechanism to explain the theory of evolution.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
3
Organisms in their environment
All organisms interact with their biotic and abiotic environment.
Observation and experiment
The different fields of biology are intertwined and cannot be studied in isolation: observation and enquiry, experimentation and fieldwork are fundamental to
biology.
Some of the ideas in this syllabus can take time to be fully understood. By linking them together through the key concepts, learners will have more opportunity for
those ideas to make sense to them and how they connect to other areas of the syllabus. The key concepts themselves will not be directly assessed; rather they are
themes that learners will be able to use to order their thoughts, themes and knowledge to express answers in examinations and interviews for work or the next stage of
their study.
As learners progress through the course, it is important that they do not regard the different topics as being totally self-contained and unconnected, studied in complete
isolation from one another. By keeping the key concepts to the fore at all stages of your teaching, you can strongly encourage learners to regard the subject as a set of
interconnected themes.
Learners should be aware that an ability to see how different strands of the syllabus can be pulled together within one key concept is a high-level transferable skill.
Linking different areas of their knowledge through a common thread of ideas, or ways of understanding and explaining, is enhancing their higher-order thinking skills.
These skills are the building blocks of deeper and broader learning, those that universities look for in their students and which allow learners to answer examination
questions fully and with links from more than one part of the syllabus.
Teachers can introduce key concepts as an integral part of their teaching approach and consolidate them when appropriate. This will help their learners to appreciate
that some themes and theories are revisited and built upon during the course and that, by bringing together very different areas of the syllabus, these themes are
fundamental to our understanding of the subject.
Focussing on these concepts will improve learners’ self-confidence in their ability to progress, as well as enabling them to revise more effectively; learners could make
mind maps across the syllabus on each of the key concepts as a way of revising. By visualising the subject as being formulated from these basic ideas, they will
become better prepared for interviews and future study at university, or be more adaptable to themes currently under research and development in industrial and
academic institutions.
There is also merit in showing learners how, during the course, they will be biologists studying in a number of inter-related fields that can be drawn together by the key
concepts. Examples of these fields - cell biology, biochemistry, physiology, genetics, evolutionary biology, microbiology, epidemiology, immunology, biotechnology,
ecology, population biology and conservation biology - can be discussed and linked to the different areas of the syllabus.
The key concepts are listed under the relevant learning objectives, those in bold are where the coverage of the learning objective makes a significant contribution to the
key concept.
Practical work
Practical work is an essential part of science. Scientists use evidence gained from prior observations and experiments to build models and theories. Their predictions
are tested with practical work to check that they are consistent with the behaviour of the real world. Learners who are well trained and experienced in practical skills will
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
4
be more confident in their own abilities. The skills developed through practical work provide a good foundation for those wishing to pursue science further, as well as for
those entering employment or a non-science career.
Twelve Practical Booklets have been developed for this syllabus, six for Paper 3 and six for Paper 5, and are available on Teacher Support at http://teachers.cie.org.uk
and are referenced within this scheme of work.
The Teaching A Level Science Practical Skills booklet is also available on Teacher Support at http://teachers.cie.org.uk which contains useful information and
suggestions for teaching A Level practical skills.
Suggested teaching order
The learning objectives and activities in this scheme of work are arranged in a suggested teaching order rather than the order that they appear in the syllabus. It has
been written for the staged route, with Units 1 to 5 covering the learning objectives to be studied by all learners in the first year, and which can be assessed by the AS
Level qualification. This is followed by Units 6 to 11 which cover all learning objectives that will be assessed by the full A Level qualification at the end of the second
year of the course.
For classes taking the linear route, where all learners take the full A Level, this allows for the integrated teaching of AS and A Level learning objectives across both
years of the A Level course. The linear route is not covered in this scheme of work.
The units within this scheme of work are:
Suggested time allocation (%)
AS Level
A Level
Unit 1. Biological molecules
Water
Carbohydrates
Lipids
Proteins
Biochemical tests
Nucleic acids
Enzymes
Unit 2. Cells as the basic units of life
Cells and microscopy
Size and magnification calculations
Plant and animal cells
Bacteria
Prokaryotic versus eukaryotic cell structure
v2.1 5Y02
2.3.d
2.2.b, 2.2.a, 2.2.c, 2.1.a(i), 2.1.b, 2.2.d, 2.2.e
2.2.f, 2.2.g, 2.1.a(ii)
2.1.a(iii), 2.3.a, 2.3.b, 2.3.c
2.1.a
6.1.a, 6.1.b
3.1.a, 3.1.b, 3.1.c, 3.1.d, 3.2.a, 3.2.b, 3.2.c, 3.2.d
1.1.d, 1.1.a, 1.1.c
1.1.b, 1.1.e
1.2.b, 1.2.c, 1.2.a
1.2.d
1.2.e
Cambridge International AS & A Level Biology (9700) – from 2016
10
9
5
Viruses
Cell membrane structure and function
Transport across membranes
Unit 3. DNA and the mitotic cell cycle
Chromosome structure
The mitotic cell cycle - overview
The mitotic cell cycle – DNA replication
The mitotic cell cycle – mitosis and cytokinesis
Protein synthesis, introduction to genes and mutation
Unit 4. Transport and gas exchange
Plant anatomy and histology
Transport of water and mineral ions
Transport of assimilates
Structure to function: plants
The mammalian circulatory system
The mammalian heart
The human gas exchange system
Carriage of respiratory gases
Unit 5. Disease and protection against disease
Disease and smoking
Infectious disease
Antibiotics
The immune response
Antibodies
Vaccination
Unit 6. The diversity of life
Definitions
Classification
Biodiversity
Fieldwork
Conservation, population control and maintaining
v2.1 5Y02
1.2.f
4.1.a, 4.1.b, 4.1.c
4.2.a(v), 4.2.c, 4.2.a(i), 4.2.d, 4.2.b, 4.2.a(ii), 4.2.a(iii), 4.2.f,
4.2.e, 4.2.a(iv)
5.1.a
5.1.c
6.1.c, 5.1.d
5.1.b, 5.1.e, 5.2.a, 5.2.b
6.2.a, 6.2.b, 6.2.c, 6.2.d
7.1.a, 7.1.b, 7.1.c
7.2.a, 7.2.c, 7.2.b, 7.2.d, 7.2.e, 7.2.f
7.2.g, 7.2.h, 7.2.i
7.1.d
8.1.a, 8.1.b, 8.1.c, 8.1.d, 8.1.e
8.2.a, 8.2.b, 8.2.c, 8.2.d
9.1.a, 9.1.b, 9.1.c, 9.1.d
8.1.f, 8.1.g, 8.1.h
10.1.a, 9.2.a, 9.2.b
10.1.b, 10.1.c, 10.1.d, 10.1.e
10.2.a, 10.2.b, 10.2.c
11.1.d, 11.1.a, 11.1.b, 11.1.e, 11.1.c, 11.1.f
11.2.a, 11.2.b, 11.2.c
11.2.d, 11.2.e
18.1.a
18.2.a, 18.2.b, 18.2.c, 18.2.d
18.1.b
18.1.c, 18.1.d, 18.1.e, 18.1.f
18.3.a, 17.3.e, 18.3.b, 18.3.g, 18.3.c, 18.3.d, 18.3.e, 18.3.f,
Cambridge International AS & A Level Biology (9700) – from 2016
7
14
10
6
6
biodiversity
18.3.h
Unit 7. Genetics, population genetics and evolutionary processes
Understanding terms
16.1.a, 16.1.b, 16.2.a(i)
Meiotic cell division and heredity
16.1.c, 16.1.d, 16.1.e
Genetic crosses
16.2.a(ii), 16.2.b, 16.2.c, 16.2.d
Biological variation
17.1.a, 17.1.c, 17.1.b, 16.2.e, 16.2.f, 16.2.g
Natural selection and population genetics
17.1.d, 17.2.a, 17.2.b, 17.2.c, 17.2.d
Evolution and speciation
17.3.a, 17.3.b, 17.3.c, 17.3.d
Artificial selection
17.2.e, 17.2.f
Unit 8. Molecular biology and gene technology
The control of gene expression
16.3.b, 16.3.a, 16.3.c, 19.1.i
Recombinant DNA technology
19.1.a, 19.1.b, 19.1.h, 19.1.e, 19.1.f, 19.1.g, 19.2.c, 19.3.a,
19.3.b, 19.3.c
Molecular biology techniques
19.1.c, 19.1.d, 19.2.g
Bioinformatics
19.2.a, 19.2.b
Prevention and treatment of inherited conditions.
19.2.d, 19.2.e, 19.2.f
Unit 9. Respiration
Energy and ATP
12.1.a, 12.1.b
Aerobic respiration and ATP synthesis
12.2.a, 12.2.b, 12.2.c, 12.2.d, 12.2.e, 12.1.c, 12.2.g, 12.2.f,
12.1.e(i), 12.1.d, 12.2.i
Anaerobic respiration
12.2.k, 12.2.l
Comparing anaerobic and aerobic respiration
12.2.j
Yeast practical
12.2.h
Respiratory substrates, RQs and respirometers
12.1.f, 12.1.g, 12.2.m, 12.1.h
Unit 10. Mammalian physiology, control and coordination
Communication systems
15.1.a
The nervous system
15.1.b, 15.1.c, 15.1.d, 15.1.e, 15.1.f, 15.1.g, 15.1.h
Muscle contraction
15.1.i, 15.1.j, 15.1.k
Homeostasis
14.1.a, 14.1.b, 14.1.c
Excretion of nitrogenous waste and osmoregulation
14.1.d, 14.1.e, 14.1.f, 14.1.g
Control of blood glucose concentration
14.1.h, 14.1.i, 14.1.j
Detection of biological molecules in blood and urine
14.1.k, 14.1.l
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
10
9
7
10
7
Hormones of the menstrual cycle
Unit 11. Plant physiology and biochemistry
Photosynthesis overview
The light dependent stage
The light dependent stage - chemiosmosis
The light independent stage
The chloroplast
Factors affecting photosynthesis.
Control and coordination in plants.
15.1.l, 15.1.m
13.1.b
13.1.c, 13.1.d, 13.1.e, 13.1.f
12.1.e(ii)
13.1.a, 13.1.g, 13.1.h
13.3.a
13.2.a, 13.2.b, 13.2.c, 13.2.d, 13.2.e, 13.3.b
15.2.a, 14.2.a, 14.2.b, 14.2.c, 15.2.b, 15.2.c, 15.2.d, 16.3.d
8
Suggested teaching order
AS Level
Unit 1, Biological molecules, could be studied either before or after Unit 2, Cells as the basic units of life. Learners with a good chemistry background will cope well with
Unit 1, others will probably find the subject matter in Unit 2 to be more approachable. If Unit 2 is covered first, then learners will need a reminder of previous knowledge
of biological molecules learned in earlier studies or a brief introduction to lipids and proteins. Knowledge and understanding from both of these will be used and applied
in the rest of the course. The role of DNA in the mitotic cell cycle, Unit 3, follows on quite logically from the work done in Units 1 and 2. Unit 5, Disease and protection
against disease is best taught after Unit 4, Transport and gas exchange, as there is a link between mammalian transport and gas exchange in mammals in Unit 4 and
non-infectious disease and cells of the immune system in Unit 5. There is much work that can be done in improving data extraction and data analysis skills in Unit 5,
where there are fewer opportunities to carry out practical work. As this unit is taught at the end of the AS Level course, teachers may wish to allocate some time to
consolidate practical skills gained earlier in the course and prepare learners fully for Paper 3.
A Level
Having studied eukaryotic and prokaryotic cell structure in Unit 2 (AS Level), Unit 6, The diversity of life, is a straightforward introduction to the A Level syllabus. This
covers knowledge and understanding that is useful for Unit 7, Genetics, population genetics and evolutionary processes. Unit 8, Molecular biology and gene
technology, allows learners to use some of the concepts covered in Unit 7. Unit 11 can be taught at any time throughout the course if carrying out practical work is
dependent on seasonal timing: if taught before Units 9 and 10, the idea of control and coordination and chemiosmosis should be covered. Units 9 and 11 are best
taught with a gap in between to avoid confusion for learners when studying the biochemical processes of respiration and photosynthesis.
Teacher support
Teacher Support (http://teachers.cie.org.uk) is a secure online resource bank and community forum for Cambridge teachers, where you can download specimen and
past question papers, mark schemes and other resources. We also offer online and face-to-face training; details of forthcoming training opportunities are posted online.
This scheme of work is available as PDF and an editable version in Microsoft Word format; both are available on Teacher Support at http://teachers.cie.org.uk. If you
are unable to use Microsoft Word you can download Open Office free of charge from www.openoffice.org.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
8
Resources
The resources for this syllabus, including textbooks endorsed by Cambridge, can be found at www.cie.org.uk and Teacher Support http://teachers.cie.org.uk.
Endorsed textbooks have been written to be closely aligned to the syllabus they support, and have been through a detailed quality assurance process. As such, all
textbooks endorsed by Cambridge for this syllabus are the ideal resource to be used alongside this scheme of work as they cover each learning objective.
Where other textbooks have shown to be useful for some learning objectives they are referred to by the first author. These include:
King T, Reiss M, Roberts M. Practical Advanced Biology. Nelson Thornes, 2nd Edition 2001. ISBN: 9780174483083
Siddiqui S. Comprehensive Practical Biology for A Level. Ferozsons, 1999. ISBN 9690015729
Bio Factsheets. Curriculum Press www.curriculum-press.co.uk
These cover a wide range of topics and are also useful for revision and extension work. Individual factsheets can be obtained, as can a complete CD-ROM.
Biological Nomenclature, published by the Society of Biology (formerly the Institute of Biology).
This publication can be ordered by emailing the Education Department at the Society of Biology https://www.societyofbiology.org. The symbols, signs and
abbreviations used in examination papers follow these recommendations.
CD-ROM
Bioscope. Cambridge University Press. ISBN: 9781845650261
A simulation of a real microscope that includes a large number of botanical and zoological microscope slides at a range of magnifications, accompanied by paperbased tasks. It can be used for whole class teaching via a whiteboard or data projector, or by individual students on PCs.
Websites:
This scheme of work includes website links providing direct access to internet resources. Cambridge International Examinations is not responsible for the accuracy or
content of information contained in these sites. The inclusion of a link to an external website should not be understood to be an endorsement of that website or the
site's owners (or their products/services).
The particular website pages in the learning resource column of this scheme of work were selected when the scheme of work was produced. Other aspects of the sites
were not checked and only the particular resources are recommended.
Websites in this scheme of work, and some other useful websites, include:
http://www.ncbe.reading.ac.uk/
http://www.saps.org.uk/
The National Centre for Biotechnology Education: protocols and useful information
Science and Plants for Schools: protocols
http://www.biology4all.com/resources_library/index.asp
http://www.s-cool.co.uk/alevel/biology.html
http://www2.estrellamountain.edu/faculty/farabee/BIOBK/BioBookTOC.html
http://www.rothamsted.ac.uk/notebook/index.php?area=&page=
Biology 4all: wide range of resources and links to other useful sites
S-cool: revision website
The Online Biology Book, hosted by Estrella Mountain Community College
The Molecular Biology Notebook
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
9
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/
http://www.cellsalive.com/
http://www.worldofteaching.com/A-ZBiologypowerpoints.html
http://www.ase.org.uk/resources/
http://www.nuffieldfoundation.org/practical-biology
http://www.nationalstemcentre.org.uk/sciencepracticals
http://www.biology-resources.com
http://www.biologyjunction.com/ap_biology_animations.htm
http://www.rsc.org/Education/Teachers/Resources/cfb/index.htm
https://www.societyofbiology.org/
v2.1 5Y02
Kimball’s Biology Pages (especially useful for teacher reference)
Cells Alive: covers a range of topics with straightforward animations
PowerPoint presentations donated by teachers
Association for Science Education: educational resources
Practical Biology: ideas and lesson plans
The National Stem Centre provides many resources including ideas for practical work
For learners to revisit IGCSE topics
Links to websites with animations - many different topics
Royal Society of chemistry: Chemistry for biologists
The Society of biology
Cambridge International AS & A Level Biology (9700) – from 2016
10
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 1: Biological molecules
Recommended prior knowledge
Learners will need some background knowledge in chemistry before embarking on this unit. They should understand the terms atom, molecule, electron and ion. They
should also have a basic understanding of covalent and ionic bonding, and of molecular and structural formulae. They should be able to write and understand simple
chemical equations. Some knowledge of energy changes (potential energy and bond energy) would be helpful.
http://www.rsc.org/Education/Teachers/Resources/cfb/basicchemistry.htm is a good starting point for learners to revise their knowledge of chemistry.
http://www.biology.arizona.edu/biochemistry/tutorials/chemistry/page1.html this also covers basic chemistry for biologists.
Context
This unit provides essential reference material for learners when studying all future units in their Cambridge International AS and A Level course. Knowledge of how the
structure and properties of biological molecules are related to their functions in cells and in organisms is fundamental to an understanding of many areas of biology.
The molecule of heredity, DNA, is a key concept. Cells can be visualised as structural units requiring biological molecules and as dynamic units carrying out
biochemical processes. Cells carry out biochemical processes, a key concept, and enzymes catalyse biological reactions. A thorough understanding of enzyme
function can be applied to studying processes such as:
DNA replication and protein synthesis in Unit 3, The role of DNA in the mitotic cell cycle;
the carriage of carbon dioxide in Unit 4, Transport and gas exchange;
gene technology in Unit 8, Molecular biology and gene technology;
respiration in Unit 9, Respiration;
photosynthesis in Unit 11, Plant physiology and biochemistry.
As part of biotechnology, enzymes are used commercially in a range of applications, with many of these using immobilised enzymes for a more efficient process.
Outline
This unit introduces learners to the biological molecules that are required by cells for both structural purposes and physiological processes. The main groups of organic
biochemicals, carbohydrates, lipids, proteins and nucleic acids, are studied. For carbohydrates, lipids and proteins, there is an emphasis on the relationship between
molecular structure, properties and functions in living organisms. Learners study the structure of nucleic acids and discuss DNA as the ideal molecule of inheritance in
preparation for Unit 3, The role of DNA in the mitotic cell cycle. Learning objective 2.3.d introduces the concepts of hydrogen bonding and solubility and considers the
roles of water in living organisms. This unit builds on knowledge of protein structure in describing and explaining enzyme activity. The mode of action of enzymes and
factors that affect enzyme action, including inhibitors, is covered. Learners are introduced to some basic enzyme kinetics. There are many opportunities to carry out
practical work, where learning can be reinforced and individual and class results can be analysed. The last section of the unit considers the differences between
enzymes free in solution and immobilised enzymes.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
11
Learning objectives
Suggested teaching activities
Learning resources
2.3.d
explain how hydrogen bonding occurs
between water molecules and relate
the properties of water to its roles in
living organisms (limited to solvent
action, specific heat capacity and
latent heat of vapourisation)
Discussion / brainstorm: the importance of water to the life of a cell, including
hydrogen bonding and as a solvent in biological systems (e.g. blood, phloem sap,
cytosol/cytoplasm). (I) (Basic).
Learners make notes, including the following:
o Draw and describe hydrogen bonding between water molecules. (I) (Basic)
o Make links between hydrogen bonding and the cohesive nature of water
molecules. (I) (Basic)
o Explain the link between hydrogen bonding and
the high specific heat capacity of water
the high latent heat of vapourisation of water. (I) (Challenging)
o Research examples to show the relationship between the properties of water
and its roles in organisms. (I) (Challenging)
Discuss the concept of polar / non-polar and the solubility or otherwise of the
biological molecules in this unit. (W) (Basic)
Online
http://faculty.fmcc.edu/mcdarby/majors
101book/chapter_03-chemistry/03Water_Properties.htm
http://www.rsc.org/Education/Teachers
/Resources/cfb/water.htm
http://www.worldofmolecules.com/solv
ents/water.htm
Key concepts
Cells as the units of life,
Biochemical processes,
Organisms in their environment
Textbooks/Publications
Bio Factsheet 30: The biological
importance of water.
Bio Factsheet 78: Chemical bonding in
biological molecules
Note
Ensure learners can use the following terms (see Unit 2):
hydrophilic
hydrophobic
polar
non-polar
charged / ionic
uncharged / non-ionic
water soluble
water-insoluble
lipid insoluble
lipid soluble
2.2.b
define the terms monomer, polymer,
macromolecule, monosaccharide,
disaccharide and polysaccharide
Key concepts
Biochemical processes,
DNA, the molecule of heredity
v2.1 5Y02
Learners write definitions for macromolecule, monomer and polymer and
consolidate. (W) (Basic)
o Match the terms with relevant examples (include an introduction of DNA and
RNA nucleotides).
o Discuss why lipids do not have monomers.
o Construct a simple table (complete bond names later).
polymer
name of bond
type of organic monomer
macromolecule
carbohydrate
monosaccharide polysaccharide
protein
amino acid
polypeptide
nucleic acid
DNA nucleotide
polynucleotide
RNA nucleotide
lipid
-
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.rsc.org/Education/Teachers
/Resources/cfb/carbohydrates.htm
Textbooks/Publications
Bio Factsheet 78: Chemical bonding in
biological molecules
12
Learning objectives
Suggested teaching activities
Learning resources
Further discussion (W) (Basic)
o The macromolecules are based on a skeleton of carbon atoms (‘life is based on
carbon'), which can form strong bonds with other atoms.
o Of the wide range of organic compounds formed, some provide energy for the
cell.
Introduce the terms condensation and hydrolysis by discussing the synthesis and
breakdown of polymers. (W) (Basic)
Brainstorm some carbohydrates and agree whether monosaccharide, disaccharide
or polysaccharide (W) (Basic)
o Learners make notes on: monosaccharides, using the terms triose, pentose and
hexose (glucose, galactose and fructose as e.g. of hexoses); disaccharides
(lactose, maltose, sucrose and cellobiose), giving their constituent
monosaccharides). (I) (Basic)
Note
Useful terms for later:
o pentose - nucleotide and nucleic acid structure in this unit,
o hexose for respiration (Unit 9 ) and photosynthesis (Unit 11).
2.2.a
describe the ring forms of -glucose
and glucose
Key concepts
Biochemical processes
2.2.c
describe the formation of a glycosidic
bond by condensation, with reference
both to polysaccharides and to
v2.1 5Y02
Provide details of the molecular structure of glucose (see 2.2.b) which, in solution, is
mainly in ring form (W) (Basic)
o Show learners how to use a logical sequence to build up the ring form of the
glucose molecule and number the carbon atoms. Learners practise then draw
the molecule from memory. (I) (Challenging)
o Learners complete a range of incomplete diagrams prepared by you, e.g. by
adding the -OH and -H groups. (F)
o Progress learners to be able to identify and draw a glucose molecule. (I)
(Basic)
Learners make molecular models of and forms of glucose using plastic sphere /
bond models or drinking straw models. (P) (Challenging)
Explain that knowledge of the and forms of glucose will help understanding of
disaccharide and polysaccharide structures and properties. (W) (Basic)
Online
http://www.biologie.uni-hamburg.de/bonline/e17/17.htm
http://www.rsc.org/Education/Teachers
/Resources/cfb/carbohydrates.htm#2
Outline how a glycosidic bond is formed to produce a disaccharide by a
condensation reaction (no details yet of molecular structure). (W) (Basic)
Learners draw the formation of an , 1-4 glycosidic bond and add the name of the
bond to their table from 2.2.b. (I) (Challenging)
Past Papers
Paper 22, Nov 2011, Q4 (b)
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 22, Nov 2011, Q4 (a)
Textbooks/Publications
13
Learning objectives
Suggested teaching activities
Learning resources
disaccharides, including sucrose
Work through the formation of a , 1-4 glycosidic bond (to form cellobiose). (W)
(Challenging)
Tell learners that the glucose monomer of sucrose is -glucose and ask them to use
a molecular diagram of a sucrose molecule to work out the structure of a fructose
molecule (no need to memorise this). (W) (Challenging)
Learners use the -glucose models previously constructed to form a glycosidic
bond. (P) (I) (Basic)
o Produce a section of a polysaccharide, e.g. from an amylose or cellulose
molecule. (G) (P) (I) (Challenging)
Bio Factsheet 78: Chemical bonding in
biological molecules
Key concepts
Biochemical processes
Note
Maltose is formed in nature from degradation reactions (i.e. breakdown) of starch, so
focus the activity on the concept of a condensation reaction to build up a
macromolecule and the formation of a glycosidic bond. The ‘formation’ of maltose
illustrates the principle of glycosidic bond formation by a condensation reaction.
2.1.a (i)
carry out tests for reducing sugars
and non-reducing sugars, the iodine
in potassium iodide solution test for
starch, the emulsion test for lipids and
the biuret test for proteins to identify
the contents of solutions
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Only the first part of this learning objective is included here: carry out tests for reducing
sugars and non-reducing sugars, and the iodine in potassium iodide solution test for
starch to identify the contents of solutions
Discuss the tests and explain they are useful to identify biochemicals in a range of
plant and animal material. (W) (Basic)
o Learners should describe the biochemical tests (‘food tests’ is a less helpful
term) and the results obtained, giving conclusions. (W) (Basic)
Practical work: carrying out the Benedict's test for reducing sugars.
o Explain that a negative test does not mean an absence of carbohydrate. (I)
(Basic)
o Learners test substances that will give positive results (e.g. glucose/fructose/
maltose/lactose solution) and negative results (e.g. sucrose solution, water,
protein/starch suspension, vegetable oil). (I) (Basic)
o Learners test natural liquefied biological materials (e.g. fruits, tubers) and
liquefied foods from the diet. (I) (Basic) (Challenging)
o Learners test a thin section of fruit placed on a microscope slide (add a few
drops of Benedict’s and heat over a spirit burner – use forceps): use a
microscope to observe colour changes. (P) (I) (Challenging)
Discuss the negative result for reducing sugar with sucrose and explain that hot acid
is used to hydrolyse sucrose, but neutralisation is required before adding Benedict’s.
(W) (Basic)
Practical work carrying out the test for a non-reducing sugar, where learners use
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
Textbooks/Publications
King p.19-22
Siddiqui p.56-60
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
14
Learning objectives
Suggested teaching activities
Learning resources
fresh samples of each of the substances that gave ‘negative’ results for the reducing
sugar test. (I) (Basic)
Practical work to consolidate reducing sugars and non-reducing sugar tests.
o Learners identify which unmarked solution is: glucose; sucrose; a mixture of both
glucose and sucrose. (I) (Basic)
o Extend this (excess of Benedict’s solution) to filtering the precipitates for
comparison and using a colorimeter (if available) to compare filtrates. (P) (I)
(Challenging)
Practical work to test for starch in a range of different types of starch (suspensions)
and food substances using iodine in potassium iodide solution. Learners see a range
of blue-black colours obtained (owing to the differing proportions of amylose to
amylopectin). (I) (Basic)
Practical booklet 2 can be carried out after this stage. See the Teacher’s practical
notes regarding the development of certain skills for Paper 3.
Note
Remind learners to control variables.
AR (analytical reagent) sucrose is preferred to LR (laboratory reagent) sucrose
(preferred to cane sugar) for the non-reducing sugar test (if cane sugar is used,
explain that it will contain impurities and may give a slight positive Benedict’s test
results).
2.1.b
carry out a semi-quantitative
Benedict’s test on a reducing sugar
using dilution, standardising the test
and using the results (colour standards
or time to first colour change) to
estimate the concentration
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Practical work: learners practise, and get a visual impression of, diluting a coloured
liquid, using water, to set concentrations. (I) (Basic)
Practical work: learners prepare glucose solutions of known concentration and then
carry out the Benedict's test, recording the time taken for the first indication of colour
change and to obtain colour standards. (I) (Basic)
o Follow-up with a semi-quantitative analysis, comparing time taken and
colour/colour depth to determine the approximate concentration of an unknown
solution. (I) (Challenging)
o Evaluate the test with learners and ask for ideas of other semi-quantitative tests
(e.g. allow precipitate to settle, dry and weigh). (W) (Challenging)
Practical booklet 2 can be carried out after this stage. See the Teacher’s practical
notes regarding the development of certain skills for Paper 3.
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 2
Online
http://www.saps.org.uk/secondary/teac
hing-resources/103-estimatingglucose-concentration-in-solution
15
Learning objectives
Suggested teaching activities
Learning resources
2.2.d
describe the breakage of glycosidic
bonds in polysaccharides and
disaccharides by hydrolysis, with
reference to the non-reducing sugar
test
Explain how a glycosidic bond can be broken by hydrolysis, referring to monomers
and monosaccharides. (W) (Basic)
Learners draw diagrams of the breakage of glycosidic bonds (by hydrolysis) of
maltose and sucrose. (I) (Challenging)
o Add annotations to explain the ideas behind the non-reducing sugar test. (I)
(Basic)
o Use the models of disaccharides previously constructed to demonstrate the
breakage of a glycosidic bond. (P) (I) (Basic)
o Extension activity: using molecular diagrams of galactose, lactose and
cellobiose, learners draw diagrams or construct models to show the breakdown
of lactose and cellobiose. (P) (I) (Challenging)
Online
http://www.rsc.org/Education/Teachers
/Resources/cfb/carbohydrates.htm#2
Key concepts
Biochemical processes,
Observation and experiment
Note
Learners should describe the breakage of the glycosidic bond in sucrose when
explaining non-reducing sugar test results (see 2.1.a)
2.2.e
describe the molecular structure of
polysaccharides including starch
(amylose and amylopectin), glycogen
and cellulose and relate these
structures to their functions in living
organisms
Key concepts
Cells as the units of life,
Biochemical processes
2.2.f
v2.1 5Y02
Use the molecular models to show short sections of amylose and amylopectin (or
strings of beads on wire) and discuss glycogen structure. (G) (Basic)
Learners describe the difference between the structures (include bonds formed) and
highlight the idea of ‘structure to function ‘.
o More compact structures for storage linked to the coiling effect (amylose) and
branching (amylopectin).
o Branching of amylopectin and glycogen provides large number of ‘ends’ to
attach /detach glucose units. (I) (Basic)
Demonstrate (molecular model / animation) how a straight chain is produced when
forming polysaccharides with alternate -glucose residues that rotate by 180°.(W)
(Basic)
Emphasise the structure to function of cellulose is different to that of the cell wall.
(W) (Basic)
Discuss the role of cellulose, then learners produce explanatory notes with diagrams
of how straight parallel chains are useful for structural purposes and how hydrogen
bonding (2.3.d) allows parallel cellulose molecules to form fibrils (links to cell wall
structure in Unit 2). (I) (Challenging)
Learners complete a gap-filling worksheet prepared by you to serve as a summary
of the main learning points for carbohydrates. (F)
Draw the general formula for a fatty acid.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.rpi.edu/dept/bcbp/molbioch
em/MBWeb/mb1/part2/sugar.htm
http://www.calfnotes.com/pdffiles/CN1
02.pdf
Textbooks/Publications
Bio Factsheet 39: Carbohydrates:
revision summary
Bio Factsheet 174: The structure and
function of polysaccharides
Past Papers
Paper 21, June 2011, Q5
Paper 22, Nov 2012, Q1 (d)
Online
16
Learning objectives
Suggested teaching activities
Learning resources
describe the molecular structure of a
triglyceride with reference to the
formation of ester bonds and relate the
structure of triglycerides to their
functions in living organisms
o Explain that it is a carboxylic acid and outline -COOH as the carboxyl group.
o Explain R is a hydrocarbon chain, and extend this to explain saturated or
unsaturated fatty acids. (W) (Basic)
Draw the molecular structure of glycerol and state that a triglyceride is produced with
the attachment of three fatty acids in condensation reactions. (W) (Basic)
o With prompting, learners work out how ester bonds form and add the name of
the bond to their table of 2.2.b. (I) (Challenging)
Learners make simple paper cut-out models of triglycerides to illustrate the absence
of polar groups and show the non-polar exposed fatty acids (so not soluble when in
contact with watery liquids). (W) (Basic)
Learners describe evidence that makes triglycerides good energy stores (many C-C
bonds; highly reduced so energy can be released by oxidation; insoluble in water so
can be localised in the organism). (G) (P) (I) (Challenging)
http://www.biotopics.co.uk/as/lipidcond
ensation.html
http://www.chemguide.co.uk/organicpr
ops/esters/background.html
Key concepts
Cells as the units of life,
Biochemical processes
Textbooks/Publications
Bio Factsheet 42: The structure and
function of lipids.
Bio Factsheet 74: The structure and
biological functions of lipids.
Bio Factsheet 78: Chemical bonding in
biological molecules
Past Papers
Paper 21, June 2011, Q5
Paper 22, June 2011, Q5 (a)(b)(i)
Paper 22, Nov 2011, Q4 (b)
2.2.g
describe the structure of a
phospholipid and relate the structure of
phospholipids to their functions in living
organisms
Key concepts
Cells as the units of life,
Biochemical processes
Learners label a printed diagram showing the structure of a phospholipid molecule
and discuss how the presence of polar groups relates to phospholipid behaviour
when in contact with watery liquids. (W) (Basic)
Discuss the function of phospholipids in forming the bulk of structure of cell
membranes, forming bilayers (link to Unit 2). (W) (Basic)
Learners do research to find out that: there are many different fatty acids and
phospholipids; some phospholipids have a nitrogen-containing (choline) portion. (H)
(Basic) (Challenging)
2.1.a (ii)
carry out tests for reducing sugars
and non-reducing sugars, the iodine in
potassium iodide solution test for
starch, the emulsion test for lipids
and the biuret test for proteins to
identify the contents of solutions
Only the second part of this learning objective is included here: carry out tests
emulsion test for lipids to identify the contents of solutions
Practical work, testing for lipids using the (ethanol) emulsion test.
o Test vegetable oil and yellow-dyed water. (I) (Basic)
o Test crushed fruits and seeds. (I) (Basic)
Practical booklet 2 is designed to be carried out after learners have used the
emulsion test as described above.
Key concepts
Note
Ensure learners understand that lipids include triglycerides (fats and oils).
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 152: Phospholipids
Past Papers
Paper 21, June 2011, Q5
Paper 22, June 2011, Q5 (a)(b)(i)(ii)
(c)(d)
Paper 22, Nov 2011, Q4 (b)
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
17
Learning objectives
Suggested teaching activities
Biochemical processes,
Observation and experiment
2.1.a (iii)
carry out tests for reducing sugars
and non-reducing sugars, the iodine in
potassium iodide solution test for
starch, the emulsion test for lipids and
the biuret test for proteins to
identify the contents of solutions
Key concepts
Biochemical processes,
Observation and experiment
2.3.a
describe the structure of an amino acid
and the formation and breakage of a
peptide bond
Key concepts
Biochemical processes
v2.1 5Y02
Learning resources
Textbooks/Publications
King p.19-22
Siddiqui p.56-60
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
Only the third part of this learning objective is included here: carry out tests biuret test
for proteins to identify the contents of solutions.
Practical work, testing for proteins using the biuret test on a solution of egg white,
skimmed milk, chicken or tofu and water. (I) (Basic)
Extension practical using a semi-quantitative biuret test: learners prepare a set of
standard solutions and compare the intensity of colour obtained of an unknown with
the standards (control variables). (P) (I) (Challenging)
Practical booklet 2 is designed to be carried out after learners have used the biuret
test as described above.
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
Textbooks/Publications
King p.19-22
Siddiqui p.56-60
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
Familiarise learners with the names of the 20 amino acids (encoded by the genetic
code – see Unit 3) and their three-letter shortened version from labelled diagrams.
Learners write out the general formula of an amino acid, and on the diagrams use a
colour code to identify the: R group; part common to them all; amine group;
carboxylic acid group. (W) (I) (Challenging)
o Learners make notes to show understanding that the ‘side-chain’ or R (residual)
group can take different forms and that the amino acids can be grouped
according to the properties of their R-group. (I) (Basic)
Learners draw simple diagrams of: peptide bond formation (choose two amino acids
from their diagram sheet) by condensation (add the name of the bond to their table
of 2.3.b); hydrolysis of the dipeptide. (I) (Challenging)
Discuss how a series of condensation reactions leads to the formation of a
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biotopics.co.uk/as/aa.html
http://www.worldofmolecules.com/life/
Textbooks/Publications
Bio Factsheet 78: Chemical bonding in
biological molecules
Bio Factsheet 80: Structure and
biological functions of proteins
Past Papers
Paper 21, June 2011, Q5
18
Learning objectives
Suggested teaching activities
polypeptide. (W) (Basic)
Learning resources
Paper 22, Nov 2011, Q4 (b)
Note
The names and structures of the amino acids are not required learning.
Learners could be introduced to the one-letter abbreviations (useful for Unit 8).
2.3.b
explain the meaning of the terms
primary structure, secondary structure,
tertiary structure and quaternary
structure of proteins and describe the
types of bonding (hydrogen, ionic,
disulfide and hydrophobic interactions)
that hold these molecules in shape
Key concepts
Biochemical processes
Learners write down their own polypeptide, 25 amino acids long (choose from the
sheet of 2.3.a) using encircled three-letter abbreviations and share with the rest of
the group to highlight how an enormous number of different polypeptides can be
obtained. Discuss the term primary structure. (W) (I) (Basic)
Make links forward to Unit 2 to the roles of cell structures in protein synthesis to fold
/ further modify the polypeptide chain. (W) (Basic)
Expand knowledge of hydrogen bonding (from 2.3.d) and 2.2.e) with an explanation
of secondary structure. (W) (Basic)
Learners suggest what will hold the chain in place to form a specific 3-D structure
before discussing tertiary structure. (W) (Basic) (Challenging)
o Include interactions between R groups and the different types of bonding. (W)
(Basic)
o Give a simple definition of quaternary structure. (W) (Basic)
o Discuss how the loss of tertiary (and quaternary where it exists) results in the
loss of function of the protein. (W) (Basic)
o Learners make notes on levels of organisation to highlight the relationship
between the structures and role of bonding in determining shape /stability. (I)
(Challenging)
Online
http://www.pdb.org/pdb/home/home.do
http://www.biology.arizona.edu/bioche
mistry/tutorials/chemistry/page2.html
Past Papers
Paper 21, Nov 2011, Q3 (a)
Note
For quaternary structure learners should know that this is a protein composed of
more than one polypeptide chain – details of the association between chains is not
required.
Do not allow learners to think that proteins with quaternary structure must be
composed of four polypeptides.
2.3.c
describe the molecular structure of
haemoglobin as an example of a
globular protein, and of collagen as an
example of a fibrous protein and relate
these structures to their functions (The
v2.1 5Y02
Show diagrams/images of globular and fibrous proteins to learners for them to
describe, and then discuss their features (include solubility) and overall roles (e.g.
mainly metabolically active versus mainly structural). Discuss the fact that many
fibrous proteins show little or no tertiary structure. (W) (G) (P) (I) (Basic)
(Challenging)
Display a diagram / image of haemoglobin for learners to identify the features of a
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://en.wikipedia.org/wiki/Hemoglobin
http://www.pdb.org/pdb/101/motm.do?
momID=4&evtc=Suggest&evta=Mole
culeof%20the%20Month&evtl=TopBa
r
19
Learning objectives
Suggested teaching activities
importance of iron in the haemoglobin
molecule should be emphasised. A
haemoglobin molecule is composed of
two alpha () chains and two beta ()
chains, although when describing the
chains the terms -globin and -globin
may be used. There should be a
distinction between collagen molecules
and collagen fibres)
globular protein and consolidate knowledge of levels of protein structure. (W)
(Basic) (Challenging)
o Give details of haem and explain the idea of a prosthetic group. (W) (Basic).
o Notes made or construct a spider diagram / concept map relating haemoglobin
structure to function. (I) (Challenging)
With textbook/internet research, learners make bullet-pointed notes on collagen
structure (include the difference between a molecule and a fibre), linking to its
function (including role in blood vessel structure – link to Unit 4). (W) (I) (Basic)
Learners construct a comparison table showing the similarities and differences
between haemoglobin and collagen. (F)
Compile a set of multiple choice questions from past papers for learners to
complete. (F)
Key concepts
Cells as the units of life,
Biochemical processes
2.1.a
carry out tests for reducing sugars and
non-reducing sugars, the iodine in
potassium iodide solution test for
starch, the emulsion test for lipids and
the biuret test for proteins to identify
the contents of solutions
v2.1 5Y02
Textbooks/Publications
Bio Factsheet 175: Haemoglobin:
structure & function
Past Papers
Paper 22, June 2011, Q3 (c)
Paper 21, Nov 2011, Q3 (c)
Note
Mention that haemoglobin has a role in the carriage of carbon dioxide (for Unit 4).
Practical investigation, without using instructions, to analyse the biochemicals in a
range of unknown solutions or liquefied solid foods. (F)
Practical booklet 2 is a suitable protocol (designed to develop skills for Paper 3).
Key concepts
Biochemical processes,
Observation and experiment
6.1.a
describe the structure of nucleotides,
including the phosphorylated
nucleotide ATP (structural formulae
are not required)
Learning resources
Practical booklet 2
Online
http://www.mrothery.co.uk/bio_web_pr
ac/practicals/2Food%20Tests.doc
http://www.mrothery.co.uk/module1/Mo
d%201%20techniques.htm
http://www.biotopics.co.uk/nutrition/foot
es.html
Textbooks/Publications
King p.19-22
Siddiqui p.56-60,
Bio Factsheet 173: How to identify
foods: Food Tests and
Chromatography
Draw a labelled diagram of a nucleotide to show the three components: phosphate,
pentose sugar and nitrogenous organic base (e.g. using a circle, pentagon and
rectangle) for learners to reproduce without help. (W) (I) (Basic)
Give out images of the structural formulae of the four RNA and four DNA
nucleotides, ensuring learners know the names of the bases and explaining carbon
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://hyperphysics.phyastr.gsu.edu/hbase/biology/atp.html
http://www.accessexcellence.org/RC/V
L/GG/basePair1.php
20
Learning objectives
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Suggested teaching activities
atom numbering. (W) (Basic)
o In a small group, learners interpret how the diagram of a nucleotide has been
derived and identify similarities and differences between the DNA and RNA
nucleotides. (G) (Basic) (Challenging)
o Learners draw a labelled generalised RNA and a DNA nucleotide, naming the
different pentose sugars and indicating the four different bases for each. (I)
(Basic)
Discuss briefly an image of the structural formula of ATP and agree it is a
phosphorylated nucleotide before learners draw a simple diagrammatic, annotated
version. Include the concept that on removal of a phosphate, energy is released
(links with 1.2.c and idea of activated nucleotides for 6.1.c and 6.2.d). (W) (I) (Basic)
Introduce DNA base-pairing for 6.1.b by showing learners structural /skeletal
formulae and diagrammatic forms. (W) (Basic)
o Allow learners to volunteer that in the diagrams: A and G are the same ‘length’
and are ‘longer’ than T and C (also the same length) as they are double ring
structures; the end where the pairs meet shows a complementary nature (e.g. A
pointed, T ‘V’ shaped; G convex, C concave).
o Introduce the concept of complementary base pairing and hydrogen bonding
between base pairs (mention also RNA/DNA base-pairing).
Learning resources
Textbooks/Publications
Bio Factsheet 129: ATP – what it is,
what it does.
Past Papers
Paper 23, Nov 2011, Q5 (a)
Note
Base names must be spelt correctly, e.g. thymine not thiamine, and learners must
be clear about the difference between adenine and adenosine.
Emphasise that the structural/skeletal formulae of the bases is not required.
6.1.b
describe the structure of RNA and
DNA and explain the importance of
base pairing and the different
hydrogen bonding between bases
(include reference to adenine and
guanine as purines and to cytosine,
thymine and uracil as pyrimidines.
Structural formulae for bases are not
required but the recognition that
purines have a double ring structure
and pyrimidines have a single ring
structure should be included)
v2.1 5Y02
Discuss phosphodiester bond (strong, covalent) formation by condensation reactions
to produce a polynucleotide (learners add the bond name to their table of 2.2.b). (I)
(Basic)
Learners prepare cut-out nucleotides and, with verbal prompts, build up a short
polynucleotide strand, learning about the sugar-phosphate backbone and noting the
variation in sequences among the class (different ‘information’). (P) (I) (H) (Basic)
Explain the concept of ‘direction’ of the strand (5′ to 3′) before learners build up the
anti-parallel complementary strand (see final activity 6.1.a). (P) (I) (Challenging)
o Point out how base pairing allows the strands to be parallel and the strength of
having many hydrogen bonds (from single weak H bonds). (W) (Basic)
Groups of learners can join together their sections to give the idea of a (short!) gene
and the class can see each gene carries different information to code for different
proteins. (W) (G) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.dnaftb.org
http://www.hhmi.org/biointeractive/dna/
index.html
http://accessexcellence.org/AB/GG/
http://www.ncbe.reading.ac.uk/ncbe/P
ROTOCOLS/DNA/extracting.html
http://learn.genetics.utah.edu/content/l
abs/extraction/
http://www.nature.com/nature/dna50/ar
chive.html
Past Papers
21
Learning objectives
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Suggested teaching activities
Learning resources
Learners fully label and annotate pre-existing diagrams of DNA. (I) (Basic)
Extension activity (see website recommended): learners read about the discovery of
DNA. (I) (Challenging)
Progress to RNA structure, giving an outline of the three types of RNA before
learners make notes, including diagrams. (W) (I) (Basic)
Learners construct a summary table of the similarities and differences between DNA
and RNA. (F)
Summary discussions (small group and class) about requirements of the ideal
molecule of inheritance, resulting in a large poster. (W) (G) (Basic) (Challenging)
o Carrying information to allow proteins to be synthesised (sequence of
nucleotides).
o Expression to obtain the proteins (transcription and translation, learned later).
o Stability (strong sugar-phosphate backbone, many H bonds).
o Faithful replication to pass on information to daughter cells (complementary
nature of the strands).
o Ability to provide variation (mutations, learned later).
Paper 21, June 2011, Q3
Paper 21, June 2012, Q6 (a)
Note
Save the nucleotides for DNA replication in Unit 3.
3.1.a
explain that enzymes are globular
proteins that catalyse metabolic
reactions
Key concepts
Cells as the units of life,
Biochemical processes
Brainstorm or provide multiple choice questions to gauge learner knowledge,
including understanding of the terms globular, metabolic and catalyst. Emphasise
that previous studies will be extended and name some enzymes they will learn about
e.g. DNA polymerase and carbonic anhydrase. (W) (Basic)
State that most enzyme names end with ‘ase’ and discuss the role of enzymes, e.g.
synthesising macromolecules; transferring groups such as phosphates; rearranging
molecules to form different ones. (W) (Basic).
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/animation__how_enzy
mes_work.html
http://www.sumanasinc.com/webconte
nt/animations/content/enzymes/enzy
mes.html
Textbooks/Publications
Bio Factsheet 163: Answering
Questions: enzyme activity.
Past Papers
Paper 23, Nov 2013, Q6 (c)
3.1.b
state that enzymes function inside cells
v2.1 5Y02
Explain that enzymes are produced within cells. Learners volunteer the meanings of
‘intra-‘ and ‘extra- ‘and discuss these with respect to enzymes that remain to function
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 24: Human digestion.
22
Learning objectives
(intracellular enzymes) and outside
cells (extracellular enzymes)
Key concepts
Cells as the units of life,
Biochemical processes
3.1.c
explain the mode of action of enzymes
in terms of an active site,
enzyme/substrate complex, lowering of
activation energy and enzyme
specificity (the lock and key hypothesis
and the induced fit hypothesis should
be included)
Key concepts
Biochemical processes
Suggested teaching activities
Learning resources
intracellularly and others that are released to act extracellularly (e.g. digestive
enzymes) (this links later to role of the Golgi body). (W) (Basic)
Note
Learners will benefit if they know the meaning of prefixes e.g. intra, extra, poly, milli,
mono. Explain that some have the same meaning but Latin or Greek origins (e.g. uni
versus mono).
Learners make notes on the mode of action of enzymes (remind them of protein
structure), highlighting structure to function. (I) (Challenging)
o Describe and explain enzyme structure, including the active site.
o Include a set of annotated diagrams of the lock and key and induced fit
mechanisms (noting the role of the R groups of amino acids at the active site in
binding with the substrate).
o Explain that many/most reactions can be catalysed in both directions.
Learners use paper cut-out models to show how enzymes can break up substrates
into smaller molecules or can build up larger molecules from smaller ones. (P) (I)
(Basic)
Discuss the concept of lowering activation energy. (W) (Challenging)
o Learners annotate a ‘boulder analogy’ graph to highlight that, although the
energy content of substrate and products is not changed, the reaction pathway
follows a lower energy course. (H) (Basic)
o Learners summarise a discussion about the different ways activation energy can
be lowered by adding notes to their diagrams or the graph. (I) (Challenging)
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/animation__how_enzy
mes_work.html
http://www.sumanasinc.com/webconte
nt/animations/content/enzymes/enzy
mes.html
http://www.learnerstv.com/animation/a
nimation.php?ani=161&cat=Biology
Past Papers
Paper 23, Nov 2013, Q6 (c)
Note
Use the term ‘complementary’ to describe how the substrate fits into, and binds at,
the active site. ‘Matches’ is incorrect.
Check understanding of the term substrate - some may have used the term reactant.
3.1.d
investigate the progress of an enzymecatalysed reaction by measuring rates
of formation of products (for example,
using catalase) or rates of
disappearance of substrate (for
example, using amylase)
v2.1 5Y02
Explain that the course of an enzyme-catalysed reaction can be shown by substrate
disappearance or product formation over time. (W) (Basic)
Emphasise that a rate measurement is given per unit time and that there will be a
change in the rate during the course of the reaction. (W) (Basic)
Learners carry out practical work using catalase (e.g. from yeast, potato, celery,
lettuce) to investigate the rate of release of oxygen (product) from hydrogen
peroxide (substrate). (W) (G) (P) (I) (H) (Basic) (Challenging)
o A graph should be constructed of volume produced (or mass lost if using an
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklets 4, 5
Online
http://www.practicalbiology.org/areas/a
dvanced/bio-molecules/factorsaffecting-enzymeactivity/investigating-an-enzymecontrolled-reaction-catalase-and-
23
Learning objectives
Suggested teaching activities
Learning resources
Key concepts
Biochemical processes,
Observation and experiment
electronic balance) over time intervals.
o Use the graph to calculate initial rate and explain the initial steep release of
product, which then flattens out.
Practical booklet 5. Learners carry out practical work using amylase to time how
long it breaks down starch. Remind learners that using iodine (in potassium iodide)
solution on samples shows the loss of starch from the reaction mixture over time.
This practical is designed to develop practical skills (itemised in the Teacher’s
practical notes) assessed in Paper 3. (W) (G) (P) (I) (H) (Basic)
Extend practical using amylase if a colorimeter is available to get quantitative
results. Trials are required to ensure that the colour of resulting solutions is not too
intense for the colorimeter for a graph. (P) (I) (Challenging)
Practical booklet 4 (carry out after Practical booklet 5) is a modification of the
method described above using catalase.
hydrogen-peroxideconcentration,47,EXP.html
www.csub.edu/~kszick_miranda/Enzy
mes%20part2.doc
http://www.saps.org.uk/secondary/teac
hing-resources/293-learner-sheet-24microscale-investigations-withcatalase
Textbooks/Publications
Bio Factsheet 130: Investigating
catalase
Past Papers
Paper 21, Nov 2011, Q2 (a)
3.2.a
investigate and explain the effects of
the following factors on the rate of
enzyme-catalysed reactions:
Temperature
pH (using buffer solutions)
enzyme concentration
substrate concentration
inhibitor concentration
Key concepts
Organisms in their environment
v2.1 5Y02
With prompting, learners explain why measuring the time taken for complete
removal of substrate is unsuitable if trying to measure the effect of substrate
concentration (with more substrate the rate of reaction is faster, but it takes longer
for it all to disappear). (W) (I) (Challenging)
Discuss with learners why, ideally, initial rates should be calculated when comparing
enzyme activity under different conditions. (W) (Challenging)
Develop planning skills: learners design an investigation in which several variables
need to be controlled and carry this out (ensure that a range of plans is covered).
(W) (I) (Basic) (Challenging)
Learners carry out practical activities on factors affecting the rate of an enzymecatalysed reaction (examples below). (P) (I) (Basic) (Challenging)
o Effect of temperature: the catalase experiment in 3.1.d.
o Effect of pH: use trypsin to digest protein in a suspension of milk powder.
o Effect of enzyme concentration or substrate concentration: use amylase or
diastase to digest a starch suspension.
Then learners present their results and contribute to whole class discussion,
following up with a written explanation. Construct and annotate graphs showing:
o the impact of rate of collisions (temperature, substrate concentration, enzyme
concentration).
o the effect on hydrogen bonding, tertiary structure, shape of active site and
complementary fit of substrate (temperature, pH, inhibitors).
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 5
Online
http://www.ncbe.reading.ac.uk/NCBE/
PROTOCOLS/menu.html
http://www.ncbe.reading.ac.uk/NCBE/
PROTOCOLS/juice.html
http://www.saps.org.uk/secondary/teac
hing-resources/95-investigating-theeffect-of-competitive-and-noncompetitive-inhibitors-on-the-enzymess-galactosidase
http://www.southernbiological.com/
http://www.saps.org.uk/secondary/teac
hing-resources/261-the-inhibition-ofcatechol-oxidase-by-lead
http://www.saps.org.uk/secondary/teac
hing-resources/106-the-effect-of-endproduct-phosphate-on-the-enzymephosphatase
Textbooks/Publications
24
Learning objectives
3.2.b
explain that the maximum rate of
reaction (Vmax) is used to derive the
Michaelis-Menten constant (Km) which
is used to compare the affinity of
different enzymes for their substrates
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Suggested teaching activities
Learning resources
(W) (I) (Basic) (Challenging)
Possibly demonstrate a practical that uses inhibitors considered to be hazardous to
the environment (minimises the volumes used). Check your local authority
regulations concerning safe disposal.
King p.64-68
Siddiqui p.69-75.
Bio Factsheet 43: Factors affecting
enzyme activity
Note
Ensure learners can interpret correctly graphs with the same shaped curve, e.g.
course of an enzyme-catalysed reaction / the effect of increasing substrate
concentration on the rate of a reaction.
For inhibitor concentration, 3.2.b should be covered first or incorporate this part of
3.2.a with 3.2.b.
To show that an inhibitor is competitive is difficult as separate reaction mixtures with
different concentrations of the substrate need to be made up.
Past Papers
Paper 21, June 2011, Q4
Paper 32, June 2013, Q1
Explain Vmax and Km (great detail not required) before learners make notes. (W) (I)
(Basic)
o Show learners how to obtain Vmax and Km from a graph.
o Learners arrive at the idea that the enzyme is saturated with substrate at the
maximum rate of reaction, Vmax.
o Show learners how to obtain Km from a graph, the concentration of substrate that
enables the enzyme to achieve half the maximum rate of reaction, or half Vmax
Learners obtain (Vmax) and (Km) using one of the graphs constructed from their
practical work. (I) (Basic)
Extend learner understanding of Km by discussion or a worksheet providing some
information accompanied by questions. (W) (I) (Challenging)
o Explain that (Km) is the affinity of enzyme for its substrate.
o Allow learners to suggest that an enzyme with a low Km
has a high affinity for its substrate
needs a lower concentration of substrate to reach Vmax than an enzyme with
a high Km.
o Explain that an enzyme with a low Km is more likely to be saturated with
substrate in the normal conditions of substrate within a cell, so variations in
substrate will have less effect on the rate of formation of product.
o Ask learners to explain why an enzyme with a high Km is likely to vary its activity
more (i.e. the concentration of substrate becomes more important).
Learners sketch out two graphs to show the differences between an enzyme with a
high Km and an enzyme with a low Km
o Annotate graphs with explanations. (I) (Challenging)
Online
http://www.worthingtonbiochem.com/introbiochem/substrate
Conc.html
Cambridge International AS & A Level Biology (9700) – from 2016
25
Learning objectives
Suggested teaching activities
Learning resources
3.2.c
explain the effects of reversible
inhibitors, both competitive and noncompetitive, on the rate of enzyme
activity
Following class discussion, learners use resources to make notes and annotated
diagrams about enzyme inhibition. (I) (Challenging)
o Draw graphs of increasing substrate concentration with and without inhibitors.
Learners construct a summary table showing the differences between competitive
and non-competitive inhibition (include the different graphs). (I) (Challenging)
Extension activity: learners investigate and discuss the use of inhibitors as medicinal
drugs, including the different uses of competitive versus non-competitive inhibitors.
(G) (P) (I) (Challenging)
Online
http://www.wiley.com/college/boyer/04
70003790/animations/enzyme_inhibiti
on/enzyme_inhibition.htm
Key concepts
Biochemical processes
3.2.d
investigate and explain the effect of
immobilising an enzyme in alginate on
its activity as compared with its activity
when free in solution
Key concepts
Observation and experiment
Textbooks/Publications
Bio Factsheet 31: Enzyme control of
metabolic pathways.
Note
Irreversible inhibition and allosteric regulation could be worth mentioning briefly
when covering 3.2.c.
Past Papers
Paper 21, Nov 2011, Q2 (b)
Practical: ‘Better milk for cats’ or similar protocol using a different enzyme.
o Discuss how immobilised enzymes are used in everyday applications. (W)
(Basic)
o Introduce the use of dipsticks containing glucose oxidase (useful for 14.1.k). (W)
(Basic)
Demonstrate the same enzymatic reaction using the enzyme free in solution.
Learners suggest the advantages of immobilising the enzyme rather than using it
free (not immobilised) and summarise with a comparison table. (W) (Challenging)
Extension practical: learners use immobilised yeast cells to investigate the
effectiveness of their sucrase or catalase enzymes. (P) (I) (Challenging)
Learners complete a worksheet prepared by you to interpret and compare graphical
and tabulated data for immobilised enzymes with free enzymes.
o Data extraction to compare both for the following factors: temperature; pH;
substrate concentration; inhibitor presence.
o Learners consider explanations of the differences between free and immobilised
enzymes, e.g. protective and stabilising effect of the alginate matrix; degradation
over time; active sites of immobilised enzymes may not all be available; time
taken for diffusion to occur; possibility of slightly altered active site shape when
immobilised, amongst others. (I) (Challenging)
Online
http://www.rpi.edu/dept/chemeng/BiotechEnviron/IMMOB/Immob.htm
http://www.scienceinschool.org/reposit
ory/docs/issue10_catmilk.pdf
http://www1.lsbu.ac.uk/water/enztech/i
meconom.html
Textbooks/Publications
King p.69-73
Siddiqui p.72-73
Bio Factsheet 148: Industrial uses of
enzymes.
Past Papers
Paper 32, June 2012, Q1 (b)
Paper 43, June 2011, Q2
Paper 43, Nov 2011, Q2 (b)
Note
Experiment and observation, a key concept, has increasingly been used to develop
biotechnological applications – here learners can appreciate how biological systems
can be used to benefit humans in the everyday world.
Learners should know the method to prepare alginate beads.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
26
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 2: Cells as the basic units of life
Recommended prior knowledge
Little prior knowledge is required but a basic knowledge of cell structure and practical knowledge of the light microscope would be helpful. The ability to carry out simple
mathematical calculations is required. Learners should understand kinetic theory (http://www.chemguide.co.uk/physical/kt/basic.html is a good basic introduction). If
Unit 1, Biological molecules, is taught after this unit, some knowledge of lipids, proteins and carbohydrates is useful.
Context
Unit 1, Biological molecules, leads on to an understanding of the structure of cells and the functions of cell structures, including biological membranes. This unit deals
with topics that are fundamental to almost every area of study covered in the AS and A Level course. Cell structure, and the functions of the various organelles, will
reappear in numerous contexts. Learners should appreciate the key concept that cells are the basic unit of life and that all living organisms are composed of one or
more cells. Learners will need to be reminded, or taught, how to use a light microscope. An understanding of how substances are transported across membranes is
essential reference material for other topics in this syllabus, especially those covering plant and animal physiology.
Outline
Early on, learners are introduced to the use of the microscope in cell studies, including use of the graticule and micrometer to measure cells. Calculations of
magnification and actual sizes are included in this unit. This unit covers the two fundamental types of cell, eukaryotic and prokaryotic. Details of cell structure are
studied, including the functions of organelles. The fluid mosaic model of membrane structure highlights how membranes can fulfil their roles. The role of the membrane
in cell signalling is introduced. The unit also covers the different mechanisms that enable the movement of substances into and out of cells.
Teaching time
It is recommended that this unit should take approximately 9% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
27
Learning objectives
Suggested teaching activities
Learning resources
1.1.d
explain and distinguish between
resolution and magnification, with
reference to light microscopy and
electron microscopy
Show images of both microscope types and agree more detail can be obtained
about cells / cell structure using microscopes. (W) (Basic)
Agree the meaning of magnification – learners write a worded version and link this
later to the formula used in 1.1.c. Explain how the overall magnification is obtained
(eyepiece x objective lens). (W) (Basic)
Introduce resolution, explaining why the resolution of electron microscopes is much
higher than that of light microscopes (only enough detail of the workings of each to
help understanding of resolution). (W) (Basic) (Challenging)
o Explain that detail smaller than 200nm (approximately half the wavelength of
light) cannot be resolved by the light microscope. (W) (Challenging)
Explain that increasing magnification is only desirable up to the limit of resolution,
e.g. up to approx. x 1000 for the light microscope (electron microscopes vary
considerably).
Compare the TEM and SEM (no details of working required) and the micrographs
produced, so learners see the difference between, and usefulness of, both.
Learners suggest advantages and disadvantages of the two types of microscope.
(G) (Basic)
Learners observe a range of photomicrographs and electron micrographs and
explain which type of microscope was used to produce the image. If these have a
mixture of magnifications and scale bars on them, they can be used in 1.1.e. (G) (P)
(Basic)
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=10
http://www.vcbio.science.ru.nl/en/virtua
llessons/#fesemsimulatie
http://www.biology.arizona.edu/cell_bio
/tutorials/cells/cells2.html
http://zeisscampus.magnet.fsu.edu/articles/basic
s/index.html
Key concepts
Observation and experiment
1.1.a
compare the structure of typical animal
and plant cells by making temporary
preparations of live material and using
photomicrographs
Key concepts
Cells as the units of life,
Observation and experiment
Practical: learning how to use the light microscope. (I) (Basic) (Challenging)
Brainstorm knowledge of the plant cell structure and animal cell structure and
discuss cells as the units of life. (W) (Basic)
Learners construct a comparison table, generalised animal cell v generalised plant
cell, the first row containing simple labelled diagrams. (I) (Basic) (Challenging)
Practical: learners make a temporary preparation, check and give comments on
technique and slides made of peers. (I) (Basic) (Challenging)
Discuss the slides and compare with the constructed table (links to the ideas in
1.1.d). (W) (Basic)
Textbooks/Publications
King p.39-41
Bio Factsheet 75: Microscopes and
their uses in Biology
Past Papers
Paper 21, June 2012, Q2 (a)
Paper 22, June 2013, Q2 (b)
Paper 22, Nov 2012, Q1 (a)
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=10
Textbooks/Publications
Siddiqui p.28-29
Note
This may be combined with 1.1.c and 1.1.e.
Diagram-drawing skills may be introduced here.
1.1.c
v2.1 5Y02
Revise the units of length commonly used during the course (see 1.1.c) with the
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 1
28
Learning objectives
Suggested teaching activities
Learning resources
use an eyepiece graticule and stage
micrometer scale to measure cells and
be familiar with units (millimetre,
micrometre, nanometre) used in cell
studies
metre (meter US) as the SI unit of length.
o Learners to perform conversions between nm, m, mm and m. (W) (Basic)
Explain how to use a stage micrometer to calibrate an eyepiece graticule. (W)
(Challenging)
o Practical booklet 1 is designed to develop the skills required by learners (see
Teacher’s practical notes) when measuring using an eyepiece graticule and a
stage micrometer.
o If learners always use the same microscope, then they can calibrate once only
for each objective lens, and keep a record of it. (I) (Challenging)
o Learners use the Bioscope to learn the principles of use. (I) (Challenging)
Learners use their calibrated eyepieces to measure a range of microscopic
specimens, choosing one specimen to draw (see 1.1.a). (I) (Basic) (Challenging)
o Learners measure the actual length of a part of a specimen on the slide and by
measuring the length drawn on their diagram, they can calculate the linear
magnification of their drawing. (I) (Basic)
CD-ROM
Bioscope – teaching and learning tool
for the skills required to use a
graticule and stage micrometer
successfully.
Key concepts
Cells as the units of life,
Observation and experiment
Note
Discourage measuring in cm as many forget to multiply by 10 to convert to mm
before converting to m.
The eyepiece graticules can be fitted permanently into the eyepiece of the
microscope.
Inexpensive stage micrometer scale kits and eyepiece graticules can be obtained
from the Cambridge publications catalogue www.cie.org.uk/cambridgefor/teachers/order-publications
1.1.b
calculate the linear magnifications of
drawings, photomicrographs and
electron micrographs
Key concepts
Observation and experiment
v2.1 5Y02
Hold up an apple, then drawings of the apple: at the same size = magnification x 1;
double the size = x 2; half the size = x 0.5. Discuss the mental calculation learners
have made to get the right answer.
o magnification = image size / actual size. (Group) (Basic)
Explain how to use scale bars to calculate magnification, emphasising that learners
should measure the scale bar length and not the image. (W) (Challenging)
Learners complete a worksheet prepared by you with images of varying stated
length (nm to mm) and with scale bars only. Use copyright-free images to prepare
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/c
ells/scale/
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=10
http://www.vcbio.science.ru.nl/en/virtua
llessons/#fesemsimulatie
http://www.biology.arizona.edu/cell_bio
/tutorials/cells/cells2.html
http://zeisscampus.magnet.fsu.edu/articles/basic
s/index.html
Textbooks/Publications
King p.20-22
Siddiqui p.42-43
Past Papers
Paper 31, Nov 2012, Q2 (b)(c)
Paper 33, Nov 2012, Q2 (b)
Paper 35, Nov 2012, Q2 (b)
Paper 12, Nov 2011, Q5
Past Papers
Paper 22, June 2011, Q4 (b)
Paper 21, June 2011, Q1 (a)
Paper 23, Nov 2011, Q1 (a)
Paper 31, June 2011, Q2 (c)
29
Learning objectives
Suggested teaching activities
Learning resources
the worksheet (e.g. Wikipedia). (P) (I) (Basic) (Challenging)
1.1.e
calculate actual sizes of specimens
from drawings, photomicrographs and
electron micrographs
Key concepts
Observation and experiment
1.2.b
recognise the following cell structures
and outline their functions:
cell surface membrane
nucleus, nuclear envelope and
nucleolus
rough endoplasmic reticulum
smooth endoplasmic reticulum
Golgi body (Golgi apparatus or
Golgi complex)
mitochondria (including small
circular DNA)
ribosomes (80S in the cytoplasm
and 70S in chloroplasts and
mitochondria)
lysosomes
centrioles and microtubules
chloroplasts (including small circular
DNA)
cell wall
plasmodesmata
large permanent vacuole and
tonoplast of plant cells
Discuss how the actual sizes can be calculated using the rearranged formula to
calculate magnifications. (W) (Basic)
o Explain also how to use scale bars to calculate actual sizes. (W) (Basic)
o Learners calculate actual sizes from diagrams and the photomicrographs and
electron micrographs from 1.1.d using the given scale bar or magnification. (P)
(I) (Basic) (Challenging)
Learners tackle worksheets prepared by you with exam-style (differentiated)
questions to calculate actual sizes and magnifications (use past papers). (I) (H) (F)
(Basic) (Challenging)
Interactive session using diagrams and electron micrographs: agree descriptions of
the cell structures and discuss their functions.
o With reference to plant and animal cells, introduce the terms eukaryote and
eukaryotic, explaining the meaning of ‘true nucleus’. (W) (Basic)
Provide an overview of how different cell structures are linked, e.g. outline sequence
of events in protein production and secretion. (W) (Basic)
Learners identify particular cell structures and state their function using electron
micrographs and photomicrographs, at various magnifications. Include examples of
both plant and animal cells (names of cell types not required). (G) (P) (I) (Basic)
(Challenging)
Learners label the cell structures on diagrams drawn from electron micrographs of
both plant cell and animal cells, and annotate each with a function. (F)
Note
Learners should understand (no definition required) that an organelle is a structure
within a cell that has a function.
Discuss the idea of the advantages of cellular compartments.
For mitochondria and chloroplasts see also 1.2.c.
Online
http://www.cellsalive.com/howbig.htm
Past Papers
Paper 21, Nov 2011, Q5 (a)
Online
http://www.biologie.uni-hamburg.de/bonline/library/falk/CellStructure/cellStr
ucture.htm
http://publications.nigms.nih.gov/inside
thecell/chapter1.html
http://www.cellsalive.com/cells/cell_mo
del.htm
http://learn.genetics.utah.edu/content/c
ells/insideacell/
http://www.bscb.org/?url=softcell/index
http://cellpics.cimr.cam.ac.uk/
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM006.html
http://www.rothamsted.bbsrc.ac.uk/not
ebook/index.html
Textbooks/Publications
Bio Factsheet 4: Structure to function
in eukaryotic cells.
Past Papers
Paper 22, Nov 2011, Q6 (a)
Paper 21, June 2012, Q2 (b)(c)(e)
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
30
Learning objectives
Suggested teaching activities
Learning resources
Extend 1.2.b so learners know that ATP is produced: in chloroplasts as a result of
the absorption of light; in mitochondria in aerobic respiration. (W) (Basic)
Discuss why a cell needs energy and the need for energy transfers within a cell. (W)
(Basic)
o Explain that ATP is the molecule used for these transfers and is described as the
universal energy currency of the cell.
o Stress that ATP is not a form of energy but that energy is released when ATP is
hydrolysed and this energy can be used by the cell.
Online
http://www.biologyinmotion.com/atp/ind
ex.html
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity
1.2.c
state that ATP is produced in
mitochondria and chloroplasts and
outline the role of ATP in cells
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 129: ATP–what it is,
what it does.
Note
This sets the scene for other learning objectives, e.g. 4.2.a, 12.1.a, 12.1.b, 13.1.f,
13.1.h and 15.1e, so do not be tempted to give too many details at this stage.
1.2.a
describe and interpret electron
micrographs and drawings of typical
animal and plant cells as seen with the
electron microscope
Key concepts
Cells as the units of life
1.2.d
outline key structural features of typical
prokaryotic cells as seen in a typical
bacterium (including: unicellular, 1-
v2.1 5Y02
Emphasise that although cells are the basic unit of life, they can have different
structures depending on their function. (W) (Basic)
State that membranes range from approximately 5-9 nm thick and allow learners to
explain that the boundary of the cell /nucleus is only seen with the light microscope
because of the contrast (membranes are not visible). (W) (Challenging)
o Learners volunteer that detail such as membranes are visible using the electron
microscope. (W) (Basic)
From electron micrographs of different cell types, learners can identify:
o whether plant or animal, stating the features that enabled the choice,
o all the cell structures seen, adding labels and annotations.
(P) (I) (H) (F) (Basic) (Challenging)
Extension activity: learners compare electron micrograph images and drawings with
those obtained with the light microscope. (P) (I) (Basic) (Challenging)
o Learners construct a descriptive list of the additional features seen. (G) (P)
(Basic)
Online
http://micro.magnet.fsu.edu/primer/tec
hniques/contrast.html
http://www.unimainz.de/FB/Medizin/Anatomie/works
hop/EM/EMAtlas.html
http://learn.genetics.utah.edu/content/c
ells/insideacell/
Short answer test to revise plant and animal cell structural details. (F)
Linking to the key concept of cells as the units of life, explain to learners that there
are two fundamental types of cell: eukaryotic and prokaryotic.
o Explain how the term ‘prokaryotic’ arose.
Online
http://www.cellsalive.com/cells/bactcell
.htm
http://www.ucmp.berkeley.edu/bacteria
/bacteria.html
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 21, June 2012, Q2
Paper 22, Nov 2012, Q1 (b)
31
Learning objectives
5m diameter, peptidoglycan cell
walls, lack of organelles surrounded by
double membranes, naked circular
DNA, 70S ribosomes)
Key concept
Cells as the units of life
Suggested teaching activities
o Discuss how the single cell comprising a unicellular organism will exhibit all the
characteristics that define life. (W) (Basic)
Build up a typical bacterial cell (example of a prokaryote) by introducing each key
structural feature in turn (e.g. overhead transparency overlays/PowerPoint slides).
(W) (Basic)
From 1.2.b, learners suggest functions of prokaryotic structures. (I) (Challenging)
Learners label a diagram, or draw a labelled diagram, of a typical bacterium /
prokaryote. (I) (Basic) (Challenging)
Annotate the diagram with an outline function. (H) (Basic)
Learning resources
Textbooks/Publications
Bio Factsheet 73: The prokaryotic cell
Past Papers
Paper 22, June 2011, Q4
Paper 23, Nov 2011, Q1
Note
Reference could be made to the bacteria responsible for cholera and TB (see Unit
5).
Archaea as prokaryotes are covered in Unit 7.
You could mention (to prepare for Unit 7), the kingdom Prokaryotae and the four
eukaryotic kingdoms, Fungi, Protoctista, Plantae and Animalia.
1.2.e
compare and contrast the structure of
typical prokaryotic cells with typical
eukaryotic cells (reference to
mesosomes should not be included)
Learners examine photomicrographs, electron micrographs and diagrams of typical
prokaryotic and eukaryotic cells. (G) (Basic)
o Learners discuss the major differences between the two cell types. (G) (Basic)
o Learners give a bullet-point list of similarities and construct a table of differences.
(I) (Challenging)
Key concepts
Cells as the units of life
Note
Mention to learners that mesosomes (in many textbooks) are now considered to be
artefacts from preparation for electron microscopy.
1.2.f
outline the key features of viruses as
non-cellular structures (limited to
protein coat and DNA/RNA)
Key concepts
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity
v2.1 5Y02
Outlining the key features of viruses for learners to produce annotated diagrams.
(W) (I) (Basic)
Learners investigate a range of viruses. (H)
o A follow-up discussion/debate about viruses as complex entities that do not fit
the cell theory of life (also applies understanding of the key concept of cells as
the units of life – are viruses living organisms?). (W) (Challenging)
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=52
Textbooks/Publications
Bio Factsheet 107: Answering exam
questions – cells
Past Papers
Paper 23, Nov 2011, Q1 (b)
Past Papers
Paper 21, June 2012, Q6 (c)
Note
Mention that some viruses have an additional outer envelope similar in nature to a
cell surface membrane (preparation for HIV in Unit 5).
Cambridge International AS & A Level Biology (9700) – from 2016
32
Learning objectives
Suggested teaching activities
Learning resources
4.1.a
describe and explain the fluid mosaic
model of membrane structure,
including an outline of the roles of
phospholipids, cholesterol, glycolipids,
proteins and glycoproteins
Learners make protein, cholesterol and phospholipid (mix of fatty acid tails – both,
saturated and unsaturated or one of each) cut-outs from templates provided by you.
(H) (Basic)
Learners complete a short test to recall knowledge of phospholipids, proteins and
carbohydrates. Go through this and make links to membrane structure. (F)
(Challenging)
o For a phospholipid, use a symbolised or molecular model to point out the
hydrophilic phosphate ‘head’ portion and the two hydrophobic hydrocarbon tails
(fatty acid residues).
o Relate protein structure to the main membrane protein types e.g. enzymes
(globular); channel (lining of amino acids with hydrophilic R groups), etc.
o Describe carbohydrate portions of glycolipids and glycoproteins as chains of
sugar molecules.
Discuss the basic model to describe the structure of membranes, explaining that the
physical boundary is based on phospholipids. (W) (Challenging)
o Draw a line indicating a water/air boundary and a diagram of a symbolised
phospholipid. Learners suggest how phospholipids would behave if they were
spread as monolayer (tails in the air, heads in water).
o Discuss the behaviour of phospholipids immersed in water (spheres, heads out,
tails to centre, natural self-assembly).
o Highlight the idea of a ‘fluid’ phospholipid bilayer forming a compartment (e.g.
cell/membranous organelle) and discuss which substances could cross the
hydrophobic core.
o Discuss the scattered (hence ‘mosaic’) proteins and their various overall roles,
e.g. enzymes, receptors for binding ligands, and the transport of polar molecules
and ions.
o Mention interspersed cholesterol molecules (lipids).
Learners use their cut-outs to build a section of a membrane, noting the larger gaps
when phospholipids with unsaturated fatty acid tails occur within the bilayer. (P) (I)
(Basic)
Discuss and explain factors affecting membrane fluidity, including: the role of
unsaturated and saturated fatty acids; how cholesterol acts to regulate; temperature.
(W) (Challenging)
Learners label the different membrane components on a range of different diagrams
(prepared by you) of the fluid-mosaic model. (I) (Basic).
Learners make notes to explain why the fluid mosaic model is an appropriate term to
use. (I) (Basic)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/754-using-beetroot-inthe-lab
www.ultranet.com/~jkimball/BiologyPa
ges/C/CellMembranes.html
http://www.wisconline.com/objects/ViewObject.aspx?
ID=ap1101
http://www.stolaf.edu/people/giannini/fl
ashanimat/lipids/membrane%20fluidit
y.swf
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 8: The cell surface
membrane.
Past Papers
Paper 21, Nov 2011, Q1 (a)
Paper 22, Nov 2012, Q2 (a)
33
Learning objectives
Suggested teaching activities
Learning resources
Link the presence of glycolipids and glycoproteins to the cell surface membrane and
outline their roles. (W) (Basic)
Learners practise drawing a labelled diagram of a section of a membrane that can
be completed under exam conditions in 3-4 minutes. (I) (F) (Challenging)
o Learners can annotate with the roles of the components. (F)
Note
Learners should know the terms given in the notes in 2.3.d (Unit 1) to explain
transport of substances across the phospholipid bilayer or using membrane proteins.
4.1.b
outline the roles of cell surface
membranes including references to
carrier proteins, channel proteins, cell
surface receptors and cell surface
antigens
Key concepts
Cells as the units of life,
Biochemical processes
4.1.c
outline the process of cell signalling
involving the release of chemicals that
combine with cell surface receptors on
target cells, leading to specific
responses
Learners suggest and list the desired features of cell surface membranes. Explain
that there are some specialised cells that can engulf e.g. bacteria to introduce
phagocytosis / endocytosis. (W) (I) (Basic)
Brainstorm a list of materials/substances entering and leaving cells. (W) (Basic)
Learners give a written explanation of the role of phospholipids and proteins in
controlling the passage of substances across the cell surface membrane, making
reference to its partially permeable nature. (I) (Challenging)
Learners research and note the differences between carrier and channel proteins
(how they act to transport solutes across the membrane), and explain how
aquaporins increase the membrane permeability to water. (I) (Basic)
Question and answer session revising protein structure, discussing cell surface
receptors for learners to make notes. (W) (Basic)
o Learners suggest / research examples of ligands, e.g. hormones,
neurotransmitters. (I) (Basic)
Outline how glycoproteins and glycolipids can act as antigens (also in Unit 5). (W)
(Basic)
Learners write out a summary of this learning objective. (F)
Online
http://www.biologymad.com/cells/cellm
embrane.htm
http://www.ncbi.nlm.nih.gov/books/NB
K9847/
A reminder of cell receptors introduces the idea of cell signalling. (W) (Basic)
Learners draw one or more annotated diagrams to show the general sequence of
events occurring in cell signalling. (I) (Challenging)
Extension work: learners apply knowledge to specific examples. (I) (Challenging)
Online
http://www.open.edu/openlearn/scienc
e-maths-technology/cellsignalling/content-section-0#
Past papers
Paper 22, June 2013, Q4 (c)
Key concepts
Cells as the units of life,
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
34
Learning objectives
Suggested teaching activities
Learning resources
Only the fifth part of this learning objective is included here: describe and explain the
processes of endocytosis and exocytosis
Learners refer to the list of substances that enter/leave cells (4.1.b)
o State that there is also ‘unwanted’ entry of, e.g. bacteria.
o Discuss how the nature of the substance and its size will direct which
mechanism of transport across the membrane is used.
o Learners place each item on the list into the correct group: through the
phospholipid bilayer; through membrane proteins; neither (too large/bulk
transport). (W) (I) (Challenging)
Learners recall membrane fluidity and read about bulk transport across membranes.
(I) (Challenging)
o Explain pinocytosis and phagocytosis (see 11.1.a in Unit 5) as forms of
endocytosis.
o Learners draw diagrams showing the sequence of events involved in
endocytosis and exocytosis (revise Golgi vesicle formation).
o Point out that endocytosis and exocytosis are active (energy-requiring)
mechanisms of movement of substances across membranes.
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
Biochemical processes
4.2.a (v)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Key concepts
Cells as the units of life,
Biochemical processes
4.2.c
calculate surface areas and volumes of
simple shapes (e.g. cubes) to illustrate
the principle that surface area to
volume ratios decrease with increasing
size
Key concepts
Observation and experiment
4.2.a (i)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
v2.1 5Y02
Learners use cubes to build 'organisms' of the same shape, with different numbers
of blocks, and calculate surface area to volume ratios. (I) (Basic)
o Discuss the discovery that SA:V decreases as size of organism (same shape)
increases.
o Highlight the relative distances from the outside to the inside.
Textbooks/Publications
Biological Nomenclature. Explains the
terminology that should be used
when teaching osmosis.
Bio Factsheet 54: Water potential
Bio Factsheet 116: Transport
Mechanisms in cells
Past Papers
Paper 21, Nov 2011, Q1 (b)
Paper 22, June 2012, Q1
Textbooks/Publications
Bio Factsheet 165: Surface Area and
Volume.
Note
This serves as an introductory exercise before considering diffusion (4.2.a (i)).
Only the first part of this learning objective is included here: describe and explain the
processes of diffusion
Explain that diffusion is a passive (thermodynamic) method of movement across
membranes. (W) (Basic)
Learners write a definition, make bullet-pointed notes to expand and draw simple
diagrams. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
35
Learning objectives
Suggested teaching activities
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Learning resources
Textbooks/Publications
Bio Factsheet 116: Transport
Mechanisms in cells
Key concepts
Cells as the units of life,
Biochemical processes
4.2.d
investigate the effect of changing
surface area to volume ratio on
diffusion using agar blocks of different
sizes
Key concepts
Observation and experiment
4.2.b
investigate simple diffusion using plant
tissue and non-living materials, such
as glucose solutions, Visking tubing
and agar
Key concepts
Cells as the units of life
4.2.a (ii)
describe and explain the processes
of diffusion, facilitated diffusion,
v2.1 5Y02
Practical: to represent ‘cubic’ organisms, learners cut different-sized agar (technical
agar better) or gelatine blocks, coloured using a pH indicator (e.g. cresol red or
phenolphthalein), then lower them carefully into dilute hydrochloric acid. Learners
time how long it takes for the cube to change colour to measure the effect of surface
area to volume ratio on diffusion. (P) (Basic)
Learners note the implications of a changing SA:V on the needs of multicellular
plants and animals (size too great; distances too far; diffusion too slow) and the
need for transport systems. (I) (Basic)
Discuss shapes that give a large surface area for the same volume (e.g. cube,
flattened to give a leaf lamina, with branching to give a plant shape). (W) (Basic)
o Explain how this means that in plants diffusion alone is sufficient for gases, so
no transport system is required (presence of stomata and lenticels mentioned).
(W) (Challenging)
Online
http://teachers.net/lessons/posts/2518.
html
http://www.neiljohan.com/projects/biolo
gy/sa-vol.htm
Practical: learners add glucose solution and/or starch suspension to lengths of
Visking tubing tied at one end, tie at the other end and place in water (and vice
versa) for a set time. The appearance of the tubing and the results of biochemical
tests on the internal and external solutions is recorded and results explained. (P) (I)
(Basic) (Challenging)
Practical: in agar (in Petri dishes) containing starch, learners cut out a central well,
add amylase solution (or use a soaked filter paper disc) and after incubation observe
the changes that occur when iodine (in potassium iodide) solution is added. (I)
(Basic)
Past Papers
Paper 35, Nov 2011, Q1
Only the second part of this learning objective is included here: describe and explain
the processes of facilitated diffusion
Emphasise that facilitated diffusion is also a passive method of movement across
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
Cambridge International AS & A Level Biology (9700) – from 2016
36
Learning objectives
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Suggested teaching activities
membranes and that it is diffusion through a channel or carrier protein. Learners
make notes and use textbooks/internet. (W) (Challenging)
Key concepts
Cells as the units of life,
Biochemical processes
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
Textbooks/Publications
Bio Factsheet 54: Water potential.
Bio Factsheet 116: Transport
Mechanisms in cells
Key concepts
Cells as the units of life,
Biochemical processes
4.2.a (iii)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport, endocytosis
and exocytosis (no calculations
involving water potential will be set)
describe and explain the processes of
diffusion, facilitated diffusion, osmosis,
active transport, endocytosis and
exocytosis (no calculations involving
water potential will be set)
Learning resources
Past Papers
Paper 22, June 2012, Q1
Only the third part of this learning objective is included here: describe and explain the
processes of osmosis (no calculations involving water potential will be set)
Remind learners that movement of water molecules by crossing the bilayer or via
aquaporins is passive. (W) (Basic)
Explain water potential. (W) (Challenging)
Learners define osmosis, make bullet-point notes and draw simple diagrams. (I)
(Basic)
Learners write a paragraph stating the similarities and differences between osmosis
and (passive) diffusion. (F)
Note
Terminology to use: partially permeable; water potential; solute potential; pressure
potential. Learners should ignore other terms that they come across such as
hypotonic and hypertonic, osmotic potential, etc.
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
Textbooks/Publications
Biological Nomenclature. Explains the
terminology that should be used
when teaching osmosis.
Bio Factsheet 54: Water potential.
Bio Factsheet 116: Transport
Mechanisms in cells
Past Papers
Paper 22, June 2012, Q1
4.2.f
explain the movement of water
between cells and solutions with
different water potentials and explain
the different effects on plant and
animal cells
v2.1 5Y02
Recall the different permeabilities of the cell surface membrane, partially permeable
and cell wall, (freely- or fully-) permeable. (W) (Basic)
Discuss the terms that can be used to describe cells: plasmolysis / plasmolysed,
flaccid, turgid / turgidity and lysis / haemolysis.
Learners describe what happens when animal and plant cells are placed into
different external solutions at the same, lower and higher water potential than that of
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 3
Online
http://www.kscience.co.uk/animations/
plasmolysis.htm
http://www.biotopics.co.uk/life/osmdia.
37
Learning objectives
Key concepts
Cells as the units of life,
Observation and experiment
Suggested teaching activities
Learning resources
the cells. Diagrams drawn and explanation given in terms of osmosis and water
potential.
Learners complete a worksheet (prepared by you) with the cellular environment and
the external solutions identified only with values of water potential. (I) (Basic)
(Challenging)
Practical: learners use water and different concentrations of salt solutions to observe
onion cells and make high power drawings. (I) (Challenging)
Extension practical: as above, learners observe changes in red blood cells (use a
safe, acceptable source). Making estimates of cell numbers makes this a semiquantitative investigation. (I) (Challenging)
html
http://www.s-cool.co.uk/alevel/biology/cells-andorganelles/revise-it/movement
http://www.neosci.com/demos/101041_cell%20processes/Presentation
.html
http://www.biologymad.com/resources/
ch%202%20%20getting%20in%20and%20out%2
0of%20cells.pdf
Past papers
Paper 52, June 2011, Q1
4.2.e
investigate the effects of immersing
plant tissues in solutions of different
water potential, using the results to
estimate the water potential of the
tissues
Learners immerse pieces of root or stem (e.g. potato tuber tissue) in sucrose
solutions of different concentrations. The water potential of the solution in which
there is no change in length or mass is the estimate of water potential of the tissue.
(I) (Basic)
Practical booklet 3 develops skills for Paper 3 (see Teacher’s practical notes),
followed up by Q1 in Paper 52, June 2011 (data interpretation).
Key concepts
Cells as the units of life,
Observation and experiment
Practical booklet 3
Online
http://www.biotopics.co.uk/life/carrot.ht
ml#top
http://www.saps.org.uk/secondary/teac
hing-resources/286-measuring-thewater-potential-of-a-potato-cell
Textbooks/Publications
King p.60-63
Siddiqui p.38, 40-43.
Past papers
Paper 52, June 2011, Q1
4.2.a (iv)
describe and explain the processes
of diffusion, facilitated diffusion,
osmosis, active transport,
endocytosis and exocytosis (no
calculations involving water potential
v2.1 5Y02
Only the fourth part of this learning objective is included here: describe and explain the
processes of active transport
Discuss examples of active transport to show why it is necessary to transport
substances against the concentration gradient. (W) (Basic)
Learners make notes on active transport, including the role of membrane (carrier)
proteins. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBooktransp.html
38
Learning objectives
Suggested teaching activities
Learning resources
will be set) describe and explain the
processes of diffusion, facilitated
diffusion, osmosis, active transport,
endocytosis and exocytosis (no
calculations involving water potential
will be set)
Learners write a paragraph stating the similarities and differences between
facilitated diffusion and active transport. (I) (Challenging)
Learners construct a summary chart with main points (see below), and then add
details. (H) (F) (Challenging)
Textbooks/Publications
Bio Factsheet 116: Transport
Mechanisms in cells
Past Papers
Paper 22, June 2012, Q1
transport mechanism
Key concepts
Cells as the units of life,
Biochemical processes
active
passive
passive
diffusion
facilitated
diffusion
bulk
transport
endocytosis
phagocytosis
v2.1 5Y02
active
transport
exocytosis
pinocytosis
Cambridge International AS & A Level Biology (9700) – from 2016
39
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 3: DNA and the mitotic cell cycle
Recommended prior knowledge
Learners should have covered cell structure in Unit 2. Building on the key concept of cells as the basic unit of life, they should be familiar with the terms unicellular and
multicellular and know the definition of a tissue. Knowledge of the cell structures involved in protein synthesis and in mitotic cell division is essential so that learners
understand where and when the biological processes described in this unit occur. The role of enzymes in biological processes should be appreciated.
Context
This unit brings together important ideas from Units 1 and 2. Eukaryotic cells can divide by mitosis and meiosis. Cells arising as a result of mitosis are genetically
identical to each other and their parent cell, owing to faithful DNA replication during the cell cycle. DNA transcription and translation occurs during the cell cycle and
results in protein synthesis. Learners will have studied the structure of nucleic acids and proteins and will know the cell structures involved in protein synthesis. DNA as
the molecule of heredity, a key concept, contains coded information for the synthesis of proteins. The central dogma describes the flow of genetic information in a cell
and is a concept that works at a molecular level to help explain the more general statement that “the nucleus controls the cell’s activities”. Mitotic division by stem cells
allows multicellular organisms to develop and to maintain their programmed structure and organisation. Malfunctioning of cells may cause uncontrolled growth and
division and lead to tumours, or could cause the early death of cells. An understanding of the processes involved in the cell cycle will underpin later studies of genetic
control and detailed knowledge of mitotic division will facilitate understanding of the events occurring in meiotic division, studied later in the scheme of work.
Outline
This unit covers the mitotic cell cycle and begins with detail of the structure of chromosomes. After gaining an overview of the cell cycle, DNA replication by the semiconservative mechanism is tackled as part of late interphase of the cell cycle and then consideration is given to the importance of mitosis to unicellular and multicellular
organisms. Stem cells are introduced and an explanation of how uncontrolled division can lead to tumours is given. To aid understanding of the events occurring during
mitosis, especially of chromosome behaviour, learners also have the opportunity to study cells in stages of mitosis in prepared or temporary slides. The unit finishes
with a molecular definition of a gene and a gene mutation, and provides detail of DNA transcription and translation, which gives learners further insight into processes
occurring during interphase of the mitotic cell cycle.
Teaching time
It is recommended that this unit should take approximately 7% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
40
Learning objectives
Suggested teaching activities
Learning resources
5.1.a
describe the structure of a
chromosome, limited to DNA, histone
proteins, chromatids, centromere and
telomeres
State that the structure of chromatin alters during the cell cycle and explain that in a
non-dividing cell, chromatin is in its least condensed state. (W) (Basic)
o Learners describe a chromosome in a non-dividing cell or a cell in interphase as
a molecule of DNA complexed with histone protein.
o Remind/explain that the length of DNA in a chromosome is organised into
functional units, genes.
Learners draw and annotate a chromosome at prophase/metaphase to include two
sister chromatids, the centromere and telomeres
o Learners write a paragraph to explain that an identical sister chromatid is formed
before cell division. (W) (I) (Basic)
Extension: learners find out more about euchromatin and heterochromatin. (I)
(Challenging)
Online
http://www.dnalc.org/resources/3d/07how-dna-is-packaged-basic.html
http://ghr.nlm.nih.gov/handbook/basics
/chromosome
Explain that only some cells carry out mitotic cell division (most remain in the
interphase state) and one mitotic cell cycle results in two cells, following a nuclear
division (mitosis) and a cell division. (W) (Basic)
Learners research and produce an outline, annotated diagram of a cell cycle. (I)
(Challenging)
o Include the two main phases, interphase and a mitotic phase and note that the
timing of cell division is controlled by a number of genes.
o Indicate that DNA replication takes place in late interphase and that protein
synthesis occurs throughout interphase.
o Indicate that cell growth occurs in interphase.
o Include for the mitotic phase (mitosis) the main stages: prophase, metaphase,
anaphase, telophase and also indicate cytokinesis following telophase.
Add background information, e.g. cytokinesis only takes place if new cells are to be
formed (without cytokinesis a multinucleate cell is formed); notes on the G1, S and
G2 phases (use a key to indicate background information only).
Learners label incomplete diagrams (prepared by you). (F)
Introduce and give a general outline of stem cells (for 5.1.e), explaining that they
divide to become more stem cells and cells that differentiate.
o Discuss the location of stem cells in the bone marrow and within epithelial tissue
(describe this as lining or surface tissue).
o For plants, use the terms ‘meristem’, ‘meristematic’ and ‘cambium’ and discuss
locations within plants where this tissue occurs. (W) (Basic)
Online
http://www.cellsalive.com/cell_cycle.ht
m
Key concepts
Biochemical processes,
DNA, the molecule of heredity
5.1.c
outline the cell cycle, including
interphase (growth and DNA
replication), mitosis and cytokinesis
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
6.1.c
v2.1 5Y02
Revise 5.1.a and 5.1.c so learners understand the need for interphase
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 22, June 2011, Q1
Paper 23, June 2011, Q1 (c)
Online
41
Learning objectives
describe the semi-conservative
replication of DNA during interphase
Suggested teaching activities
Key concepts
Biochemical processes,
DNA, the molecule of heredity
chromosomes (and hence DNA) to replicate before mitosis occurs. (W) (Basic)
Learners match events/descriptions (printed on strips of card) to unlabelled
diagrams of semi-conservative replication to correctly describe the sequence of
events that occur in the process (you’ll need to prepare this in advance). (P) (I)
(Challenging)
o Ensure learners are clear about the role of DNA polymerase and DNA ligase and
the concept of activated nucleotides.
o Include a description pointing out that replication occurs in opposite directions for
each strand.
Learners explain what is meant by (define) semi-conservative replication. (I) (Basic)
Learners use their cut-outs of DNA nucleotides to simulate DNA replication.
o Use very short sections of double strands, separate them to show the template
strands and build up the two complementary strands. (P) (I) (Basic)
o Extension: simulate as it occurs – one strand built-up in one direction as a
continuous process and the other in Okazaki fragments (not required
knowledge). (P) (I) (Challenging)
Discuss how this process allows for faithful replication to produce identical DNA
molecules and hence genetically identical sister chromatids, ready for mitotic cell
division. (W) (Basic)
Learning resources
http://www.wiley.com/college/pratt/047
1393878/student/animations/dna_repl
ication/index.html
http://highered.mcgrawhill.com/sites/dl/free/0072437316/120
076/bio23.swf
http://www.accessexcellence.org/AB/G
G/dna_replicating.html
Textbooks/Publications
Bio Factsheet 207: How science
works: Meselson and Stahl’s classic
experiment.
Past Papers
Paper 22, Nov 2011, Q4 (c)(d)
Paper 23, Nov 2011, Q5 (b)
Note
The Meselsohn and Stahl investigation is not required learning but learners could be
given the information to test application of knowledge and understanding.
The poster (from Unit 1, DNA as the ideal molecule of inheritance) should remain
visible as this unit is covered.
5.1.d
outline the significance of telomeres in
permitting continued replication and
preventing the loss of genes
Key concepts
DNA, the molecule of heredity
v2.1 5Y02
Explain that DNA replication results in loss of a short section of the ends of the
chromosome and that telomeres are made from repeating sequences of nucleotides.
(W) (Basic)
Learners suggest how telomeres are useful, with a follow-up outline of their role
discussed and notes made: (W) (I) (Challenging)
o Telomeres serve to prevent the ends of chromosomes from being degraded.
o Without telomeres the ends would appear damaged to the cell’s repair
machinery so they prevent the ends from being joined to the ends of other
chromosomes.
o Telomeres protect genes and the integrity of the genetic material and allow
continued replication.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/c
hromosomes/telomeres/
42
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners investigate the shortening of telomeres with age and the role of
telomerase. (I) (Challenging)
5.1.b
explain the importance of mitosis in the
production of genetically identical cells,
growth, cell replacement, repair of
tissues and asexual reproduction
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
5.1.e
outline the significance of mitosis in
cell replacement and tissue repair by
stem cells and state that uncontrolled
cell division can result in the formation
of a tumour
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
v2.1 5Y02
Ensure that learners know the definition of a tissue. (W) (Basic)
Discuss with learners how their own growth occurs and how damaged tissue is
repaired. Remind them that replacement of cells can occur when cells are old/die
thorough programmed cell death.
Refer to the poster (DNA as the ideal molecule of inheritance) and agree that it is
essential that each daughter cell contains the same complete set of instructions and
the same number of chromosomes as the parent (i.e. genetically identical). (W)
(Basic)
Discuss how cells could be rejected (attack by the immune system) if the daughter
cells were genetically different and not recognised as ‘self’ (link to antigens in Unit 2
and see Unit 5). (W) (Challenging)
Learners investigate simple examples where mitosis is involved in reproduction e.g.
Hydra, or a plant that reproduces asexually. (H) (Basic)
Discuss briefly the terms clone and vegetative propagation. (W) (Basic)
Learners make brief notes summarising the discussions. (H) (F)
Online
http://www.nature.com/scitable/topicpa
ge/replication-and-distribution-of-dnaduring-mitosis-6524841
http://www.ncbi.nlm.nih.gov/pmc/article
s/PMC256985/pdf/03-10043_p214.pdf
http://sciencecases.lib.buffalo.edu/cs/c
ollection/
Learners research examples, e.g. the repair of damage to intestinal epithelial cells,
replacement of old cells in the gas exchange system. (I) (Basic)
o Extend learning to discuss how cells that are structurally and functionally the
same need to be genetically identical. (W) (Basic)
o Remind learners that all cells in the body have the same set of instructions and
explain that control of cell function is by the organised ‘switching on’ of relevant
genes. (W) (Challenging)
Explain (see 5.1.c) that the timing of cell division is under genetic control; an
alteration in a gene could lead to the cell dividing uncontrollably to form a tumour –
an example of how a cell malfunctioning upsets the delicate balance. (W)
(Challenging)
Learners sequence a set of diagrams (prepared by you) showing changes that occur
to result in a tumour (should include an abnormal mass from which two arrows
emerge to a benign growth and a cancerous (malignant) growth (see Unit 5). (I)
(Basic).
o Following research, learners add brief annotations to the diagrams. (H)
(Challenging)
o Extension: learners research differences between the two types of tumour. (I)
Online
http://stemcells.nih.gov/info/basics/pag
es/basics4.aspx
http://www.medicalnewstoday.com/info
/stem_cell/
http://science.education.nih.gov/supple
ments/nih1/cancer/guide/guide_toc.ht
m
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 23, June 2011, Q1 (b)
Past Papers
Paper 21, Nov 2011, Q4 (b)
43
Learning objectives
Suggested teaching activities
Learning resources
(Challenging)
Extend 5.1.c to discuss the statement: "Stem cells allow multicellular organisms to
develop and to maintain their programmed structure and organisation”. (W) (G)
(Challenging)
Extension: learners investigate biotechnological applications, e.g. the use of adult
stem cells in research and therapy. (I) (Challenging)
5.2.a
describe, with the aid of
photomicrographs and diagrams, the
behaviour of chromosomes in plant
and animal cells during the mitotic cell
cycle and the associated behaviour of
the nuclear envelope, cell surface
membrane and the spindle (names of
the main stages of mitosis are
expected)
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
5.2.b
observe and draw the mitotic stages
visible in temporary root tip squash
preparations and in prepared slides of
root tips of species such as those of
v2.1 5Y02
Demonstrate using a model of a cell (2n=4) (2 short and 2 long pipe cleaners =
chromosomes; cell surface membrane and nuclear envelope = string). (W) (Basic)
o Model the events as a continuous process.
o Model replication by attaching a second pipe cleaner to the first. Simulate
nuclear envelope disassembly by cutting the string into smaller lengths.
o Cytokinesis should be described for both animal and plant cells.
o Learners describe and make suggestions as to why various events occur. (W)
(Basic) (Challenging)
From a list (prepared by you), learners match an event that occurs in relation to the
spindle fibres and spindle (centrioles in animal cells only) to the behaviour of the
chromosomes during the mitotic cell cycle. (W) (Basic)
Learners work with their own models and talk through each stage. (P) (Challenging)
Learners make annotated diagrams of stages in mitosis. (I) (Challenging)
Learners practise identification of the stages and description of events using a range
of photomicrographs and diagrams of both plant and animal cells. (I) (Basic)
(Challenging)
Learners sequence images of a cell at various stages during the cycle, naming the
stages and noting chromosome behaviour. (F)
CD-ROM
Bioscope – has material which covers
this
Online
http://www.rothamsted.bbsrc.ac.uk/not
ebook/courses/guide/movie/mitosis.ht
m
http://faculty.nl.edu/jste/mitosis.htm
http://www.biology.arizona.edu/cell_bio
/tutorials/cell_cycle/main.html
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter2/animation__control_of_
the_cell_cycle.html
Textbooks/Publications
Bio Factsheet 76: The eukaryotic cell
cycle and mitosis
Note
Condensation/coiling of DNA to form the prophase chromosome can be simulated
by taking a very long piece of thin wire that is then wrapped round a pencil (which is
removed) to make a coiled, string-like structure that is now much shorter, fatter and
more visible.
Past Papers
Paper 21, June 2011, Q1 (c)
Paper 23, June 2011, Q1 (a)
Paper 21, Nov 2011, Q4 (c)
Learners draw from a prepared slide a plan diagram of a root tip to indicate: the root
cap; meristematic area (zone of cell division); zone of elongation (expansion); and
zone of differentiation. (I) (Basic)
Learners identify, draw and annotate cells (high power) in all stages of mitosis. (I)
(Challenging)
Online
http://www.microscopyuk.org.uk/micropolitan/index.html
http://www.saps.org.uk/secondary/teac
hing-resources/552-floating-garlic-
Cambridge International AS & A Level Biology (9700) – from 2016
44
Learning objectives
Suggested teaching activities
Learning resources
Vicia faba and Allium cepa
Learners prepare a root tip squash (e.g. garlic or onion root tips with acetic orcein or
toluidine blue) and examine their slide and those of others for stages of mitosis. (G)
(I) (Basic)
Learners use the eyepiece graticule by measuring the relative length and width of
chromosomes and cells. (I) (Challenging)
o Learners use the calibrated eyepiece graticule to measure the size of
chromosomes in m. (I) (Challenging)
Extension: learners investigate why each step of the procedure in the root tip squash
preparation is necessary. (I) (Challenging)
growing-rootshttp://www.saps.org.uk/secondary/teac
hing-resources/288-investigatingmitosis-in-allium-root-tip-squash
http://www.saps.org.uk/secondary/teac
hing-resources/109-staining-a-roottip-and-calculating-its-mitotic-index
Learners recall primary structure and a polypeptide (Unit 1) and suggest a definition
of a gene from previous learning objectives.
o Refer to the ‘DNA as the ideal molecule’ poster and ensure learners understand
the idea of the term ‘coded’ (see 6.2.c, 6.2.d). (W) (Basic)
o Discuss the fact that the sequence of nucleotides comprising a gene codes for
the amino acid sequence in a polypeptide chain. (W) (Basic)
Background discussion/extension research about the human genome project. (W) (I)
(Basic) (Challenging)
Online
http://evolutionlist.blogspot.co.uk/2006/
10/new-definitions-of-gene.html
http://www.sanger.ac.uk/
http://www.yourgenome.org/
Key concepts
Cells as the units of life
6.2.a
state that a polypeptide is coded for by
a gene and that a gene is a sequence
of nucleotides that forms part of a DNA
molecule
Key concepts
Biochemical processes,
DNA, the molecule of heredity
6.2.b
state that a gene mutation is a change
in the sequence of nucleotides that
may result in an altered polypeptide
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
v2.1 5Y02
Textbooks/Publications
King p.236, 207, 209
Siddiqui p.79-81.
Note
If learners query the origin of RNA, explain that there are genes that code for tRNAs
and rRNAs and that mRNA is an intermediate molecule in producing the
polypeptide. (W) (Basic).
For A Level, learners should understand that these proteins, including enzymes, will
ultimately allow development and control of cells and hence organisms (i.e. they
determine the nature of organisms).
After learners write this definition, use question and answer to recall (from Unit 1)
that primary structure determines secondary and tertiary structure, which then
determine the shape and shape of, e.g. active site, specific channel, receptor site.
This determines the function of the protein. (W) (Basic)
Stress to learners that the gene is responsible for a particular feature, trait or
characteristic and that a mutation is just an alternative form of the gene, an allele.
(W) (Basic)
Online
http://ghr.nlm.nih.gov/handbook/mutati
onsanddisorders/genemutation
http://www.yourgenome.org/dgg/gener
al/var/var_3.shtml
Note
Cambridge International AS & A Level Biology (9700) – from 2016
45
Learning objectives
Suggested teaching activities
Learning resources
Online resources may be best understood after learning about the genetic code and
transcription and translation
Learners do not need to define an allele at this point, see 16.2.a.
6.2.c
describe the way in which the
nucleotide sequence codes for the
amino acid sequence in a polypeptide
with reference to the nucleotide
sequence for HbA (normal) and HbS
(sickle cell) alleles of the gene for the
-globin polypeptide
Key concepts
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
Learners write out definitions of a gene and a gene mutation. (F)
Learners suggest why DNA needs to remain in the nucleus (large size, less prone to
degradation).
o Lead the discussion to explain that a ‘messenger’ molecule needs to be formed,
in transcription, to take the information to the ribosomes. (W) (Basic)
Discuss the concepts involved in the central dogma
(http://en.wikipedia.org/wiki/Central_dogma_of_molecular_biology overlap with ideas
in 6.2.d). (W) (Basic)
o Learners produce an annotated flow chart representing the flow of information,
beginning with DNA and ending in a functioning protein.
o Learners identify the point at which the nucleotide sequence becomes an amino
acid sequence.
o State that the process is termed translation (details in 6.2.d).
Learners study a DNA genetic dictionary/ DNA triplet table to work out, from specific
nucleotide base sequences, specific amino acid sequences. (P) (I) (Basic)
(Challenging)
o Explain this is the sequence on the strand (the template strand) that is used to
produce the polypeptide
o Include the sections where the nucleotide sequences of normal and sickle-cell
alleles differ.
Online
http://www.yourgenome.org/dgg/gener
al/proteins/proteins_2.shtml
http://www.kumc.edu/gec/
http://www.youtube.com/watch?v=J3H
VVi2k2No
Past Papers
Paper 23, June 2011, Q2 (b)(c)
Paper 21, Nov 2011, Q3 (b)
Paper 21, Nov 2013, Q5
Note
Learners should also be able to use the sequence on the non-template strand to
work out the amino acid sequence (using the DNA triplet table)
The sickle cell -globin polypeptide and sickle cell anaemia also occur in Units 5 and
7.
It is a common error for learners to state that DNA is a chain of amino acids. When
learners guess or are given incorrect matches, many will learn the incorrect match,
so only reinforce the correct relationship between nucleotides and DNA / RNA, and
between amino acids and protein.
6.2.d
describe how the information in DNA is
v2.1 5Y02
Previous learning objectives have included enough additional information to prepare
learners for the details of transcription and translation.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/
46
Learning objectives
Suggested teaching activities
Learning resources
used during transcription and
translation to construct polypeptides,
including the role of messenger RNA
(mRNA), transfer RNA (tRNA) and the
ribosomes
Learners sequence a set of events to describe and explain the process of
transcription. (P) (I) (Basic) (Challenging)
o Ensure learners realise that mRNA transcripts pass out through the nuclear
pores to the ribosomes. (W) (Basic)
o Explain post-transcriptional modification: sections not required, introns (now
known to have a role, not ‘genetic junk’ as previously believed), may be cut out
of the initial transcript and the ‘meaningful’ sections, exons, re-sealed to give
shorter mRNA transcripts. (W) (Challenging)
Formalise knowledge of the genetic code (universal, non-overlapping, degenerate,
sequential), by introducing the mRNA genetic dictionary / mRNA codon table.
For translation, provide learners with a set of diagrams (prepared by you) that can
be annotated and discussed.
Learners research the different ways the polypeptide formed can be modified in
post-translational modification. (I) (Challenging)
Learners write a paragraph on each of mRNA, tRNA and the ribosomes, explaining
their roles in transcription and translation. (H) (F) (Challenging)
Find the DNA nucleotide sequences of sections of proteins (choose from the
syllabus) to produce a worksheet (and mark scheme).
o Learners use the genetic code and one or more pieces of information to work out
missing information. Completed worksheets show the tRNA molecules involved
and the sequences of template and non-template DNA strands, mRNA and
amino acids. (H) (F) (Basic) (Challenging)
o Extension: learners explain why a DNA nucleotide sequence worked out only
using an amino acid sequence may not represent the actual DNA. (I)
(Challenging)
Learners produce a large annotated diagram to show transcription and translation in
relation to the different locations within the cell. (H) (Challenging)
Extension: learners research how post-transcriptional modification (removal of
introns and resealing of exons) allows one gene to be able to produce variations of
the protein product. (I) (Challenging)
molecules/transcribe/
http://www.brookscole.com/chemistry_
d/templates/student_resources/share
d_resources/animations/protein_synt
hesis/protein_synthesis.html
http://www.pbs.org/wgbh/aso/tryit/dna/
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Textbooks/Publications
Bio Factsheet 22: Protein synthesis I –
nucleic acids
Bio Factsheet 49: Protein synthesis II –
mechanisms
Past Papers
Paper 21, June 2011, Q3 (c)
Paper 23, June 2011, Q2 (d)
Paper 23, Nov 2011, Q5 (c)
Paper 22, Nov 2011, Q4 (b)
Paper 22, Nov 2011, Q4 (c)(d)
Note
TransCription comes before transLation alphabetically as well as in protein
synthesis.
With website animations, check the level of detail before recommending to learners.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
47
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 4: Transport and gas exchange
Recommended prior knowledge
Knowledge of cell structure, as covered in Unit 2, will enable learners to apply knowledge to cells involved in transport and gas exchange. An understanding of
diffusion, osmosis and active transport from Unit 2 is required, including confidence in understanding the movement of water in terms of differences in water potential.
Learners will need to have an understanding of haemoglobin structure and of hydrogen bonding between water molecules from Unit 1. It will be helpful if learners have
acquired basic knowledge of the mammalian circulatory system in previous studies.
Context
This unit extends the key concept of cells as the units of life by looking at the way in which cells and tissues of plants and mammals, multicellular organisms, are
provided with their requirements and how humans, as multicellular organisms, exchange gases in the lungs. The unit builds on learner knowledge of cell structure and
movement into and out of cells and highlights the importance of water as a transport medium. The work on blood in this unit leads into the immunity section in Unit 5.
Much of this unit lays the foundations for further work on physiology at A Level. In Unit 9, learners will study the way in which oxygen is used by cells for the
biochemical process of aerobic respiration, and how carbon dioxide is produced as a result of this process.
Outline
The topic of transport in plants is introduced by improving learner knowledge of plant anatomy and histology and their understanding of the relation between the
structure and function of transport tissues. Details of transport of water and minerals are covered, including a consideration of the factors affecting the rate of
transpiration, which gives learners the opportunity to carry out investigative practical work. Adaptations of organisms to their environment are exemplified by reference
to xerophytes. The transport of assimilates by phloem tissue is also covered. The topic of mammalian transport is introduced by considering the meaning of a closed
double circulation and then progresses to structure and function of the blood vessels, blood and heart. A comparison of blood, tissue fluid and lymph is made. The
carriage of respiratory gases is covered, which includes revisiting the structure and function of haemoglobin from Unit 1. Detail of gas exchange at the alveolus is
covered. The gross and fine structure of the human gas exchange system will allow learners to see the link between structure and function. Learners will make
comparisons in this unit, for example between xylem and phloem tissue, between an artery and vein, between blood, tissue fluid and lymph, and between the two sides
and upper and lower chambers of the heart .There are many good opportunities within this unit for learners to improve their microscope handling, observational and
diagram-drawing skills, and to develop manipulative and dissection skills if they choose to dissect a mammalian heart.
Teaching time
It is recommended that this unit should take approximately 14% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
48
Learning objectives
Suggested teaching activities
Learning resources
7.1.a
draw and label from prepared slides
plan diagrams of transverse sections
of stems, roots and leaves of
herbaceous dicotyledonous plants
using an eyepiece graticule to show
tissues in correct proportions
(see 1.1.c)
Revise a simple diagram of a plant: leaves and petioles, stem, (soil level), root(s)
and piliferous / root hair region. (W) (Basic)
o Explain the difference between: tissue and organ; transverse and longitudinal
sections (TS and LS).
o Explain what is meant by a herbaceous (i.e. non-woody) dicotyledon.
Discuss tissue distribution in leaves, roots and stem sections by projecting an
electronic image onto a screen. (W) (Basic)
o Learners see what they should observe later using the microscope (revise use).
o Describe how to draw the image as a plan diagram.
Learners identify tissues (especially the distribution of the vascular tissue) and make
plan diagrams (low power) from slides of TS of a leaf, stem or root (dicotyledonous
plants e.g. Ranunculus and Ligustrum), using the eyepiece graticule to gauge the
correct proportions. (I) (Challenging)
Learners draw labelled diagrams of stem and leaf sections and construct a table
comparing the two; similarities run across the columns, differences in separate
columns. (I) (Challenging)
CD-ROM
Bioscope
Key concepts
Cells as the units of life,
Observation and experiment
Note
Learners should be able to recognise: epidermis, endodermis, mesophyll, xylem,
phloem, cambium, cortex, pith.
High quality microscope slides are available to order, including those used in
previous practical examinations from the Cambridge publications catalogue
www.cie.org.uk/cambridge-for/teachers/order-publications
7.1.b
draw and label from prepared slides
the cells in the different tissues in
roots, stems and leaves of herbaceous
dicotyledonous plants using transverse
and longitudinal sections
Key concepts
Cells as the units of life,
Observation and experiment
Learners observe slides showing LS. An eyepiece graticule and stage micrometer
can be used for measurement. (I) (Challenging)
Learners draw and label individual cells under high power (from TS and LS slides).
(I) (Challenging)
Extension: learners practise using the eyepiece graticule and stage micrometer to
estimate actual dimensions of the cells. (I) (Challenging)
Background: discuss briefly differences between monocotyledons and dicotyledons.
(W) (Basic)
An extension discussion: outlining the anatomical transition in the area where the
root becomes the stem.
Note
High quality microscope slides are available to order, including those used in
previous practical examinations from the Cambridge publications catalogue
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Online
University biology department and
microscope manufacturer websites,
e.g.:
http://micro.magnet.fsu.edu/index.html
http://images.botany.org
Textbooks/Publications
Siddiqui p.5-7, 112, 115-124, 135-139
Past Papers
Paper 23, June 2011, Q3
Paper 35, June 2011, Q2
Paper 31, June 2011, Q2
Paper 34, June 2011, Q2
Paper 33, June 2013, Q2
CD-ROM
Bioscope – Superb slides and learning
tasks, including chloroplasts in
Elodea, a variety of leaf sections,
including sun and shade leaves.
Online
University biology department and
microscope manufacturer websites,
e.g.
http://www.vcbio.science.ru.nl/en/virtua
llessons/leaf/
http://www.mhhe.com/biosci/pae/botan
y/histology/html/ptmodov.htm
49
Learning objectives
Suggested teaching activities
www.cie.org.uk/cambridge-for/teachers/order-publications
Learning resources
http://leavingbio.net/FLOWERING%20
PLANTS.htm
http://images.botany.org/
Textbooks/Publications
Siddiqui p.5-7, 112, 115-124, 135-139
Bio Factsheet 19: Plant tissues
Past Papers
Paper 23, Nov 2011, Q3 (a)
7.1.c
draw and label from prepared slides
the structure of xylem vessel elements,
phloem sieve tube elements and
companion cells and be able to
recognise these using the light
microscope
Use photomicrographs and diagrams to illustrate and discuss, with teacher prompts,
the structure of xylem vessel elements, phloem sieve tube elements and companion
cells. (G) (I) (Challenging)
Learners add annotations to labelled diagrams of these three cell types. (F)
Key concepts
Cells as the units of life,
Observation and experiment
CD-ROM
Bioscope – useful for this section.
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/P/PlantTissues.html
http://leavingbio.net/FLOWERING%20
PLANTS.htm
http://www.mhhe.com/biosci/pae/botan
y/histology/html/ptmodov.htm
Textbooks/Publications
Siddiqui p.5-7, 112, 115-124, 135-139
Bio Factsheet 19: Plant tissues
Bio Factsheet 146: Tracheids, vessels
and sieve tubes
Bio Factsheet 132: Phloem
7.2.a
explain the movement of water
between plant cells, and between them
and their environment, in terms of
water potential (see 4.2. No
calculations involving water potential
will be set)
v2.1 5Y02
Provide learners with an overview diagram of the movement of water down a water
potential gradient from soil to air. (W) (Basic)
o Learners add given numerical values of water potential to the different locations,
for comparison, and annotate the diagram. (I) (Challenging)
Learners recall osmosis and the concept of water potential.
o Learners complete a worksheet (prepared by you) containing examples of
adjacent cells / cells and their environment with water potential values. Learners
work out and explain which way water will flow. (H) (F) (Basic) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologymad.com/resources/
transpiration.swf
Textbooks/Publications
Bio Factsheet 225: Synoptic biology:
water potential.
50
Learning objectives
Suggested teaching activities
Learning resources
From a diagram, learners suggest how a root hair cell is adapted for water and
mineral ion uptake (e.g. large surface area, lack of cuticle, thin cell walls, membrane
transport proteins, mitochondria). (W) (G) (Challenging)
Learners suggest how mineral ions are taken up by the root hair cell. (W) (Basic)
Learners research the most important mineral ions that are required, giving reasons.
(H)
Ensure that learners know the difference between the apoplastic pathway and
symplastic pathway (include the vacuolar pathway).
o Agree that osmosis is not involved in the apoplast pathway (no membranes).
o Use a model to explain why water has to take a symplastic pathway at the
endodermis (suberised Casparian strip).
o Learners use arrows and labels to show the different pathways on diagrams and
annotate, using the terms water potential and water potential gradient. (W) (I)
(Basic) (Challenging)
Learners stand small plants (intact root systems, soil washed off) in dye (e.g. eosin)
for 10-30 minutes, then cut thin sections to investigate the distribution of the dye and
show the position and continuous nature of xylem vessels (the dye collects in the
leaf as water is lost by transpiration). (I) (Challenging)
Learners use cut petioles of variegated leaves to make sections and observe xylem
tissue. (P) (I) (Basic)
Discuss briefly the concept of root pressure (outline only). (W) (Basic)
Online
http://www.microscopyuk.org.uk/mag/artmar00/watermvt.ht
ml
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/X/Xylem.html
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::600::480::/sites/dl/free/007353224
x/788092/Water_Uptake.swf::Water%
20Uptake
Key concepts
Cells as the units of life,
Organisms in their environment
7.2.c
describe the pathways and explain the
mechanisms by which water and
mineral ions are transported from soil
to xylem and from roots to leaves
(include reference to the symplastic
pathway and apoplastic pathway and
Casparian strip)
Key concepts
Cells as the units of life,
Biochemical processes
Textbooks/Publications
Bio Factsheet 82: Transport in
flowering plants
Bio Factsheet 108: Water movement
across the root
Past Papers
Paper 23, June 2011, Q3 (a)
Note
Root hairs can be seen clearly on newly-germinated seedlings, such as mung
beans, if these are grown on damp filter paper or cotton wool.
Do not discuss the concept of capillarity.
Learners are better to explain water movement in terms of water potential gradients
to avoid confusion with mass flow in phloem.
7.2.b
explain how hydrogen bonding of
water molecules is involved with
movement in the xylem by cohesion-
v2.1 5Y02
Tackle cohesion-tension first: use a question and answer session to help learners
make the link between hydrogen bonding of water molecules (cohesive forces) and
the concept of transpiration pull. (W) (Basic)
Discuss the concept of adhesion. Remind learners that the attraction of water
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://chemwiki.ucdavis.edu/Physical_
Chemistry/Physical_Properties_of_M
atter/Atomic_and_Molecular_Properti
51
Learning objectives
Suggested teaching activities
Learning resources
tension in transpiration pull and
adhesion to cellulose cell walls
molecules to the secondary cell wall of xylem vessel elements is mainly as a result
of hydrophilic cellulose (which is impregnated with lignin). (W) (Basic)
Learners write a paragraph explaining the difference between cohesion and
adhesion in the movement of water up the xylem. (F)
Learners research what is meant by a transpiration stream. (H) (Basic)
es/Intermolecular_Forces/Cohesive_
And_Adhesive_Forces
http://www.microscopyuk.org.uk/mag/artmar00/watermvt.ht
ml
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/X/Xylem.html.
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::600::480::/sites/dl/free/007353224
x/788092/Water_Uptake.swf::Water%
20Uptake
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 82: Transport in
flowering plants
Bio Factsheet 108: Water movement
across the root
Past Papers
Paper 23, June 2011, Q3 (a)
7.2.d
define the term transpiration and
explain that it is an inevitable
consequence of gas exchange in
plants
Key concepts
Cells as the units of life
v2.1 5Y02
Learners write a definition of transpiration. (I) (Basic)
Learners draw a large diagram of a vertical section through part of a leaf, adding
numbered annotations to show the pathway of water (beginning with water leaving
xylem vessels) and the sequence of events occurring, using correct water potential
terminology. (I) (Challenging)
o Emphasise the need to refer to water evaporated from the moist cell walls of the
spongy mesophyll cells as water vapour.
Discuss the association between transpiration (reduces the water potential at the top
of the plant) and tension (of cohesion-tension). (W) (Basic)
Learners explain the differences between transpiration and evaporation. (F)
Discuss cuticular transpiration (links to 7.2.f, leaves of xerophytes). (W) (Basic)
Learners study a graph showing how the rate of transpiration varies during a 24-hour
day and interpret using a word list (stomata, open, closed, photosynthesis, oxygen,
carbon dioxide, gas exchange, transpiration). (I) (Basic)
Extension: take climate into account and interpret a graph (prepared by you) with
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/T/Transpiration.html
Textbooks/Publications
Bio Factsheet 64: Transpiration
Bio Factsheet 81: Gas exchange in
plants
Past Papers
Paper 23, Nov 2011, Q3 (b)
Paper 22, Nov 2013, Q3 (a)
52
Learning objectives
Suggested teaching activities
Learning resources
transpiration varying over a few days. (I) (Challenging)
Learners research the advantages of transpiration and produce a list. (H) (Basic)
7.2.e
investigate experimentally and explain
the factors that affect transpiration rate
using simple potometers, leaf
impressions, epidermal peels, and
grids for determining surface area
Key concepts
Observation and experiment
Demonstrate the use (or show diagrams) of a standard commercial potometer to
measure water uptake (e.g. Thoday). (W) (Basic)
o Discuss the reasons for: a slanting cut across the leafy shoot; submerging in
water; use of petroleum jelly round the joint; drying leaves. (W) (Challenging)
Practical: learners make a simple potometer using a long piece of capillary tubing
that has a short length of rubber tubing attached at one end. The whole apparatus
can be supported vertically.
o Learners record the height of the air/water meniscus at suitable time intervals.
(P) (I) (Basic)
o Discuss how to make results quantitative, e.g. using grids to determine the
surface area of leaves; using the volume of a cylinder to calculate the volume of
water taken up. (W) (Basic)
Extension practical: learners enclose part of a plant inside a plastic bag and use
data-logging equipment and a humidity-recording sensor to investigate the effect of
transpiration on humidity. (P) (I) (Challenging)
Learners plan and/or carry out a controlled investigation into the effect of wind
speed, temperature or light on the rate of transpiration.
o Learners present results (or are given results) in graphical form and give
explanations for the shape of the graph. (P) (I) (Challenging)
Learners make temporary slides of epidermal strips from leaves of different species
(use nail varnish or ‘new skin’ liquid plaster and peel off when dry). (I) (Basic)
Practical booklet 6 is designed to develop some of the practical skills (listed in the
Teacher’s practical notes) assessed in paper 3.
Practical booklet 6
Online
http://www.mhhe.com/biosci/genbio/virt
ual_labs/BL_10/BL_10.html
http://www.saps.org.uk/secondary/teac
hing-resources/115-potometermeasuring-transpiration-rates
http://www.mikecurtis.org.uk/Potomete
r/potometer.html
http://www.saps.org.uk/secondary/teac
hing-resources/299-measuringstomatal-densityTextbooks/Publications
King p.142-146
Siddiqui p. 140-144, 146-147
Note
Remind learners that potometers measure rates of water uptake only and that a cut
end of a stem is not the same as uptake via root hairs.
If a potometer is placed on a balance sensitive to small changes in mass, then it is
possible to measure water uptake and transpiration.
7.2.f
make annotated drawings, using
prepared slides of cross-sections, to
show how leaves of xerophytic plants
v2.1 5Y02
Explain the terms mesophyte, hydrophyte and xerophyte and discuss ways in which
plants can reduce their water loss. (W) (Basic)
Learners consider the mesophyte leaf and give comparative descriptions (e.g.
thicker waxy cuticle, fewer stomata per unit area of leaf, etc.) using diagrams of
Cambridge International AS & A Level Biology (9700) – from 2016
CD-ROM
Bioscope – has suitable images.
Online
53
Learning objectives
Suggested teaching activities
Learning resources
are adapted to reduce water loss by
transpiration
leaves from a range of xerophytes. (P) (I) (Basic)
Learners use prepared slides of cross-sections of leaves of xerophytes to make
annotated plan diagrams and detailed drawings. (I) (Basic)
o Learners describe features and explain how each helps to reduce water loss. (I)
(Challenging)
o Extend this to a circus of activities with, e.g. living examples; photographs and
photomicrographs; Bioscope; microscope slides; electron micrographs. (P) (I)
(Challenging)
Learners make temporary slides of epidermal strips from leaves of mesophytes and
xerophytes and estimate the number of stomata per unit area to make quantitative
comparisons. (I) (Challenging)
o Extension: some may know how to use the t-test to see if differences are
significant (not required at AS Level). (P) (I) (Challenging)
www.worldofteaching.com/powerpoints
/biology/Xerophytes.ppt
Key concepts
Natural selection,
Organisms in their environment
7.2.g
state that assimilates, such as sucrose
and amino acids, move between
sources (e.g. leaves and storage
organs) and sinks (e.g. buds, flowers,
fruits, roots and storage organs) in
phloem sieve tubes
Key concepts
Cells as the units of life,
Biochemical processes
7.2.h
explain how sucrose is loaded into
phloem sieve tubes by companion
cells using proton pumping and the cotransporter mechanism in their cell
surface membranes
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Explain the term assimilates and discuss examples. (W) (Basic)
Introduce translocation as the movement of assimilates from the source (area where
they are produced) to the sink (area where they are used / stored).
o As an example, state that sucrose is loaded into phloem at the source, and then
removed at the sink.
o Learners suggest source and sink locations within the plant. (W) (Basic)
Note
Learners should also be familiar with the term photosynthates.
Use learner knowledge of membranes and transport mechanisms to describe and
explain the events that occur. (W) (Challenging)
Learners write out a set of cards containing relevant points and practise re-ordering
them to give a sequential account.
o These could range from main points to a detailed account (see table for
examples). (P) (I) (Basic) (Challenging)
o Learners write an account from memory. (F)
H+ actively pumped out of companion
cells
concentration of H+ builds up outside
Textbooks/Publications
Bio Factsheet 29: Plant and animal
adaptations to dry habitats
Bio Factsheet 84: Xerophytes and
hydrophytes
Online
http://leavingbio.net/FLOWERING%20
PLANTS.htm
Textbook/Publications
King p.146-147
Siddiqui p.135-136
Past Papers
Paper 23, June 2011, Q5 (b)(ii)
Online
http://www.uic.edu/classes/bios/bios10
0/lectf03am/sucrosepump.jpg
Past Papers
Paper 23, June 2011, Q5 (c)
Paper 21, Nov 2011, Q5 (b)
Paper 22, Nov 2011, Q6 (b)
ATP required
membrane impermeable to H+ so
Cambridge International AS & A Level Biology (9700) – from 2016
54
Learning objectives
Suggested teaching activities
the membrane
H+ diffuses back in via a membrane
carrier protein
cotransport of sucrose occurs
sucrose diffuses into phloem sieve
tube element
Learning resources
they cannot diffuse back in
down the electrochemical gradient
H+ and sucrose bind to the protein
(conformational change occurs)
via plasmodesmata
Note
Emphasise that the entry of sucrose into the phloem sieve tube is passive but the
whole process is sometimes described as ‘active loading’.
7.2.i
explain mass flow in phloem sap down
a hydrostatic pressure gradient from
source to sink
Key concepts
Cells as the units of life
Learners sort out cards (prepared by you) containing details such as below before
making notes. (P) (I) (Basic)
at the source, sucrose enters the phloem sieve tube
this lowers the water potential
this draws (extra) water into the sieve tube by osmosis
this increases the hydrostatic pressure
at the sink, sucrose leaves the phloem sieve tube
water follows osmotically
the hydrostatic pressure at the source is higher than at the sink
fluid / phloem sap moves from source to sink
down this pressure gradient
by mass flow
Online
http://highered.mcgrawhill.com/sites/9834092339/student_vi
ew0/chapter38/animation__phloem_loading.html
Textbook/Publications
Bio Factsheet 132: Phloem.
Past Papers
Paper 23, June 2011, Q5 (c)
Paper 21, Nov 2011, Q5 (b)
Note
Learners should understand that phloem translocates soluble organic compounds.
7.1.d
relate the structure of xylem vessel
elements, phloem sieve tube elements
and companion cells to their functions
Key concepts
v2.1 5Y02
For xylem vessel elements, use diagrams to aid a ‘structure to function’ discussion.
Recall the role of xylem in the transport of water and mineral ions and introduce the
need for lignification (see also 7.2.a) because of the tension created by the
transpiration pull.
o Learners suggest other functions of lignin and continue to provide other
examples of structure to function. (W) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
CD-ROM
Bioscope – useful for this section.
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/P/PlantTissues.html
55
Learning objectives
Suggested teaching activities
Learning resources
Cells as the units of life
o Learners match statements about structure to statements about function. The
activity could be divided into the main points and additional points. (P) (I) (Basic)
(Challenging)
Learners use resources (see also 7.1.c) to label diagrams of phloem sieve tube
elements and companion cells. (I) (Basic)
o Learners point out the relationship between structure and function for these two
cell types. (W) (Basic)
o Learners make bullet-pointed notes, using one colour for a structural detail and a
different colour for a link to a function. (I) (Challenging)
http://leavingbio.net/FLOWERING%20
PLANTS.htm
http://www.mhhe.com/biosci/pae/botan
y/histology/html/ptmodov.htm
Note
It is now believed that protein strands are not present in living, functioning phloem
tissue.
8.1.a
state that the mammalian circulatory
system is a closed double circulation
consisting of a heart, blood vessels
and blood
Key concepts
Cells as the units of life
v2.1 5Y02
Display an image giving an overview of the whole circulatory system and check that
learners can describe what is meant by pulmonary and systemic circulations. (W)
(Basic)
Use a question and answer session to determine that arteries carry blood away from
the heart and veins towards the heart. (W) (Basic)
Extension (useful for later studies): discuss names given to blood vessels serving
organs e.g. pulmonary + lungs; coronary + heart, hepatic + liver; renal + kidney. (W)
(Basic)
Learners make brief written notes explaining closed circulation and double
circulation. (I) (Basic)
Learners label diagrams of double circulation, including the heart chambers, the two
types of circulation and the names of the main blood vessels. (I) (Basic)
Learners describe the journey made by a red blood cell in one complete circuit of the
mammalian blood system. (H) (F) (Basic)
Extension: learners research and contrast the mammalian circulatory system with
organisms organised differently, e.g. insect, squid, fish and amphibians. Search
online for images of diagrams of insect, fish, amphibians and squid circulatory
systems. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 19: Plant tissues
Bio Factsheet 146: Tracheids, vessels
and sieve tubes
Bio Factsheet 132: Phloem
Past Papers
Paper 23, June 2011, Q5 (a)
Paper 22, June 2013, Q2 (a)
Online
http://www.bbc.co.uk/schools/gcsebite
size/pe/appliedanatomy/0_anatomy_
circulatorysys_rev1.shtml
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/AnimalHearts.html
56
Learning objectives
Suggested teaching activities
Learning resources
8.1.b
observe and make plan diagrams of
the structure of arteries, veins and
capillaries using prepared slides and
be able to recognise these vessels
using the light microscope
Gauge learner knowledge of the basic structure of arteries, veins and capillaries with
a brainstorming session before providing labelled diagrams. (W) (Basic)
Learners study photomicrographs of (muscular) arteries and veins (TS), and an
electron micrograph of capillaries. Learners label the layers and, with prompting,
annotate with details. (W) (I) (Basic)
Learners observe prepared TS slides, and draw labelled plan diagrams. Practise
measurement using an eyepiece graticule. (I) (Basic) (Challenging)
Extension: learners investigate the elasticity of blood vessels by suspending weights
on sections of arteries and veins. (P) (Challenging)
Learners carry out research into other types of blood vessels, including elastic
arteries, arterioles and venules (stress this is not required learning). (H)
(Challenging)
Learners sort out statements (prepared by you) into three columns for each of the
three blood vessel types. (F)
CD-ROM
Bioscope – has appropriate slides.
Key concepts
Cells as the units of life,
Observation and experiment
Online
http://sln.fi.edu/biosci/vessels/vessels.
html
http://www.histology.leeds.ac.uk/circul
atory/arteries.php
http://www.nuffieldfoundation.org/practi
cal-biology/elastic-recoil-arteries-andveins
http://library.med.utah.edu/WebPath/C
VHTML/CVIDX.html
Textbooks/Publications
Siddiqui p.175-177
8.1.c
explain the relationship between the
structure and function of arteries, veins
and capillaries
Learners construct a table showing the relationship between structure to function for
each of the three blood vessel types. (I) (Challenging)
Learners label the layers on diagrams of an artery, vein and capillary in TS, and then
annotate to link structure to function. (F)
Online
http://nsb.wikidot.com/2-2-3-comparethe-structure-of-arteries-capillariesand-vein
Key concepts
Cells as the units of life
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
57
Learning objectives
Suggested teaching activities
Learning resources
8.1.d
observe and draw the structure of red
blood cells, monocytes, neutrophils
and lymphocytes using prepared slides
and photomicrographs
Learners observe blood cells using the light microscope or use other images. (I)
(Basic)
o Learners draw labelled diagrams of the different cell types and make tables to
compare: red blood cells with white blood cells; monocytes with neutrophils. (I)
(Challenging)
Learners use resources to explain how the structural features of a red blood cell are
related to the function of oxygen transport. (I) (Challenging)
CD-ROM
Bioscope – has appropriate images.
Key concepts
Cells as the units of life,
Observation and experiment
Note
The terms erythrocyte and leucocyte should also be mentioned (not required
learning).
The function of the white blood cells and details of B-lymphocytes compared to Tlymphocytes are covered in Unit 5.
To help later understanding, explain that monocytes take on a different appearance
when they mature to become macrophages, and that these cells are usually in
locations other than blood tissue.
Online
http://micro.magnet.fsu.edu/index.html
http://education.vetmed.vt.edu/Curricul
um/VM8054/Labs/Lab6/Lab6.htm
Textbooks/Publications
King p.120-122, 164-165
Siddiqui p. 179-182
Bio Factsheet 62: Animal tissues I –
epithelia and blood
Bio Factsheet 36: Structure and
function of blood and lymph
Past Papers
Paper 22, June 2011, Q3 (a)(b)
8.1.e
state and explain the differences
between blood, tissue fluid and lymph
Key concepts
Cells as the units of life
Brainstorm the composition of blood and discuss the need for exchange with cells.
(W) (Basic)
o Discuss how and why the concentrations of substances in blood, such as
oxygen, carbon dioxide and dissolved glucose, can vary. (W) (Challenging)
Explain how pressure changes from the arterial to the venous end of the capillary
network. Ask for suggestions, with reasons, as to which of the components would be
able to leave the network. (W) (Challenging)
Learners use resources to label and annotate a diagram of a capillary network,
including explanations of how tissue fluid and lymph are formed and arrows to show
direction of blood flow, formation of tissue fluid and formation of lymph. (I)
(Challenging)
o Learners add arrows of different colours or styles (use a key) to represent the
movement of substances such as dissolved glucose and amino acids, oxygen
and carbon dioxide. (I) (Basic)
Learners construct a comparative table of differences between blood, tissue fluid
and lymph. (H) (F)
Textbooks/Publications
Bio Factsheet 36: Structure and
function of blood and lymph
Bio Factsheet 89: Tissue fluid
Bio Factsheet 171: Answering exam
questions: the formation and
drainage of lymph
Past Papers
Paper 21, June 2011, Q2 (b)
Note
Highlight the difference between blood and blood plasma.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
58
Learning objectives
Suggested teaching activities
Learning resources
8.2.a
describe the external and internal
structure of the mammalian heart
Learners check their knowledge of the internal structure of the heart by adding as
many labels as possible to a diagram. Go through this, allowing learners to add any
missing e.g. tendinous cords and papillary muscles, sinoatrial node, atrioventricular
node and Purkyne tissue. (I) (Basic)
Show learners images of the external structure of the heart and agree labels. (W)
(Basic)
Learners match up a set of labels with a set of descriptions. (I) (Basic)
Learners practise adding labels, with descriptive features, to a range of internal and
external diagrams of the heart. (H) (F) (Basic) (Challenging)
Learners study models of the heart or dissect a heart (or observe) obtained from
butchers, abattoirs or suppliers. (G) (P) (I) (Basic) (Challenging)
o Heart models are useful for learners to get a 3-D understanding if dissection is
not carried out.
Online
http://www.learnerstv.com/animation/a
nimation.php?ani=321&cat=biology
http://www.nhlbi.nih.gov/health/dci/Dis
eases/hhw/hhw_anatomy.html
http://www.sciencelearn.org.nz/Context
s/See-through-Body/SciMedia/Animations-andInteractives/Label-the-heart
http://library.med.utah.edu/WebPath/C
VHTML/CVIDX.html
Key concepts
Cells as the units of life
Note
Hearts obtained for dissection have often lost their blood vessels and some or all of
their atria. Obtaining heart and lungs may provide a more complete heart (useful for
the gross structure of the gas exchange system, studied later).
8.2.b
explain the differences in the thickness
of the walls of the different chambers
in terms of their functions with
reference to resistance to flow
Key concepts
Cells as the units of life
Learners complete a short test or sort statements into the correct order to remind
them about the pathway of blood in one complete circuit of the body. (F)
Explain that the differences in pressure between the left and right ventricles are
related to the ability to overcome resistance to flow by the blood vessels as blood
travels to the body tissues.
o Learners volunteer that there is a far lower resistance to flow in the pulmonary
circulation than in the systemic.
o Remind learners that the thicker the wall of a heart chamber, the more cardiac
muscle there is to generate force when it contracts.
Relate the thinner atrial walls (compared to the thicker ventricle walls) to the much
lower resistance that blood has to overcome to travel the short distance to the
ventricles. (W) (Basic)
Textbooks/Publications
King p.128-130
Siddiqui p.173-174
Bio Factsheet 35: Structure and
function of the mammalian heart
Online
http://www.physiologymodels.info/cardi
ovascular/arterioles.htm
Past Papers
Paper 22, June 2013, Q6 (b)
Note
Pulmonary capillaries are very delicate (very small diameter) so an increase from
normal pressure of blood leaving the right ventricle increases the likelihood of damage.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
59
Learning objectives
Suggested teaching activities
Learning resources
8.2.c
describe the cardiac cycle (including
blood pressure changes during systole
and diastole)
A discussion should switch the focus from a description of one complete circuit of
the body to one cardiac cycle.
o Remind learners that a decrease in volume of a heart chamber when the cardiac
muscle contracts means an increase in blood pressure within the chamber. (W)
(Basic)
o Associate the events occurring during one cardiac cycle to changes in blood
pressure , explaining that valves are pushed open and shut by differences in
pressure on either side. (W) (Challenging)
Learners produce a table describing the sequence of events (including the status
of the valves) occurring in one cardiac cycle and highlighting that both sides of the
heart contract and relax in unison: (I) (Challenging)
Online
http://www.pbs.org/wgbh/nova/eheart/h
uman.html
http://library.med.utah.edu/kw/pharm/h
yper_heart1.html
Key concepts
Cells as the units of life
right side of heart
Past Papers
Paper 23, Nov 2011, Q2 (b)
left side of heart
Learners annotate a set of diagrams (prepared by you) showing the heart during one
cardiac cycle. (F)
Use OHP overlays / PowerPoint presentation to build up a graph showing the
pressure and volume changes on one side of the heart (left side is most commonly
shown).
o Add heart diagrams below the x-axis in the different stages of the cycle,
corresponding to the correct times on the graph.
o Learners volunteer explanations throughout. (W) (Challenging)
Learners annotate a pressure change graph describing the event in the cardiac
cycle that correlates to the change shown on the graph (including points at which
named valves open and shut). (I) (Challenging)
Learners practise extracting information and interpreting questions based on
pressure change graphs (prepared by you). (I) (F) (Basic) (Challenging)
Note
ECGs (not required learning), accompanied by explanations, may be given as stimulus
material in a question.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
60
Learning objectives
Suggested teaching activities
Learning resources
8.2.d
explain how heart action is initiated
and controlled (reference should be
made to the sinoatrial node, the
atrioventricular node and the Purkyne
tissue, but not to nervous and
hormonal control)
Use explanations, interspersed with questions requiring thoughtful suggestions, to
present the following ideas:
o The heart is myogenic (initiates heart beat without receiving nerve impulses from
outside).
o The sinoatrial node (SAN - primary pacemaker) initiates muscle cell
depolarisation and atrial systole.
The insulating ring of non-conducting (connective) tissue (fibrous ring): prevents the
atria and ventricles from contracting at the same time; forces the wave of
depolarisation to pass through the atrioventricular node (AVN), delaying its passage
so the atria complete systole before ventricular systole begins.
The Purkyne tissue passes the depolarisation down to the apex of the heart so that
the ventricles contract from the bottom up, squeezing blood out up the arteries. (W)
(Challenging)
In the correct locations on a diagram of the heart, learners number the events
occurring in sequence, making notes underneath for each number. (I) (Basic)
Learners place in sequence statements of each of the events occurring, starting with
the SAN. (P) (I) (Basic)
o Create a second column so that statements of cardiac cycle events correspond
with the timing. (P) (I) (Challenging)
Online
http://hyperphysics.phyastr.gsu.edu/hbase/biology/sanode.ht
ml
http://www.nhlbi.nih.gov/health/healthtopics/topics/hhw/
Key concepts
Cells as the units of life
Textbooks/Publications
Bio Factsheet 139: Answering exam
questions on the heart
Bio Factsheet 7: Comparing transport
in plants and animals.
Past Papers
Paper 23, Nov 2011, Q2 (a)
Note
‘Wave of excitation’ or ‘impulses’ are acceptable terms, not signal, wave, pulse,
message or nerve impulse.
Learners should understand that the wave of depolarisation spreads across the
network of cardiac muscle fibres to bring about systole, and that the fibres do not
fatigue (no other details of cardiac muscle required).
9.1.a
describe the gross structure of the
human gas exchange system.
Key concepts
Cells as the units of life
v2.1 5Y02
Agree that the mammalian transport system carries the respiratory gases, oxygen
and carbon dioxide and contrast this with plant vascular tissue (not involved with gas
transport). Explain that the gas exchange system facilitates exchange with the
external environment. (W) (Basic)
Learners revise previous knowledge by labelling familiar structures on a diagram of
the human gas exchange system, using resources to complete labelling and add
annotations. (I) (Basic)
o Ensure learners know that the specialised gas exchange surface is the alveolus.
(I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Siddiqui p.183
61
Learning objectives
Suggested teaching activities
Learning resources
9.1.b
observe and draw plan diagrams of the
structure of the walls of the trachea,
bronchi, bronchioles and alveoli
indicating the distribution of cartilage,
ciliated epithelium, goblet cells, smooth
muscle, squamous epithelium and
blood vessels
Project images or show photomicrographs of the named structures and give
guidance as to how to identify the named structures and learn about the distribution
of the named features. (W) (Basic)
Learners observe, interpret, and draw plan diagrams of prepared slides. (I)
(Challenging)
o Learners also identify cilia, mucous glands and elastic fibres to prepare for 9.1.c.
(I) (Challenging)
o Learners complete a table (tick = present, cross = absent) such as below. (I)
(Challenging)
o Learners compare their diagrams and table with textbook versions. (I) (Basic)
Online
http://www.meddean.luc.edu/lumen/Me
dEd/Histo/frames/Histo15.html
http://micro.magnet.fsu.edu/index.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM040.html
Key concepts
Cells as the units of life
structure
cartilage
ciliated
epithelium
goblet cells
smooth
muscle
squamous
epithelium
Textbooks/Publications
King p.89-91
Siddiqui p.184-185
blood
vessels
trachea
bronchus
bronchiole
alveoli
Learners label diagrams of sections through the trachea, bronchus and bronchiole
and complete blank tables as above. (F)
Note
Learners should know the singular and plural: bronchus and bronchi; alveolus and
alveoli.
Explain that there are only a few goblet cells in the bronchiole (some textbooks may
state none are present) and discuss the reason for this, i.e. avoiding mucus
hindering gas exchange in the alveoli.
9.1.c
describe the functions of cartilage,
cilia, goblet cells, mucous glands,
smooth muscle and elastic fibres and
recognise these cells and tissues in
prepared slides, photomicrographs and
electron micrographs of the gas
exchange system
Discuss the reasons for the distribution of the various features within the gas
exchange system by explaining their functions. (W) (Basic)
Learners match statements: features with correct functions. (I) (Basic)
Reinforce learning by providing photomicrographs and electron micrographs for
learners to identify the features. (P) (I) (Challenging)
Learners give written explanations linking the presence / location of the features in
the different areas of the gas exchange system to their function. (F)
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.meddean.luc.edu/lumen/Me
dEd/Histo/frames/Histo15.html
http://micro.magnet.fsu.edu/index.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM040.html
Textbooks/Publications
King p.89-91
Siddiqui p.184-185
62
Learning objectives
Suggested teaching activities
Learning resources
Cells as the units of life
Past Papers
Paper 21, June 2011, Q1
Paper 22, Nov 2011, Q1
9.1.d
describe the process of gas exchange
between air in the alveoli and the
blood
Key concepts
Cells as the units of life
Discuss the roles of blood flow and ventilation in maintaining diffusion gradients for
oxygen and carbon dioxide between the alveoli and blood.
o Incorporate a question and answer session so learners can apply knowledge of
the function of haemoglobin (Unit 1). (W) (Basic)
Learners draw and annotate diagrams with key features of the process, adding
arrows to indicate the direction of exchange of oxygen and carbon dioxide. (I)
(Challenging)
Learners write a short account of how concentration gradients are maximised for
efficient gas exchange. (I) (Basic)
Learners produce a written description explaining gas exchange in terms of the
structure of the alveolus and capillary and diffusion across cell surface membranes.
(I) (Challenging)
o The account should make clear the difference between diffusion across alveolar
and capillary walls and diffusion across membranes.
Using a diagram of an alveolus and associated capillaries, learners give an account
of how the structure of the gas exchange surface is adapted for its function. (F)
Online
http://www.johnwiley.net.au/highered/in
teractions/media/Respiration/content/
Respiration/resp1a/frameset.htm
http://www.johnwiley.net.au/highered/in
teractions/media/Respiration/content/
Respiration/resp2a/bot.htm
Textbooks/Publications
Bio Factsheet 26: Gas exchange in
animals
Note
A common written error in examinations is to state that diffusion occurs across
‘epithelial cell walls’ or ‘the cell walls of the capillary’.
It is not sufficient to state that red blood cells take up oxygen: learners should refer
to oxygen uptake by haemoglobin in red blood cells.
8.1.f
describe the role of haemoglobin in
carrying oxygen and carbon dioxide
with reference to the role of carbonic
anhydrase, the formation of
haemoglobinic acid and
carbaminohaemoglobin (details of the
chloride shift are not required)
Use a question and answer session to revise haemoglobin structure (Unit 1) before
providing further details of oxygen binding and carriage and oxygen release. (W)
(Challenging)
With teacher prompting, learners construct a diagram summarising the carriage of
carbon dioxide by haemoglobin at the respiring tissue (ensure they understand that
the reverse happens in the lung tissue). (I) (Challenging)
o The labelled diagram to include the red blood cell, the endothelium with pores,
and the body cells.
o Discuss in stages, with learners adding information, the sequence of events
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=8
http://www.mrothery.co.uk/circulation/ci
rculationotes.htm#BLOOD
Textbooks/Publications
Bio Factsheet 175: Haemoglobin:
structure & function
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
63
Learning objectives
Suggested teaching activities
Learning resources
Cells as the units of life,
Biochemical processes
occurring.
Discuss the importance of carbonic anhydrase (recall enzyme knowledge), also
highlighting that haemoglobin is not the only protein found in red blood cells. (W)
(Basic)
Learners produce a written explanation of the events occurring in the: respiring
tissues, using a diagram as stimulus material; in the lungs. (H) (F) (Challenging)
Learners explain the roles of haemoglobin in the carriage of carbon dioxide in
buffering hydrogen ions and transporting carbon dioxide directly as
carbaminohaemoglobin. (I) (Challenging)
Past Papers
Paper 21, June 2011, Q2 (a)(c)
Paper 22, June 2011, Q3 (d)(e)
Note
Learners should not describe oxygen binding to haemoglobin as ‘bonding’.
8.1.g
describe and explain the significance
of the oxygen dissociation curves of
adult oxyhaemoglobin at different
carbon dioxide concentrations (the
Bohr effect)
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Introduce the oxygen dissociation curve step-by-step (a difficult concept to grasp),
returning to previous steps if necessary.
o Introduce partial pressure as a measure of concentration and ‘availability’ of
oxygen and the percentage saturation of haemoglobin as ‘affinity’ for oxygen.
o Explain that the oxygen dissociation curve is constructed from results of
experimental measurements.
o Explain the loading of oxygen in the lung (see 8.1.f).
o Explain the release of oxygen (i.e. oxyhaemoglobin dissociation) as a result of
the lower partial pressure in other body tissue (resting). (W) (Challenging)
Learners annotate their own diagrams of the oxygen dissociation curve of adult
haemoglobin. (I) (Challenging)
Learners suggest why the steep part of the curve is important and beneficial
(efficient unloading in partial pressures common in respiring tissues). (W)
(Challenging)
Explain the Bohr shift in relation to carbon dioxide carriage by haemoglobin, using a
summary diagram from 8.1.f.
o Explain that haemoglobin dissociates to a greater extent in working tissue as the
presence of increased carbon dioxide concentrations facilitates the unloading of
‘more’ oxygen by haemoglobin.
o Ask learners to suggest the significance of the greater dissociation (greater need
of tissues for oxygen as they are more actively respiring). (W) (Challenging)
Learners complete worksheets involving data extraction and interpretation of the
curve. (P) (I) (F) (Challenging)
Extension: learners research (using textbooks/internet), consider and explain the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=8
http://www.mrothery.co.uk/circulation/ci
rculationotes.htm#BLOOD
http://www.wiley.com/college/fob/anim/
http://www.wiley.com/college/fob/quiz/
quiz07/7-7.html
http://www.wiley.com/college/fob/quiz/
quiz07/7-12.html
Textbooks/Publications
Bio Factsheet 175: Haemoglobin:
structure & function
Bio Factsheet 9: Oxygen dissociation
curves
Past Papers
Paper 21, June 2011, Q2 (a)(c)
Paper 22, June 2011, Q3 (d)(e)
Paper 21, June 2011, Q2 (d)
Paper 23, June 2011, Q4
64
Learning objectives
Suggested teaching activities
Learning resources
oxygen dissociation curves of myoglobin and foetal haemoglobin. (H) (Challenging)
8.1.h
describe and explain the significance
of the increase in the red blood cell
count of humans at high altitude
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Learners make bullet-point notes after discussing how an increase in red blood cell
count is linked to an increase in haemoglobin, and how this compensates for the
lower saturation that occurs at high altitudes (hence ensuring that body tissues
receive sufficient oxygen). (W) (I) (Basic)
Learners complete a worksheet (prepared by you) to make comparisons of red blood
cell counts at different altitudes, including giving percentage changes. (H) (Basic)
(Challenging)
Extension: learners research the benefits to athletes of training at high altitude, or
investigate if communities who have always lived at high altitude are different to
others. (I) (H) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.sportsci.org/traintech/altitud
e/wgh.html
Textbooks/Publications
Bio Factsheet 149: High altitude
biology
65
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 5: Disease and protection against disease
Recommended prior knowledge
Some introductory knowledge of sickle cell anaemia would be useful, which may have arisen from additional information acquired when learning about sickle cell
haemoglobin in Unit 1, or about mutations in Unit 3. Also from Unit 1, an appreciation of protein structure to function will help when studying antibody structure and
function. Learners should have a good understanding of cell structure, the role of cell surface membrane receptors and the mechanism of endocytosis from Unit 2. They
should appreciate the difference between eukaryotes, prokaryotes and viruses. An understanding of how uncontrolled cell division may result in a tumour, studied in
Unit 3, is required. From Unit 4, learners should be familiar with the histology of the gas exchange system and have knowledge of white blood cells.
Context
Previous units have looked at living organisms on the molecular and cellular scale, before moving on to organs and systems. Disease is an outcome of the
malfunctioning of cells through altered biochemical processes. Infectious diseases show how humans interact with pathogens. These interactions are one component
of the key concept Organisms in their environment. A multicellular organism must organise, control and coordinate activities so that they have defence mechanisms
and can develop immunity from disease. A link is provided to another key concept, Natural selection, with a consideration of the development of antibiotic resistance by
bacteria. Learners are also introduced to monoclonal antibodies, one important aspect of biotechnology. Monoclonal antibodies are the result of observation and
experiment, which is a key concept.
Outline
An understanding is gained of what is meant by disease and what the differences are between infectious and non-infectious diseases. Learners are provided with
examples of non-infectious disease by learning more about sickle cell anaemia and considering how tobacco smoking affects the gas exchange and cardiovascular
systems. Five infectious diseases of global importance are studied in some detail: cause; transmission; prevention and control, including the use of antibiotics. The unit
continues with a consideration of the factors that influence the global patters of TB, malaria and HIV/AIDS. Smallpox is introduced as an infectious disease so that
learners can appreciate how vaccination programmes have helped to eradicate the disease. Penicillin is studied as an example of an antibiotic and learners then
progress to study antibiotic resistance and consider the steps taken to alleviate this problem. There are good opportunities within this unit for learners to develop their
skills in data analysis, particularly with respect to disease statistics. Natural and artificial immunity is studied, including the structure and function of antibodies. Learners
will be provided with more detail about phagocytes and the way in which they function to protect against disease. The events occurring during a specific immune
response are covered. A brief consideration is given to the outcome to the body when the immune system fails to work correctly, using myasthenia gravis as an
example. An account of the production of monoclonal antibodies and how they are used in the diagnosis of disease and treatment of disease is included. The unit
concludes with a study of vaccination and a comparison of the effectiveness of vaccination programmes in the prevention and control of the infectious diseases studied.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
66
Learning objectives
Suggested teaching activities
Learning resources
10.1.a
define the term disease and explain
the difference between an infectious
disease and non-infectious disease
(limited to sickle cell anaemia and lung
cancer)
Ask learners for their ideas for the definition of disease (see examples below).
o An abnormal condition affecting an organism, which reduces the effectiveness of
its function.
o An absence of one or more of physical, social and mental well-being. (W)
(Basic)
Learners name common infectious diseases and suggest the type of causative
organism, the pathogen (use both terms).
o Add examples to cover bacteria, viruses and fungi.
o Introduce protoctists as pathogens (causative pathogen of malaria) using simple
ideas (e.g. eukaryotes, many are unicellular, organisms not fitting into other
groups / kingdoms). (W) (Basic)
Learners give examples of non-infectious diseases.
o Ensure they include diseases of the gas exchange system (linked with tobacco
smoking) and sickle cell anaemia.
o Discuss the cause of sickle cell anaemia (see 6.2.c), Unit 3)). (W) (Basic)
Learners explain why lung cancer and sickle cell anaemia are not considered to be
infectious diseases.
Learners summarise discussions in a comparison table or in comparative sentences.
(I) (Basic)
Extension: learners research the term pathogen, e.g. ‘a biological agent (e.g. a virus,
bacterium, fungus or protoctist) that causes disease and has proteins (foreign/nonself antigens) as part of its structure that are different from those of the human host’.
Online
http://edis.ifas.ufl.edu/in722
Key concepts
Cells as the units of life,
Biochemical processes,
Natural selection
Textbooks/Publications
Bio Factsheet 40: Disease and
defence
Past Papers
Paper 21, Nov 2011, Q4 (b)
Paper 22, Nov 2011, Q2 (b)(i)
Note
‘Germs’ as an alternative to ‘pathogens’ is not acceptable.
A common error is to use the term disease rather than pathogen, e.g. “the disease
enters cells” or to name the disease instead of the pathogen e.g. “malaria enters red
blood cells”.
9.2.a
describe the effects of tar and
carcinogens in tobacco smoke on the
gas exchange system with reference to
lung cancer and chronic obstructive
pulmonary disease (COPD)
Key concepts
Cells as the units of life,
v2.1 5Y02
In a question and answer session, learners explain why chronic bronchitis and
emphysema are also non-infectious diseases (in addition to lung cancer). (W)
(Basic)
Check learner knowledge of the terms carcinogen and carcinogenic. (W) (Basic)
Learners volunteer examples before projecting/showing the long list of carcinogens
in tobacco smoke. (W) (Basic)
o Explain that lung cancer may happen naturally, but the risk is increased by a
range of different environmental factors, identifying tar as a main causative
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.lung.ca/diseasesmaladies/index_e.php
http://library.med.utah.edu/WebPath/L
UNGHTML/LUNGIDX.html
http://www.ash.org.uk/information/facts
-and-stats
http://www.insidecancer.org/
http://www.cancer.org/cancer/cancerca
67
Learning objectives
DNA, the molecule of heredity,
Observation and experiment
Suggested teaching activities
agent. (W) (Basic)
Relate back to Unit 3 and ask learners to write out an outline sequence of
consequential events leading to a tumour and the development of cancer. (W) (I)
(Basic)
Discuss the imprecision in the statement: “Cigarettes cause lung cancer” and ask
learners to suggest improvements, e.g. “There is a correlation between tobacco
smoking and the development of lung cancer”, “Tar in tobacco smoke is known to be
a cause of lung cancer”. (W) (Challenging)
Learners investigate how carcinogens can promote the mutation of two important
types of genes involved in the control of cell division, proto-oncogenes (form
oncogenes, associated with the development of cancer) and tumour suppressor
genes (may mutate so that they can no longer act as a control). (W) (I) (H)
(Challenging)
Name chronic bronchitis and emphysema as the two diseases of COPD. (W)
(Basic)
o For each, learners make short notes summarising the changes that occur in the
gas exchange system that lead to the symptoms of disease. (I) (Challenging)
Extension: learners use data from the WHO website to practise data handling and
investigate the occurrence of deaths from cancers. (P) (I) (Basic) (Challenging)
Learners collect, display and analyse data about a smoking-related disease of the
gas exchange system and give a short presentation to the class. (W) (H)
(Challenging)
Learning resources
uses/geneticsandcancer/oncogenesa
ndtumorsuppressorgenes/oncogenes
-tumor-suppressor-genes-andcancer-mutations-and-cancer
http://www.who.int/en/
http://www.sanger.ac.uk/genetics/CGP
/Census/
http://info.cancerresearchuk.org/cancer
stats/causes/genes/cancergenes/inde
x.htm
http://www.parliament.the-stationeryoffice.co.uk/pa/cm199900/cmselect/c
mhealth/27/9120907.htm
Textbooks/Publications
Bio Factsheet 104: Biological basis of
cancer.
Past Papers
Paper 22, Nov 2011, Q1 (c)(d)(e)
Note
Explain the difference between a mutagen (an agent that increases the mutation rate
of DNA) and a carcinogen (an agent that can cause cancer).
To help make links to changes that occur in the gas exchange system, learners will
benefit from an outline of the signs and symptoms that the diseases share in
common and those that are characteristic for each disease.
9.2.b
describe the short-term effects of
nicotine and carbon monoxide on the
cardiovascular system
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Explain what is meant by the term cardiovascular. (W) (Basic)
Introduce carbon monoxide and nicotine as two components of smoke that can
easily pass across the alveolar wall to the bloodstream.
o Discuss how the presence of these components can cause short-term effects,
which may lead to other short-term effects (consequential outcomes) and to
long-term effects. (W) (Basic)
Explain the affinity of haemoglobin to carbon monoxide (links to Unit 4) and the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.ash.org.uk/files/documents/
ASH_111.pdf
http://www.bhf.org.uk/
http://library.med.utah.edu/WebPath/A
THHTML/ATHIDX.html
http://library.med.utah.edu/WebPath/C
VHTML/CV005.html
68
Learning objectives
Suggested teaching activities
permanency of this association. (W) (Basic)
o Learners discuss the consequences of this with respect to: uptake of oxygen;
delivery to tissues (especially the extremities); effect on heart rate. (W) (G)
(Basic)
State that carbon monoxide can also cause damage to the endothelial lining, which
is a starting point for vascular disease (atheroma/atherosclerosis). (W) (Basic)
Learners make bullet-point notes about the effects of carbon monoxide. (F)
Learners research the short-term effects of nicotine and produce a concept map or
spider diagram (with links to consequential effects).
o Examples: damage to endothelial lining, which can cause turbulent blood flow
and increase risk of clotting (thrombosis); increase in blood pressure owing to
release of adrenaline (can also damage the endothelial lining); making platelets
‘sticky’(increasing platelet aggregation), so increasing thrombosis risk; increased
heart rate; vasoconstriction, which can reduce blood flow to extremities; increase
in LDLs (low-density lipoprotein). The summary could be in the form of a concept
map/spider diagram. (P) (I) (Challenging)
Extension: learners research how the short-term effects can lead to longer term
effects (e.g. atheroma and atherosclerosis, peripheral arterial disease). (H)
(Challenging)
Learning resources
Textbooks/Publications
Bio Factsheet 218: Biology of risk
factors 1: Smoking
Bio Factsheet 37: Ischaemic
(coronary) heart disease (for
extension work)
Past Papers
Paper 22, June 2011, Q6
Paper 22, Nov 2013, Q6 (b)
Note
The addictive effects of nicotine are not related to the cardiovascular system, so are
not required.
10.1.b
state the name and type of causative
organism (pathogen) of each of the
following diseases: cholera, malaria,
tuberculosis (TB), HIV/AIDS, smallpox
and measles (detailed knowledge of
structure is not required. For smallpox
(Variola) and measles (Morbillivirus)
only the name of genus is needed)
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Explain the convention for naming the organisms: upper case (capital) letter for the
first letter of the generic name, lower case letter for the specific epithet. (W) (Basic)
You may wish to concentrate on one disease and work through 10.1.b to 10.1.e
before moving onto the next disease. Alternatively two to four learners work together
(lesson and homework), to research information about one disease and prepare a
presentation for the class, sharing notes. (G) (H) (Challenging)
o Learners then make learning notes on each of the five diseases. (I) (H) (Basic)
Learners research the required information and complete the first two columns of a
large summary headed table. (I) (H) (Basic)
Learners carry out a mix and match card exercise (prepared by you) with the name
of disease, type of causative organism/pathogen, name of causative organism /
pathogen. (F)
Online
http://textbookofbacteriology.net/tuberc
ulosis.html
http://textbookofbacteriology.net/choler
a.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM018.html
Past Papers
Paper 22, Nov 2012, Q4 (a)
Note
Cambridge International AS & A Level Biology (9700) – from 2016
69
Learning objectives
Suggested teaching activities
Learning resources
In their own handwriting learners should underline the species name, in print they
are in italics.
A brief discussion of the term species will help understanding (defined in Unit 6).
Learners should spell species names correctly.
For malaria, parasite will be seen in addition to pathogen.
10.1.c
explain how cholera, measles, malaria,
TB and HIV/AIDS are transmitted
Key concepts
Cells as the units of life,
Organisms in their environment
See 10.1.b for group work.
Discuss what is meant by a transmission cycle, noting that the causative organism is
transmitted when a disease spreads.
o Learners suggest reasons for some diseases spreading more rapidly than
others.
o Summarise on a poster learner suggestions as to main modes of transmission.
o Learners assign a mode of transmission to each named disease and write a
paragraph for each. (W) (Basic)
Learners add key points to their summary table. (I) (Challenging)
Online
http://www.who.int/en/
http://www.who.int/research/en/
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=36
Note
Ensure learners know the difference between the causative organism of malaria, the
protoctist Plasmodium, and the mosquito vector, Anopheles.
10.1.d
discuss the biological, social and
economic factors that need to be
considered in the prevention and
control of cholera, measles, malaria,
TB and HIV/AIDS (a detailed study of
the life cycle of the malarial parasite is
not required)
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
v2.1 5Y02
See 10.1.b for group work.
Begin with a general discussion, learners suggesting what is meant by ‘social’
factors (relating to human society and interdependence - the idea of benefit to all as
a result of cooperation).
o Discuss the distinction between prevention and control. (W) (Basic)
Learners study information (provided by you), including statistics, about a recent
outbreak of one of the named diseases. (G) (Basic)
o Discuss the availability of vaccines and treatments (including drugs) for the
disease. (W) (Basic)
Outline what antibiotics are and when they are useful in the treatment of disease.
(W) (Basic)
Learners use information sheets to suggest ways of breaking the transmission cycle
for each disease, and the difficulties in making this happen.
o Learners consider biological, social and economic factors in relation to
prevention and control. (G) (P) (Challenging)
Learners research where these diseases are currently prevalent and how this affects
people in different parts of the world. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.who.int/en/
http://www.who.int/research/en/
http://www.cdc.gov/
Past Papers
Paper 23, Nov 2011, Q4
70
Learning objectives
Suggested teaching activities
Learning resources
Note
Learners should be aware that antibiotics can be antifungal.
10.1.e
discuss the factors that influence the
global patterns of distribution of
malaria, TB and HIV/AIDS and assess
the importance of these diseases
worldwide
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
See 10.1.b for group work.
From 10.1.d, learners give reasons why some countries are better able to prevent
and control a particular disease. (I) (Basic)
Learners choose one of the named diseases to research and produce a short report.
(H) (Challenging)
o Learners contribute from their report to a group discussion. (W) (Basic)
o Point out how there is often a correlation in disease pattern, e.g. high incidence
of TB in people with HIV/AIDS. (W) (Basic)
o Learners make summary learning notes on each disease. (I) (Basic)
Learners fill in details on a partially completed table summarising all the main points
for 10.1.b to 10.1.e (see Note). (F)
Online
http://www.cdc.gov/malaria/malaria_wo
rldwide/impact.html
http://www.ncbi.nlm.nih.gov/pubmed/2
1728152
http://www.who.int/hiv/mediacentre/ne
ws60/en/
Note
Display world maps showing the areas most affected by each disease.
10.2.a
outline how penicillin acts on bacteria
and why antibiotics do not affect
viruses
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Outline the difference between bacteriostatic and bactericidal antibiotics. (W)
(Basic)
Explain that the penicillin group of antibiotics are also known as beta lactams
(describes their structure). (W) (Basic)
Review learner knowledge of bacterial cell wall structure and use a question and
answer session to build up the action of penicillin.
o Explain that transpeptidase enzymes (glycoprotein peptidases) catalyse
formation of peptide cross links between peptidoglycan chains, which complete
the strength of the cell wall.
o Prompt learners to recall knowledge of enzyme inhibition before they suggest
how penicillin acts to inhibit transpeptidases.
o Learners suggest why penicillin is only active against growing bacteria that are
laying down new cell wall components. (W) (Challenging)
Display key terms and key points for learners to write a summary of the discussion.
(F)
Extension: learners research the other main ways in which antibiotics act and
explain why penicillin and other antibiotics do not harm human cells. (I)
(Challenging)
Microbiology practical: learners place filter paper discs impregnated with different
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.cellsalive.com/pen.htm
http://www.biology.ed.ac.uk/research/g
roups/jdeacon/microbes/penicill.htm
http://pathmicro.med.sc.edu/fox/antibio
tics1.htm
http://textbookofbacteriology.net/antimi
crobial.html
Textbooks/Publications
King p.172-173
Siddiqui p.52
Past Papers
Paper 22, June 2013, Q3 (b)
71
Learning objectives
Suggested teaching activities
Learning resources
antibiotics (e.g. Mast rings), or different concentrations of the same antibiotic, onto a
Petri dish with nutrient agar inoculated with non-hazardous bacteria (e.g. Bacillus
subtilis).
o Learners measure zones of inhibition created around the discs on the lawn of
bacteria and compare to determine the efficacy of each antibiotic (or antibiotic
concentration). (P) (I) (Challenging)
Learners write a paragraph explaining why antibiotics do not affect viruses (see Unit
2, viral structure), extending this to use HIV as an example. (I) (Challenging)
o Remind learners that there are anti-viral drugs effective against HIV. (W) (Basic)
10.2.b
explain in outline how bacteria become
resistant to antibiotics with reference to
mutation and selection
Key concepts
DNA, the molecule of heredity,
Natural selection,
Organisms in their environment
10.2.c
discuss the consequences of antibiotic
resistance and the steps that can be
taken to reduce its impact
v2.1 5Y02
Learners suggest changes in bacteria that could lead to the ‘inactivation’ of penicillin.
(W) (Challenging)
o Ensure the discussion covers: mutations in genes lead to new proteins; the new
protein can be an enzyme; the enzyme can breakdown penicillin; hence
antibiotic resistance.
o Introduce beta lactamase (formerly penicillinase) as the enzyme.
o Mention that plasmids often carry genes for antibiotic resistance.
Learners suggest how new proteins could act in other ways to provide resistance,
e.g. membrane proteins pumping out antibiotics (efflux pumps) or inactivating them.
(W) (Challenging)
Learners recall why it is important to complete a course of antibiotics in the
treatment of TB.
o Discuss how the presence of antibiotic acts as a selection pressure, so resistant
bacteria (with a mutation) are selected for, and those that are killed are selected
against.
o Explain the different ways (vertical and horizontal transmission) that resistance
can be passed. (W) (Challenging)
Learners write a summary of the discussions. (F)
Online
http://www.hpa.org.uk/Topics/Infectiou
sDiseases/InfectionsAZ/Antimicrobial
Resistance/
http://www.tufts.edu/med/apua/index.s
html
http://www.antibioticresistance.org.uk/
http://www.s-cool.co.uk/alevel/biology/evolution/reviseit/evolution-in-action
http://textbookofbacteriology.net/resant
imicrobial.html
Textbooks/Publications
Bio Factsheet 100: Antibiotics and
antibiotic resistance
Bio Factsheet 71: The control of
bacteria.
Note
Two common errors: stating that resistance to the antibiotic develops in people, not
in bacteria; confusing resistance with immunity.
Past Papers
Paper 22, June 2011, Q4 (c)(d)
Learners cover this learning objective by researching a chosen bacterium that shows
multiple drug resistance and present their findings to the rest of the group.
o Points to consider in reducing impact: dosage; length of treatment; use of narrow
spectrum antibiotics; identify correctly the causative organism; hygiene and
aseptic conditions in areas such as hospitals; measures to reduce the impact of
Online
http://www.bbsrc.ac.uk/web/FILES/Pub
lications/bioscience_behind_superbu
gs.pdf
Cambridge International AS & A Level Biology (9700) – from 2016
72
Learning objectives
Key concepts
Natural selection,
Organisms in their environment,
Observation and experiment
11.1.d
explain the meaning of the term
immune response, making reference to
the terms antigen, self and non-self
Key concepts
Cells as the units of life
11.1.a
state that phagocytes (macrophages
and neutrophils) have their origin in
bone marrow and describe their mode
of action
Key concepts
Cells as the units of life
v2.1 5Y02
Suggested teaching activities
Learning resources
antibiotic therapy with farm animals. (W) (I) (H) (Challenging)
Learners suggest mechanisms considered as ‘first line of defence’ (e.g. skin,
stomach acid).
o Explain that the next defence will be responses to invasion of body tissue.
o Discuss how the body can distinguish between non-self and self and recall
previous work on antigens. (W) (Basic)
Learners write a definition of antigen, referring to self and non-self, the production of
specific antibody to form an antigen-antibody complex and including examples (e.g.
a molecule on the outside of a bacterium, virus, parasite, allergen or tumour cell). (I)
(Basic)
Discuss the meaning of immune response (a complex series of reactions of the
body, involving white blood cells, to a non-self antigen) before learners make notes.
(W) (I) (Challenging)
o Ensure learners understand that the non-specific (innate) response involves
phagocytes and the specific (adaptive) response involves lymphocytes, and that
the responses interact.
o Explain that the reactions result in destruction of the foreign invader and prepare
the body for a faster response to a second invasion (so the person will have few
or no symptoms).
Past Papers
Paper 21, Nov 2011, Q6 (c)
Remind learners that all blood cells have their origin in the bone marrow (Unit 3,
5.1.c): stem cells) and that some mature elsewhere in the body.
o Learners recall that monocytes mature into macrophages, which are phagocytes
(see Note 8.1.d, Unit 4). (W) (Basic)
Learners draw annotated labelled diagrams of a neutrophil, a monocyte, and a
macrophage (arrow pointing from monocyte). Learners include a label to (Fc)
receptors that can bind to antibodies. (I) (Basic)
Explain that phagocytes can respond to isolated pathogens or to antibodies bound
to antigens of pathogens. (W) (Basic)
Learners sequence and label diagrams (provided by you) showing events occurring
during phagocytosis, recalling studies on endocytosis, the role of receptors and
function of lysosomes.
o Learners should know the term antigen presenting cell (APC). (I) (Basic)
CD-ROM
Bioscope – has relevant images.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://education.vetmed.vt.edu/Curricul
um/VM8054/Labs/Lab6/Lab6.htm
http://micro.magnet.fsu.edu/index.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM001.html
http://library.med.utah.edu/WebPath/HI
STHTML/EM/EM002.html
http://highered.mcgrawhill.com/sites/0072507470/student_vi
73
Learning objectives
Suggested teaching activities
(Challenging)
Learners match cards of descriptive text (provided by you) to diagrams of stages. (F)
Learners compare and contrast phagocytes and lymphocytes on microscope slides.
(I) (Basic)
Learning resources
ew0/chapter3/animation__phagocyto
sis.html
Textbooks/Publications
King p.164-165
Siddiqui p.181-182
Past Papers
Paper 21, Nov 2011, Q6
Paper 22, Nov 2011, Q2 (a)
11.1.b
describe the modes of action of Blymphocytes and T-lymphocytes
Key concepts
Cells as the units of life
v2.1 5Y02
Discuss how the non-specific response of phagocytes to infection differs from the
specific response of B-lymphocytes and T-lymphocytes, which each have different
modes of action. (W) (Basic)
Using a step-by-step teacher-prompted approach or by individual research, learners
draw an annotated flow diagram to show how specific B-lymphocytes respond
(humoral response):
o Recognition and binding of specific antigen.
o Activation/sensitisation followed by clonal expansion (mitotic division).
o Differentiation to produce (i) plasma cells that make antibodies in a primary
immune response and (ii) memory cells (see 11.1.e).
o There are important interactions with the T-lymphocytes response. (I)
(Challenging)
Discuss the similarity of the T-lymphocyte response (cell-mediated immunity) to the
humoral response, before outlining other key points.
o T-helper cells activation produces a clone of cells that release cytokines, which
stimulate and strengthen both the humoral response and macrophage response.
o T-killer (cytotoxic) cells activation produces a clone of cells that can directly kill,
for example, infected cells.
o Both types produce memory cells. (W) (Basic)
Learners choose to show the information in a flow diagram or with written notes. (I)
(Challenging)
Distinguish between receptors of B-lymphocytes and T-lymphocytes that bind nonself antigen: for B-lymphocytes the receptor is immunoglobulin (slightly different to a
secreted antibody); the T-receptor recognises antigens displayed on the surface of
APCs (see T-helper cells) or infected or foreign cells (see T-killer cells). (W)
(Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/B/B_and_Tcells.html
http://www.merckmanuals.com/home/i
mmune_disorders/biology_of_the_im
mune_system/acquired_immunity.ht
ml?qt=immune%20response&alt=sh
http://www.accessexcellence.org/AB/G
G/antibodies.html
http://www.cellsalive.com/antibody.htm
http://library.med.utah.edu/WebPath/H
EMEHTML/HEMEIDX.html
http://www.bu.edu/histology/p/21001oo
a.htm
Past Papers
Paper 23, Nov 2013, Q.1 (b)
Paper 21, Nov 2011, Q6 (c)
74
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners research the effect of active HIV in human T-lymphocytes (also
attacks phagocytes) and see the consequences of a reduction in numbers of white
blood cells (helps to explain why people with HIV/AIDS are prone to opportunistic
infections). (I) (Challenging)
Note
Refer to humoral and cell-mediated responses (not required knowledge) as learners
will see these terms in resources used.
11.1.e can be incorporated into this learning objective.
11.1.e
explain the role of memory cells in
long-term immunity
Key concepts
Cells as the units of life
Discuss why the presence of memory cells means that a secondary immune
response will be faster and stronger than a primary response. (W) (Basic)
Learners suggest meanings for the term immunity and write out an agreed
explanation of immunity and long-term immunity.
Learners could draw and annotate a sketch graph showing antibody concentrations
against time during an immune response. (I) (Basic)
o Learners reproduce this graph at a later date, with more detailed annotations. (F)
Online
http://www.biology.arizona.edu/immun
ology/tutorials/immunology/09t.html
Note
Encourage use of scientific terminology and explanations: phrases such as
‘remembers the disease’ and ‘fights the disease’ are unacceptable.
11.1.c
describe and explain the significance
of the increase in white blood cell
count in humans with infectious
diseases and leukaemias
Provide learners with information about leukaemias. Learners write an account
explaining the difference between an increase in white blood cell count
accompanying infectious diseases with that of leukaemias. (F)
Learners explain why people with leukaemia are susceptible to infections. (I) (Basic)
Extension: learners research the difference between acute and chronic leukaemias.
(H) (Challenging)
Key concepts
Cells as the units of life
11.1.f
explain, with reference to myasthenia
gravis, that the immune system
sometimes fails to distinguish between
self and non-self
Online
http://www.lls.org/diseaseinformation/
managingyourcancer/newlydiagnose
d/understandingdiagnosis/labimaging
tests/bloodtests/bloodcounts/
Textbooks/Publications
Siddiqui p.182-183
Use myasthenia gravis as an example to explain what is meant by autoimmune
disease, provide learners with a straightforward information sheet from which they
can make their own bullet-pointed notes. (I) (Basic)
Extension: learners research other auto immune diseases to highlight the range of
immune dysfunctions that can exist. (H)
Online
http://www.nlm.nih.gov/medlineplus/en
cy/article/000816.htm
https://www.mgacharity.org/information-mg
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
75
Learning objectives
Suggested teaching activities
Learning resources
Revise protein structure with a short written test. (F)
Discuss the basic structure of an immunoglobulin (e.g. IgG) and how these
molecules interact with antigens. (W) (Basic)
Explain that the variable regions in different antibodies have different sequences of
amino acids and ask for suggestions as to how this related to the specificity of
antibodies. (W) (Basic)
Learners use, for example, a ribbon diagram of IgG to explain how primary,
secondary, tertiary and quaternary structures of proteins are shown. (P) (I)
(Challenging)
Learners draw a labelled, annotated diagram linking the structure of an antibody to
its function, reproducing this diagram at a later stage. (I) (F) (Challenging)
Online
http://www.accessexcellence.org/RC/V
L/GG/ecb/antibody_molecule.php
http://www.biology.arizona.edu/immun
ology/tutorials/antibody/structure.html
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/AntigenReceptors.
html
Cells as the units of life
11.2.a
relate the molecular structure of
antibodies to their functions (see 2.3.b)
Key concepts
Biochemical processes
Past Papers
Paper 21, June 2013, Q2
Paper 23, Nov 2013, Q1
Note
Learners may be interested to know that antibodies are glycoproteins.
Mention the different antibody classes and refer to the term antitoxins (not required
learning) for interest.
There is potential confusion between antibodies and antibiotics – apply error-free
learning.
11.2.b
outline the hybridoma method for the
production of monoclonal antibodies
Key concepts
DNA, the molecule of heredity,
Observation and experiment
Learners review antigens, antibodies, specificity, B-lymphocytes, plasma cells and
cancer cells with a brainstorming session. (W) (Basic) (Challenging)
With guidance, learners work through the hybridoma method and produce either a
summary flow diagram, set of notes, or completed table. Learners highlight the main
stages of the process and the steps that occur within each stage are described and
explained. (I) (Challenging)
Ask learners to state the desirable features which are contributed by each cell that
become incorporated into the hybridoma cell (this contains the genetic material of
both cells). (W) (Basic)
Learners describe the distinction between the hybridoma cell and the monoclonal
antibody (see Note). (W) (Challenging)
Learners could make a list of all the cells involved in the production and state the
role of each. (I) (Basic)
Discuss why there has been a move to produce humanised antibody rather than
mouse antibody. (W) (Challenging)
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/M/Monoclonals.html
http://www.bio.davidson.edu/Courses/
molbio/MolLearners/01rakarnik/mab.
html
http://www.nap.edu/openbook.php?rec
ord_id=9450&page=8
Past papers
Paper 41, June 2012, Q2
Note
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
76
Learning objectives
Suggested teaching activities
Learning resources
Ensure learners understand that:
o a clone (group of genetically identical cells formed from one original ‘ancestor’
cell) of hybridoma cells produces one type of specific antibody, monoclonal
antibody;
o the ‘ancestor’ cell forms from the fusion of a specific plasma cell (B-lymphocyte)
and a myeloma cell.
In this rapidly-developing area of biotechnology, learners need to apply biological
principles and concepts to new situations.
11.2.c
outline the use of monoclonal
antibodies in the diagnosis of disease
and in the treatment of disease
Key concepts
Observation and experiment
Explain that a sample of fluid taken from a person with an infectious disease could
contain both pathogen (with non-self antigens) and specific antibody. (W) (Basic)
Learners study a set of diagrams showing the steps occurring in a direct enzymelinked immunosorbent test (ELISA) and answer a set of questions that require
application of the principles of immune response and knowledge of monoclonal
antibody. (I) (Challenging)
o Extension: learners describe what is occurring in an indirect ELISA test for the
presence of circulating specific antibody. (I) (Challenging)
Learners research one example of the use of monoclonal antibody in the treatment
of disease and present their findings to the class. (H) (W) (Basic) (Challenging)
Note
Learners do not need to know the term ELISA or the details of the test.
Online
http://www.mayoclinic.com/health/mon
oclonalantibody/CA00082
http://www.hhmi.org/biointeractive/imm
unology/vlab.html.
http://web.archive.org/web/200803290
02645/http://www.molecular-plantbiotechnology.info/hybridoma-andmonoclonal-antibodies-mabs/uses-ofmonoclonal-antibodies.htm
http://www.sumanasinc.com/webconte
nt/animations/content/pregtest.html
Textbooks/Publications
Bio Factsheet 112: Monoclonal
antibodies
Bio Factsheet 219: Monoclonal
antibodies: An update
Past papers
Paper 41, June 2012, Q2 (b)(c)
11.2.d
distinguish between active and
passive, natural and artificial immunity
and explain how vaccination can
control disease
v2.1 5Y02
Discuss the principles behind passive immunity before learners produce an account
explaining why (i) passive immunity is immediate but short-lived and active immunity
is delayed but longer-term, and (ii) passive immunity does not produce memory
cells whereas active immunity does. (W) (I) (Basic) (Challenging)
Learners draw an annotated version of the immune response curve to show how
vaccines act to give immunity. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.spmsd.co.uk/cat.asp?catid=
9
http://www.polioeradication.org/
http://www.who.int/features/factfiles/pol
io/en/
77
Learning objectives
Suggested teaching activities
Learning resources
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
Learners construct a summary chart, leaving enough room to add features and
examples to show the differences between the categories, or, the chart of immunity
is divided into active and passive, each divided into natural and artificial. (I) (Basic)
Immunity
Natural
Active
Passive
Artificial
Active
Textbooks/Publications
Bio Factsheet 99: Vaccines
Bio Factsheet 71: The control of
bacteria.
Past Papers
Paper 21, June 2011, Q6
Passive
Discuss briefly how vaccination can provide immunity to avoid the spread of disease.
Include the term herd immunity. (W) (Basic)
Extension (highly relevant): learners access current information on the programme
to eradicate polio.
11.2.e
discuss the reasons why vaccination
programmes have eradicated
smallpox, but not measles,
tuberculosis (TB), malaria or cholera
Key concepts
Cells as the units of life,
Organisms in their environment
Discuss the features that contributed to the success of the smallpox vaccination
programme, which was considered the main factor in the eradication of the disease.
(W) (Basic)
o Learners contribute information about the progress of vaccination programmes
for the other diseases. (W) (Basic)
Working in groups of four, each member researches one of the four named
diseases, making comparisons with the smallpox vaccination programme.
o Provide a list of terms to be incorporated into the group study, e.g. antigenic
concealment, antigenic drift, boosters, long/short-term, etc. (G) (Challenging)
Online
http://www.who.int/features/2010/small
pox/en/
http://en.wikipedia.org/wiki/Ali_Maow_
Maalin
http://www.who.int/topics/vaccines/en/
http://www.s-cool.co.uk/alevel/biology/immunity/reviseit/problems-with-vaccines
http://www.who.int/immunization/en/
http://www.iavi.org/Pages/default.aspx
Past Papers
Paper 22, Nov 2011, Q2 (b)(ii)(iii)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
78
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 6: The diversity of life
Recommended prior knowledge
Learners should have a good understanding of the difference between plant and animal cells and of the difference between prokaryotes and eukaryotes from Unit 2.
Also from Unit 2, learners should know the basic structure of viruses. They should also be familiar with ecological concepts, such as: the meaning of the terms
population and community; the flow of energy through the different trophic levels of the ecosystem; and interactions between organisms.
Context
This unit, above all the others, belongs to the learner. This is their opportunity to get to know the local environment, with opportunities for fieldwork and for research into
local conservation issues and local conservation projects, allowing a practical application of the key concepts of organisms in their environment and of observation and
experiment. Stimulating an interest in biodiversity will lead appropriately to the next unit, Unit 7, Genetics, population genetics and evolutionary processes.
Outline
The unit begins with a discussion of the meaning of the terms species, ecosystem and niche so that learners will have a good grounding for later ecological studies,
and then continues with a more detailed study of classification and taxonomy. Biodiversity is considered at three different levels, and species biodiversity is further
explored by fieldwork opportunities in a local area. Spearman’s rank correlation and Pearson’s linear correlation, together with Simpson’s diversity of index are
introduced as analytical tools for the data collected from fieldwork. The unit also covers the threats to the maintenance of biodiversity and discusses both issues
concerning conservation and practical ways to conserve endangered species and restore degraded habitats. One aspect of the key concept of organisms in their
environment is how humans can interact with their environment in ways that can have a great impact on ecosystems. Here, consideration is given to the part humans
may play in the extinction of species.
Teaching time
It is recommended that this unit should take approximately 6% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
79
Learning objectives
Suggested teaching activities
Learning resources
18.1.a
define the terms species, ecosystem
and niche
Carry out a brainstorming exercise to indicate how much learners can recall of each
term. (W) (Basic)
Discuss the species concept (and difficulties in defining the term – there are over 20
definitions) before learners make notes.
o Expand ideas of: reproductively isolated; production of fertile offspring; members
have the same (very similar) features in morphology, anatomy, physiology,
behaviour and biochemistry; occupy the same niche; defined by same (very
similar) DNA. (W) (I) (Basic)
Extension: learners explore difficulties in defining species in terms of fertile offspring
by researching examples, e.g. between plant species or between mammalian
species (polar bear and brown bear - rare; canid hybrids - common). (H)
(Challenging)
Extension: learners consider how the species concept works for asexually
reproducing organisms and for interspecific plasmid transfer between bacteria. (H)
(Challenging)
Learners write a definition of an ecosystem, incorporating the following ideas and the
same (or equivalent) terminology: (I) (Basic)
o a self-sustaining unit consisting of abiotic and biotic factors interacting together
o includes all organisms of all populations (in a given area)
o energy flows through and cycling of minerals occur.
Learners make notes on (ecological) niche, the functional role of a species, to
include: a description of its habitat; how it is adapted to its environment; interactions
with other organisms; features of its life-cycle. (I) (Basic)
Learners visit an ecosystem to place into context these terms and concepts,
describing in terms of: energy flow / trophic levels; interactions between organisms;
interactions between organisms and the physical environment. Examples of species
and of niche are described. (G) (P) (Basic) (Challenging)
Explain that an ecosystem can vary in size and could be temporary or permanent.
(W) (Basic)
Online
http://purchon.com/ecology/
http://www.ecologydictionary.org/
Key concepts
Natural selection,
Organisms in their environment
Textbooks/Publications
Bio Factsheet 131: Ecological niche
Past Papers
Paper 22, June 2011, Q2
Paper 41, June 2012, Q1 (a)
Note
A niche is often described in terms of an organism or a population.
A field trip should be considered before covering 18.1.c) to 18.1.f). If a trip is not
possible, visiting any suitable area populated by plants and animals, within or near to
school, will be a rewarding experience for learners.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
80
Learning objectives
Suggested teaching activities
Learning resources
18.2.a
describe the classification of species
into the taxonomic hierarchy of
domain, kingdom, phylum, class,
order, family, genus and species
Learners suggest a method to sort all the different organisms in the world and then
share ideas. (W) (G) (Basic)
Introduce the idea of sorting as ‘classification’ and agree that a hierarchical
approach is sensible.
o State that levels in the hierarchy are termed taxonomic ranks, with each example
of a rank known as a taxon (plural: taxa).
o Explain that the members of a group share common (homologous) features
based on phylogenetic / evolutionary patterns (more details in Unit 7). (W)
(Basic)
Display a ‘tree of life’ with the three domains and briefly outline the other taxonomic
ranks, asking for suggestions why the species taxon is considered to be the only
natural classification group.
o Outline the classification of humans, with learners contributing their ideas. (W)
(Basic)
Learners note down the taxonomic ranks listed and decide a good mnemonic to help
remember the hierarchical order. (P) (I) (Basic)
Extension: choose one or more organisms to classify from domain through to the
species, for example, organisms encountered during fieldwork. (H) (Basic)
(Challenging)
Extension: learners research classification systems based on analogous features. (I)
(Basic)
Online
http://www.microscopyuk.org.uk/mag/indexmag.html?http://
www.microscopyuk.org.uk/mag/artmay98/classif.html
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Class
ification/classification.htm
Learners complete a short written test (produced by you, with mark scheme) about
prokaryotes and eukaryotes. (F)
Explain that the Archaea and Bacteria are both prokaryotic but have quite different
features, reflecting their evolutionary history.
o State some features of the Archaea that contrast with Bacteria: e.g. different cell
wall structure, which can be quite varied (not murein); different types of
membrane lipids (not phospholipids); differences in tRNA and ribosomes.
o Discuss the specialised habitats of some members of the Archaea: high
temperatures, extreme saline, and anaerobic environments. (W) (Basic)
Learners use resources (textbooks, internet, etc.) to produce a list of the main
features of each domain. (I) (Basic)
Online
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Evolution/index.htm
http://www.ucmp.berkeley.edu/alllife/th
reedomains.html
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
18.2.b
outline the characteristic features of
the three domains Archaea, Bacteria
and Eukarya
Key concepts
Cells as the units of life,
DNA, the molecule of heredity,
Organisms in their environment
Textbooks/Publications
Bio Factsheet 91: Taxonomy and
classification.
Bio Factsheet 170: Answering Exam
Questions: Classification and Keys
Note
For this syllabus learners should use ‘Bacteria’ and not ‘Monera’.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
81
Learning objectives
Suggested teaching activities
Learning resources
18.2.c
outline the characteristic features of
the kingdoms Protoctista, Fungi,
Plantae and Animalia
Learners brainstorm the names of the kingdoms. Write down all ideas so any
incorrect can be put into context (i.e. see 18.2.a).
o Agree the kingdoms and discuss criteria used for classification into Fungi,
Animalia or Plantae kingdom, e.g. animals are eukaryotic, multicellular, feed as
heterotrophs. Point out that absent features also helps confirm the classification,
e.g. no cells with cell walls, don’t photosynthesise.
o Discuss the Protoctista as the kingdom that contains organisms that do not quite
fit into the other kingdoms.
o Learners make notes using resources. (W) (Basic)
Learners make up an imaginary ‘named’ organism and produce a sticky note or label
with enough of a description for it to be classified into a kingdom. The notes could be
stuck around the class for a class activity, learners revealing their answers at the
end of the activity. (W) (I) (Basic) (Challenging).
Online
http://www.ucmp.berkeley.edu/plants/p
lantae.html
Key concepts
Cells as the units of life,
DNA, the molecule of heredity,
Organisms in their environment
18.2.d
explain why viruses are not included in
the three domain classification and
outline how they are classified, limited
to type of nucleic acid (RNA or DNA)
and whether these are single stranded
or double stranded
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
18.1.b
explain that biodiversity is considered
at three different levels:
variation in ecosystems or habitats
the number of species and their
relative abundance
genetic variation within each
species
Key concepts
v2.1 5Y02
Textbooks/Publications
Bio Factsheet 91: Taxonomy and
classification
Bio Factsheet 170: Answering Exam
Questions: Classification and Keys
Past Papers
Paper 43, June 2011, Q1 (c)
Paper 43, Nov 2011, Q1 (c)
Paper 41, Nov 2012, Q11 (a)
Check learner knowledge of the main features of viruses (1.2.f) with a question and
answer session.
o Add more information about the genetic material: either single or doublestranded RNA or single or double-stranded DNA, but never both RNA and DNA.
o Learners produce a generalised diagram that is annotated. (W) (I) (Basic)
Learners suggest why viruses are not included in the three domain classification.
o Remind learners of the Unit 2 discussion (viruses do not fit the key concept of
cells as the basic units of life) and see if they have any other points to contribute.
(W) (Basic)
Online
http://www.eoearth.org/view/article/51c
bef267896bb431f69cb9a/?topic=51cb
fc78f702fc2ba8129e70
http://www.johnkyrk.com/virus.html
A discussion about the term biodiversity will highlight that a simple definition may be
difficult. Introduce the idea of three different ‘levels’ of biodiversity, ecosystem,
species, and genetic. (W) (Challenging)
o Point out the transition from an ecological to a molecular biological approach.
o Explain that ecosystem biodiversity is more difficult to measure, as ecosystems
may merge at their ‘boundaries’ (so not easy to define) and vary greatly in size.
Explain that biodiversity can be considered at a local, national and global level. (W)
(Basic)
Give a definition of a habitat, for reference only, e.g. the particular location and type
of local environment occupied by a population or organism, characterised by its
Online
http://www.eoearth.org/topics/view/494
80/
http://www.bbsrc.ac.uk/web/FILES/Exh
ibitions/pod2-factsheet.pdf
http://www.geography.learnontheintern
et.co.uk/topics/ecosystem.html
http://wwf.panda.org/about_our_earth/
biodiversity/what_is_biodiversity/
http://www.iucn.org/iyb/about/?gclid=C
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 32: Viruses made
simple.
82
Learning objectives
DNA, the molecule of heredity,
Organisms in their environment
Suggested teaching activities
physical features or by its dominant producers. (W) (Basic)
Learners volunteer the different types of medium-scale (meso) ecosystems in their
region: e.g. wood/forest, lake/river, field, rocky shore (ecosystem biodiversity).
o To understand how biodiversity can be reduced, learners suggest an occurrence
for each ecosystem that would lead to its loss. (W) (Basic)
In groups, volunteer states a habitat within one of the named ecosystems, choosing
the next person to give another habitat and so on. (G) (Basic) (Challenging)
Reinforce, using examples, learner understanding of the differences between
ecosystem and habitat, e.g. the habitat of a catfish is a freshwater stream versus the
catfish is part of the freshwater ecosystem; removal of boulders from the stream bed
reduces the variety/number of different habitats in the ecosystem. (W) (Basic)
Learners consider species biodiversity within a community.
o Give a definition of community (reference only), e.g. all of the populations of all
of the different species within a specified area at a particular time.
o Explain, using examples, the difference between number of species (count of
how many species exist within a particular community), and relative abundance
of species (count how many members of each species there are - the population
size).
o Expand the discussion to consider species diversity on a global scale. (W)
(Challenging)
For genetic biodiversity, explain that a genome is the sum total of all the hereditary
information in an organism, and discuss how, although each species can be
identified by a characteristic genome, there will still be variation (link to Unit 7).
o Learners recall from Unit 3, the different nucleotide sequences for HbA (normal)
and HbS (sickle cell) alleles and their definition of a mutation (6.2.b).
o Explain that genetic biodiversity (variation) can be within a population or
between populations. (W) (Basic)
Learners summarise discussions with their own notes, using examples to help their
explanation. (F)
Extension: learners consider further examples of how ecosystem biodiversity can be
affected by different factors: trophic levels, food chains/webs and energy flow; the
cycling of nutrients; interactions. (H) (Challenging)
Learning resources
J7n2a2576QCFQsGbAodI3nz1A
Note
When tackling variation in ecosystems or habitats, reference to some of the issues in
18.3.a and 18.3.h will help for later studies.
18.1.c
v2.1 5Y02
Random sampling is best demonstrated by holding up one page from a large
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 11
83
Learning objectives
explain the importance of random
sampling in determining the
biodiversity of an area
Key concepts
Organisms in their environment,
Observation and experiment
Suggested teaching activities
newspaper that contains words of different sized fonts, images and blank areas.
o Explain that this simulates a field, which has no more than 26 species living
there, each species represented by a letter of the alphabet. (W) (Basic)
o Learners discuss a method to determine how many different species and how
many individuals of each species there are (and only 30 minutes to carry out the
task). (G) (Challenging)
o Discuss a suitable strategy, highlighting the importance of: having to sample;
taking a number of samples (the sample may be unrepresentative, e.g. a
photograph could represent a bare rock, so no individuals would be found);
choosing the correct size/area of each sample; random sampling (biased
sampling - any measurements can only apply to the sample, not to the whole
area). (W) (Basic)
Learning resources
Online
http://www.countrysideinfo.co.uk/howto
.htm
http://fua.field-studiescouncil.org/media/59629/how_to_carr
y_out_a_random_sample.pdf
Note
Learning objectives 18.1.c to 18.1.f are best understood, and could be carried out, in
the context of fieldwork. Practical booklet 11 may provide suitable protocols and
should be consulted first.
18.1.d
use suitable methods, such as frame
quadrats, line transects, belt transects
and mark-release-recapture, to assess
the distribution and abundance of
organisms in a local area
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
See Note for 18.1.c.
Learners use resources to note the difference between distribution and abundance.
(I) (Basic)
Discuss different techniques for estimating, e.g. counting numbers of each of the
different species within the quadrat; ‘by eye’ estimation of percentage of quadrat
covered by each particular plant species; using an abundance scale (e.g. ACFOR).
o Learners suggest what to do with their data in order to make calculations of
estimates of population size. (W) (Basic)
Discuss how quadrats of a known area can be used for random sampling and the
importance of: choosing the right size of frame quadrat (e.g. size of organisms, area
to cover; reducing edge effects); when to use a quadrat with a grid. (W) (Basic)
Explain line and belt transects for systematic sampling.
o Learners suggest advantages and disadvantages of belt versus line transects.
o Explain the difference between interrupted belt transects (quadrats placed at
regular intervals) or continuous belt transects (quadrats laid side by side). (W)
(Basic)
Learners consider different (theoretical) fieldwork tasks and choose whether frame
quadrats randomly placed, line transects, interrupted belt transects or continuous
belt transects would be most the appropriate, justifying their answers. (H) (F) (Basic)
(Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 11
Online
http://www.countrysideinfo.co.uk/howto
.htm
http://fua.field-studiescouncil.org/media/59629/how_to_carr
y_out_a_random_sample.pdf
http://fua.field-studiescouncil.org/teaching-equipment-andmethods.aspx
http://www.biologymad.com/resources/
RevisionM5Ch4.pdf
http://www.nuffieldfoundation.org/appli
ed-science/distribution-andabundance-species
Textbooks/Publications
King Chapter 11
Siddiqui, Chapter 7
84
Learning objectives
18.1.e
use Spearman’s rank correlation and
Pearson’s linear correlation to analyse
the relationships between the
distribution and abundance of species
and abiotic or biotic factors
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Suggested teaching activities
Learning resources
Discuss the concept behind the mark-release-recapture technique and situations
where mark-release-recapture would be appropriate. Show the formula to use:
number in the first sample x number in second sample
number marked in second sample
o Explain the problem if there is a low rate of recapture, e.g. 20 animals caught
and marked, 1 marked in 10 captured the second time, estimate of total number
=200/1 = 200, but 2 marked individuals recaptured makes the estimate only 100.
(W) (Basic)
o Learners practise this using a container of beans or beads. Remove a small
handful to be marked for the first sample, add them back to the container (shake
them up), remove a second sample for the ‘recapture’ (closed eyes) and record
results, obtaining the estimate using the formula. (P) (I) (Basic)
Learners obtain estimates of population size from several different sets of data using
the mark-release-recapture formula. (I) (Basic)
o Learners extract the required numerical data from paragraphs of prose to
estimate the population size (no formula provided). (F)
Learners make notes on the mark-release-recapture technique, annotating the
formula to use and explaining some of the assumptions made: marked animals
returned to the population mix randomly; the marking had no effect (e.g. non-toxic,
more visible to predators); the marking remained on individuals; equal chance of
capturing marked and unmarked individuals; no immigration or emigration during the
sampling. (I) (Challenging)
Learners carry out fieldwork, using each of the methods listed to assess the
distribution and abundance of organisms. (G) (P) (Basic) (Challenging)
Bio Factsheet 5: An idiot’s guide to
populations.
Bio Factsheet 68: Fieldwork
techniques
Bio Factsheet 184: Investigating sand
dunes.
See Note for 18.1.c.
Discuss instances in fieldwork where differences in species abundance or
distribution occurred (or provide examples). Explain that the next step is to find out if
these correlate with some factor, either biotic or abiotic (see 18.1.a).
o Explain the measure of association between two variables ranges from
completely negatively correlated, -1, to completely positively correlated, +1; the
closer to these values, the stronger the relationship.
o Explain that a statistical test cannot confirm a relationship between the two, but
can lends support to it. (W) (Basic)
Discuss situations when Pearson’s linear coefficient calculation is carried out: when
there is interval (quantitative) data that shows a linear relationship and a statistical
assessment of the strength of the correlation is required (e.g. data plotted on a
Practical booklet 11
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.statstutor.ac.uk/topics/corre
lation/pearsons-correlationcoefficient/
http://www.statstutor.ac.uk/topics/corre
lation/spearmans-correlationcoefficient/
http://www.heckgrammar.co.uk/index.p
hp?p=10310
85
Learning objectives
Suggested teaching activities
Learning resources
scattergraph; a ‘by-eye’ judgment of correlation is not always reliable). (W)
(Challenging)
o Learners work through an example, with guidance, starting with a null hypothesis
statement before using the formula to calculate the Pearson product moment
correlation. Learners use a table of critical values to reject or accept the null
hypothesis and make a statistically valid statement about the strength of the
correlation and its significance. (W) (I) (Basic) (Challenging)
Explain that if one variable increases and the other increases (or decreases) then
Spearman’s rank correlation can be carried out, even if the relationship is non-linear,
and that ordinal data can also be used with this test. (W) (Challenging)
o Work through examples with learners, as with Pearson’s test, and discuss how
to use Spearman’s table. (W) (I) (Basic) (Challenging)
Learners analyse relationships by practising a number of different examples using
either Spearman’s rank correlation or Pearson’s linear correlation.
o Learners then work with calculated values to analyse the data and make
judgements about the strength of the relationship. (I) (Basic) (Challenging)
Discuss how correlation does not imply causation, e.g. abundance of a plant species
appears to decrease with increasing altitude. Applying caution with cause and effect
would consider other factors that change with altitude (oxygen concentration,
temperature, soil nutrients etc.). (W) (Basic)
Textbooks/Publications
Bio Factsheet 144: Spearman’s rank
correlation coefficient.
Note
Learners should work through examples themselves before using other resources
available to them.
Learners could use spreadsheet software to enter the relevant figures and obtain a
scattergraph and the final calculated value, and then explain what the results are
showing. You could set up spreadsheets of data for learners to access (see learning
resources).
Practical booklet 11 includes the chi-squared test for association. This is another
use in addition to the ‘goodness of fit’ test (see 16.2.d).
18.1.f
use Simpson’s Index of Diversity (D) to
calculate the biodiversity of a habitat,
using the formula D = 1–(Σ(n/N)2) and
state the significance of different
values of D
v2.1 5Y02
See Note for 18.1.c.
Explain that Simpson’s Index of Diversity gives an overall measure of diversity by
taking into account the number of different species in a sample and the abundance
of each species.
o Explain that a high D value represents high biodiversity, indicating a high
number of species, evenly spread for abundance. The value of D goes down if
there are fewer species, or if, for example, one or a few species are very
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 11
Online
http://www.countrysideinfo.co.uk/simps
ons.htm
http://www.nuffieldfoundation.org/appli
ed-science/ecology-and-simpsons-
86
Learning objectives
Suggested teaching activities
Key concepts
Organisms in their environment,
Observation and experiment
abundant and others are very rare.
o Discuss how this can be used to compare biodiversity over time in any one area.
(W) (Basic)
Learners use their fieldwork data (or be given data) to calculate a biodiversity value
and state its significance. (I) (Challenging)
18.3.a
discuss the threats to the biodiversity
of aquatic and terrestrial ecosystems
(see 18.1 b)
Key concepts
Organisms in their environment,
Observation and experiment
To check understanding of the terms, learners give examples of specific local
terrestrial and aquatic ecosystems. (W) (Basic)
Discuss the global food and energy demands (from increasing population size,
developing nations and increasing industrialisation) that may affect ecosystems (also
to a lesser extent, demand for ‘living’ space). (W) (Basic)
o Learners consider these factors on a local basis, suggest ways to satisfy these
demands and consider the consequential effects of this action on one chosen
local terrestrial or aquatic ecosystem. (P) (Challenging)
o Point out that global effects, such as climate change and global warming can still
affect at a local level. (W) (Basic)
o Learners add their ideas to master sheets headed, ‘demand for food’, ‘demand
for energy’ and ‘demand for living space’ (each sheet divided vertically into
‘terrestrial ecosystems’ and ‘aquatic ecosystems’) and follow up with a class
discussion. It is highly likely that their ideas will reflect what is happening
globally. (W) (Basic)
Learners produce a general list, using local and global examples to help explain
each point. (H) (Challenging)
Note
The effect of introducing alien species into an ecosystem is also an important
feature, covered in 18.3.f (you may prefer to teach 18.3.f with 18.3.a).
17.3.e
explain why organisms become
extinct, with reference to climate
change, competition, habitat loss and
killing by humans
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
Discuss what is meant by extinction, pointing out that it is a natural process and part
of the theory of evolution by natural selection (see Unit 7).
o Explain that there is a threshold number below which extinction is inevitable.
o Learners suggest why species become extinct (check that those referenced in
17.3.e are covered). (W) (Basic)
Learners find examples (relevant to them) of plant and animal species that have
become extinct or are near extinction for the reasons listed in 17.3.e and produce
poster displays. (G) (P) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
diversity-index
Textbooks/Publications
Bio Factsheet 34: Species diversity
Online
http://evolution.berkeley.edu/evolibrary
/news/120301_chipmunks
http://www.wri.org/resources/maps
http://www.iucnredlist.org/initiatives/fre
shwater/panafrica/threats
http://www.biodiv.be/biodiversity/threat
s
http://environment.nationalgeographic.
co.uk/environment/
Textbooks/Publications
Bio Factsheet 27: Biological effect of
deforestation
Bio Factsheet 203: Climate change
and ecological decoupling
Bio Factsheet 197: Biology of coral
reef ecosystems
Past Papers
Paper 41, June 2011, Q8 (a)(b)
Online
http://www.bbc.co.uk/lastchancetosee/
sites/about/extinction.shtml
http://www.iucnredlist.org/
Past Papers
Paper 43, June 2011, Q1 (a)
87
Learning objectives
Suggested teaching activities
Learning resources
18.3.b
discuss the reasons for the need to
maintain biodiversity
Learners research the reasons to maintain biodiversity. (H) (Basic)
o In a follow-up discussion include the following ideas: maintenance of gene pools;
preservation of genetic diversity; applications of the use of gene technology (see
Unit 8); current and new uses of organisms; discovery of new species (may have
use in the future); aesthetic and spiritual benefits; practical value of animals (e.g.
dolphins helping autistic children); the awe of the vast range of organisms, their
attractive or unusual appearances and different methods of survival. (W) (Basic)
Agree some main categories, e.g. genetic, future uses, current uses, spiritual /
aesthetic, etc. (W) (Basic)
o Learners place each idea on the list in the correct category, with an
accompanying explanation. (I) (Challenging)
Online
http://www.nationalgeographic.com/xp
editions/lessons/08/g68/preserve.htm
l
http://www.davidsuzuki.org/search/?q=
biodiversity&x=0&y=0
http://wwf.panda.org/about_our_earth/
biodiversity/biodiversity/
Key concepts
Organisms in their environment,
Observation and experiment
Textbooks/Publications
Bio Factsheet 224: Why we need
biodiversity
Past Papers
Paper 41, June 2012, Q6 (b)(ii)
Paper 41, June 2013, Q9 (a)
Paper 43, Nov 2013, Q5 (a)(iii)
Online
http://wwf.panda.org/
http://www.cites.org/
Key concepts
Organisms in their environment,
Observation and experiment
Learners suggest what is meant by ‘NGOs’. Discuss the advantages of nongovernmental organisations, such as greater cooperation between nations,
international agreements that can be reached sooner than inter-governmental
agreements.
o Introduce WWF and CITES.
o Learners are shown or browse CITES Appendices I, II and III. (W) (Basic)
Learners check the websites or read summary print-out sheets to become familiar
with a variety of NGOs active in conservation.
o Agree a definition for the term ‘conservation’. (W) (Basic)
o Learners write a short account summarising the role of the WWF and CITES and
the benefits of NGOs in general. They could also add details of a local
conservation group. (H) (Basic)
18.3.c
discuss methods of protecting
endangered species, including the
roles of zoos, botanic gardens,
conserved areas (national parks and
marine parks), ‘frozen zoos’ and seed
Introduce the International Union for Conservation of Nature (IUCN). Discuss what is
meant by the term ‘endangered’ (refer learners to work on biodiversity).
o Discuss (or display the IUCN web page) the criteria used to classify an organism
as endangered. (W) (Basic)
o Learners write a definition of the term ‘endangered’, researching a named
example and include the species name and the reasons for it being endangered.
Online
http://www.iucn.org/knowledge/tools/
http://www.iucnredlist.org/
https://worldwildlife.org/species/directo
ry?direction=desc&sort=extinction_st
atus
18.3.g
discuss the roles of non-governmental
organisations, such as the World Wide
Fund for Nature (WWF) and the
Convention on International Trade in
Endangered Species of Wild Fauna
and Flora (CITES), in local and global
conservation
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
88
Learning objectives
Suggested teaching activities
banks
Key concepts
Organisms in their environment,
Observation and experiment
(H) (Basic)
o Learners findings are shared in a class presentation. (W) (Basic)
Learners refer to the species identified in their fieldwork for 18.1.d and use the IUCN
Red List to determine their category. (I) (Basic)
Discuss what is meant by a frozen zoo and a seed bank. (W) (Basic)
o Learners research the variety of methods employed to help protect endangered
species in one of: zoos, botanic gardens, national parks, marine parks. Include
any advantages or disadvantages of each method. (G) (Basic) (Challenging)
o Learners produce a summary sheet of their research to share with the class. (W)
(G) (Challenging)
o Produce one card for each member of the group. On each card write one of the
categories listed (zoo, national park etc.). Give out the cards randomly. Learners
give a written outline of methods used to protect endangered species. (F)
Learners research local and national efforts to protect endangered named species.
(H) (Basic)
With reference to genetic improvement and the maintenance of the gene pool,
learners research examples of wild relatives of crop plants, landraces of crop plants
and rare breeds of livestock. (H) (Basic)
A visit to a national park, nature reserve, zoo or botanic garden will enable learners
to see the work that is being done locally or nationally.
Note
Point out that the IUCN list does not cover all groups of organisms.
Learning resources
http://www.endangeredspecie.com/
http://www.kew.org/index.htm
http://www.zsl.org/conservation/
http://www.petermaas.nl/extinct/index.
html
http://www.eoearth.org/topics/view/495
13/
http://www.bbsrc.ac.uk/society/schools
/secondary/extinct.aspx
http://www.satavic.org/biodiversity.htm
http://www.jic.ac.uk/corporate/about/pu
blications/substainable.pdf
http://www.sandiegozooglobal.org/wha
t_we_do_banking_genetic_resources
/frozen_zoo/
http://animals.nationalgeographic.co.uk
/animals/conservation/
Textbooks/Publications
Bio Factsheet 65: Conservation
Bio Factsheet 208: Captive breeding
and the role of zoos
Past Papers
Paper 43, Nov 2011, Q1 (a)(b)
Paper 42, June 2012, Q6 (a)
18.3.d
discuss methods of assisted
reproduction, including IVF, embryo
transfer and surrogacy, used in the
conservation of endangered mammals
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Explain that humans can assist reproduction in endangered mammals and, with
learner input, discuss the techniques involved.
o Learners suggest the considerations when deciding that assisted reproduction
should be used, such as: research to decide on appropriate method (not always
easy to study reproduction in rare mammals); modify technique to be specific to
the mammal; evaluating success. (W) (Basic)
Learners make notes, using resources, outlining the main stages and the main
principles involved. (I) (Challenging)
o Learners apply the principles to examples they have been given or have
researched. (H) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.cvmbs.colostate.edu/bms/P
DF/640_RM_endangsld.pdf
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/S/Sexual_Reproduct
ion.html#ART
http://www.eplantscience.com/index/bi
otechnology/animal_biotechnology/m
anipulation_of_reproduction_and_tra
nsgenic_animals/biotech_in_vitro_fert
ilization_technology.php
89
Learning objectives
Suggested teaching activities
Learning resources
Learners could be asked to sort statements, some irrelevant to be discarded, to end
up with a set of notes that could be used as a summary of assisted reproduction. (I)
(Basic)
http://nationalzoo.si.edu/SCBI/reprodu
ctivescience/consendangeredcats/
Note
Learners may have included ideas from this in their research for 18.3.c.
Although this learning objective is about endangered mammals, not about assisted
reproduction for humans, the techniques are similar and learners may gain useful
information by researching them.
18.3.e
discuss the use of culling and
contraceptive methods to prevent
overpopulation of protected and nonprotected species
Key concepts
Organisms in their environment,
Observation and experiment
18.3.f
use examples to explain the reasons
for controlling alien species
Key concepts
Organisms in their environment,
Observation and experiment
Past Papers
Paper 41, June 2011, Q3 (a)
Paper 42, June 2013, Q5
Ensure learners know what is meant by the two terms, and then explain that there
are frequently debates about the issue, including deciding when a population is
considered to be ‘over-populated’. (W) (Basic)
Learners research examples meaningful to them, including the different reasons
given to either culling or use of contraceptive methods, and explaining why one
method was favoured. (I) (Basic)
Provide new examples: learners write a short article weighing up the advantages
and disadvantages of culling versus contraceptive methods. (F)
Organise a mini debate. (W) (H) (Basic) (Challenging)
Online
http://www.tams.act.gov.au/parksrecreation/plants_and_animals/urban
_wildlife/local_wildlife/kangaroos/kan
garoo_population_control_methods
http://www.egzac.org/whyusecontrace
ption.aspx
http://www.ceru.up.ac.za/elephant/faqs
.php
Note
Stress that learners will need to develop the ability to apply principles to new
situations
Textbooks/Publications
Bio Factsheet 65: Conservation.
Discuss how, in many ecosystems throughout the world, the introduction of alien
species has had harmful economic or ecological effects (termed ‘alien-invasive’
species). Balance this with a discussion of how some alien species have been of
benefit. (W) (Basic)
Learners research examples of alien species (local, national and global) that are
now considered unwelcome, and for each explain the reasons for controlling them.
(H) (Basic)
Online
http://www.birdlife.org/worldwide/progr
ammes/invasive-alien-species
http://eol.org/info/460
http://www.galapagos.org/conservation
/invasive-species/
Note
This may have been discussed with 18.3.a.
Some agencies give ‘alien’ and ‘exotic’ slightly different meanings, others use them
interchangeably. Also seen are ‘non-indigenous’, ‘non-native’ and ‘introduced’.
v2.1 5Y02
Textbooks/Publications
Bio Factsheet 105: Manipulation and
control of reproduction.
Some parts of this are relevant.
Cambridge International AS & A Level Biology (9700) – from 2016
Past papers
Paper 41, June 2011, Q8 (a)(b)
90
Learning objectives
Suggested teaching activities
Learning resources
18.3.h
outline how degraded habitats may be
restored with reference to local or
regional examples
Discuss the concept of restoration ecology and the need for scientific planning and
understanding when restoring degraded habitats or ecosystems. (W) (Basic)
Learners research one example and present their findings to the group. (W) (I)
(Challenging). Points to consider:
o A description of the habitat before degradation.
o Reasons for the degradation and what may happen if degradation continues.
o What could be / is being carried, with overall aims, e.g. re-establishing what was,
improving by addition of species or physical factors, modifying to create a new
habitat.
o The benefits to the community of restoration.
Online
http://en.wikipedia.org/wiki/Restoration
_ecology
http://www.ser.org/
http://www.nature.com/scitable/knowle
dge/library/restoration-ecology13339059
Key concepts
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
91
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 7: Genetics, population genetics and evolutionary processes
Recommended prior knowledge
Learners should have a good knowledge and understanding of the mitotic cell cycle from Unit 3. They should be able to describe the structure of DNA and the events
occurring in DNA replication, in transcription and in translation from Unit 3, including an understanding of the genetic code. Learners should have a good understanding
of what is meant by a gene, an allele and a gene mutation. An appreciation of the diversity of life, from Unit 6, will stimulate interest in how diversity has come about.
Context
This unit builds on AS Level work, especially Unit 3, DNA and the mitotic cell cycle. It leads on from Unit 6, The diversity of life, so that learners are provided with an
explanation of how the mechanisms of natural selection and isolation can lead to the formation of new species. This unit strongly incorporates the key concepts of cells
as the basic units of life, biochemical processes, DNA, the molecule of heredity and observation and experiment. Knowledge and understanding gained in this unit will
be particularly useful for Unit 8, Molecular biology and gene technology.
Outline
The unit begins with an introduction to ideas and terms that will be needed. The mechanism and significance of meiosis is dealt with, showing how genetic information
passes from parent to offspring. A link is made to gamete formation in animals and plants. Genetic crosses are practised and the chi-squared test is used. The nature of
genes and alleles and their role in determining the phenotype is discussed, including human conditions that result from gene mutations. Once an understanding of basic
genetics is gained, the unit leads to a consideration how the passage of information from parent to offspring is translated to population genetics. Variation, and its
importance for the mechanism of natural selection, is studied before considering the role of natural selection in evolution and speciation. Natural selection is a key
concept in biology, with mutation acting as the raw material for evolution. The unit considers how selection pressures allow successful individuals to survive to pass on
genes to the next generation and how changes in the genetic make-up of the population, coinciding with isolation, can lead to speciation. The key concept of
observation and experiment is exemplified by studying the improvement of the milk yield of dairy cattle and the improvement of crop plants by humans. Humans can
apply the principles of natural selection to artificial selection and speed up the process of biological change.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
92
Learning objectives
Suggested teaching activities
Learning resources
16.1.a
explain what is meant by homologous
pairs of chromosomes
Introduce the topic explaining that a fertilised egg cell will have a set of
chromosomes from the mother and a set from the father, to give pairs of
chromosomes in cells. (W) (Basic)
Discuss the features of homologous chromosomes. (W) (Basic)
o Learners list the similarities and differences between a pair of homologous
chromosomes and note the differences between the X and Y chromosomes. (I)
(Basic)
Online
http://www.nature.com/nature/journal/v
423/n6942/fig_tab/423810a_F1.html
Key concepts
DNA, the molecule of heredity
Note
Avoid using 46 chromosomes and 23 pairs of chromosomes in explanations (also for
16.1.b): a common error is stating these when answering questions about other
organisms.
The term bivalent is the same as one pair of homologous chromosomes.
16.1.b
explain the meanings of the terms
haploid and diploid and the need for a
reduction division (meiosis) prior to
fertilisation in sexual reproduction
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
From 16.1.a, explain that cells with one set of chromosomes are termed haploid (n),
and a particular species has a specific haploid number. Extend this to explain the
term diploid (2n). (W) (Basic)
o Discuss why a diploid organism needs a reduction division (meiosis) to produce
haploid cells. Use phrases such as ‘restore the diploid number on fertilisation’,
‘to avoid doubling the number of chromosomes’. (W) (I) (Basic)
Extension: learners outline the differences between asexual and sexual reproduction
and between asexual reproduction in eukaryotes and asexual reproduction in
prokaryotes (background information - refer to binary fission). (H) (Challenging)
Online
http://www.accessexcellence.org/RC/V
L/GG/ecb/haploiddiploid_sexual_reproduction.php
Note
Do not go into details of meiosis for this learning objective.
Mention that some organisms only have one set of chromosomes, while others have
one set for some part of their life cycle
16.2.a (i)
explain the terms gene, locus, allele,
dominant, recessive, codominant,
linkage, test cross, F1 and F2,
phenotype, genotype, homozygous
and heterozygous
Key concepts
Biochemical processes,
v2.1 5Y02
Only part of this learning objective is included here: explain the terms gene, locus,
allele, dominant, recessive, phenotype, genotype, homozygous and heterozygous
Learners recall previous studies:
gene 6.2.a definition
allele 6.2.b concept of new alleles forming by mutation
6.2.c HbA and HbS alleles.
Use pipe cleaner or string models, with sticky labels for alleles, to help explain gene,
allele, locus, dominant, recessive, heterozygous, homozygous, genotype, then
discuss the meaning of phenotype. (W) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biology.arizona.edu/vocabul
ary/mendelian_genetics/mendelian_g
enetics.html
http://www.genome.gov/glossary/index
.cfm?id=8
Textbooks/Publications
Bio Factsheet 156: Dominant and
93
Learning objectives
Suggested teaching activities
Learning resources
DNA, the molecule of heredity
Learners write definitions for the terms and draw diagrams of homologous
chromosomes to annotate locus and allele and, using examples, draw homologous
chromosomes with different genotypes (homozygous alleles and heterozygous
alleles; dominant and recessive), indicating the phenotype. (I) (Challenging)
Learners match a set of cards with terms to a second set with definitions. (F)
Recessive Alleles.
Bio Factsheet 45: Gene expression
Past Papers
Paper 41, Nov 2011, Q9 (a)
Note
It is useful to introduce the term early so learners can correlate the behaviour of
chromosomes in meiosis and the formation of gametes with allele behaviour (and
enhance understanding of genetic crosses).
16.1.c
outline the role of meiosis in
gametogenesis in humans and in the
formation of pollen grains and embryo
sacs in flowering plants
Key concepts
Cells as the units of life
State that meiosis involves two divisions to produce four cells. Explain what is meant
by the term ‘gamete’. Highlight the role of meiosis in terms of a reduction division
and the production of genetically different cells. (W) (Basic)
Using resources, learners write out a definition and give an outline of
gametogenesis, naming the ovary and testis as the organs involved and including
the role of meiosis. (I) (Challenging)
Learners draw a fully labelled human life cycle. (I) (Basic)
Using resources and teacher input, learners produce annotated diagrams to outline
the formation of pollen grains and embryo sacs.
o Diploid pollen mother cells in pollen sacs (in the anther) divide by meiosis to
form 4 haploid microspores. These mature to become pollen grains (details of
mitosis not required.
o In the ovule the megaspore mother cell divides by meiosis to form 4 haploid
megaspores: one survives to divide by mitosis to produce an eight-nucleate
embryo sac. (I) (Challenging)
Learners compare the main similarities and differences between gametogenesis in
humans with pollen grain and embryo sac formation in plants.
o Include a flow chart diagram to highlight the stages where meiosis and mitosis
occur. (H) (Challenging)
Online
http://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter28/animation__unique_fe
atures_of_meiosis.html
http://wps.prenhall.com/esm_freeman_
biosci_1/0,6452,501052-,00.html
http://highered.mcgrawhill.com/sites/0072495855/learner_vi
ew0/chapter28/animation__spermato
genesis__quiz_1_.html
Textbooks/Publications
Bio Factsheet 168: Gamete Formation
in Animals
Note
Details of ovary and testis histology are not required.
Learners should be familiar with the terms oogenesis and spermatogenesis.
16.1.d
describe, with the aid of
photomicrographs and diagrams, the
v2.1 5Y02
With a short written test (prepared by you, with mark scheme), assess learner recall
of mitosis. (F)
Show learners diagrams or photographs of an ordered haploid chromosome set
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologymad.com/CellDivisio
n/CellDivision.htm
94
Learning objectives
behaviour of chromosomes in plant
and animal cells during meiosis, and
the associated behaviour of the
nuclear envelope, cell surface
membrane and the spindle (names of
the main stages are expected, but not
the sub-divisions of prophase)
Suggested teaching activities
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
16.1.e
explain how crossing over and random
assortment of homologous
chromosomes during meiosis and
random fusion of gametes at
fertilisation lead to genetic variation
including the expression of rare,
recessive alleles
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
v2.1 5Y02
(karyotype), e.g. human sperm and egg to review knowledge of homologous
chromosomes, haploid, diploid, sex chromosomes. (W) (Basic)
Learners model meiosis with teacher guidance. Use pipe cleaners (or string or wool)
to demonstrate the behaviour of 4 chromosomes. Explain the use of e.g. one
homologous pair (i.e. maternal and paternal) = 2 (sister chromatids) light blue and 2
dark blue pipe cleaners; the second homologous pair use a different colour, light and
dark.
o Learners model late interphase (DNA replication means 1 pipe cleaner becomes
2 identical) before moving onto the stages of meiosis. Learners suggest ‘what
happens next’ and explain why each stage occurs.
o At the appropriate points explain the concepts of chiasmata formation, crossing
over and independent assortment. (P) (I) (Basic) (Challenging)
o Learners model meiosis (no help, noting the comparisons with mitosis (correct
spellings). (P) (I) (Challenging)
Learners study prepared slides, photomicrographs and diagrams. (I) (Basic)
Learners draw a series of annotated diagrams, or annotate prepared diagrams. (I)
(Basic)
Learners construct a table of differences between mitosis and meiosis or sort a set
of statements into comparative statements, into two columns. (I) (Basic)
(Challenging)
Learners recall their understanding of a gene and an allele. Emphasise the
importance of using the terms in the correct context. (W) (Basic)
Use the pipe cleaner models of a homologous pair (label ‘A’ on each chromatid of
one homologue and label ‘a’ on each chromatid of the other) to explain how
reduction division separates the two alleles of a gene.
o Mention how this creates variation when gametes fuse randomly at fertilisation.
o Discuss how this allows rare recessive alleles to come together. (W) (Basic)
Choose two different organisms, e.g. fruit fly (n=4) and humans. Using 2n, learners
work out how many different types of gamete could be formed with two homologous
pairs assorting randomly and independently at metaphase I of meiosis. (I)
(Challenging)
Make a pipe cleaner / string model for a second homologous pair using ‘B’s and ‘b’s.
Learners show how random assortment in one cell can produce AB and ab gametes,
and in another Ab and aB gametes.
o Using this example, learners explain how random fusion contributes to variation.
o Learners draw annotated diagrams to illustrate the concepts. (W) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
www.biology.arizona.edu/cell_bio/tutori
als/meiosis/page3.html
http://www.biologyinmotion.com/cell_di
vision/index.html
http://www.sumanasinc.com/webconte
nt/animations/content/meiosis.html
http://www.cellsalive.com/meiosis.htm
Textbooks/Publications
Bio Factsheet 50: Sources of genetic
variation.
Past Papers
Paper 43, June 2011, Q7 (a)
Online
http://www.biologymad.com/CellDivisio
n/CellDivision.htm
www.biology.arizona.edu/cell_bio/tutori
als/meiosis/page3.html
http://www.biologyinmotion.com/cell_di
vision/index.html
http://www.sumanasinc.com/webconte
nt/animations/content/meiosis.html
http://www.cellsalive.com/meiosis.htm
http://www.biozone.co.uk/biolinks/GEN
ETICS.html#Inheritance
http://www.contexo.info/DNA_Basics/M
eiosis.htm
http://www.sumanasinc.com/webconte
nt/animations/content/independentas
95
Learning objectives
Suggested teaching activities
Add labels (‘alleles’) ‘D’ to the homologue with ‘A’ genes, and ‘d’ to the homologue
with ‘a’ genes. Explain that if the genes are on the same chromosome, they are said
to be linked.
o Demonstrate crossing over to show how this can lead to even more variation in
the gametes (AD, ad = parental: Ad, aD = recombinant).
o Explain that the longer the chromosome pair, the greater the number of possible
crossovers.
o Learners draw annotated diagrams to illustrate the concept. (W) (Challenging)
Learners give written and diagrammatic descriptions of random assortment, crossing
over and random fusion, explaining how each of these leads to genetic variation. (F)
Learning resources
sortment.html
Past Papers
Paper 43, June 2011, Q7 (b)
Note
Explain that homologous pairs assort randomly at metaphase I and this means they
are assorting independently of other homologous pairs.
16.2.a (ii)
explain the terms gene, locus, allele,
dominant, recessive, codominant,
linkage, test cross, F1 and F2,
phenotype, genotype, homozygous
and heterozygous
Key concepts
Biochemical processes,
DNA, the molecule of heredity
v2.1 5Y02
Only part of this learning objective is included here: explain the terms codominant,
linkage, test cross, F1 and F2
Using the pipe cleaner / string models, discuss the meaning of the term codominant.
(W) (Basic)
Remind learners of a simple monohybrid cross from previous studies and using the
terms already discussed show what is meant by F1 and F2. Briefly explain a test
cross for learners to define. (W) (I) (Basic)
Learners match a set of cards with terms from 16.2.a to a second set with all the
definitions. (F)
Note
These definitions are best understood when tackling 16.2.b.
A full explanation of test cross should be reserved for later.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biology.arizona.edu/vocabul
ary/mendelian_genetics/mendelian_g
enetics.html
http://www.genome.gov/glossary/index
.cfm?id=8
Textbooks/Publications
Bio Factsheet 156: Dominant and
Recessive Alleles.
Bio Factsheet 45: Gene expression
96
Learning objectives
Suggested teaching activities
Learning resources
16.2.b
use genetic diagrams to solve
problems involving monohybrid and
dihybrid crosses, including those
involving autosomal linkage, sex
linkage, codominance, multiple alleles
and gene interactions (the term
epistasis does not need to be used;
knowledge of the expected ratio for
various types of epistasis is not
required. The focus is on problem
solving)
Using resources, learners write out what is meant by a monohybrid cross and a
dihybrid cross, and explain what is meant by true (or pure) breeding, multiple alleles,
pedigree diagrams, autosomal chromosome and sex chromosome. (I) (Basic)
Monohybrid cross: using a visual (photographs/drawings) simple example (e.g.
purple and white flowers in pea plants), demonstrate how to set out a genetic
diagram (circles should be drawn around the gametes).
o Learners explain why they can be certain of the genotype if a pea plant has
white flowers.
o Explain test crosses. (W) (Basic)
o Learners work though one problem themselves and peer-check the quality of the
genetic diagrams. (I) (Basic)
Learners construct genetic diagrams, working through monohybrid cross problems,
including pedigree diagrams. Learners also performing test crosses. (P) (I) (F)
(Basic) (Challenging)
Codominance: describe an example of codominance and the convention to
represent this (alleles as superscripts). Many examples involve a ‘colour’ gene:
ensure learners know that C is for colour, not codominance.
o Go through the different ratios obtained and ask learners to explain why no test
cross is required. (W) (Basic)
o Learners work through some codominance problems (monohybrid crosses). (I)
(Basic) (Challenging)
Multiple alleles: as an example, discuss the inheritance of human blood groups
(ABO system) to illustrate multiple alleles, dominance, recessiveness and
codominance before learners work through problems. (W) (I) (Challenging) (Basic)
Sex linkage: describe the largely non-homologous X and Y chromosomes to explain
why the male genotype has only one allele for genes located on sex chromosomes.
o Using an example of a sex-linked trait, e.g. eye colour in Drosophila, explain how
to annotate the allele symbol as a superscript by the X (Y- shows that the allele
is absent in the Y chromosome). (W) (Basic)
o Learners write down the possible genotypes for this trait, then tackle a
monohybrid cross problem, covering the reciprocal cross. (I) (Basic)
o Emphasise that not all problems indicating numbers of individuals of each sex,
or stating ‘female crossed with male’ will be sex-linked inheritance. (W) (Basic)
o Learners state and explain the pattern of inheritance associated with sex-linkage
and then practise questions. (I) (Challenging)
Learners model using pipe cleaners / string, or draw diagrams, to show how a
written genetic cross correlates to events occurring at meiosis and fertilisation. (P) (I)
Online
http://learn.genetics.utah.edu/content/i
nheritance/
http://www.dnaftb.org
http://www.biology.arizona.edu/mendel
ian_genetics/mendelian_genetics.htm
l
http://faculty.baruch.cuny.edu/jwahlert/
bio1003/genetics.html
http://www.utilitypoultry.co.uk/sexlinkag
e.shtml
http://udel.edu/~mcdonald/mythintro.ht
ml
http://www.pc.maricopa.edu/Biology/rc
otter/BIO%20181/Lab/181Labpdf/10
MendelianGenetics.pdf
http://www.mendelmuseum.com/eng/1online/experiment
.htm
http://www.sumanasinc.com/webconte
nt/animations/content/mendel/mendel
.html
http://www.learnerstv.com/animation/a
nimation.php?ani=2&cat=Biology
Key concepts
DNA, the molecule of heredity,
Organisms in their environment,
Observation and experiment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 23: Genetics made
simple: I
Bio Factsheet 97: A guide to sex
linkage
Bio Factsheet 93: The ABO Blood
Group System
Bio Factsheet 183: Variations from
expected Mendelian Monohybrid
Ratios.
Bio Factsheet 115: Answering
Examination Questions: Genetics
97
Learning objectives
Suggested teaching activities
Learning resources
(Challenging)
Dihybrid cross: explain that these involve two genes located on non-homologous
chromosomes (unlinked / separate linkage groups). Work through a dihybrid cross,
e.g. Mendel’s pea plants, showing how to write out genotypes e.g. AaBb and not
ABab. (W) (Basic)
o Learners work out the possible gametes from crossing the double
heterozygotes. Guide learners how to construct a Punnett square and complete
it correctly before they work out the phenotypic ratio (explain that 9:3:3:1 still fits
the 3:1 monohybrid crosses ratio: each gene shows a 12:4 ratio). Learners work
through a test cross. (W) (I) (Challenging)
Linkage: remind learners of the concept of linkage and of crossing over (16.1.e)):
two linked genes involve only one homologous chromosome pair. Using a model or
diagrams, explain how linked genes could result in both parental and recombinant
types in the gametes and offspring, but not in the standard Mendelian ratios.
o Discuss why genes close together will produce few, if any, recombinant types
(the further apart the greater proportion of recombinant to parental types). (W)
(Challenging)
Learners tackle a range of differentiated questions involving two genes. (I) (F)
(Basic) (Challenging)
Past Papers
Paper 43, June 2011, Q9 (b)
Paper 41, June 2012, Q7
Note
The terms backcross and incomplete dominance are no longer used.
There are two approaches: (i) cover the theory of the learning objective, then
learners work on genetics problems or (ii) have a set of problems prepared for each
type of cross and learners practise these as they are taught.
Some human genetic traits used as examples in schools are now known to be more
complex than at first thought, Learners should be discouraged from analysing
patterns of inheritance in their family.
16.2.c
use genetic diagrams to solve
problems involving test crosses
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
This learning objective is covered in 16.2.b.
Consolidate by agreeing that a test cross should be performed to find out the
genotype of an organism that is known to have a dominant trait but could be
homozygous dominant or heterozygous. (W) (Basic)
Note
Learners should appreciate the advantage of carrying out test crosses in terms of the
ratios between the phenotypic classes when compared to a cross involving two
heterozygotes.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://learn.genetics.utah.edu/content/i
nheritance/
http://www.dnaftb.org
http://www.mendelmuseum.com/eng/1online/experiment
.htm
98
Learning objectives
Suggested teaching activities
Learning resources
16.2.d
use the chi-squared test to test the
significance of differences between
observed and expected results (the
formula for the chi-squared test will be
provided) (see Mathematical
requirements)
Revise different ratios obtained with the different types of genetic cross,
emphasising that these are theoretical (based on probability) ratios.
o Learners mentally calculate expected numbers from totals e.g. with 40 offspring,
how many of each if expecting a 3:1 ratio? (W) (Basic)
Approach the concept using observed results: learners suggest and justify the type
of genetic cross when given actual genotype numbers, e.g. codominance, for a ratio
of 32 red, 26 pink, 10 white flowers (ratio approximating 1:2:1). (W) (Basic)
o Learners debate a result of: 15 red, 20 pink, 13 white. Agree that a statistical test
is needed to compare the observed ratio to the expected: near enough for
differences to be due to chance effects or so different that other factors should
be considered. (W) (Challenging)
Practical booklet 11. Work through, with guidance (if not covered in 18.1.e, in the
context of field study), examples of the use of the chi-squared test. (I) (Basic)
Learners use a calculated chi-squared value to:
o State the critical value at a stated probability level.
o State where the chi-squared value fits in the range of probabilities.
o Make a conclusion, referring to a null hypothesis and significance level. (I)
(Basic) (Challenging)
Learners use results from a genetic cross (increasing difficulty)to:
o Practise the calculations involved in the chi-squared test
o Interpret the results to write a valid conclusion about the nature of the genetic
cross. (I) (Basic) (Challenging)
Note
See also the syllabus section, Mathematical requirements.
Learners should be able to:
o Identify the situations where the use of the test is applicable
o Use the table of critical values and state the probability of obtaining their results
by chance.
Learners should consider :
o The use of stating the actual probability value (p), which they can calculate using
software
o The probabilities of 0.05 and 0.01 (often used to report results).
Online
http://www.blc.arizona.edu/courses/mc
b422/MendelStarFolder/merChiSquar
e.html
Explain that biological variation describes the variation within a population (members
of the same species).
o Learners suggest examples of variation that is: inherited / genetic; not inherited /
environmental; likely to be due to both genetic and environmental sources.
Online
http://www.nature.com/scitable/knowle
dge/library/mutations-are-the-rawmaterials-of-evolution-17395346
Key concepts
Observation and experiment
17.1.a
describe the differences between
continuous and discontinuous variation
and explain the genetic basis of
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 79: The chi-squared test
for goodness of fit.
Past papers
Paper 43, Nov 2013, Q1
Paper 51, Nov 2011, Q2
Paper 53, Nov 2011, Q2
99
Learning objectives
Suggested teaching activities
Learning resources
continuous (many, additive genes
control a characteristic) and
discontinuous variation (one or few
genes control a characteristic)
(examples from 16.2.f) may be used to
illustrate discontinuous variation;
height and mass may be used as
examples of continuous variation)
o Explain the equation Vp = Vg +Ve, (no need to learn) and use an example (e.g.
blood groups) to show Ve = 0 when a trait is due only to genetic effects.
o Discuss the use of monozygotic twins, (Vg = 0), to study the effects of the
environment on variation. (W) (Basic)
Learners produce a list of causes of genetic variation for sexually reproducing
organisms and for asexually reproducing organisms (i.e. only mutation), as well as
causes of environmental variation (disease, edaphic factors, climate, water
availability, etc.). (I) (Challenging)
Using resources, learners define discontinuous variation (include a bar chart) and
continuous variation (include a histogram), and give examples. (I) (Basic)
o Learners consider a trait that has a genetic basis and describe what is likely to
be occurring to if the variation is (i) discontinuous (one/two genes), and (ii)
continuous (polygenic, environmental effects may also contribute). (I)
(Challenging)
http://www.nature.com/scitable/topicpa
ge/genomics-enables-scientists-tostudy-genetic-variability-6526364
http://www.bbc.co.uk/schools/gcsebite
size/science/edexcel_pre_2011/gene
s/genesrev1.shtml
Explain the situations where the t-test would be applicable and work through an
example. (W) (Basic)
Learners work through a number of examples, stating a null hypothesis and using a
table of critical values to state the probability of obtaining the result. (W) (I) (Basic)
(Challenging)
Learners choose from a list of outlines of investigations those for which the t-test
could be used. (F)
Practical booklet 10
Key concepts
DNA, the molecule of heredity,
Natural selection,
Organisms in their environment
17.1.c
use the t-test to compare the variation
of two different populations (see
Mathematical requirements)
Key concepts
Observation and experiment
Note
There is information about this test in the syllabus (Mathematical requirements
section).
Practical booklet 10 gives learners the opportunity to use the t-test on data that
they have collected themselves
Textbooks/Publications
Bio Factsheet 50: Sources of genetic
variation
Online
http://www.theseashore.org.uk/theseas
hore/Stats%20for%20twits/T%20Test
.html
http://archive.bio.ed.ac.uk/jdeacon/stati
stics/tress4a.html
Textbooks/Publications
Bio Factsheet 3: Which stats test
should I use?
Past papers
Paper 51, June 2012, Q1
Paper 52, June 2011, Q2
17.1.b
explain, with examples, how the
environment may affect the phenotype
of plants and animals
v2.1 5Y02
Learners recall the difference between genotype and phenotype and describe the
flow of information from DNA to the phenotype. (W) (Basic)
Explain that the term ‘environment’ encompasses everything that is not considered
genetic. (W) (Basic)
Learners research examples that they are given and provide explanations for the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.flowersbulbs.com/ql_hydran
gea_color.htm
http://www.nature.com/scitable/topicpa
ge/environmental-influences-on-
100
Learning objectives
Suggested teaching activities
Learning resources
Key concepts
DNA, the molecule of heredity,
Organisms in their environment
observations. (I) (Basic) (Challenging)
Learners research further examples and report back to the class. (H) (Basic)
gene-expression-536
http://www.nature.com/scitable/topicpa
ge/phenotypic-range-of-geneexpression-environmental-influence581
http://www.nature.com/scitable/content
/gene-environment-interactions-fromepidemiological-studies-33011
http://www.newscientist.com/article/dn
1520-iq-is-inherited-suggests-twinstudy.html
http://www.nature.com/scitable/topicpa
ge/the-collective-set-of-alleles-in-a6385985
16.2.e
explain that gene mutation occurs by
substitution, deletion and insertion of
base pairs in DNA and outline how
such mutations may affect the
phenotype
Use questioning to gauge knowledge of DNA structure, the definition of a gene
mutation, protein synthesis and protein structure. (W) (Basic)
Outline the changes that occur to give base substitution, deletion and insertion
mutations. Point out how frameshift mutations arise. Learners can produce summary
notes. (W) (Basic)
o Learners research and give an account of how a base substitution in the Hb A
allele to produce the Hb S allele leads to the altered amino acid in sickle cell
anaemia. (W) (Challenging)
o Learners work out the new amino acid sequences for examples of insertion and
deletion mutations and suggest how this could affect the protein synthesised
(include examples leading to premature stop codons). (I) (Challenging)
Discuss how it is possible that some changes in DNA nucleotide sequences have no
(e.g. same amino acid specified), or little (e.g. non-structural amino acid replaced)
consequential effects while others have profound effects. (W) (Challenging)
Extension: learners research examples of gene mutations resulting in cystic fibrosis
(differing severities). (W) (Challenging)
Online
http://www.dnaftb.org/dnaftb/27/conce
pt/index.html
http://www.who.int/genomics/public/ge
neticdiseases/en/index2.html
http://chroma.gs.washington.edu/outre
ach/genetics/sickle/
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/M/Mutations.html
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
Note
Focus on gene mutation, but alert learners to the existence of chromosomal
mutations (sections of chromosomes/many genes and chromosome number).
16.2.f
outline the effects of mutant alleles on
v2.1 5Y02
Learners construct a flow chart to show how a gene mutation can lead to symptoms
of sickle cell anaemia. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 94: Gene Mutations
Bio Factsheet 179: Answering Exam
Questions: Mutation
Past Papers
Paper 43, June 2011, Q9 (a)
Online
http://www.s-cool.co.uk/a-
101
Learning objectives
Suggested teaching activities
Learning resources
the phenotype in the following human
conditions: albinism, sickle cell
anaemia, haemophilia and
Huntington’s disease
Learners research one other condition from the list then work with others (that have
covered the same condition) to produce an information sheet to present to the class
to use as notes. (W) (G) (H) (Basic) (Challenging)
level/biology/evolution/reviseit/evolution-in-action
Notes on sickle cell anaemia.
Textbooks/Publications
Bio Factsheet 110: Genetic Disease in
Humans.
Key concepts
DNA, the molecule of heredity,
Organisms in their environment
16.2.g
explain the relationship between
genes, enzymes and phenotype with
respect to the gene for tyrosinase that
is involved with the production of
melanin
Provide information about the role of tyrosinase. Learners produce an annotated
flow diagram to illustrate the relationship between the gene, the enzyme and the
phenotype. (I) (Challenging)
Online
http://ghr.nlm.nih.gov/gene/TYR
Discuss how named examples of animals, plants and bacteria with different
genotypes and hence phenotypes (e.g. bacteria and antibiotic resistance) may differ
in their chances of survival or in their reproductive capacity. (W) (Basic)
Learners suggest why ‘more likely to survive to reproduce’ is more important for the
species than ‘more likely to survive’ (idea of passing on genetic information. (W)
(Basic)
Learners debate the advantages and disadvantages of asexual and sexual
reproduction. (G) (Basic)
Online
http://learn.genetics.utah.edu/content/v
ariation/sources/
http://darwiniana.org/evolution.htm
http://www.eoearth.org/article/Genetic_
variation
http://www.wellcometreeoflife.org/
Key concepts
Biochemical processes,
DNA, the molecule of heredity
17.1.d
explain why genetic variation is
important in selection
Key concepts
Natural selection
Note
Learners should have an outline of selection – covered in detail later.
17.2.a
explain that natural selection occurs as
populations have the capacity to
produce many offspring that compete
for resources; in the ‘struggle for
existence’ only the individuals that are
v2.1 5Y02
Introduce the idea that organisms have high reproductive potential and given ideal
conditions, exponential or explosive population growth occurs (starting with a few
individuals).
o Describe examples of ideal conditions and for each ask learners to suggest
phenotypes (and hence genotypes) that are more likely to survive (introduce the
term differential survival) if ideal conditions are not maintained.
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 43, Nov 2013, Q2 (c)
Online
http://www.bbsrc.ac.uk/web/FILES/Exh
ibitions/pod1-factsheet.pdf
http://www.biologycorner.com/workshe
ets/peppermoth_paper.html
http://www.accessexcellence.org/AE/A
102
Learning objectives
Suggested teaching activities
best adapted survive to breed and
pass on their alleles to the next
generation
Key concepts
Natural selection
o Remind learners of variation within a population and explain that some
organisms are better adapted to survive when selection pressures act to control
population size (most populations oscillate about a mean size).
o Explain that individuals that are better adapted to survive are said to be fitter
than those who do not have the adaptations. (W) (Basic)
Learners list examples of selection pressures and describe phenotypes that are
selected for and those selected against. (I) (Basic)
Learners summarise discussions with bullet-point notes and complete the idea of
natural selection with the following points:
o Individuals selected for pass on their alleles to their offspring when they
reproduce (differential reproduction)
o The frequency of the allele in the population increases. (I) (Challenging)
Explain that a gene pool describes the sum of all alleles for all the genes in a
population. (W) (Basic)
Explain that most mutations are not beneficial. Learners complete a worksheet
(prepared by you) describing and explaining changes to allele frequencies / the gene
pool following mutation: (a) if the mutation is not beneficial and is a (i) dominant
allele and (ii) recessive allele; (b) if environmental factors change and the mutation
becomes beneficial. (F)
Learners research examples of natural selection and produce a summary table:
example, different phenotypes involved, selection pressure(s) involved, adaptation
possessed, and additional notes.
o Suggestions: warfarin resistance in rats; melanism in peppered moths;
cyanogenic clover; antibiotic resistance in bacteria; resistance in insects to
insecticides. (H) (Challenging)
Learners choose one example from the summary table and write a sequential
account to explain how allele frequencies within a population can change. (F)
Learning resources
EPC/WWC/1995/camouflage.html
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/P/Populations2.html
http://www.eoearth.org/article/Populati
on_ecology
http://www.pbs.org/wgbh/evolution/libr
ary/01/2/l_012_02.html
www.biologyinmotion.com/evol/
http://anthro.palomar.edu/synthetic/syn
th_4.htm
Past Papers
Paper 43, June 2011, Q8
Note
Avoid using the phrase ‘survival of the fittest’ (different phenotypes can be equally
fit).
Background: take some time to discuss the work of Charles Darwin and Alfred
Russel Wallace.
An understanding of abiotic and biotic limiting factors and of density-dependent and
density-independent factors will be beneficial.
17.2.b
v2.1 5Y02
Explain that in most cases the environment remains relatively stable and so the
Cambridge International AS & A Level Biology (9700) – from 2016
Online
103
Learning objectives
explain, with examples, how
environmental factors can act as
stabilising, disruptive and directional
forces of natural selection
Suggested teaching activities
same phenotype has a selective advantage in each generation.
Discuss how the environment acts as a stabilising force of natural selection, so that
selection pressures act to remove the extremes of the phenotype (e.g. birth weight in
human babies).
Discuss the other two modes of selection: directional, where allele frequencies
change in one direction (e.g. drug resistance in bacteria) and disruptive, where the
extremes of the phenotype are favoured (e.g. size of male Pacific salmon). (W)
(Basic)
Learners draw annotated graphs for each of stabilising, directional and disruptive
selection to show the frequency of phenotypes ‘before’, ‘during’ and ‘after’ a period
of time when selection occurred. (I) (Basic)
Learners research and describe one further example for each of the three types. (H)
(Challenging)
http://www.eoearth.org/article/Evolutio
n?topic=49508
http://www.blackwellpublishing.com/ridl
ey/a-z/Stabilizing_selection.asp
http://www.nature.com/nature/journal/v
313/n5997/abs/313047a0.html
Learners should consider how natural selection can affect the level of genetic
variation for any one heritable trait.
o Use an example (e.g. melanism in Biston betularia) to discuss how a different
set of selection pressures in a different environment affects allele frequencies
and leads to different outcomes for the population. (W) (Basic)
Learners research the link between sickle cell anaemia and malaria to describe and
explain the differences in allele frequencies between areas free of malaria and areas
where malaria is endemic. (H) (Challenging)
Learners use beads to model the effect on allele frequency in a population by
differential survival of two different genotypes for one gene.
o Place a large (known) number of beads of two different colours (alleles) in a
container (the population). Decide on a percentage survival rate for the
homozygous recessive genotype, e.g. 60%.
o Pick out pairs of beads at random, discarding four out of every ten pairs of
recessive beads. When all beads have been used, only replace the ones which
'survived' (not discarded) and repeat for the next generation.
o Record numbers of each genotype in each generation and construct graphs to
show the effect of selection over time. (G) (Challenging)
Introduce Darwin’s finches and outline the main points of the founder effect for
learners to summarise. (W) (I) (Challenging)
Explain that genetic drift involves chance effects, known as sampling errors, where
the allele frequencies of a small founding (ancestor) group are unlikely to be
Online
http://www.pbs.org/wgbh/evolution/libr
ary/06/3/l_063_03.html
http://www.nature.com/scitable/knowle
dge/library/natural-selection-geneticdrift-and-gene-flow-15186648
http://biology4.wustl.edu/cloverproject/
Assets/White%20Clover%20Backgro
und%20for%20Teachers.pdf
http://evolutiontextbook.org/content/free/notes/ch18
_WN18Dc.html
http://sickle.bwh.harvard.edu/malaria_s
ickle.html
http://wps.prenhall.com/esm_freeman_
evol_3/0,8018,849374-,00.html
http://evolution.berkeley.edu/evolibrary
/home.php
Key concepts
Natural selection,
Organisms in their environment
17.2.c
explain how selection, the founder
effect and genetic drift may affect allele
frequencies in populations
Key concepts
Natural selection
v2.1 5Y02
Learning resources
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 44: Evolution.
Also useful for 17.3c).
Past Papers
Paper 42, June 2012, Q1 (a)
Paper 42, June 2013, Q8 (b)
Textbooks/Publications
Bio Factsheet 191: What have we
learned from Darwin’s finches?
104
Learning objectives
Suggested teaching activities
Learning resources
representative of the larger main population (the smaller the population the greater
the likely effect).
o Exemplify the concept using Darwin’s finches. (W) (Basic)
Learners suggest the similarities and differences between natural selection and
genetic drift and then engage in class discussion. (W) (P) (Basic) (Challenging)
o Similarities: both involve changes in allele frequency and can contribute to
change (evolution).
o Differences: natural selection is a directed process, genetic drift is not; only
natural selection involves adaptations; with natural selection the frequency of the
‘advantageous’ allele increases whereas with genetic drift, allele frequencies
change by chance/sampling error (the frequency of a ‘disadvantageous’ allele
could increase). (W) (G) (Challenging)
17.2.d
use the Hardy-Weinberg principle to
calculate allele, genotype and
phenotype frequencies in populations
and explain situations when this
principle does not apply
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
Explain that Hardy and Weinberg considered the behaviour of genes in idealised
populations.
o Work through an example to show how allele frequencies can be used to
calculate genotype frequencies and how genotype frequencies can be used to
calculate allele frequencies. (W) (Basic)
o Learners work through simple examples using the Hardy-Weinberg equation and
make notes. (I) (Basic)
Learners use an example where the number of individuals with the recessive trait is
known to calculate the proportion, and hence number of, heterozygotes in a
population. (W) (Challenging)
Learners make notes to:
o Explain the differences between allele frequencies, genotype frequencies and
phenotype frequencies.
o Explain the conditions that need to be met for the Hardy-Weinberg principle to
apply. (I) (Challenging)
Learners suggest reasons why an unchanging allele frequency from one generation
to the next is rarely encountered in nature (non-random breeding; not all individuals
produce offspring; not a static population as there is emigration/immigration;
selection occurs; mutation occurs).
o Discuss how these frequencies would change if mutations occurred (e.g. harmful
recessive mutations; heterozygote advantage etc.), so that learners appreciate
the potential for change by evolution. (W) (Basic)
Explain to learners that the Hardy-Weinberg equations can be used to determine
frequencies for ‘at this moment in time’ occurrences.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://anthro.palomar.edu/synthetic/syn
th_2.htm
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/H/Hardy_Weinberg.
html
http://highered.mcgrawhill.com/sites/0767424263/student_vi
ew0/chapter4/the_hardyweinberg_equilibrium.html#
http://www.wwnorton.com/college/biolo
gy/discoverbio3/core/content/ch17/an
imations.asp
http://www.perinatology.com/calculator
s/Hardy-Weinberg.htm
Textbooks/Publications
Bio Factsheet 211: Hardy Weinberg
and population genetics.
105
Learning objectives
Suggested teaching activities
Learning resources
o Learners use an example, e.g. the incidence of cystic fibrosis to calculate the
allele frequencies and work out the carrier frequency (the heterozygotes) in the
population. (I) (Challenging)
17.3.a
state the general theory of evolution
that organisms have changed over
time
Key concepts
Natural selection
17.3.b
discuss the molecular evidence that
reveals similarities between closely
related organisms with reference to
mitochondrial DNA and protein
sequence data
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Natural selection
17.3.c) includes the idea that species have formed from pre-existing species.
Discuss the ideas of ‘change over time’ and of common descent - there is
overwhelming evidence to suggest that all life is related. (W) (Basic)
Learners research examples of evolution to outline how change over time has
occurred. (H) (Challenging)
o A class discussion will help learners appreciate that the pace of change can be
different for different examples.
Learners suggest the type of evidence used to determine whether organisms were
closely related (i.e. comparative morphology and anatomy, fossils, classification and
embryology). (W) (Basic)
o Explain how the continually improving techniques to obtain DNA base/nucleotide
sequences and protein amino acid sequences (e.g. rapid sequencing) has
provided databases to improve understanding of relationships. (W)
(Challenging)
Explain that evolutionary related proteins that belong in a group (protein family) can
be most usefully compared between organisms. (W) (Basic)
Introduce the use of a single letter code for the amino acids before learners analyse
(in terms of closely related organisms) sequence data of a number of organisms
(e.g. for cytochrome C). (I) (Challenging)
With prompting, learners suggest how mitochondrial DNA differs from nuclear DNA
(inherited only from the mother; doesn’t swap genetic material with paternal
mitochondrial DNA and higher mutation rate).
o Discuss the usefulness, in terms of close relationships, of databases for
comparing mitochondrial DNA sequences of different organisms. (W) (I)
(Challenging)
Online
http://evolution.berkeley.edu/evolibrary
/article/evo_47
Textbooks/Publications
Jones, Fosbery, Taylor, Gregory,
pages
253-254 (2007), or pages 374-375
(2013), includes the Darwin-Wallace
theory and a discussion about
speciation.
Online
http://evolution.berkeley.edu/evolibrary
/news/100501_xwoman
http://www.wiley.com/college/pratt/047
1393878/instructor/activities/phylogen
etic_trees/index.html
http://www.indiana.edu/~ensiweb/lesso
ns/molb.ws.pdf
Past papers
Paper 43, Nov 2013, Q2
Note
This has close links to 19.2.a) and bioinformatics.
Learners should understand that there are freely accessible databases available to
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
106
Learning objectives
Suggested teaching activities
Learning resources
researchers.
17.3.c
explain how speciation may occur as a
result of geographical separation
(allopatric speciation), and ecological
and behavioural separation (sympatric
speciation)
Key concepts
Natural selection,
Observation and experiment
17.3.d
explain the role of pre-zygotic and
v2.1 5Y02
Review learner understanding of the terms species and gene pool by a question and
answer session. (W) (Basic)
Define speciation.
o Discuss the importance in speciation of (i) reproductive isolation and (ii) natural
selection acting within a population in different ways on different groups. (W)
(Basic)
Give examples (e.g. separating land masses millions of years ago and road laying
dividing up forests) illustrating ways that sub-populations are formed by geographical
separation and brainstorm other examples. (W) (Basic)
o Discuss how the different abilities of organisms to move from one area to
another are an important factor in the formation of new species.
o Remind learners that the process of allopatric speciation requires that the
populations remain separated and interbreeding is prevented. (W) (Basic)
Learners research one or two examples and use these to explain what is meant by
allopatric speciation. (I) (Basic)
Extension: learners research how the observations made of the four species of
mockingbirds in the Galapagos Islands are believed to have had a large influence on
Darwin’s development of the concept of natural selection. (H) (Challenging)
Introduce the idea of sympatric speciation: occurring within the same geographic
area by reducing gene flow between groups of the same population.
o State that two of the many ways to do this is by ecological separation and by
behavioural separation and ask learners to suggest what this means or to
volunteer examples. (W) (Basic)
o Learners research one example of each to explain the principles involved and
share their findings with the group. (W) (I) (Challenging)
Learners research the evolution of cichlid fish in the great lakes of Africa, e.g. Lake
Victoria, and present arguments as to whether speciation has occurred by allopatric
speciation, sympatric speciation, or both. (I) (Challenging)
Learners continue their work on Darwin’s finches and the founder effect to explain
how speciation has occurred by both allopatric and sympatric speciation. (I)
(Challenging)
Learners write a paragraph comparing allopatric and sympatric speciation. (F)
Remind learners that isolating mechanisms provide a barrier to gene flow and when
successful interbreeding no longer occurs a new species is considered to have been
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://people.rit.edu/rhrsbi/GalapagosP
ages/DarwinFinch.html
http://www98.homepage.villanova.edu/
robert.curry/Nesomimus/index.html
http://www.sciencedaily.com/releases/
2011/10/111003080523.htm
http://www.thescientist.com/?articles.view/articleNo/
23704/title/Evidence-for-sympatricspeciation/
http://www.nature.com/scitable/topicpa
ge/polyploidy-1552814
http://www.evolutionsbiologie.unikonstanz.de/pdf1-182/P089.pdf
http://evolution.berkeley.edu/evolibrary
/news/090301_cichlidspeciation
Textbooks/Publications
Bio Factsheet 142: Modern Examples
of Evolution in Action
Bio Factsheet 92: Isolation
Mechanisms
Past Papers
Paper 41, June 2011, Q8 (c)
Paper 41, June 2012, Q1
Online
http://www.biologyaspoetry.com/terms/
107
Learning objectives
Suggested teaching activities
post-zygotic isolating mechanisms in
the evolution of new species
Key concepts
Natural selection
17.2.e
describe how selective breeding
(artificial selection) has been used to
improve the milk yield of dairy cattle
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
formed. (W) (Basic)
Learners write out definitions of the two types of reproductive isolating mechanisms
and then decide whether the examples from 17.3.c are pre-zygotic or post-zygotic.
(I) (Basic)
Post-zygotic isolating mechanisms may need further discussion and summary with
individual notes.
o Discuss what is meant by a hybrid (hybridisation from 17.2.f is a different
context). Explain that generally a hybrid dies as an embryo or is sterile if it
survives, so a sub-population on the verge of becoming a separate species is
unlikely with interbreeding to incorporate back into the main population – the
gene pools are sufficiently different.
o Explain that hybrids that manage to produce fertile offspring tend to be less fit
than others and with natural selection will die out. (W) (I) (Challenging)
Provide descriptive examples of speciation on separate cards for learners to
produce two piles, pre-zygotic or post-zygotic and then compare with a partner. (P)
(I) (Basic)
Learners produce a written outline of the overall role of isolating mechanisms in
speciation and then describe, using examples, the contribution of pre-zygotic and
post-zygotic isolating mechanisms.
o The account should highlight the differences between the two. A word list or a
hints sheet could be provided. (F)
Explain that in selective breeding, humans have applied knowledge of natural
selection to make ‘improvements’. (W) (Basic)
Discuss why selective breeding to improve the milk yield of dairy cattle must take
place over several generations. (W) (Basic)
o Learners suggest main stages involved in the selective breeding programme,
before presenting ideas to the group. (W) (G) (Basic)
o Learners research details, guided by prompts such as: ‘Explain whether one or
many genes are involved’; ‘State what needs to be considered for improved milk
yield’; ‘Describe other desirable features for the cattle involved’. (H)
(Challenging)
Learners describe (e.g. in a table) the similarities and differences between selective
breeding and natural selection. (F)
Learners use data for milk yield of different generations in a selective breeding
programme to carry out a statistical comparison (t-test). (I) (Challenging)
Learners discuss the balance between improving features and maintaining genetic
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
postzygotic_barrier.html
http://wps.pearsoncustom.com/wps/me
dia/objects/5697/5834441/ebook/htm/
0cc6e.htm?14.03
Textbooks/Publications
Bio Factsheet 92: Isolation
Mechanisms
Past papers
Paper 43, Nov 2013, Q2 (c)
Online
http://www.embryoplus.com/cattle_ayr
shire.html
http://www.ilri.org/InfoServ/Webpub/full
docs/SmHDairy/chap5.html#Dairy%2
0cattle
http://rstb.royalsocietypublishing.org/co
ntent/360/1459/1479.full#abstract-1
http://babcock.wisc.edu/node/182
http://www.petermaas.nl/extinct/articles
/selectivebreeding.htm
Textbooks/Publications
Bio Factsheet 187: Selective Breeding
of Cattle
108
Learning objectives
Suggested teaching activities
Learning resources
diversity. (G) (Challenging)
Past Papers
Paper 43, Nov 2011, Q8
17.2.f
outline the following examples of crop
improvement by selective breeding:
the introduction of disease
resistance to varieties of wheat and
rice
the incorporation of mutant alleles
for gibberellin synthesis into dwarf
varieties so increasing yield by
having a greater proportion of
energy put into grain
inbreeding and hybridisation to
produce vigorous, uniform varieties
of maize
Key concepts
Natural selection,
Observation and experiment
v2.1 5Y02
Continue the theme of 17.2.e with a discussion about the need to supply an
increasing global population and the improvement of crop plants.
o Learners suggest the most important crop plants grown (the three most
important are maize wheat and rice – grain crops).
o Outline the difference between crop improvement by conventional means,
selective breeding, and improvement by genetic modification. (W) (Basic)
Learners may be able to name a disease to which wheat (e.g. stem rust) and rice
(e.g. sheath blight) are susceptible; discuss the need to breed crop plants resistant
to disease (e.g. disease lowers yield and some can leave harmful toxins in the crop).
o Learners recall the steps involved in selective breeding and suggest desirable
features, e.g. resistant to infection, maintaining resistance for a long time,
localising infection to one area of the plant, resistance to toxin accumulation,
seed (kernel) resistance, able to produce a high yield when infected. (W)
(Challenging)
o Learners research the steps involved in introducing disease resistance into
wheat or rice (cover one crop each and share notes). (P) (Basic)
State that the presence of gibberellins leads to stem elongation and explanations will
be covered in Unit 11 (15.2.d, 16.3.d).
o Explain that the sd-1 gene encodes an enzyme (GA20-oxidase) involved in the
later stages of gibberellin biosynthesis.
o Learners suggest an outcome if mutations in this gene occur (very low levels of
gibberellins resulting in dwarf varieties).
o Explain that some varieties of crops such as rice and barley have these semidwarf / dwarf varieties. (W) (Challenging)
Learners write definitions of inbreeding and hybridisation and explain what is meant
by inbreeding depression, outbreeding, and hybrid vigour. (I) (Basic)
o Discuss the difficulties in maize in achieving the balance between homozygosity
and heterozygosity. (W) (Basic)
o Learners list the advantages and disadvantages of inbreeding and outbreeding
in maize. (I) (Challenging)
o Learners explain how selective breeding has produced homozygous maize
plants that can be crossed with other homozygous plants, to produce hybrids
with combinations of desirable features. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://archaeology.about.com/od/dome
stications/qt/wheat.htm
http://www.dupont.com/corporatefunctions/our-approach/globalchallenges/food.html
http://irri.org/our-work/research/betterrice-varieties/disease-and-pestresistant-rice
http://www.lsuagcenter.com/en/crops_l
ivestock/crops/rice/Diseases/
http://www.agprofessional.com/resourc
e-centers/wheat/disease/news/Dodisease-resistant-wheat-varietiespay-a-price-in-yield-229754951.html
http://www.businessinsider.com/10crops-that-feed-the-world-20119?op=1
http://5e.plantphys.net/article.php?ch=
20&id=355
Past Papers
Paper 43, June 2011, Q4 (a)
Paper 41, Nov 2013, Q5
109
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners research the ‘Green Revolution’ and debate the advantages and
disadvantages of this. (W) (Basic)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
110
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 8: Molecular biology and gene technology
Recommended prior knowledge
The structure of proteins and the structure of DNA from Unit 1 should be well understood. In addition, from Unit 3, learners should be familiar with semi-conservative
replication of DNA and understand the principles of transcription, the genetic code and translation in the synthesis of proteins. Knowledge from Unit 7 of gene
expression, including an understanding of how some mutations affect gene expression is also required.
Context
This unit provides learners with the opportunity to consider some of the latest developments in biology and appreciate the key concept of observation and experiment.
In this unit, learners will see how humans can make use of living systems and organisms to benefit themselves, such as in the development of genetically modified
plants and in improvements in genetic screening, in the treatment of genetic disorders and advancements in forensic science. Knowledge and understanding of
biological facts, principles and concepts from previous units will help their understanding of the techniques applied.
Outline
The lac operon is studied as an example of gene regulation and control in eukaryotes is touched upon with a discussion of the role of transcription factors. The study of
gene expression with the use of microarrays is covered. Recombinant DNA is explained and steps involved in genetic engineering are covered, including the use of
enzymes, plasmids, markers and control sequences, including promoters. Two main applications of genetic engineering, the production of proteins of medical
importance and the production of genetically modified crops and livestock are studied. Gel electrophoresis and the amplification of DNA by the polymerase chain
reaction are two techniques that are described and an application of these is considered with an outline of the technique associated with genetic fingerprinting.
Learners see that the pace of development of genetic technology can be partly attributed to bioinformatics. Other aspects of genetic technology that are covered are
the sequencing of genomes, screening for genetic conditions and gene therapy. The unit also includes a discussion on the social and ethical issues and implications of
genetic technology.
Teaching time
It is recommended that this unit should take approximately 9% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
111
Learning objectives
Suggested teaching activities
Learning resources
16.3.b
explain genetic control of protein
production in a prokaryote using the
lac operon
Learners complete a short written test (prepared by you, with mark scheme) to
remind them of previous knowledge and help understanding of this unit.
o Include relevant questions on: prokaryote structure (including plasmids and
genes for antibiotic resistance); definition of a gene; DNA structure and
replication; protein synthesis. (F)
o Go through the answers before proceeding. (W) (Basic)
Explain that in protein synthesis, gene expression describes the whole process
where DNA is transcribed to produce mRNA, which is translated to produce
polypeptides (that form proteins).
o Discuss the need to control gene expression, as all genes cannot be switched
on at any one time. (W) (Basic)
Explain the concept of an operon, then display a diagram of the arrangement in the
lac operon and describe the gene products of gene Z and gene Y.
o Discuss the roles of lactose permease and -galactosidase in lactose uptake
and metabolism, encouraging learners to contribute using AS Level knowledge.
(W) (Challenging)
Learners participate in a group demonstration using a large model set-up.
o Sheets of coloured paper stuck together represent the operon (promoter,
operator, genes Z, Y and A); the operator gene has a shape cut out,
complementary to the shape of the repressor protein; a separate sheet of paper
represents the regulatory gene (located elsewhere on the genome); use different
shapes for each of glucose, lactose, RNA polymerase and repressor protein.
o Discuss each gene and then place on top of them cards with their labels
(remove to test learners).
o Involve learners to describe the state of the operon when: no lactose is present
and glucose is present; when no glucose is present and lactose is present. (W)
(Challenging)
o Repeat, but this time allow learners to take charge and share out the
demonstration. (W) (I) (Challenging)
Learners annotate a set of diagrams and give explanations. (I) (Challenging)
Learners complete a gap-filling exercise that serves as their notes. (I) (Basic)
Learners sort out a set of statements to show the sequence of events occurring (F)
Online
http://www.sumanasinc.com/webconte
nt/animations/content/lacoperon.html
http://pathmicro.med.sc.edu/mayer/gen
eticreg.htm
http://highered.mcgrawhill.com/sites/0072556781/student_vi
ew0/chapter12/animation_quiz_4.htm
l
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/L/LacOperon.html
Key concepts
Biochemical processes,
DNA, the molecule of heredity
Textbooks/Publications
Bio Factsheet 45: Gene Expression
Note
The lac operon of Escherichia coli was the first example of genetic control
discovered and investigated.
Details of cAMP and the catabolite activator protein are not required.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
112
Learning objectives
Suggested teaching activities
Learning resources
16.3.a
distinguish between structural and
regulatory genes and between
repressible and inducible enzymes
Learners make notes on the differences between: structural and regulatory genes;
repressible and inducible enzymes. (I) (Basic)
o Learners also explain that a repressor protein is the product of a regulatory
gene.
o Learners determine whether the enzyme products of the lac operon structural
genes are repressible or inducible enzymes (they are inducible). (I) (Basic)
Online
http://textbookofbacteriology.net/regula
tion.html
http://www.sumanasinc.com/webconte
nt/animations/content/lacoperon.html
http://pathmicro.med.sc.edu/mayer/gen
eticreg.htm
http://highered.mcgrawhill.com/sites/0072556781/student_vi
ew0/chapter12/animation_quiz_4.htm
l
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/L/LacOperon.html
Explain that RNA polymerase in eukaryotic cells cannot initiate transcription alone:
binding of transcription factors (proteins) to the DNA and to each other allow RNA
polymerase to bind; others bind to the RNA polymerase (the whole complex is
termed the transcription initiation complex). (W) (Basic)
o Learners draw annotated diagrams to visualise the function of transcription
factors. (I) (Basic)
Extension: learners investigate more detail of transcription factors, e.g. how inactive
transcription factors can be activated. (I) (Challenging)
Online
http://biotech.about.com/od/proteinengi
neering/f/transcriptfact.htm
http://bcs.whfre.d
eman.com/thelifewire/content/chp14/1
402002.html
Discuss how each cell of a multicellular organism contains the same genes, but
some will be inactive and there will be no gene expression (link back to 16.3.b).
o Learners suggest why detection of mRNA is carried out to measure gene
activity. (W) (Basic)
Explain, step-by-step, the principles behind the use of microarrays, with learners
making notes.
o Researchers can now access a database of nucleotide sequences (often called
‘gene sequences’) for different genes.
o Multiple copies of the sequences are placed by robotic machines (micro-scale
process) into separate areas on a solid surface, e.g. glass slide.
o Using reverse transcriptase, cDNA is synthesised using fluorescent nucleotides
from the mRNA collected, indirectly ‘labelling’ the genes that are most active.
o cDNA added to the microarray surface ‘hybridises’ (complementary copy) with
their particular gene sequence.
Online
http://www.bio.davidson.edu/courses/g
enomics/chip/chip.html
http://www.genome.gov/glossary/index
.cfm?id=125
http://www.webbooks.com/MoBio/Free/Chap9.htm
http://learn.genetics.utah.edu/content/l
abs/microarray/
Key concepts
Biochemical processes,
DNA, the molecule of heredity
16.3.c
explain the function of transcription
factors in gene expression in
eukaryotes
Key concepts
Biochemical processes,
DNA, the molecule of heredity
19.1.i
explain, in outline, how microarrays are
used in the analysis of genomes and in
detecting mRNA in studies of gene
expression
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
113
Learning objectives
Suggested teaching activities
Learning resources
o The intensity of the fluorescent-coloured areas can be detected using scanners
and the most active genes identified. (W) (Challenging)
Discuss a use of microarrays for learners to research further, e.g. comparing gene
activity of healthy and diseased cells.
o E.g. use red fluorescent nucleotides to ‘label’ the cDNA of a healthy cell, use
green for that of the tumour cell. A combined image of the two scans will show
red, green and yellow areas: red = genes from healthy cell expressed more than
tumour cell; green = genes from the tumour cell expressed more; yellow = both
cells expressing the genes equally. (W) (H) (Challenging)
19.1.a
define the term recombinant DNA
Key concepts
DNA, the molecule of heredity
v2.1 5Y02
Remind learners that, in Unit 7, ‘recombination’ and ‘recombinant’ are terms used in
the context of crossing over and the production of genetically different gametes and
offspring. (W) (Basic)
Explain that there are many definitions of recombinant DNA: learners need the idea
that novel DNA is formed by joining together DNA/genes from different sources.
o Explain that DNA can be added to plasmids, hence the term ‘recombinant
plasmid’, and transferred from one organism to another, hence ‘recombinant
host’. (W) (Basic)
Learners write a definition, qualifying with reference to recombinant plasmids and
recombinant hosts. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://higheredbcs.wiley.com/legacy/col
lege/voet/0470129301/animated_figs/
ch03/3-26.html
114
Learning objectives
Suggested teaching activities
Learning resources
19.1.b
explain that genetic engineering
involves the extraction of genes from
one organism, or the synthesis of
genes, in order to place them in
another organism (of the same or
another species) such that the
receiving organism expresses the
gene product
Remind learners that genes code for proteins and in genetic engineering the desired
product is a protein.
o Learners suggest why it is necessary to use another organism to produce the
protein. (W) (Basic)
Talk learners through the outline construction of a large flow diagram: brief
explanations for each step will help for 19.1.c, 19.1.e, 19.1.f, 19.1.g and 19.1.h,
when they can add further notes (see below). (W) (I) (Basic)
Online
http://www.learner.org/interactives/dna/
engineering.html
http://www.biology.arizona.edu/molecul
ar_bio/problem_sets/Recombinant_D
NA_Technology/recombinant_dna.ht
ml
Textbooks/Publications
Bio Factsheet 13: Genetic engineering
Key concepts
DNA, the molecule of heredity,
Observation and experiment
Past Papers
Paper 41, Nov 2011, Q7
Learners suggest why mRNA is sometimes used to obtain the gene (many more
copies of the mRNA in the cell than the genes; a host bacterial cell cannot cut out
introns from the RNA transcripts of eukaryotic DNA). (W) (Challenging)
Introduce the idea that DNA libraries are now available. (W) (Basic)
Explain that a vector (carrier) is frequently used (often a plasmid) to get the desired
gene into the host. (W) (Basic)
o Discuss when gene cloning occurs: producing many initial copies of the desired
gene and as the host cell replicates. (W) (Challenging)
Learners revise 17.2.a and give an account of the similarities and differences
between genetic engineering and selective breeding. (H) (Challenging)
Learners investigate what is meant by a cDNA library. (I) (Challenging)
Note
19.1.b can be amalgamated with 19.1.h.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
115
Learning objectives
Suggested teaching activities
Learning resources
19.1.h
explain the roles of restriction
endonucleases, reverse transcriptase
and ligases in genetic engineering
Outline the role of restriction endonucleases and DNA ligases.
o Explain how different endonucleases cleave at different, specific sequences to
obtain blunt or ‘sticky’ / overlapping ends.
o Learners add the enzymes to their main flow-chart from 19.1.b and annotate.
(W) (Basic)
Provide learners with details of different restriction endonucleases. On nucleotide
sequence diagrams, learners indicate the cleavage sites and state whether blunt or
sticky ends are produced and the number of fragments formed. (P) (I) (Challenging)
Outline the role of reverse transcriptase.
o Learners annotate their flow chart.
o Explain where DNA polymerase would be required (amplifies the gene). (W) (I)
(Basic)
Learners sequence a set of cards, each containing a single step involved in genetic
engineering. With a second set of cards containing more detail, allocate these to the
correct step. (F)
Learners produce a summary table of names of enzymes involved in genetic
engineering and details of the reactions they catalyse. (H) (Basic)
Extension: learners research the origins of these enzymes. (I) (Basic)
Online
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::535::535::/sites/dl/free/007243731
6/120078/bio37.swf::Restriction%20E
ndonucleases
http://www.geogene.com/genetic-engbasics.html
Discuss features of plasmids and ask learners to suggest advantages: found in
bacteria (will be taken up); small (easy to manipulate/easily taken up); replicate
semi-conservatively (identical copies); replicate independently within bacteria (so
gene cloning occurs); can be removed from one bacterial species and be taken up
by another (greater flexibility); can be cut at specific locations by restriction
endonucleases (for gene insertion). (W) (Challenging)
o Learners add annotations in the relevant steps of their flow chart of 19.1.b. (I)
(Basic)
Explain that once bacteria have taken up the plasmid, they are said to be
‘transformed’. (W) (Basic)
Background: explain that plasmids are more easily taken using, for example,
electroporation or by using calcium ions and heat shock (the bacteria are said to be
‘competent’). (W) (Basic)
Online
http://www.addgene.org/mol_bio_refer
ence/plasmid_background/
Key concepts
Biochemical processes,
Observation and experiment
19.1.e
describe the properties of plasmids
that allow them to be used in gene
cloning
Key concepts
Cells as the units of life,
DNA, the molecule of heredity,
Observation and experiment
Past Papers
Paper 42, June 2012, Q4 (a)(i)
Note
It is preferable to state that plasmids are taken up, rather than ‘placed in’ bacteria.
Learners should appreciate that other organisms, such as yeasts, are useful in
genetic engineering, as they can carry plasmids.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
116
Learning objectives
Suggested teaching activities
Learning resources
19.1.f
explain why promoters and other
control sequences may have to be
transferred as well as the desired gene
Learners recall (16.3.b) that a promoter is a nucleotide sequence on the DNA where
RNA polymerase attaches to initiate transcription.
o Explain that the transcription start point (the first nucleotide to be transcribed) is
within the sequence and the promoter allows the RNA polymerase to recognise
which DNA strand is the template.
o Remind learners of the involvement of transcription factors and that there are
genes coding for these, and that other control sequences exist (no detail
required). (W) (Basic)
With these discussed, learners suggest why, in genetic engineering, promoters and
other control sequences may need to be transferred with the desired gene. (W)
(Challenging)
Learners make brief annotations to their summary flow-chart from 19.1.b. (I) (Basic)
Learners write a short paragraph to explain the role of promoters and why they can
be said to control the expression of a gene. (F)
Extension: learners investigate how the early production of insulin by genetic
engineering used the machinery of the lac operon to control gene expression. (I)
(Challenging)
Online
http://www.addgene.org/mol_bio_refer
ence/promoter_background/
Key concepts
DNA, the molecule of heredity,
Observation and experiment
Past Papers
Paper 42, June 2012, Q4 (a)(ii)
Paper 41, June 2013, Q2 (c)(ii)
Note
In bacteria, RNA polymerase recognises and binds to the promoter with the aid of
one main protein transcription factor but in eukaryotes binding is enabled by a
complex of transcription factors.
19.1.g
explain the use of genes for
fluorescent or easily stained
substances as markers in gene
technology
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Learners recall the concepts involved in DNA uptake to produce recombinant hosts
(19.1.b).
o Explain that a cut plasmid may (with DNA ligase present) re-circularise and be
taken up by a host bacterial cell, or a bacterial cell may not be transformed (take
up the plasmid). These bacteria would not have the desired gene.
o Agree that some method to identify the recombinant bacteria is desirable
(‘screening for recombinants’) in order to avoid wasting money if all bacterial
forms were cultured together. (W) (Basic)
Use images to explain how the gene encoding GFP, green fluorescent protein (most
commonly used gene), is placed between the promoter and the desired gene.
Transcription of both genes occurs and GFP and the desired product result.
o Discuss how UV light enables selection of host cells for large scale culturing,
while non-recombinant bacteria will not fluoresce. (W) (Challenging)
o Learners add annotations to their flow-chart from 19.1.b about screening for
successful recombinants and write a paragraph of explanation. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.dnaftb.org/34/problem.html
http://www.chm.bris.ac.uk/motm/GFP/
GFPh.htm
http://www.conncoll.edu/ccacad/zimme
r/GFP-ww/GFP-1.htm
http://www.scholarpedia.org/article/Flu
orescent_proteins
http://www.microscopyu.com/articles/li
vecellimaging/fpintro.html
http://micro.magnet.fsu.edu/primer/tec
hniques/fluorescence/fluorescentprot
eins/fluorescentproteinshome.html
http://www.gmocompass.org/eng/safety/human_healt
117
Learning objectives
Suggested teaching activities
Learners research one example where genes for enzymes that produce fluorescent
or easily stained substances are now used as markers. Examples are presented to
the class. (W) (G) (P) (Basic)
Note
Background: provide learners with a brief historical perspective on the use of
antibiotic resistance markers to enable screening and explain why these are
becoming less favoured.
19.2.c
explain the advantages of producing
human proteins by recombinant DNA
techniques (reference should be made
to some suitable examples, such as
insulin, factor VIII for the treatment of
haemophilia and adenosine
deaminase for treating severe
combined immunodeficiency (SCID))
Key concepts
Cells as the units of life,
Biochemical processes,
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Discuss the advantages of producing human proteins by genetic engineering /
recombinant DNA techniques (‘genetic manipulation’ is also a term used).
o Discuss how some of the diseases were not previously treatable with the natural
protein: could not be extracted or produced (e.g. adenosine deaminase);
expensive to produce and purify; required extraction from many blood donations
(e.g. factor VIII); problems with the protein used for treatment (e.g. insulin from
pigs or other mammals).
o Discuss additional benefits such as: fewer/no allergic responses from
contaminants; lower/no immune responses from non-self antigen detection; no
risk of disease from contaminating pathogens; ethically/religiously/morally more
acceptable.
o Include an outline of the benefits of using bacteria, yeast or mammalian cells in
tissue culture. (W) (Basic)
Learners research the genetically engineered protein products for treatment of
people with the conditions listed. Provide guidance.
o State whether the protein could be extracted for treatment before genetic
engineering techniques.
o State the function of the protein and if the protein is deficient or absent.
o State how successful the treatment is and whether there are alternative
treatment methods. (H) (Challenging)
Learners make outline notes following discussion on their research. Fill in any gaps
with further explanation.
o Explain that some people require the protein insulin to regulate their blood
glucose concentration (covered in Unit 10). (W) (Basic)
o Explain that factor VIII is a protein required in the cascade of reactions involved
in blood clotting and is used to treat haemophilia (16.2.f, Unit 7). (W) (Basic)
o For SCID, explain that mutations of the ADA gene result in a lack of adenosine
deaminase: a build-up of the substrate (deoxyadenosine) is toxic to immune
Cambridge International AS & A Level Biology (9700) – from 2016
Learning resources
h/126.position_efsa_antibiotic_resista
nce_markers.html
http://www.medicalnewstoday.com/ar
ticles/31227.php
Past Papers
Paper 41, Nov 2012, Q3 (a)(ii)
Paper 41, June 2013, Q2 (b)
Online
http://www.diabetes.co.uk/insulin/huma
n-insulin.html
http://resources.schoolscience.co.uk/u
nilever/1618/proteins/Protch4pg3.html
http://ghr.nlm.nih.gov/condition/adenos
ine-deaminase-deficiency
Past Papers
Paper 43, Nov 2011, Q5 (b)
118
Learning objectives
Suggested teaching activities
Learning resources
system cells (background information: an autosomal recessive disorder). (W)
(Basic)
Learners list the benefits, giving relevant examples where relevant. (F)
Note
The benefits of using bacteria or yeast cells as hosts could be a useful extension
discussion.
19.3.a
explain the significance of genetic
engineering in improving the quality
and yield of crop plants and livestock
in solving the demand for food in the
world, e.g. Bt maize, vitamin A
enhanced rice (Golden riceTM) and GM
salmon
Key concepts
Observation and experiment
Learners recall selective breeding in cattle and in crop plants (17.2.f) and
discussions about the global demand for food (and energy).
o Learners suggest ways in which crops and livestock may be genetically modified
to benefit populations.
o Discuss why Golden riceTM providing vitamin A is considered an improvement in
the quality of a crop plant.
o Explore further ideas that crops may be modified to give a higher yield: two main
ways are making crops resistant to herbicides and resistant to pests (insects).
o Learners suggest why livestock improvements (far less common) are not as
universally approved. Discuss the idea of livestock such as sheep, cattle, hens
and goats growing faster, larger and being more resistant to disease.
o Debate the farming of GM salmon (not strictly ‘livestock’), which can grow to a
marketable size much quicker than non-GM salmon. (W) (Basic) (Challenging)
Learners write an account explaining why crops genetically modified for herbicide
and pest resistance would lead to increased yields. (I) (Basic)
Learners state ways in which livestock can be modified, giving examples to help
their answer. (I) (Basic)
Learners outline the advantages and disadvantages of crop improvement by
conventional breeding techniques compared to genetic modification. (F)
Extension: learners research examples of crop improvement by genetic modification
(such as frost resistance, ability to fix nitrogen, increased time for fruit spoilage,
drought resistance, etc.) and of livestock improvement. (H) (Challenging)
Online
http://www.cato.org/sites/cato.org/files/
serials/files/regulation/2003/4/v26n14.pdf
http://www.newscientist.com/article/dn
3364-gm-crops-boost-yields-more-inpoor-countries.html#.UvhpJ_s9BOo
http://www.europabio.org/do-gm-cropsreally-have-higher-yields
http://www.gmocompass.org/eng/agri_biotechnology/
breeding_aims/147.pest_resistant_cr
ops.html
http://www.efsa.europa.eu/en/topics/to
pic/gmanimals.htm
Textbooks/Publications
Bio Factsheet 13: Genetic engineering
Bio Factsheet 69: Genetic engineering
in agriculture
Bio Factsheet 192: Investigating
weeds and crop yield.
Past Papers
Paper 43, June 2011, Q5 (a)
Paper 42, June 2012, Q4 (a)
19.3.b
outline the way in which the production
of crops such as maize, cotton,
v2.1 5Y02
In groups, learners use resources to prepare annotated flow diagrams summarising
one example of crop improvement from the list in the learning objective.
o Copies of the summary diagrams are made and shared with the rest of the class.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.gmocompass.org/eng/grocery_shopping/c
119
Learning objectives
Suggested teaching activities
Learning resources
tobacco and oil seed rape, may be
increased by using varieties that are
genetically modified for herbicide
resistance and insect resistance
Learners research and produce summary notes about the use of Agrobacterium
tumefaciens as one of the most common vectors and other methods such as
electroporation and ‘gene guns’ to deliver genetic material into host plant cells.
Learners find, analyse and evaluate data that compares the yields of GM crops with
non-GM crops. (H) (Challenging)
rops/24.genetically_modified_rice.ht
ml
http://www.nature.com/scitable/knowle
dge/library/use-and-impact-of-btmaize-46975413
http://en.wikipedia.org/wiki/Golden_rice
http://www.goldenrice.org/
Key concepts
Observation and experiment
Textbooks/Publications
Bio Factsheet 13: Genetic engineering
Bio Factsheet 69: Genetic engineering
in agriculture
Bio Factsheet 192: Investigating
weeds and crop yield.
19.3.c
discuss the ethical and social
implications of using genetically
modified organisms (GMOs) in food
production
Key concepts
Observation and experiment
Learners use guidelines to research some ethical and social implications of using
GMOs, and then debate and discuss these points in class. (W) (H) (Basic)
Learners produce summary points about the topic. (I) (Challenging)
Note
Advise learners to look at the source of funding and editorial policy of websites to
gauge whether the information is objective and impartial.
Online
http://technyou.education.csiro.au/mod
ule/ethics-food-andagriculture/page/204/issues
http://www.i-sis.org.uk/GE-ethics.php
http://www.beep.ac.uk
http://www.salmonnation.com/fish/gefis
h.html
http://www.oceanconservancy.org/ourwork/aquaculture/aquaculturegenetically.html
Textbooks/Publications
Bio Factsheet 13: Genetic engineering.
Bio Factsheet 106: Ethical issues in Alevel Biology
Bio Factsheet 137: GM Farm Scale
Evaluation Trials.
Past Papers
Paper 43, June 2011, Q5 (b)(c)(d)
Paper 42, June 2012, Q4 (e)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
120
Learning objectives
Suggested teaching activities
Learning resources
19.1.c
describe the principles of the
polymerase chain reaction (PCR) to
clone and amplify DNA (the role of Taq
polymerase should be emphasised)
Use a question and answer session to agree that: the desired gene used in the
genetic engineering process needs to be cloned (19.1.b); DNA polymerase is
required to replicate DNA (Unit 3); the DNA strands are held together strongly by
many (individually) weak hydrogen bonds. (W) (Basic)
Explain that, outside the cell, heat (approximately 90°C) can be used to separate the
DNA strands.
o Learners explain why heat stable polymerase enzymes are required.
o Introduce Taq polymerase derived from the thermophilic bacterium Thermus
aquaticus, and discuss how this enzyme’s thermostable structure also allows it
to have a long shelf life.
o Explain what primers are before explaining their role in dictating the correct
section of DNA to be copied and enabling Taq polymerase attachment. (W)
(Challenging)
Using diagrams, provide an overview of PCR. Involve learners in explanations of the
benefits of Taq polymerase stability (heating and many cycles). (W) (Basic)
o Learners label the diagrams and produce a two-column table: main stage and
corresponding explanations. (I) (Challenging)
Learners match statements of the main stages with explanations of why they are
carried out, they then sequence them. (F)
Learners match statements of the components involved to their role in the process.
(F)
Online
http://www.genome.gov/Glossary/index
.cfm?id=159
http://www.webbooks.com/MoBio/Free/Ch9E.htm
http://www.saps.org.uk/secondary/teac
hing-resources/119-investigatingplant-evolution-amplifying-dna-usingpcr
http://www.rothamsted.ac.uk/notebook/
pcr.htm
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Observation and experiment
Textbooks/Publications
Bio Factsheet 67: Modern techniques
in biology: genetics.
Note
Explanation of a primer can be limited to the idea of a short nucleotide sequence
that binds to the DNA template strand at a specific sequence, so enabling chain
elongation.
T. aquaticus was discovered in 1969 in Yellowstone National Park in Wyoming,
USA, noted for its hot springs and geysers.
19.1.d
describe and explain how gel
electrophoresis is used to analyse
proteins and nucleic acids, and to
distinguish between the alleles of a
gene (limited to the separation of
polypeptides and the separation of
DNA fragments cut with restriction
endonucleases)
v2.1 5Y02
Show learners an electrophoresis kit (or a photograph of a kit), explaining the
principles and outlining the technique.
o Include discussion on: the composition of the gel (size of ‘pores’ formed by the
fibrous matrix); ability to alter the voltage applied and/or the ‘run’ time; methods
used e.g. stains or fluorescent dyes to ‘see’ separated bands (if not visible).
o Prompt learners to suggest and explain the factors affecting movement through
the gel. Ensure they appreciate that separation of a mixture will be based on:
size/length/mass; and charge (discuss resistance to flow). (W) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 12
Online
http://www.genome.gov/Glossary/?id=
56
http://www.life.uiuc.edu/molbio/geldige
st/electro.html#run
http://www.ncbe.reading.ac.uk/NCBE/
MATERIALS/menu.html
121
Learning objectives
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Suggested teaching activities
Learning resources
Learners explain why samples of DNA/RNA will move towards the anode
(phosphate groups give a negative charge), and how restriction enzymes (see
19.1.h) will give specific different-sized fragments.
o Explain that the solution containing the DNA fragments can be treated so the
charge is the same for all; hence they are separated by size/length (all
fragments same shape).
o Discuss how RNA molecules will be of different lengths and hence separation by
size will work. (W) (Basic)
Learners use kits (or simulations) to carry out gel electrophoresis of DNA. (I)
(Challenging)
Using resources, learners draw an annotated diagram that helps to outline the
principles behind the process, using nucleic acids as an example. (I) (Basic)
Learners recall protein molecular structure to realise that a mixture can be different
lengths, charges and shapes, hence requiring a different electrophoresis set-up to
DNA. (W) (Basic)
o Explain that a buffer can be used to provide a uniform negative charge and
unfold the proteins.
Learners research identification of a protein by protein blotting or antibody tagging.
(H) (Challenging)
Learners investigate the uses of gel electrophoresis in the analysis of proteins and
nucleic acids and a ‘class list’ made of each to display. (W) (H) (Basic)
Extension: learners research the advantages and disadvantages of the two main
gels, agarose and polyacrylamide. (I) (Challenging)
Learners discuss the differences that may exist between alleles of a gene.
o Discuss how alleles of only slightly different length can be detected with the
correct gel composition.
o Explain that if alleles are the same or similar, undetectable length, restriction
enzymes could be used to obtain fragments: different fragments with different
sequences can be detected. An alternative is using a DNA probe.
o Mention that there are DNA sequence ‘libraries’ to obtain known sequences to
act as markers.
o Use sickle cell anaemia to exemplify how differences between alleles can
sometimes be detected by sampling the protein products, e.g. the two types of
haemoglobin (confirms carrier status). (W) (Challenging
Practical booklet 12 is a protocol for separating dyes by gel electrophoresis that
demonstrates the principles involved in separating DNA.
http://www.bio-rad.com/
http://www.edvotek.com/
http://www.medicine.mcgill.ca/physio/vl
ab/Other_exps/endo/electrophoresis.
htm
http://www.bio-rad.com/enca/applications-technologies/proteinelectrophoresis
http://bcs.whfreeman.com/lehninger5e/
content/cat_020/0301_gel_electropho
resis.html?v=chapter&i=03020.01&s=
03000&n=00020&o=7
http://learn.genetics.utah.edu/content/l
abs/gel/
http://www.neosci.com/demos/101091_DNA/Labs_RestrictionEnzyme.
swf
http://www.biotechlearn.org.nz/themes/
dna_lab/gel_electrophoresis
www.ncbe.reading.ac.uk/ncbe/protocol
s/PDF/DiceSG.pdf
http://www.stanford.edu/group/hopes/c
gi-bin/wordpress/2011/03/genetictesting/
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 67: Modern techniques
in Biology: Genetics.
Past Papers
Paper 41, June 2012, Q3 (b)
Paper 42, June 2013, Q2 (b)
122
Learning objectives
Suggested teaching activities
Learning resources
Note
Generally, small agarose gels are used to separate DNA (lower voltage for
approximately 1-2 hours) whereas large polyacrylamide gels are required for
proteins (higher voltages for about 4 hours). Different electrophoresis tanks and
power packs are required.
Links to 19.2.d: genetic screening can involve gel electrophoresis, e.g. identifying
carriers. In some cases restriction enzymes are used, or probes to locate specific
base sequences.
o Cystic fibrosis: some mutant alleles have large deletions.
o Huntington’s disease: the mutant allele of the Huntington gene has tri-nucleotide
repeat sequences.
o Some cases of haemophilia: a mutant allele in the factor VIII gene has an
insertion that inactivates the gene.
19.2.g
outline the use of PCR and DNA
testing in forensic medicine and
criminal investigations
Key concepts
DNA, the molecule of heredity,
Observation and experiment
v2.1 5Y02
Explain that pure DNA or DNA mixed with other biological materials (e.g. in a tissue
sample such as dried blood) is analysed and compared to existing profiles or known
markers.
o Explain what variable number tandem repeats (VNTRs) are and detail their
importance in an analysis, including: a particular VNTR occurs at a specific
locus; for a particular VNTR different individuals can have a different number of
repeats (so different lengths of the DNA section); VNTRs that are very variable
in different individuals can be used as markers. (W) (Challenging)
Learners suggest the role of PCR (amplify the quantity of each VNTR marker in the
sample). (W) (Basic)
Ensure learners understand that the chance that two individuals (except for identical
twins) have exactly matching DNA profiles (genetic fingerprints) for these selected
markers is virtually nil. (W) (Challenging)
Learners use resources to extract the main points of the technique of genetic
fingerprinting and list as bullet points. (I) (Challenging)
Learners carry out analyses of different results of genetic fingerprints or make up
their own worksheet containing simulated results from a crime scene to swap within
the class for another learner to analyse. (P) (I) (Basic)
Learners explain the role of PCR in DNA fingerprinting and outline the principles as
applied to VNTRs:
o Very small samples of DNA can be analysed.
o Millions of DNA copies can be produced (so can run many tests on the same
original DNA sample).
Cambridge International AS & A Level Biology (9700) – from 2016
Online
https://koshland-sciencemuseum.org/sites/all/exhibits/exhibitd
na/index.jsp
http://learn.genetics.utah.edu/content/l
abs/pcr/
http://technyou.education.csiro.au/mod
ule/dna-profiling/page/220/dnaprofiles-forensic-use
http://www.pbs.org/wgbh/nova/sheppar
d/analyze.html
Past Papers
Paper 41, June 2012, Q3 (a)
123
Learning objectives
Suggested teaching activities
Learning resources
o Longer VNTRs will be impeded more by the gel (move a shorter distance in the
same time than the shorter VNTRs). (I) (Challenging)
19.2.a
define the term bioinformatics
Key concepts
Observation and experiment
19.2.b
outline the role of bioinformatics
following the sequencing of genomes,
such as those of humans and
parasites, e.g. Plasmodium (details of
methods of DNA sequencing are not
required)
Key concepts
v2.1 5Y02
Learners work out what the term bioinformatics means: biology and data, computer
science and information technology merged into one (remind them about statistics).
(W) (G) (Basic)
Explain that there are linked databases holding freely available, continually updated,
information on: nucleotide sequences of genes (gene sequences); whole genome
sequences; mutation sequences; amino acid sequences of proteins; protein
structures; phenotypic data.
o Ideas for learners to consider: input, storage and retrieval of biological
information for analysis; data that can be searched is increasing exponentially.
o Learners define the term bioinformatics and list the principles involved. (W) (I)
(Challenging)
Demonstrate how to use BLAST (basic local alignment search tool), which compares
nucleotide or protein sequences to databases. When a match is found, the statistical
significance of the match is calculated.
o Show learners how a nucleotide sequence can be matched to an amino acid
sequence and how these may match up to known genes belonging to
organisms. (W) (Challenging)
Learners explore the world of bioinformatics for themselves if there is internet
access and report back findings. (W) (H) (Challenging)
Note
Suitable databases to explore are Ensembl (genome), GenBank (DNA sequence),
UniProt (protein sequence), PDB (protein structure) and COSMIC (somatic
mutations in cancer).
Online
http://www.yourgenome.org/downloads
/genomiclinks.pdf
http://www.bioinformatics.org/wiki/Bioin
formatics_FAQ
http://www.ploscompbiol.org/article/info
%3Adoi%2F10.1371%2Fjournal.pcbi.
1002789
http://www.biotnet.org/trainingmaterials/das-game
http://www.genecards.org/#
http://www.genome.gov/glossary/index
.cfm?id=17
http://www.malacards.org/
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/WTDV027167.htm
http://www.ebi.ac.uk/about
http://www.bioinformaticsatschool.eu/
http://www.nature.com/scitable/topicpa
ge/genomics-enables-scientists-tostudy-genetic-variability-6526364
Give an outline of the human genome project (HGP).
o With prompting, learners suggest the role of bioinformatics, such as in: targeting
drug design to the individual; investigating evolutionary links by comparing gene
and protein sequence data; searching for the functions of genes; identifying
mutations; identifying genetic risk factors; gene therapy. (W) (Challenging)
Revise Plasmodium and the control of malaria, including problems with finding a
vaccine (Unit 5). (W) (Basic)
o Then open up a discussion about the role of bioinformatics following the
sequencing of genomes of the species of Plasmodium.
Online
http://www.yourgenome.org/downloads
/genomiclinks.pdf
http://www.bioinformatics.org/wiki/Bioin
formatics_FAQ
http://www.genecards.org/#
http://www.genome.gov/glossary/index
.cfm?id=17
http://www.malacards.org/
Cambridge International AS & A Level Biology (9700) – from 2016
124
Learning objectives
Suggested teaching activities
Learning resources
Natural selection,
Observation and experiment
o Learners suggest the benefits in identifying the genes involved in antigenic
variation and in evading the immune response (information gained about how
some species are more invasive than others).
o Learners discuss how information could be used in the search for new drugs and
vaccines. (W) (G) (Challenging)
Learners write an account of the role of bioinformatics following the sequencing of
genomes, referring to the HGP and the Plasmodium genome and making relevant
links to other relevant learning objectives. (F)
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/WTDV027167.htm
http://www.ebi.ac.uk/about
http://www.bioinformaticsatschool.eu/
http://www.nature.com/scitable/topicpa
ge/genomics-enables-scientists-tostudy-genetic-variability-6526364
http://www.sanger.ac.uk/resources/do
wnloads/protozoa/plasmodiumfalciparum.html
http://www.nature.com/nature/journal/v
419/n6906/full/nature01097.html
http://web.ornl.gov/sci/techresources/H
uman_Genome/project/timeline.shtml
http://web.ornl.gov/sci/techresources/H
uman_Genome/project/info.shtml
http://web.ornl.gov/sci/techresources/H
uman_Genome/publicat/genegatewa
y/GeneGatewayHandout.pdf
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/T/Taxonomy.html
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/WTDV027173.htm
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Genes-Genomes-andHealth/Videos-genomes-and-genetictesting/WTDV027199.htm
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
125
Learning objectives
Suggested teaching activities
Learning resources
19.2.d
outline the advantages of screening for
genetic conditions (reference may be
made to tests for specific genes such
as those for breast cancer, BRCA1
and BRCA2, and genes for
haemophilia, sickle cell anaemia,
Huntington’s disease and cystic
fibrosis)
Learners suggest what is involved in genetic screening (using family history and, if
the test is available, analysing tissue samples for DNA) and name conditions for
which genetic screening is available.
o Ensure the conditions listed are included and explained. (W)
Explain what is meant by genetic counselling. (W) (Basic)
Brainstorm advantages of screening for genetic conditions and complete the list if
necessary.
o Provides information about increased risk of having genetic conditions.
o Identifies carriers.
o Early diagnosis, including identification of disorders in embryos.
o Identifies conditions in foetuses (early treatment may be possible and allows
parents to prepare.
o Enables decisions to be made about having children or having follow-up
treatment. (W) (Challenging)
Learners research and make outline notes on the genetic conditions named, then
match up advantages from the brainstorm list to each condition. (I) (Basic)
Extension: learners suggest some of the disadvantages of screening. (I)
(Challenging)
Online
http://www.nlm.nih.gov/medlineplus/cy
sticfibrosis.html
http://ghr.nlm.nih.gov/gene/CFTR
http://www.ygyh.org/cf/whatisit.htm
http://resources.schoolscience.co.uk/B
BSRC/casestudies/cystic.pdf
http://learn.genetics.utah.edu/content/d
isorders/screening/
http://www.hdfoundation.org/html/hdsat
est.php
http://www.merck.com/mmhe/sec22/ch
256/ch256b.html
Key concepts
DNA, the molecule of heredity,
Natural selection,
Observation and experiment
Note
This topic needs careful handling.
Background: some genetic conditions are more common in certain groups as a
result of common ancestry (sharing similar genetic make-up), e.g. cystic fibrosis is
most common in Caucasians; sickle cell anaemia is common in West and East
African, African-American and Mediterranean populations; Huntington’s disease is
more common in Europe and countries with European links.
19.2.e
outline how genetic diseases can be
treated with gene therapy and discuss
the challenges in choosing appropriate
vectors, such as viruses, liposomes
and naked DNA (reference may be
made to SCID, inherited eye diseases
and cystic fibrosis)
Key concepts
DNA, the molecule of heredity,
v2.1 5Y02
Explain that in gene therapy, the aim is for affected cells to take up the normal, nonmutated gene and produce the normal, functioning protein product.
o Prompt learners to suggest methods of delivery of the normal gene, such as
viruses and liposomes (you may need to describe liposomes). (W) (Basic)
Learners discuss in groups why viruses may be ideal vectors, and then share ideas
with the class. Features: small; can be manipulated to incorporate the gene, be
harmless and not trigger an immune response; target particular cells and enter, or
inject the gene into the cell; have mechanisms to pass through the mucus lining
cells; can integrate their nucleic acid into the target cell genome.
o Explain that the ‘ideal’ virus is difficult to find as it will be almost impossible to fit
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 110: Genetic Disease in
Humans.
Bio Factsheet 134: Cystic Fibrosis
Bio Factsheet 215: Genetic Testing
and Screening
Online
http://www.nlm.nih.gov/medlineplus/cy
sticfibrosis.html
http://ghr.nlm.nih.gov/gene/CFTR
http://www.ygyh.org/cf/whatisit.htm
http://resources.schoolscience.co.uk/B
BSRC/casestudies/cystic.pdf
http://learn.genetics.utah.edu/content/d
isorders/screening/
http://www.hdfoundation.org/html/hdsat
est.php
126
Learning objectives
Observation and experiment
Suggested teaching activities
all the criteria. (W) (G) (Challenging)
Learners research the advantages of the type of virus used in the gene therapy for
eye disease and explain why the eye is a good candidate for gene therapy. (I)
(Challenging)
Learners research (also use knowledge of cell surface membrane structure) why
liposomes can be used as vectors.
o Learners explain how liposomes have been used in clinical trials for the
treatment of cystic fibrosis.
o Extension: learners include an account of the problems faced in treating this
condition. (I) (Challenging)
Explain that SCID has been a successful candidate for gene therapy: the gene for
adenosine deaminase is introduced into T-lymphocytes removed from children with
SCID. The lymphocytes are cultured in tissue culture with a viral vector and then the
cells injected back into the child. (W) (Basic)
Extension: learners research the historical work done by French-Anderson, Blaese
and Rosenburg on SCID gene therapy and explain how the therapy was carried out.
(H) (Basic)
Discuss any recent successes in naked DNA therapy. Explain that initial results
showed that direct injection into muscle has indicated some success in uptake; there
has also been uptake by liver cells. (W) (Basic)
Learning resources
http://www.merck.com/mmhe/sec22/ch
256/ch256b.html
http://learn.genetics.utah.edu/content/g
enetherapy
http://www.visionresearch.eu/index.php?id=696
http://www.newscientist.com/article/dn
24879-gene-therapy-restores-sightin-people-with-eye-disease.html
http://www.newscientist.com/article/mg
22029413.200-bubble-kid-successputs-gene-therapy-back-on-track.html
http://history.nih.gov/exhibits/genetics/
sect4.htm
http://www.genemedresearch.ox.ac.uk/
genetherapy/cfgt.html
http://www.extremetech.com/extreme/1
71873-naked-dna-gene-therapyused-to-non-invasively-cure-heartdisease
http://ghr.nlm.nih.gov/handbook/therap
y/procedures
Textbooks/Publications
Bio Factsheet 51: Gene therapy
Past Papers
Paper 41, Nov 2011, Q5
Paper 43, Nov 2013, Q10 (a)
19.2.f
discuss the social and ethical
considerations of using gene testing
and gene therapy in medicine
(reference should be made to genetic
conditions for which treatments exist
and where none exist, also to IVF,
embryo biopsy and preselection and to
v2.1 5Y02
Explain that there are social and ethical considerations (see Note) of using gene
testing and gene therapy.
o Agree that not all genetic conditions are treatable.
o Discuss issues arising from: gene testing embryos by performing an embryo
biopsy; couples deciding on IVF treatment for embryo testing and preselection
for implantation.
o If not discussed in 19.2.d, explain briefly what is meant by therapeutic abortion.
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.medscape.com/viewarticle/
505222_4
http://ghr.nlm.nih.gov/handbook/therth
e/ethics
Textbooks/Publications
Bio Factsheet 51: Gene therapy
127
Learning objectives
Suggested teaching activities
therapeutic abortions)
(W) (Basic)
Learners write their ideas under four headings on pieces of paper ‘Gene testing –
social consideration’; ‘Gene testing – ethical consideration’; ‘Gene therapy - social
consideration’; Gene therapy - ethical consideration’.
o Learners justify their statements to a small group and, if agreed, add it to a
poster.
o Display the posters for learners to consider and make notes. (G) (I) (Basic)
(Challenging)
Key concepts
Observation and experiment
Learning resources
Past Papers
Paper 41, Nov 2011, Q5
Note
This needs to be treated with sensitivity.
Social = related to human society, e.g. interdependence, mutual relationships,
cooperation for all to benefit.
Ethics = set of agreed standards, determine what is acceptable, followed by a group
of individuals, regulated behaviour.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
128
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 9: Respiration
Recommended prior knowledge
Learners should be familiar with the concept of energy transfer and understand that energy contained within biological compounds can be released for use by the cell.
They should have a sound understanding of what a molecule is, and understand chemical formulae and equations. It would be helpful if they understood the concept of
oxidation and reduction, at least at a simple level.
Context
This unit considers the key concept of biochemical processes and focuses on how the energy contained within food molecules such as glucose is transferred into the
universal energy currency of ATP for use in the cell. All unicellular and multicellular organisms use the organic compound ATP to drive the energy-requiring processes
that occur in cells. There are many direct links to other areas of the syllabus, such as: the structure and role of glucose and lipids from Unit 1; mitochondrion structure
and function from Unit 2; the role of enzymes in metabolic reactions from Unit 2; and ATP from Units 1 and 3. The unit has close links with photosynthesis in Unit 11,
which also covers the concept of energy transfer and ATP synthesis. Throughout the syllabus there are examples of the use of ATP for biochemical processes.
Outline
This unit covers the need for energy in living organisms and the universal occurrence of ATP as energy currency. The four main stages of aerobic respiration,
glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation are described. A distinction is made between the synthesis of ATP by substrate-linked
reactions and by oxidative phosphorylation; the role of coenzymes in these stages is made clear. A comparison is made between aerobic and anaerobic respiration in
mammals and in yeast. An explanation of RQ is given and different respiratory substrates are considered. Learners use respirometers to make quantitative studies of
respiration and have an opportunity to improve planning and evaluative skills. This unit lends itself to sequential descriptions and the construction of flow diagrams to
illustrate the many different stages that occur within the overall process.
Teaching time
It is recommended that this unit should take approximately 7% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
129
Learning objectives
Suggested teaching activities
Learning resources
12.1.a
outline the need for energy in living
organisms, as illustrated by anabolic
reactions, such as DNA replication
and protein synthesis, active transport,
movement and the maintenance of
body temperature
Brainstorm ideas to construct a disorganised set of statements. Encourage learners
to include examples from prokaryotes and eukaryotes. (W) (Basic)
o Learners give headings for main uses of energy in organisms, accompanied by
bullet-point notes.
o Agree that some examples from the brainstorming session could be grouped,
e.g. under ‘movement’. Bullet points could include: bacteria and flagellar
movement (outline the difference between prokaryotic and eukaryotic flagella);
protoctists and amoeboid movement, synchronous rhythm of cilia and flagellar
movement; discharge of spores in fungi; muscle contraction in animals;
translocation of sugars or closure of flytrap (see 15.2.a) in plants.
o Learners recall Unit 1, Biological molecules, for relevant bullet points for
anabolic reactions. (I) (Basic)
Online
http://www.elmhurst.edu/~chm/vchem
book/592energy.html
http://www.rsc.org/Education/Teacher
s/Resources/cfb/index.htm
Key concepts
Cells as the units of life,
Biochemical processes
Note
Ensure that learners understand the meanings of the terms metabolism and
catabolism.
12.1.b
describe the features of ATP that
make it suitable as the universal
energy currency
Key concepts
Biochemical processes
Use questioning to remind learners of the structure of an ATP molecule. Ensure
learners realise that energy is released at each step of the complete hydrolysis of
ATP:
ATP ADP AMP
(W) (Basic)
Write out a list of features that make ATP suitable as the universal energy currency.
o Learners add brief notes to explain each feature, including a diagram showing
the one-step process of release of energy from ATP hydrolysis and synthesis of
ATP from ADP and Pi (inorganic phosphate). (I) (Basic)
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/ATP.html
http://staff.jccc.net/pdecell/metabolism
/entrans.html#atpadp
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBookATP.html
Textbooks/Publications
Bio Factsheet 129: ATP – what it is,
what it does
Past Papers
Paper 41, June 2011, Q7 (a)
12.2.a
list the four stages in aerobic
respiration (glycolysis, link reaction,
Krebs cycle and oxidative
phosphorylation) and state where
each occurs in eukaryotic cells
v2.1 5Y02
Learners recall an overall equation for aerobic respiration:
glucose + oxygen energy + water + carbon dioxide
o State that ATP should be substituted for ‘energy’.
o Learners write out a balanced equation using the correct chemical formulae (for
completeness, mention heat energy). (W) (Basic)
Learners write out the overall equation for aerobic respiration and produce a large
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://leavingbio.net/RESPIRATION%28ordinary%20level%29.htm
http://leavingbio.net/respiration%28higher%20level%29.htm
130
Learning objectives
Key concepts
Cells as the units of life,
Biochemical processes,
Natural selection
12.2.b
outline glycolysis as phosphorylation
of glucose and the subsequent
splitting of fructose 1,6-bisphosphate
(6C) into two triose phosphate
molecules, which are then further
oxidised to pyruvate with a small yield
of ATP and reduced NAD
Key concepts
Biochemical processes
Suggested teaching activities
diagram (full page) of a cell (cytoplasm labelled), containing a (not-to-scale) large
labelled mitochondrion with visible cristae (1.2.b, Unit 2).
o Learners write the heading of each of the four stages in the correct locations
and add to this later. (I) (Basic)
Learning resources
Past Papers
Paper 41, June 2011, Q7 (b)(iii)
Note
Glycolysis: can be shown later as glucose pyruvate.
Link reaction: pyruvate entering the mitochondrial matrix and the reaction with
coenzyme A, acetyl coenzyme A, enters the cycle.
Krebs cycle: main stages of the cycle only, showing involvement of FAD and NAD,
decarboxylation and ATP production.
Oxidative phosphorylation: NADH and FADH leaving the cycle to the crista, ATP
formation.
Highlight to learners the similar biochemistry in different species of organisms (link
to the evidence for evolution in Unit 7).
Build up the idea that: (i) respiration is a series of enzyme-controlled metabolic
reactions, (ii) it takes place in all living cells, and (iii) energy contained in molecules
such as glucose is used to make ATP molecules. (W) (Basic)
Explain that glycolysis occurs in the cytoplasm (in virtually every organism) in both
anaerobic and aerobic respiration. (W) (Basic)
Learners copy out a skeleton flow diagram of glycolysis, with glucose, the two
intermediates, and pyruvate shown (missing intermediate stages could be signified
by the correct number of arrows in between).
o With question and answer prompts, learners build up their flow charts with detail
and explanatory annotations. Ensure they understand that: coenzyme NAD is
required to act as an electron (hydrogen) carrier for the enzyme-catalysed
reaction (see 12.1.d); NADH has different fates, depending on whether or not
oxygen is available.
o Learners show clearly the tally of ATP use and production.
o The number of carbons for each of the molecules in the process is shown in
brackets. (W) (I) (Challenging)
Explain that in glycolysis ATP can be formed when another phosphorylated organic
compound transfers a phosphate to ADP: so ATP is synthesised as a product in a
substrate-linked reaction (see 12.1.c). (W) (Basic)
Online
http://glycolysis.co.uk/
www.science.smith.edu/departments/
Biology/Bio231/glycolysis.html
http://www.sumanasinc.com/webconte
nt/animations/content/cellularrespirati
on.html
http://www.johnkyrk.com/glycolysis.ht
ml
http://highered.mcgrawhill.com/sites/9834092339/student_vi
ew0/chapter7/how_glycolysis_works.
html
http://resources.teachnet.ie/foneill/res
pir.html
Past Papers
Paper 41, Nov 2011, Q6 (a)(b)
Note
If able learners are given a more complete picture, stress that the additional
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
131
Learning objectives
Suggested teaching activities
Learning resources
intermediate steps and compounds are not required learning.
Mention that ‘substrate-level phosphorylation’ is an alternative term to substratelinked ATP synthesis.
12.2.c
explain that, when oxygen is available,
pyruvate is converted into acetyl (2C)
coenzyme A in the link reaction
Key concepts
Biochemical processes,
Organisms in their environment
Explain that pyruvate travels from the cytosol through the inner and outer
mitochondrial membranes to enter the matrix where the link reaction occurs. (W)
(Basic)
Learners study and comment on the link reaction equation before making notes.
They should note that:
o Coenzyme A transfers an acetyl group to the Krebs cycle (see 12.1.d).
o Carbon dioxide is given off, hence decarboxylation* occurs.
o NAD acts as an electron (hydrogen) carrier, hence dehydrogenation* occurs.
o The reaction occurs twice for each original glucose molecule. (G) (I) (Basic)
(Challenging)
Note
See 12.2.e also.
12.2.d
outline the Krebs cycle, explaining that
oxaloacetate (a 4C compound) acts as
an acceptor of the 2C fragment from
acetyl coenzyme A to form citrate (a
6C compound), which is reconverted
to oxaloacetate in a series of small
steps
Key concepts
Biochemical processes
Build up the simple diagram showing the required steps in the Krebs cycle, including
the number of carbon atoms for the three named compounds.
o Emphasise: its cyclic nature; enzyme-controlled reactions (no names required);
more steps are involved than is shown. (W) (I) (Basic)
Explain that two carbon dioxide molecules are released for one turn of the cycle and
ask learners to decide where this is and add to the diagram.
o Tell learners where substrate-linked phosphorylation occurs (see 12.2.b and
12.1.c) so they can add ATP formation to their diagram (knowledge of GTP not
required).
o Learners volunteer the role of NAD and FAD, and then add the formation of
NADH and FADH to their cycle (see 12.2.d). (I) (Basic)
Learners state and explain how many turns of the cycle occur for each molecule of
glucose. (I) (Basic)
Allow learners a short time to look at their diagrams, and then talk through the steps
while they draw the cycle. (F)
Online
http://www.saps.org.uk/learners
http://www.wiley.com/legacy/college/b
oyer/0470003790/animations/tca/tca.
htm
http://www.science.smith.edu/departm
ents/Biology/Bio231/krebs.html
http://www.johnkyrk.com/krebs.html
http://highered.mcgrawhill.com/sites/0072507470/student_vi
ew0/chapter25/animation__how_the
_krebs_cycle_works__quiz_1_.html
Online
http://www.saps.org.uk/learners
http://www.wiley.com/legacy/college/b
oyer/0470003790/animations/tca/tca.
htm
http://www.science.smith.edu/departm
ents/Biology/Bio231/krebs.html
http://www.johnkyrk.com/krebs.html
Past Papers
Paper 43, June 2011, Q6 (a)(b)
Note
Learners should avoid websites that have far more detail than required.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
132
Learning objectives
Suggested teaching activities
12.2.e
explain that reactions in the Krebs
cycle involve decarboxylation and
dehydrogenation and the reduction of
NAD and FAD
Learners add annotations to the Krebs cycle:
o dehydrogenation occurs: the NADH and FADH contain hydrogen atoms protons
and electrons (from the respiratory substrate)
o decarboxylation of intermediates occurs: carbon dioxide is given off. (I) (Basic)
Give learners time to assimilate the information on their diagrams before testing
them. (I) (Challenging)
Key concepts
Biochemical processes
12.1.c
explain that ATP is synthesised in
substrate-linked reactions in glycolysis
and in the Krebs cycle
Learning resources
Note
Dehydrogenase and decarboxylase enzymes could be mentioned here (not required
learning).
Learners add an explanation of ATP synthesis by substrate-linked reactions to their
summary diagram of 12.2.a. (W) (Basic)
Online
http://sandwalk.blogspot.co.uk/2007/1
2/how-cells-make-atp-substratelevel.html
Learners label a basic diagram of the membrane carriers of the electron transport
chain (ETC) and the ATP synthase (synthetase) complex in the inner mitochondrial /
crista membrane (include labels for the mitochondrial matrix and the intermembrane space).
With prompting and guidance, learners show on their diagram the transfer of
hydrogen to the membrane from NADH and FADH and the release of the
coenzymes for re-use in the Krebs cycle. (W) (Basic)
Learners contribute to build up the rest of the diagram. For the electron transport
chain include:
o Hydrogen from NAD/FAD split into protons and electrons.
o Oxidation-reduction reactions are involved (hence ‘oxidative’) as electrons are
transported down the ETC (i.e. to lower energy levels).
o Energy provided by the electron transfer is used to pump protons from the
matrix into the intermembrane space.
o Oxygen (final electron acceptor) + electrons + protons produce water as a waste
product.
For chemiosmosis, use learner knowledge of AS Level to discuss:
o The relatively impermeability of the membrane to protons (so allowing a buildup).
Online
http://www.science.smith.edu/departm
ents/Biology/Bio231/etc.html
http://bcs.whfreeman.com/thelifewire/c
ontent/chp07/0702001.html
Key concepts
Biochemical processes
12.2.g
explain that during oxidative
phosphorylation:
energetic electrons release energy
as they pass through the electron
transport system
the released energy is used to
transfer protons across the inner
mitochondrial membrane
protons return to the mitochondrial
matrix by facilitated diffusion
through ATP synthase providing
energy for ATP synthesis (details of
ATP synthase are not required)
Key concepts
Biochemical processes
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 12: Respiration
Past Papers
Paper 42, June 2013, Q4 (a)(i)
133
Learning objectives
Suggested teaching activities
Learning resources
o Facilitated diffusion of protons through the enzyme complex down their
concentration (and electrical) gradient.
o The enzyme-catalysed synthesis of ATP from ADP and inorganic phosphate by
the movement of protons (proton-motive force). (W) (I) (Challenging)
Learners sort a set of statements into a correct sequence to outline oxidative
phosphorylation and then add an outline to their summary diagram of 12.2.a. (P) (I)
(Basic) (Challenging)
Learners write a sequential account of the process. (F)
12.2.f
outline the process of oxidative
phosphorylation including the role of
oxygen as final electron acceptor (no
details of the carriers are required)
Key concepts
Biochemical processes
Assess understanding of 12.2.g by agreeing an outline summary with learners.
o Oxidative phosphorylation is the last stage in the release of energy from the
initial respiratory substrate and oxygen is the final electron acceptor.
o The two linked parts to the process are the events involving the electron
transport chain and the events linked with a process known as chemiosmosis.
o The sources of the ‘energetic’ electrons are NADH and FADH from the Krebs
cycle and NADH from the link reaction.
o ATP formation by oxidative phosphorylation is a process involving oxidationreduction reactions, where the energy needed for ATP synthesis is from the
transfer of electrons from a higher energy electron donor to a lower energy
electron acceptor.
Learners add an outline of the link reaction, Krebs cycle and oxidative
phosphorylation to their summary diagram of 12.2.a. (I) (Basic)
Online
http://www.stolaf.edu/people/giannini/fl
ashanimat/metabolism/mido%20e%2
0transport.swf
Past Papers
Paper 43, June 2011, Q6 (c)
Note
Carriers do not need identifying but explain that these are membrane proteins.
Learners should be able tackle the concepts involved in 12.2.h if they have
mastered the outline of 12.2.g.
Chemiosmosis as a term is not specified in a learning objective, but learners should
be familiar with the term.
12.1.e (i)
explain that the synthesis of ATP is
associated with the electron
transport chain on the membranes
of mitochondria and chloroplasts
(see 12.2.g)
Only part of this learning objective is included here: explain that the synthesis of ATP is
associated with the electron transport chain on the membranes of mitochondria (see
12.2.g)
With a brief written test, confirm learner knowledge and understanding of this
learning objective (all details previously covered). (I) (Basic)
In preparation for Unit 11, explain that there is also an ETC located in the thylakoid
membranes of chloroplasts. (W) (I) (Basic)
Online
http://www.ncbi.nlm.nih.gov/books/NB
K21063/
Key concepts
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
134
Learning objectives
Suggested teaching activities
Learning resources
Explain that many enzymes require a non-protein (co-)factor, in their active site to
help in catalysis, and that organic cofactors that associate with the enzyme during
catalysis and then dissociate are known as coenzymes. (W) (Basic)
Ensure learners now understand that NAD and FAD are electron (hydrogen)
carriers, so become reduced and can give electrons to electron acceptors during
respiration (becoming oxidised again).
o Learners should be clear that the oxidation of NADH and FADH releases energy
that can be used to synthesise ATP. (W) (Basic)
Online
http://www.ebi.ac.uk/thorntonsrv/databases/CoFactor/index.php
From electron micrographs of mitochondria, learners identify the outer and inner
membrane, cristae and matrix.
o Learners check if 70S ribosomes and small circular DNA is visible. (P) (I)
(Basic)
Learners construct an annotated diagram summarising how the structure of a
mitochondrion is adapted for its functions. (I) (Challenging)
Online
http://www.johnkyrk.com/mitochondrio
n.html
Use flow diagrams to explain the lactate pathway in mammals and the ethanol
pathway in yeast, with learners providing the main outline of glycolysis (glucose to
pyruvate) and naming the location (cytoplasm). (W) (Basic)
Explain that these pathways occur when oxygen is not available, with pyruvate and
ethanol acting as the final electron acceptors to produce lactate and ethanol as
waste products. (W) (Basic)
Learners suggest why pyruvate needs to be processed further when no more ATP
is produced (the regeneration of NAD to allow glycolysis to continue - there is a very
limited quantity of NAD in each cell). (W) (Basic)
Learners add an outline to their summary diagram of 12.2.a after making their own
flow diagrams. (I) (Basic)
Learners begin with oxidative phosphorylation and work backwards through earlier
stages to write down a series of statements showing the consequences if oxygen is
not available. (F) (Challenging)
Learners research the concept of oxygen debt and write an explanation.
Online
http://www.emc.maricopa.edu/faculty/f
arabee/BIOBK/BioBookGlyc.html#An
aerobic
http://www.brianmac.demon.co.uk/oxd
ebit.htm
Cells as the units of life,
Biochemical processes
12.1.d
outline the roles of the coenzymes
NAD, FAD and coenzyme A in
respiration
Key concepts
Biochemical processes
12.2.i
describe the relationship between
structure and function of the
mitochondrion using diagrams and
electron micrographs
Key concepts
Cells as the units of life,
Biochemical processes
12.2.k
explain the production of a small yield
of ATP from respiration in anaerobic
conditions in yeast and in mammalian
muscle tissue, including the concept of
oxygen debt
Key concepts
Biochemical processes,
Natural selection
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 61: Chloroplasts and
mitochondria
Textbooks/Publications
King p.84
Siddiqui p.101
Past Papers
Paper 43, June 2013, Q4 (b)
135
Learning objectives
Suggested teaching activities
Learning resources
o Annotations can be added to the lactate pathway to show how, when oxygen
becomes available, lactate can be converted back to pyruvate, which can then
be converted to glucose and glycogen for storage, or enter the Krebs cycle. (H)
(Challenging)
Extension practical: learners investigate the effect of different concentrations of
ethanol on rates of respiration in yeast. (I) (Challenging)
Note
Mention to learners that anaerobic respiration in yeast is also known as alcoholic or
ethanol fermentation and that anaerobic respiration in mammalian tissues is also
known as lactic acid or lactate fermentation.
Explain to learners that the reduction of pyruvate to lactate is common in many
bacteria. Highlight that these reactions are similar in widely different species of
organism.
12.2.l
explain how rice is adapted to grow
with its roots submerged in water in
terms of tolerance to ethanol from
respiration in anaerobic conditions and
the presence of aerenchyma
Key concepts
Organisms in their environment
12.2.j
distinguish between respiration in
aerobic and anaerobic conditions in
mammalian tissue and in yeast cells,
contrasting the relative energy
released by each (a detailed account
v2.1 5Y02
Remind learners of xerophytes and adaptation to survival in arid conditions (7.2.f)
and introduce rice as a plant adapted to survive with its roots submerged in water,
which has little oxygen. (W) (Basic)
Explain that an ethanol build-up is toxic to yeast cells and that plant cells also
produce ethanol when in anaerobic conditions.
o Agree that continuous or prolonged anaerobic conditions as experienced by rice
when it is growing in flooded fields means that root cells need to be tolerant to
ethanol. (W) (Basic)
Check learner understanding of the terms used in the learning objective: submerged
and tolerance. (W) (Basic)
Learners use a light microscope to observe aerenchyma in root and stem sections
of prepared slides. (I) (Basic)
To summarise, learners list and explain the features that make rice adapted to grow
with roots that are submerged in water, and explain why most plants cannot survive
when their roots are submerged in water. (F)
Online
http://plantsinaction.science.uq.edu.au
/edition1/?q=content/18-1-2adaptive-responses-waterlogging
www.biologymad.com/resources/Crop
%20Plants.pps
Learners suggest what is meant by respiration: brainstorm ideas such as: the
release of energy from food; the production of ATP; ATP for use by the cell; the
process occurs in the cell.
o Expand the discussion to distinguish between aerobic respiration and
respiration in anaerobic conditions. (W) (Basic)
Emphasise that most of the ATP is synthesised as a result of oxidative
Textbooks/Publications
Jones, Fosbery, Taylor, Gregory, has
on page 205 (2007), or on page 277
(2013), a balance sheet of ATP use
and synthesis. This could be used to
give learners an idea of the
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 41, Nov 2011, Q4 (a)(b)
Paper 42, June 2013, Q10 (b)
136
Learning objectives
Suggested teaching activities
of the total yield of ATP from the
aerobic respiration of glucose is not
required)
phosphorylation, requiring the reduced coenzymes from the link reaction and Krebs
cycle (compare with the 2ATPs produced without oxygen). (W) (Basic)
Learners make notes comparing respiration in aerobic and anaerobic conditions.
(W) (Basic)
Key concepts
Biochemical processes
12.2.h
carry out investigations to determine
the effect of factors such as
temperature and substrate
concentration on the rate of respiration
of yeast using a redox indicator (e.g.
DCPIP or methylene blue)
Key concepts
Biochemical processes,
Organisms in their environment,
Observation and experiment
12.1.f
explain the relative energy values of
carbohydrate, lipid and protein as
respiratory substrates and explain why
lipids are particularly energy-rich
Key concepts
Biochemical processes
v2.1 5Y02
Note
‘Balance sheets’ are not required. There are different totals for ATP production in
aerobic respiration, varying from 32, to 36, to 38 in older text books. In more recent
texts, the estimate of ‘1NADH = 3ATP’ is now seen as approximately 1NADH =
2.5ATP (also 1FADH = 1.5ATP).
Learning resources
difference in relative energy
released.
Past Papers
Paper 41, June 2011, Q7 (b)(ii)
Paper 41, Nov 2011, Q6 (c)
Remind learners that yeast is not a plant but a fungus. Emphasise that yeast
respires aerobically and in anaerobic conditions. (W) (Basic)
Explain that redox dyes are used as indicators of hydrogen transfer and in
investigations can be used as artificial hydrogen acceptors to provide a visual check
on the rate of respiration (the reduction of NAD or FAD cannot be ‘seen’). (W)
(Basic)
o State that methylene blue is blue in the oxidised state (without hydrogens) and
turns colourless as hydrogens are accepted and it becomes reduced. (W)
(Basic)
o With this knowledge, small groups can be set the task of planning an
appropriate investigation to carry out. (G) (Challenging)
Note
These investigations are a good opportunity to develop planning skills.
Experiments with yeast and anaerobic respiration require the substrate solution
(e.g. glucose) to be boiled (to remove oxygen) and cooled.
Learners recall the overall equation for aerobic respiration and understand how it
balances. (W) (Basic)
Explain that many cells can use other respiratory substrates, such as other sugars,
lipids and proteins, and that different substrates have different energy values per
unit mass. (W) (Basic)
Reflect back to 12.1.e to remind learners about the importance of supplying
hydrogen to the ETC for electron flow and the release of energy for ATP production.
Learners consider ratios of C, H and O, to explain and note down the relative
energy values of proteins, carbohydrates and lipids, noting that lipids, with
proportionately more hydrogen per g of substrate, will yield more energy. (W) (I)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://mutuslab.cs.uwindsor.ca/schurk
o/animations/bombcal/animation4.ht
m
http://highered.mcgrawhill.com/sites/0073040541/learner_vi
ew0/chapter7/animation__bomb_cal
orimeter.html#
137
Learning objectives
Suggested teaching activities
Learning resources
(Basic)
Note
Knowledge of how the energy values are obtained is not required (see learning
resources / endorsed textbooks for background information).
12.1.g
define the term respiratory quotient
(RQ) and determine RQs from
equations for respiration
Key concepts
Biochemical processes,
Organisms in their environment
12.2.m
carry out investigations, using simple
respirometers, to measure the effect
of temperature on the respiration rate
of germinating seeds or small
invertebrates
Key concepts
Observation and experiment
Learners write out the definition of respiratory quotient and the formula to use when
calculating RQ values.
o Explain that volumes or moles or molecules can be used but for any one
calculation they should not be mixed.
o Learners calculate the RQ value for glucose. (W) (I) (Basic)
When provided with equations, learners calculate the RQs for named substrates.
(P) (I) (Basic) (Challenging)
o Learners construct a summary table for carbohydrates, proteins and lipids
(approximate values). (I) (Basic)
o Learner explain the link between high RQ values and anaerobic respiration. (I)
(Basic)
Learners try SAQ 15.8, in Jones, Fosbery, Taylor, Gregory (2007), to calculate an
RQ for a fatty acid. (I) (Challenging)
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Phot
osynResp/PhotosynResp.htm
Explain how to use a simple respirometer to determine the rate of oxygen uptake
and rate of carbon dioxide production. (W) (Basic)
Discuss the benefits of using thermostatically-controlled water baths to maintain a
constant temperature.
o Learners suggest other ways of maintaining a constant temperature, with peer
evaluation of the method. (P) (I)
Practical booklet 7 involves using a simple respirometer and provides opportunity
for data analysis and planning for Paper 5. Learners plan an investigation to find the
optimum temperature for respiration. Learners swap and carry out a partners plan
exactly as written, each to provide their partner with an evaluation of the plan. (P) (I)
(Challenging)
Practical booklet 7
Note
You may wish to save time and also carry out the requirement of 12.1.h.
Simple designs, using a single syringe and capillary tubing (as in Practical booklet
7) are far more sensitive to temperature and require minimal handling.
The simple respirometers are more reliable in yielding results than the modifications
of the Barcroft respirometer, usually given in practical guides.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
In Jones, Fosbery, Taylor, Gregory,
pages 208-209 (2007), or page 281
(2013), explains respiratory quotient
and has worked examples.
Past Papers
Paper 43, Nov 2012, Q8 (c)
Online
http://www.phschool.com/science/biol
ogy_place/labbench/lab5/features.ht
ml
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Phot
osynResp/PhotosynResp.htm
Textbooks/Publications
King p.80-83
Siddiqui p.101-103
138
Learning objectives
Suggested teaching activities
Learning resources
Temperature compensation by having two tubes linked by a manometer results in
well controlled experiments, but introduces potentially leaky joints.
A teacher demonstration of a temperature-compensated respirometer is advisable,
so learners see both types.
12.1.h
carry out investigations, using simple
respirometers, to determine the RQ of
germinating seeds or small
invertebrates (e.g. blowfly larvae)
Learners carry out an investigation to measure RQ using the simple respirometers
(planning skills may be developed here),
o e.g. learners measure carbon dioxide production and oxygen absorption by
germinating seeds, and calculate RQ. This has the potential to develop abilities
evaluating investigations. (I) (Challenging)
Key concepts
Observation and experiment
Practical booklet 7
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Phot
osynResp/PhotosynResp.htm
http://www.phschool.com/science/biol
ogy_place/labbench/lab5/features.ht
ml
Textbooks/Publications
King p.80-83
Siddiqui p.101-103
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
139
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 10: Mammalian physiology, control and coordination
Recommended prior knowledge
Learners should have a good understanding of cell structure and the structure of a cell surface membrane. They should have an appreciation of the role of the various
components, particularly the role of glycoproteins as receptors in cell signalling and of membrane transport proteins. They should understand the concept of water
potential and have good knowledge of transport mechanisms across membranes, including facilitated diffusion and active transport from Unit 2.
Context
This unit builds on the key concept of cells as the basic units of life to consider how mammals, as multicellular organisms, control and coordinate activities and how
homeostatic mechanisms enable a balance to be maintained. The maintenance of homeostatic mechanisms for healthy functioning, such as in controlling blood
glucose concentrations, extends learner understanding of non-infectious disease. Cell structure, cell membranes, transport across membranes and the mammalian
circulatory system are topics covered at AS Level that are an important foundation for the learning objectives studied in this unit. A study of dipsticks, biosensors and
the contraceptive pill highlights the dependence of humans on biotechnology: biotechnology results from observation, enquiry and experiment, a key concept. The
examples studied here extend learner knowledge from those already covered in Unit 8.
Outline
This unit begins by highlighting the importance of responding to external and internal stimuli with effective control and coordination by the nervous system and by the
endocrine system. The structure and function of the motor and sensory neurone is covered and there is a detailed study of the transmission of nerve impulses,
including transmission across the synapse and the neuromuscular junction, followed by a consideration of the sliding filament theory of muscle contraction. Learners
consider the involvement of the nervous and endocrine systems in homeostatic mechanisms and discuss the role of negative feedback. Thermoregulation,
osmoregulation and blood glucose regulation exemplify the importance of homeostasis in mammals. The production of urea and the role of the kidney in the excretion
of nitrogenous wastes are described. Detail of the control of blood glucose concentration and water content (by the kidney) illustrates the concept of homeostasis.
Biotechnological applications are included by considering the use of dipsticks and biosensors in the detection of glucose in the blood and urine, and of protein and
ketones in urine. The unit concludes with a study of the menstrual cycle and the role of hormones in the cycle, which leads to a description of the contraceptive pill.
Teaching time
It is recommended that this unit should take approximately 10% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
140
Learning objectives
Suggested teaching activities
Learning resources
15.1.a
compare the nervous and endocrine
systems as communication systems
that co-ordinate responses to changes
in the internal and external
environment (see 14.1.a) and 14.1.b)
Discuss the need for communication between organs in a multicellular organism and
how activities need to be controlled and coordinated. (W) (Basic)
Use a brainstorm session to gauge learner knowledge and to discuss the main
features of each. As individuals make suggestions and agree whether they are
referring to the nervous or endocrine system. (W) (Basic)
o Learners note down that the two systems are for control, coordination and
internal communication, and that they can interrelate and affect each other. (W)
(Basic)
Learners research and give definitions of the terms: stimulus, receptor, effector,
control centre and response. (I) (Basic)
Learners list the features of an endocrine gland (an organ or tissue), with teacher
guidance. (W) (I) (Basic)
o Learners sketch endocrine glands onto a cut-out / diagram of a body and name
the hormones that they secrete. Fill in any gaps in knowledge, mentioning those
particularly that are in this syllabus. (I) (Basic)
o Learners name the target cells / tissues of each hormone, consolidating
understanding of hormones acting at a distance from their origin and at particular
sites of action. (W) (Basic)
Focus on the nervous system and ask what the equivalent to the hormones would
be to enable coordination. Encourage learners to use the terms nerve impulses or
impulses. (W) (Basic)
Continue the discussion for learners to name the brain as the main control centre,
and muscles and glands, including endocrine glands, as effectors.
Divide the class into two. One half participates in a group discussion to suggest
examples of internal changes in organisms, stating for each one: the organs /
systems that are affected; receptor(s); communication method; effector(s); and
response(s). The other half suggests examples of changes in external environment.
The two groups come together to share ideas. (W) (G) (Basic).
CD-ROM
Bioscope – has images of nerves (LS
and TS).
Key concepts
Cells as the units of life,
Organisms in their environment
Online
http://www.udel.edu/Biology/Wags/hist
opage/colorpage/cp/cp.htm
http://www.s-cool.co.uk/alevel/biology/nervous-and-hormonalcontrol
Textbooks/Publications
Bio Factsheet 38: Animal hormones
and hormone action.
King p. 151-152
Siddiqui p.164-167, 171
Past Papers
Paper 41, June 2011, Q9 (a)
Note
It will be noted that both systems involve negative feedback – a verbal clarification of
this mechanism is sufficient as learners will define the term later.
Understanding of all terms will be consolidated as learners cover specific examples
within the unit.
15.1.b
describe the structure of a sensory
v2.1 5Y02
Explain that nerves are composed of many specialised nerve cells, neurones, held
by connective tissue. (W) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www2.estrellamountain.edu/facul
141
Learning objectives
Suggested teaching activities
Learning resources
neurone and a motor neurone
Learners draw, label and annotate a sensory and a motor neurone. (I) (Basic)
o Learners compare the diagrams with electron micrographs. (I) (Challenging)
Learners explain how the structure of the neurone is related to its function (or wait
until after 15.1.d has been covered). (H) (Basic)
Learners complete unlabelled and incomplete diagrams (the diagrams could lack
nuclei, myelin sheaths and synaptic knobs). (F)
ty/farabee/biobk/BioBookNERV.html#
The%20Neuron
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/N/Neurons.html
Explain the difference between a sensory receptor cell and a sense organ, e.g.
tongue = organ of taste; taste cells are chemoreceptors (sensory receptor cells)
found in clusters called taste buds. (W) (Basic)
Explain that the different forms of energy arriving at the sensory receptor get
converted (transduced) into electrical energy of the nerve impulse.
o State that all sensory receptors are transducers. (W) (Basic)
Learners research and list the different sensory receptors in humans and name the
forms of energy received by each receptor. (P) (I) (Basic)
Describe the sensory neurone with a resting potential and explain how a stimulus
leads to membrane depolarisation and impulse transmission.
o State that depolarisation causes an action potential to be generated and explain
that details are covered later. (W) (Challenging)
Choose for example, chemoreceptors as sensory receptors and state that they
detect specific molecules or classes of molecule.
o Learners suggest internal and external stimuli that are detected by
chemoreceptors and give examples of responses (e.g. the difference between
harmful / toxic substances taken into the mouth and food). (W) (Basic)
Show learners a diagram of a sensory receptor cell / chemoreceptor and explain that
a taste cell has contact with a sensory neurone.
o Explain that the binding of molecules to receptors on the cell surface membrane
(many microvilli) of the taste cell leads to depolarisation, which is passed onto
the sensory neurone and the control centre.
o Learners state the type of transduction that has occurred. (W) (Challenging)
Learners produce a diagram of a sensory receptor cell, showing synapses with
dendrites of a sensory neurone.
o Learners annotate the sequence of events occurring from the detection of a
stimulus to an impulse being transmitted along the sensory neurone. (I)
(Challenging)
Introduce the terms receptor potential and all-or-nothing law/rule, either by teacher-
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp44/4402001.html
http://faculty.washington.edu/chudler/t
wopt.html
http://www.answers.com/topic/tasteand-smell
Key concepts
Cells as the units of life
15.1.c
outline the roles of sensory receptor
cells in detecting stimuli and
stimulating the transmission of nerve
impulses in sensory neurones (a
suitable example is the chemoreceptor
cell found in human taste buds)
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 43, Nov 2011, Q9 (a)
Textbooks/Publications
King p.180-183
Past Papers
Paper 41, Nov 2011, Q11 (a)
142
Learning objectives
Suggested teaching activities
Learning resources
led discussion or by textbook/internet research. (W) (I) (Challenging)
Practical: learners carry out experiments to investigate touch, temperature and pain
receptors in the skin. (P) (I) (Basic)
Note
Explain to learners that some sensory receptors are also sensory neurones, while
others are specialist receptor cells that synapse with sensory neurones.
Learners should feel confident applying the principles of the process to other
examples of sensory receptor cells.
15.1.d
describe the functions of sensory, relay
and motor neurones in a reflex arc
Key concepts
Cells as the units of life
Explain that a reflex arc is the neural pathway behind a reflex action.
o Introduce the relay neurone before asking learners to draw and annotate a reflex
arc. (W) (I) (Basic)
Practical: learners look at prepared slides of cross-sections of the spinal cord to
identify features. (I) (Basic)
Practical: learners carry out an experiment on a particular reflex action.
o For each, learners draw a reflex arc and annotate to show the function of the
neurones. (F)
Learners research examples of reflexes using the spinal cord and the brain,
detailing: stimulus; receptor; effector; and response. (H) (Basic)
o Learners share examples with the class. (W) (Basic)
Online
http://www.sumanasinc.com/webconte
nt/animations/content/reflexarcs2.htm
l
http://www.sciencejoywagon.com/explr
sci/media/reflex.htm
http://www.intelligencetest.com/reflex/i
ndex.htm
Textbooks/Publications
Bio Factsheet 58: Reflex action
Note
Point out that some reflex actions (e.g. the pupil reflex) involve the brain rather than
the spinal cord.
15.1.e
describe and explain the transmission
of an action potential in a myelinated
neurone and its initiation from a resting
potential (the importance of sodium
and potassium ions in impulse
transmission should be emphasised)
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Describe an action potential as a rapid, temporary change in a membrane potential,
explaining that this acts as a ‘booster’ to ensure the impulse (see 15.1.a) travels the
distance. (W) (Basic)
Explain the potential difference across the neurone membrane (mention also the
presence of large anions inside the axon).
o Build on AS Level knowledge to discuss how the resting potential is maintained
(membrane polarised) by the sodium-potassium pump.
o Explain the presence of non-voltage gated channels and facilitated diffusion of
K+ outwards.
o Describe the voltage-gated channels (NaV and KV) specific to the two ions
(which are closed). (W) (Challenging)
Learners set the scene by drawing an annotated diagram of the axon at rest /
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp44/4402002.html
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=40
http://www.biologymad.com/NervousS
ystem/nerveimpulses.htm
http://outreach.mcb.harvard.edu/anima
tions/actionpotential_short.swf
Past Papers
Paper 41, Nov 2011, Q11 (a)
143
Learning objectives
Suggested teaching activities
v2.1 5Y02
Learning resources
polarised. (I) (Basic)
Revisit understanding of ‘partially permeable’ and discuss ‘relatively impermeable’
and ‘relatively permeable’.
o Explain that open voltage-gated channels will increase membrane permeability
to the ion concerned (Na+ or K+). (W) (Basic)
Display diagrams showing the outside and the inside of a neurone – one at a time or
project an animation – to explain what occurs when depolarisation in the previous
section increases the membrane voltage above a threshold value (relate back to allor-nothing from 15.1.c). Include diagrams for:
o Depolarisation: explain how the open NaV channels stimulate more channels to
open (further depolarisation = positive feedback); action potential = the large
change in membrane potential.
o Repolarisation: Describe the changes occurring to NaV and KV channels and
movement of ions.
o (Temporary) undershoot: explain that the membrane is more permeable to K+
than at rest, until their channels close.
o Refractory period: explain how closed voltage-gated channels and action of the
sodium-potassium pump restores the resting potential.
o At each stage, learners suggest permeability states to the different ions,
highlighting the slower-to-react KV channels and the importance of inactivity of
NaV channels. (W) (Challenging)
Learners prepare the axes on graph paper and sketch the changes to potential as
each stage is discussed. (I) (Basic)
o Learners annotate the graph, explaining what is occurring at different time
points: resting potential, rising and falling phases of action potential, undershoot,
refractory period. (F)
Discuss how Na+ entering the axon establishes a local circuit between this and the
negatively charged resting potential in the area ahead. (W) (Challenging)
o Learners suggest how current flow changes membrane permeability to Na+ to
cause self-propagation of the action potential, and how/why this is in one
direction only. (W) (Challenging)
Discuss the two phases of the refractory period. (W) (Challenging)
Learners draw four diagrams of the same section of axon (e.g. draw a simple
cylinder to show the outside and inside of the neurone), headed ‘resting potential’
‘depolarisation’ ‘repolarisation’ ‘refractory period’.
o Learners draw on the location or movement of Na+ and K+, giving a summary
under each diagram. (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
144
Learning objectives
Suggested teaching activities
Learning resources
Learners explain the difference between the following: absolute refractory period and
relative refractory period; resting potential and action potential; polarised and
depolarised; impulse and action potential. (H) (Challenging)
Note
There are no action potentials in short neurones as current flow is sufficient to
ensure the impulse travels the short distance.
15.1.f
explain the importance of the myelin
sheath (saltatory conduction) in
determining the speed of nerve
impulses and the refractory period in
determining their frequency
Key concepts
Cells as the units of life
15.1.g
describe the structure of a cholinergic
synapse and explain how it functions,
including the role of calcium ions
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners use resources to draw a labelled, annotated diagram showing transmission
of an action potential in a myelinated axon.
o Learners add explanations to show how saltatory conduction is brought about,
noting the high concentration of voltage-gated channels at the nodes.
o Learners note how saltatory conduction has a great effect on speed of
transmission of impulses. (I) (Challenging)
Learners link the inactivated sodium voltage-gated channels during the falling phase
and part of the undershoot of the action potential (see 15.1.e), to an inability to
trigger another action potential immediately if a second depolarisation arrives.
o Learners annotate their action potential graph. (W) (I) (Challenging)
Learners interpret diagrams and electron micrographs of an axon with a myelin
sheath, identifying Schwann cells and nodes of Ranvier.
o Learners study electron micrographs of unmyelinated axons and make
comparisons. (I) (Basic)
Online
http://www.bu.edu/histology/m/t_electr.
htm
http://www.bu.edu/histology/p/21201lo
a.htm
http://www.unimainz.de/FB/Medizin/Anatomie/works
hop/EM/EMSchwannE.html
Learners copy out a definition of a synapse. Explain they will study a cholinergic
synapse, which is a chemical synapse. (W) (I) (Basic)
Learners draw and label a diagram of a synapse. (I) (Basic)
Learners compare electron micrographs and diagrams of synapses. (I) (Basic)
Remind learners of links with AS Level before outlining events in synaptic
transmission: for example, mitochondria, exocytosis, diffusion, membrane proteins,
hydrolysis catalysed by enzymes. (W) (Basic)
One learner makes the first statement in the sequence of events in synaptic
transmission and chooses another learner to describe the next event, and so on. (G)
(Basic)
A learner chooses a diagram in the sequence and a partner describes what is
occurring and what will happen next. (P) (Basic)
Learners rearrange a set of diagrams to arrive at the correct sequence of events in
synaptic transmission. (F) (Basic)
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp44/4402003.html
http://www.sumanasinc.com/webconte
nt/animations/content/synaptictransmi
ssion.html
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/D/Drugs.html
Cambridge International AS & A Level Biology (9700) – from 2016
Past Papers
Paper 41, June 2011, Q6 (c)
Textbooks/Publications
Bio Factsheet 20: Nerves and
synapses
Bio Factsheet 155: Answering exam
questions on neurones and synapse
145
Learning objectives
Suggested teaching activities
Learning resources
o Learners add annotations to the sequenced diagrams and if necessary make
additional bullet points. (F) (Challenging)
Extension: discuss the effects of drugs on the transmission across the synapse and
show learners how to apply knowledge and understanding to new situations. (W)
(Basic)
Past Papers
Paper 43, Nov 2011, Q9 (b)
Note
Explain that there are other types of chemical synapses, and mention electrical
synapses.
15.1.h
outline the roles of synapses in the
nervous system in allowing
transmission in one direction and in
allowing connections between one
neurone and many others (summation,
facilitation and inhibitory synapses are
not required)
Key concepts
Cells as the units of life
15.1.i
describe the roles of neuromuscular
junctions, transverse system tubules
and sarcoplasmic reticulum in
stimulating contraction in striated
muscle
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners suggest and note down which features ensure one-way transmission of
impulses across a synapse (vesicles with transmitter substance only found in the
presynaptic neurone; specific receptor proteins only located on the postsynaptic
membrane). (W) (I) (Basic)
Discuss the fact that one neurone can have many synapses relating to it, thus
allowing interconnection of numerous nerve pathways. (W) (I) (Basic)
Background: discuss the benefits of interconnection (a stimulus can lead to a range
of responses; can collect more information; excitatory and inhibitory synapses
provide more flexibility in response, hence a wider range of behaviour. (W) (Basic)
Extension: learners carry out some simple investigations into learning that involves
synapses. (P) (I) (Challenging)
Online
http://www.skoool.ie/skoool/examcentr
e_sc.asp?id=2879
Learners study one or more labelled diagrams and establish that: striated muscle is
voluntary; skeletal muscle, the multinucleate cells are also known as muscle fibres
and contain a bundle of myofibrils.
o Learners note that the cell surface membrane of the muscle fibre is termed
sarcolemma, and the cytoplasm is sarcoplasm.
o Explain that the sarcoplasmic reticulum is in contact with the myofibrils and is
similar to SER (Unit 1) and that transverse system tubules are infoldings of the
cell surface membrane. (W) (Basic)
Learners label a diagram of a neuromuscular junction, adding labels using resources
and knowledge of synaptic transmission.
o Learners note that the neuromuscular junction is a form of synapse that is
necessary to allow the effector to respond. (I) (Basic)
Learners sort cards containing details of the sequence of events occurring following
depolarisation at the synaptic terminal of the motor neurone (end with calcium ion
release by the sarcoplasmic reticulum – see 15.1.k).
Online
http://www.bu.edu/histology/p/21501oo
a.htm
https://highered.mcgrawhill.com/sites/0072495855/student_vi
ew0/chapter10/animation__function_
of_the_neuromuscular_junction__qui
z_3_.html
http://www.getbodysmart.com/ap/musc
letissue/fibers/sr/tutorial.html
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
King p.202-205.
Past Papers
Paper 41, Nov 2012, Q1 (b(i)
Textbooks/Publications
Bio Factsheet 190: Neuromuscular
junctions
146
Learning objectives
Suggested teaching activities
Learning resources
o Learners make notes, highlighting roles of the named items in the learning
objective. (P) (I) (Challenging)
Extension: learners research myasthenia gravis (Unit 11) and compare a normal and
a myasthenic neuromuscular junction. (H) (Challenging)
15.1.j
describe the ultrastructure of striated
muscle with particular reference to
sarcomere structure
Key concepts
Cells as the units of life
15.1.k
explain the sliding filament model of
muscular contraction including the
roles of troponin, tropomyosin, calcium
ions and ATP
Key concepts
Biochemical processes
14.1.a
discuss the importance of homeostasis
in mammals and explain the principles
of homeostasis in terms of internal and
external stimuli, receptors, central
control, co-ordination systems,
effectors (muscles and glands)
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Discuss the idea of a sarcomere (see 15.1.i diagrams) as the basic unit of
contraction, a repeating unit of a pattern made by thick and thin protein filaments.
(W) (Basic)
Learners label and annotate diagrams of the same sarcomere (i) relaxed, (ii)
contracting, and (iii) fully contracted, to prepare for 15.1.k.
o Learners compare electron micrographs with their diagram. (I) (Basic)
Online
http://www.bu.edu/histology/p/21601oo
a.htm
Explain the sliding filament model while learners add labels to prepared diagrams.
o Discuss the role of the released calcium ions in binding to sites on troponin and
shifting the position of tropomyosin to expose the myosin binding sites. (W)
(Basic)
Learners annotate their diagrams from 15.1.j. (I) (Challenging)
As a whole group, the first member states the first event occurring, ‘depolarisation of
the membrane of the synaptic terminal’ and then chooses the next member of the
group to continue the ‘story’. (W) (Challenging)
Learners produce a written account, or a flow chart diagram, summarising the
sequence of events occurring from the arrival of an action potential at the synaptic
terminal of the motor neurone to the contraction of the sarcomere. (F)
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp47/4702001.html
http://www.wellcome.ac.uk/Educationresources/Education-andlearning/Big-Picture/Allissues/Exercise-energy-andmovement/WTDV033020.htm
Learners write an explanation of what is meant by homeostasis.
o Explain that they should think of main ideas and use appropriate terminology
(e.g. give choice as below).
Maintenance of, an internal / a cellular, environment …
at a constant level / set point / norm / normal level / stable level or within
normal limits …
despite changes / fluctuations in the internal or external environment …
using negative feedback control mechanisms …
so that cells can function efficiently. (I) (Basic)
Learners suggest the different parameters or physiological factors that should be
kept at / around a set point (e.g. temperature, blood glucose concentration, blood pH
/ carbon dioxide concentration, water balance / water potential, metabolic wastes)
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Hom
eostasis/Homeostasis.htm
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
Bio Factsheet 46: Muscles.
147
Learning objectives
Suggested teaching activities
Learning resources
and explain the importance of maintaining the balance.
o Encourage use of the terms negative feedback (defined in 14.1.b) receptors and
effectors. (W) (Basic)
Learners use separate cards (limit 10-12) to write out definitions and features of the
terms stimulus, receptor, effector, control centre, response.
o Learners swap with a partner, who can write down the relevant term that is being
described. (P) (I) (Challenging)
14.1.b
define the term negative feedback and
explain how it is involved in
homeostatic mechanisms
Key concepts
Cells as the units of life
Learners write out the simple definition using resources and then qualify further after
discussion:
o Physiological processes or a changing external environment can cause variation
from the set point.
o A mechanism brings the internal environment back to the set point, or small
oscillations about the set point.
o Negative feedback always involves a receptor and effector and often involves a
control centre. (W) (I) (Challenging)
Using a named example, learners draw a flow chart to summarise homeostatic
control and negative feedback, showing the named receptor(s), effector(s) and
control centre (if present). (H) (Basic)
Learners are provided with a paragraph describing a named example of homeostatic
control and construct an annotated diagram as a summary. (F)
14.1.c
outline the roles of the nervous system
and endocrine system in co-ordinating
homeostatic mechanisms, including
thermoregulation, osmoregulation and
the control of blood glucose
concentration
Learners write a paragraph explaining what the two systems have in common and
then construct a table of the differences. (I) (Challenging)
Learners to research the difference between: excretion and secretion; an endocrine
gland and an exocrine gland. (H) (Basic)
Using resources, learners outline the involvement of the nervous system and
endocrine system in each of the named mechanisms, including naming, and
describing the role of, any hormones. (I) (Basic)
Key concepts
Cells as the units of life,
Biochemical processes
Note
There are close links to 15.1.a.
The research on osmoregulation and blood glucose concentration is useful for later
studies.
14.1.d
describe the deamination of amino
Learners suggest the distinction between excretion and egestion. (W) (Basic)
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologyonline.org/4/1_physiological_homeost
asis.htm
http://scienceaid.co.uk/biology/humans
/homeostasis.html
http://science.jrank.org/pages/3365/Ho
meostasis.html
Textbooks/Publications
Bio Factsheet 28: Feedback control
mechanisms
Bio Factsheet 161: Negative Feedback
Mechanisms
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp41/41020.html
http://www.abpischools.org.uk/page/m
odules/homeostasis_sugar/sugar2.cf
m
Online
http://www.ilng.in/pdf/mtg_bio_final.pdf
148
Learning objectives
Suggested teaching activities
Learning resources
acids and outline the formation of urea
in the urea cycle (biochemical detail of
the urea cycle is not required)
Describe how deamination removes the toxic part of an amino acid molecule,
forming highly toxic ammonia, and leaves a useful keto acid (chemical energy for
respiration or conversion for energy storage).
o Explain that in many terrestrial animals the ammonia is immediately converted to
the less toxic urea. (W) (Basic)
Learners annotate an outline diagram of deamination and the urea (ornithine) cycle
as you provide additional information, including: takes place in the liver; enzyme
controlled; ATP required; urea transported dissolved in the blood. (I) (Basic)
Extension: learners draw a molecule of urea highlighting that it is a small organic
compound (useful for later work on the kidney). (W) (Basic)
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/U/UreaCycle.html
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 59: Excretion.
Note
Explain that amino acids are not stored in the body.
14.1.e
describe the gross structure of the
kidney and the detailed structure of the
nephron with its associated blood
vessels using photomicrographs and
electron micrographs
Key concepts
Cells as the units of life
Agree with learners the location of their kidneys. (W) (Basic)
Show learners, on a whole kidney, what is meant by transverse and longitudinal
sections before learners identify structures from images.
o Learners hold up to the light the prepared slides of rat kidney to show the shape
of the entire kidney in LS or TS, and the areas of cortex and medulla. (W) (I)
(Challenging)
Learners dissect (e.g. from a sheep), or use images of, a whole kidney to make
annotated drawings of the external appearance and a section through the kidney. (I)
(Challenging)
Go through a diagram of nephron structure, including the associated blood vessels.
Refer also to the high blood pressure in the renal artery.
o Explain that the venous system does not begin immediately after the glomerulus,
and that there is a dense capillary network serving the nephrons. (W) (Basic)
o Learners label and annotate the diagram. (I) (Basic)
Note
If a kidney is dissected, learners can trace the renal artery, renal vein and ureter,
and follow the blood vessels into the cortex.
CD-ROM
Bioscope – has images of kidney
sections.
Online
http://www.histology.leeds.ac.uk/urinar
y/kidney.php
http://library.med.utah.edu/WebPath/R
ENAHTML/RENALIDX.html
http://www.cie.org.uk/cambridgefor/teachers/order-publications/
Textbooks/Publications
King p.155-156
Siddiqui p.191-194
Bio Factsheet 1: The kidney: excretion
and osmoregulation
Past Papers
Paper 32, June 2011, Q2
Paper 41, June 2012, Q10 (a)
14.1.f
describe how the processes of
v2.1 5Y02
For an overview, learners annotate a large diagram as you outline the processes
occurring in each region. (W) (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
149
Learning objectives
Suggested teaching activities
Learning resources
ultrafiltration and selective
reabsorption are involved with the
formation of urine in the nephron
Explain how sufficient pressure is present for ultrafiltration.
o Discuss how the presence of the plasma proteins remaining in the blood has
some effect on water potential and the filtration process. (W) (Basic)
Learners annotate diagrams to explain how the structure of the Bowman’s capsule
and glomerulus allows the process of ultrafiltration to occur.
o Explain the role of the basement membrane as the true dialysing filter. (I)
(Challenging)
Learners make a list of the components of glomerular filtrate and list the components
of blood that are too large for ultrafiltration. (I) (Basic)
Learners interpret tables showing the concentration of various substances in the
blood plasma and the glomerular filtrate to make comparisons. (I) (Basic)
Learners annotate diagrams of selective reabsorption in the proximal convoluted
tubule (PCT), with teacher-led prompts
o To consolidate, learners make bullet point notes using resources. (I)
(Challenging)
Learners produce a summary listing the mechanisms of transport used in selective
reabsorption and the substances that are transported. (I) (Basic)
Learners explain how the structure of the cuboidal epithelial cells of the PCT are
suited to their function. (H) (F) (Challenging)
Background: learners research the principles behind kidney dialysis. (I)
(Challenging)
et/BiologyPages/K/Kidney.html
www.biologyinmotion.com/nephron/ind
ex.html
http://www.biologymad.com/resources/
kidney.swf
http://www.sumanasinc.com/webconte
nt/animations/content/kidney.html
Key concepts
Cells as the units of life,
Biochemical processes
Textbooks/Publications
Bio Factsheet 1: The kidney: excretion
and osmoregulation
Bio Factsheet 59: Excretion
Bio Factsheet 150: Answering Exam
Questions on the Kidney
Past Papers
Paper 41, June 2012, Q10 (b)
Note
For the overview diagram, explain that in the loop of Henle most water is
reabsorbed, and that the outward movement of sodium (and chloride) ions into the
interstitial fluid occurs to create a very low water potential. No details of the
mechanism or the countercurrent multiplier are required.
14.1.g
describe the roles of the
hypothalamus, posterior pituitary, ADH
and collecting ducts in osmoregulation
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners recall from 14.1.c and AS Level why it is important to control the water
content of the blood (refer to water potential gradients and osmosis).
o Learners discuss the consequences and the conflict between maintaining a
constant volume of blood and maintaining constant water potential, e.g. when
someone has a meal high in salt. (W) (Basic)
Learners rearrange a set of linked, sequential statements to give a description of the
roles in osmoregulation of the hypothalamus, posterior pituitary; ADH and collecting
duct (CD). Include one statement to show the role of the distal convoluted tubule
(DCT).
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/K/Kidney.html
www.biologyinmotion.com/nephron/ind
ex.html
http://www.biologymad.com/resources/
kidney.swf
http://www.sumanasinc.com/webconte
nt/animations/content/kidney.html
150
Learning objectives
Suggested teaching activities
Learning resources
o Reminded learners that the surrounding (interstitial) fluid has a very low water
potential. (P) (I) (Challenging)
o Learners use the statements as the basis for their notes. (I) (Basic)
Learners are later given only a few of these statements to sequence and fill in the
missing details. (F)
Learners produce a flow chart to show the negative feedback control of water in the
blood. (H) (Basic)
As a summary, learners interpret data from tables or graphs to explain and relate
concentrations of different substances in each part of the nephron. (I)
(Challenging).
14.1.h
explain how the blood glucose
concentration is regulated by negative
feedback control mechanisms, with
reference to insulin and glucagon
Key concepts
Cells as the units of life,
Biochemical processes
Learners suggest (i) why it is important for blood glucose concentration to be kept
relatively constant, and (ii) why, in healthy people, oscillations around the norm
concentration is inevitable. (W) (Basic)
Using resources, learners construct a table similar to the incomplete table below. (I)
(Basic)
norm/set point of 90-120mg of glucose
100cm-3 blood
increases above
decreases below
stimulus detected by
beta () cells
alpha () cells
pancreas
pancreas
hormone released
insulin
glucagon
main target tissues of liver and muscles
liver
hormone
(+adipose tissue)
main effects of
stimulates uptake of
stimulates
hormone
glucose
breakdown of
………………..
glycogen to glucose
……………………
…………………….
final outcome
blood glucose
concentration
decreases
Textbooks/Publications
Bio Factsheet 1: The kidney: excretion
and osmoregulation
Bio Factsheet 59: Excretion
Bio Factsheet 150: Answering Exam
Questions on the Kidney
Online
http://www.biologyreference.com/BlCe/Blood-Sugar-Regulation.html
http://www.mydr.com.au/gastrointestin
al-health/pancreas-and-insulin
http://www.betacell.org/content/articlevi
ew/article_id/1/
Textbooks/Publications
Bio Factsheet 145: Blood sugar and its
control
Past Papers
Paper 43, Nov 2011, Q7
blood glucose
concentration
increases
Learners describe the sequence of events occurring in the body after having a
carbohydrate-rich meal (illustrating homeostasis). (H) (Basic)
Learners construct a flow chart to show negative feedback control of blood glucose
concentration involving insulin and glucagon.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
151
Learning objectives
Suggested teaching activities
Learning resources
o Learners add annotations or bullet points and include the terms homeostasis,
stimulus, receptor, effector and negative feedback. (F)
Extension: learners investigate the effect of diabetes mellitus on the control of blood
glucose concentration. Links: use of dipsticks, 14.1.k; insulin production by genetic
engineering, 19.2.c. (H) (Basic)
Note
Accurate spelling is important: both glucagon and glycogen are terms used in this
topic.
14.1.i
outline the role of cyclic AMP as a
second messenger with reference to
the stimulation of liver cells by
adrenaline and glucagon
Key concepts
Biochemical processes
Use a question and answer session to remind learners of membrane proteins that
function as receptors and enzymes.
o Explain that liver cells have different receptors to bind adrenaline and glucagon.
o Learners suggest why the hormones are unable to trigger directly reactions
within the cell (hydrophilic, do not enter cell).
o Use a diagram to outline how binding causes production in the cytoplasm of
cyclic AMP, which then stimulates the enzymatic conversion of glycogen to
glucose. (W) (Basic)
Learners write a paragraph to explain the difference between first and second
messengers. (F)
Online
http://courses.washington.edu/conj/gpr
otein/cyclicamp.htm
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::535::535::/sites/dl/free/007243731
6/120109/bio48.swf::Action%20of%2
0Epinephrine%20on%20a%20Liver%
20Cell
Note
Muscle cells have receptors for adrenaline but not for glucagon.
Names of the specific receptors are not required.
Notes are not necessary at this point as a summary of 14.1.j will suffice
14.1.j
describe the three main stages of cell
signalling in the control of blood
glucose by adrenaline as follows:
hormone-receptor interaction at the
cell surface (see 4.1c))
formation of cyclic AMP which binds
to kinase proteins
an enzyme cascade involving
activation of enzymes by
phosphorylation to amplify the signal
v2.1 5Y02
Discuss the role of adrenaline so learners understand the need for a higher-thannormal blood glucose concentration. (W) (Basic)
Discuss the sequential process using diagrams. (W) (Challenging)
Learners annotate copies of the diagrams, highlighting how one event triggers the
next:
o Binding of adrenaline and activation of G (membrane) protein.
o Enzyme-catalysed formation of cyclic AMP at the membrane and consequential
activation of kinase proteins.
o Phosphorylation of enzymes involved in carbohydrate and lipid metabolism, e.g.
for the breakdown of glycogen to glucose-1-phosphate. (I) (Challenging)
Learners re-order statements to show the sequential process (F)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=s
wf::535::535::/sites/dl/free/007243731
6/120109/bio48.swf::Action%20of%2
0Epinephrine%20on%20a%20Liver%
20Cell
http://www2.estrellamountain.edu/facul
ty/farabee/BIOBK/biobookendocr.htm
l
http://courses.washington.edu/conj/gpr
otein/cyclicamp.htm
152
Learning objectives
Suggested teaching activities
Learning resources
Remind learners how a dipstick is used to detect glucose and then explain the
principles of operation before learners make notes.
o Learners write out a worded reaction and explain why a reaction catalysed by
glucose oxidase will confirm the presence of glucose (enzyme specificity,
Unit 1).
o Explain that peroxidases are used so that the hydrogen peroxide product reacts
with a chemical (chromogen) that produces a coloured product. (W) (I) (Basic)
Practical: if available, learners compare Clinistix to Diastix. (W) (Basic)
Outline the operation of the biosensor by incorporating questions to link to AS Level
topics: partially permeable membrane, diffusion of glucose molecules (from the
blood sample), immobilised enzymes and specificity.
o Discuss how the reaction needs to be detected, e.g. use of electrodes; a
decrease in oxygen; increase in hydrogen peroxide; production of gluconic acid.
o Learners explain how the digital read-out is proportional to the concentration of
glucose in the sample. (W) (Challenging)
Discuss how dipsticks and portable devices to detect glucose and measure
concentrations are considered great improvements for people with diabetes
(compared to times before glucose biosensors and the Benedict’s tests. (W) (Basic)
Learners compare the use of glucose dipsticks and glucose biosensors, explaining
advantages of each. (I) (Challenging)
Learners draw a diagram to show the main parts of a biosensor and annotate to
show the principles of operation. (F)
Online
http://www.southernbiological.com/kitsand-equipment/specialisedlaboratory-and-field-equipment/urinetesting/g10-41-diastix/
Key concepts
Cells as the units of life,
Biochemical processes
14.1.k
explain the principles of operation of
dip sticks containing glucose oxidase
and peroxidase enzymes, and
biosensors that can be used for
quantitative measurements of glucose
in blood and urine
Key concepts
Biochemical processes,
Observation and experiment
Textbooks/Publications
Bio Factsheet 157: Diabetes –
Management or Cure?
Bio Factsheet 167: Biosensors
Past Papers
Paper 41, Nov 2011, Q2 (b)
Note
Link with previous work on insulin (14.1.h) and a practical for immobilised enzymes
(3.2.d).
Note that some textbooks state that the oxidation of glucose produces,
gluconolactone, which is an intermediate of gluconic acid.
Discuss ideas and developments in the commercial production of glucose
biosensors, e.g. devices that can control and regulate insulin doses.
Learners should be able to use the principles of operation to apply to a design that
they may not have come across.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
153
Learning objectives
Suggested teaching activities
Learning resources
14.1.l
explain how urine analysis is used in
diagnosis with reference to glucose,
protein and ketones
Learners reflect back to14.1.f and explain why glucose and proteins would not
normally be found in urine in detectable levels.
Explain that ketones are products of carbohydrate, protein and lipid metabolism, but
high levels in urine may indicate ill health, such as in uncontrolled type I diabetes.
Explain that a urine analysis could indicate a condition: glycosuria and diabetes
mellitus; proteinuria / albuminuria / microalbuminuria and renal disease or damage
e.g. that may have been caused as a result of long-term type II diabetes. (W)
(Basic)
o Learners make outline notes on each of the three named urine compounds.
o Notes to include the diagnostic role of urine dipsticks (specific for each or
multiple combination strips testing for all three). (I) (Basic)
Online
http://www.patient.co.uk/doctor/urinedipstick-analysis
http://www.medicinenet.com/urine_test
s_for_diabetes/article.htm
Key concepts
Biochemical processes,
Observation and experiment
Past Papers
Paper 41, Nov 2011, Q2 (a)
Note
Very low concentrations are excreted by healthy people, levels detected by urine
dipsticks are indicative of possible health problems.
Details of other tests that can be performed on urine are not required.
15.1.l
explain the roles of the hormones FSH,
LH, oestrogen and progesterone in
controlling changes in the ovary and
uterus during the human menstrual
cycle
Key concepts
Cells as the units of life,
Biochemical processes
v2.1 5Y02
Learners review the endocrine system and hormones with a short written test.
Discuss the different origins of the named hormones involved in the menstrual cycle,
explaining target tissues differ.
o Emphasise for later their importance in synchronising activities of the ovary and
uterus. (W) (Basic)
Use diagrams to describe the maturation of the follicle in the ovary, ovulation and the
formation of the corpus luteum.
o Describe the events occurring in the uterus. (W) (Basic)
Learners draw a large outline graph. The x-axis being time (to 28 days – explain that
cycles may be longer or shorter), y-axis being hormone concentration (arbitrary
units).
o Learners sketch diagrams of (i) the physical changes in the uterus over 28 days
(above the graph), and (ii) the changes occurring in the ovary (below the graph).
(I) (Basic)
o Using description and question and answers build up the graph to show the
changing concentrations of the hormones over the 28 days (use a method to
distinguish oestrogen and progesterone, the sex hormones, from FSH and LH,
the two pituitary hormones.
o Discuss the feedback mechanisms that occur to enable the cycle to be
controlled, learners annotate or add bullet point notes. (W) (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/Horm
ones/Hormones.htm
http://highered.mcgrawhill.com/sites/0072495855/learner_vi
ew0/chapter28/animation__positive_
and_negative_feedback__quiz_1_.ht
ml
http://highered.mcgrawhill.com/sites/0072495855/learner_vi
ew0/chapter28/animation__maturatio
n_of_the_follicle_and_oocyte.html
Textbooks/Publications
Bio Factsheet 57: Oestrous cycles.
Includes the menstrual cycle
Past Papers
Paper 41, June 2012, Q5 (a)
Paper 42, Nov 2013, Q4
154
Learning objectives
Suggested teaching activities
Learning resources
Extension: learners investigate the role of gonadotrophin releasing hormone (GnRH)
in the control of the menstrual cycle. (I) (Challenging)
Learners discuss the changes to the graph(s) for shorter / longer cycles, explaining
the reasons for their choices. (G) (Challenging)
Learners describe specific examples within the cycle of positive and negative
feedback mechanisms. (I) (Challenging)
Learners complete unlabelled diagrams and graphs showing the events in the
menstrual cycle. (F)
Note
It may be beneficial for learners to know the full names of FSH and LH: they are not
required learning.
15.1.m
outline the biological basis of
contraceptive pills containing
oestrogen and/or progesterone
Key concepts
Observation and experiment
v2.1 5Y02
Learners research how the combined oral contraceptive pill prevents pregnancy and
compare this with the progesterone /progestin-only pill. (H) (Basic)
Learners consider how concentrations of oestrogen and progesterone differ in
women who are taking the contraceptive pill.
o Learners explain the effects of these differences in terms of the feedback
mechanisms discussed in 15.1.l. (I) (Challenging)
Online
http://www.patient.co.uk/search.asp?s
earchTerm=contraceptive+pill&collect
ions=Condition_Leaflets
http://hcd2.bupa.co.uk/fact_sheets/htm
l/hormonal_contraception.html
Note
The role of oestrogen and/or progesterone in controlling fertility is an extension of
learners’ knowledge and understanding of the menstrual cycle.
Past Papers
Paper 43, June 2011, Q3 (b)
Cambridge International AS & A Level Biology (9700) – from 2016
155
Scheme of work – Cambridge International AS and A Level Biology (9700) from 2016
Unit 11: Plant physiology and biochemistry
Recommended prior knowledge
As with respiration, learners should be familiar with the concept of energy transfer, for example from light energy to chemical energy. They should have a sound
understanding of what a molecule is, and understand chemical formulae and equations. It would be helpful if they understood the concept of oxidation and reduction, at
least at a simple level. Knowledge from AS Level of plant cell structure and of gene expression will help understanding of the role of gibberellin in cell elongation. It
would be helpful if learners had an appreciation of the importance of communication, control and coordination in multicellular organisms.
Context
This unit considers another aspect of the key concept of biological processes and studies the transfer of energy from light energy to the energy contained in organic
compounds in living organisms. It has close links to Unit 9, Respiration, and revisits the concepts involved in the synthesis of ATP by chemiosmosis. It builds on
material covered at AS Level: enzymes and biological molecules, especially glucose and starch, from Unit 1; plant cell structure and chloroplast structure and function
from Unit 2; and leaf structure, including stomata from Unit 4. Having considered mammalian physiology in Unit 10, the plant hormones abscisic acid and gibberellin are
used to exemplify communication, control and coordination in plants. Learners first come across gibberellin when studying selective breeding in Unit 7. This unit could
be taught before Unit 9, Respiration, if it is felt more logical to introduce learners first to the process involved with the initial input of energy into the ecosystem.
Outline
The unit begins with an overview of photosynthesis, highlighting the transfer of energy and the link between the light dependent and light independent stages. The light
absorbing pigments are introduced and linked to the concepts involved with absorption and action spectra: learners can also separate photosynthetic pigments by
chromatography. The light dependent and light independent stages of photosynthesis are described. The concept of limiting factors is introduced and learners have the
opportunity of investigating factors affecting the rate of photosynthesis. A consideration of how this knowledge can be applied to crop plants is included. More detail is
provided of the ways in which the structure of a chloroplast is suited to its functions. Learners also consider how some plants have evolved to cope with life in hot
environments. Response to an external stimulus is exemplified by a study of the Venus fly trap. Stomatal closure and opening, including the role of abscisic acid, the
role of auxin in cell elongation and the effect on gene activation of gibberellin is covered. There are numerous practical opportunities within this unit to develop skills
relating to planning, data analysis and the evaluation of investigations.
Teaching time
It is recommended that this unit should take approximately 8% of the complete A Level course.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
156
Learning objectives
Suggested teaching activities
Learning resources
13.1.b
state the sites of the light dependent
and the light independent stages in the
chloroplast
Project or show an image or diagram of a chloroplast and check learner knowledge
from Unit 1 by a question and answer session.
o Learners explain why the thylakoid membranes are the location of ATP
synthesis (refer back to mitochondrial membranes: site of ATP synthase,
location for photosynthetic pigments).
o Learners suggest why the stroma is the site of the Calvin cycle (enzyme
reactions). (W) (Challenging)
Online
http://resources.teachnet.ie/foneill/phot
o.html
Key concepts
Cells as the units of life,
Biochemical processes
13.1.c
describe the role of chloroplast
pigments (chlorophyll a, chlorophyll b,
carotene and xanthophyll) in light
absorption in the grana
Key concepts
Cells as the units of life
Note
A review may be necessary of the anatomy of the leaf, so that learners can visualise
mesophyll tissue and mesophyll cells containing chloroplasts.
13.3.a may be taught first to give a visual overview of where the processes of
photosynthesis occur.
Allow learners to state the role of chlorophyll before raising the level of
understanding to explain that the light energy needs to be transferred. Explain that:
o Absorption occurs in areas of the thylakoid membrane that contain
photosystems.
o Chlorophyll a and chlorophyll b are two types of chlorophyll molecule in a typical
photosystem, along with other photosynthetic pigments, e.g. carotenes and
xanthophylls.
o Each type of pigment absorbs certain wavelengths of light and reflects others
(mention the antenna complex).
o Absorbed energy is passed on to a special pair of chlorophyll molecules that can
pass on energetic/excited electrons to electron acceptors. (W) (Challenging)
Learners label and annotate an unlabelled diagrammatic version of a photosystem
as you talk them through the various components.
o Learners note that: the special pair act as the reaction centre and the others as
accessory pigments; in Photosystem I (PI) the pair have a characteristic
absorption wavelength of 700 nm (P700), and in PII of 680 nm (P680).
o Refer to the higher energy state of the electrons as photoactivation of
chlorophyll. (I) (Challenging)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/283-photosynthesishow-does-chlorophyll-absorb-lightenergy
http://phototroph.blogspot.ca/
Textbook/Publications
Bio Factsheet 63: Pigments in plants
Note
Explain that xanthophylls and carotenes are carotenoids.
This overlaps with 13.1.f so details of the photosystems may be taught there.
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
157
Learning objectives
Suggested teaching activities
Learning resources
13.1.d
interpret absorption and action spectra
of chloroplast pigments
Background practical to help understanding: learners follow, or have demonstrated
or described, a protocol to measure an absorption spectrum to see how the curve on
the graph is obtained.
o Explain that absorption is measured using a spectrophotometer). (W) (P) (I)
Learners study separate absorption graphs for each of the chloroplast pigments (i.e.
each has a characteristic absorption spectrum): check understanding with a
worksheet. (I) (Basic)
Provide learners with a ‘classic’ absorption spectrum graph (includes the main
pigments) and a set of questions assessing ability to extract data and show
understanding.
o Learners suggest the advantages to plants of having different pigments (extends
the range of light wavelengths absorbed). (F)
Explain how the graph for the action spectrum of photosynthesis is obtained. (W)
(Basic)
Show learners a ‘classic’ action spectrum with peaks in the red and blue regions and
sketch an absorption spectrum graph of pigment ‘X’ (actually chlorophyll a) and a
separate one for a pigment ‘Y’ (peaking in the green region).
o Learners suggest, with a reason, which is most likely to be involved in light
absorption for photosynthesis, so that the correlation between absorption and
action spectra is seen. (W) (Basic)
Explain that there are more pigments involved than those usually shown, so the
absorption spectrum graph is only similar to the action spectrum graph.
o Explain that there are different carotenes and xanthophylls and different plants
have a characteristic set of pigments. (W) (Basic)
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/ActionSpectrum.ht
ml
http://www.saps.org.uk/secondary/teac
hing-resources/130-the-effect-of-lightcolour-and-intensity-on-the-rate-ofphotosynthesis
Key concepts
Cells as the units of life,
Organisms in their environment,
Observation and experiment
Textbooks/Publication
Siddiqui p.91
Past papers
Paper 51, Nov 2011, Q1 (a)(b)
Note
Check that the absorption spectrum is well understood before moving onto the
action spectrum, ensuring that learners make the association between the two.
13.1.e
use chromatography to separate and
identify chloroplast pigments and carry
out an investigation to compare the
chloroplast pigments in different plants
(reference should be made to Rf values
in identification)
Practical: learners could carry out the separation for pigments of one plant, and
compare results with others that have used different plants.
o Learners make measurements and calculate Rf values, comparing with
published values to make identifications. (G) (I) (Basic)
Practical booklet 8 is a protocol for separating chloroplast pigments by paper
chromatography. Colours fade relatively quickly so measurements should be made
as soon as possible (or take photographs) after removing chromatograms from the
solvent.
Online
http://www.saps.org.uk/secondary/teac
hing-resources/181-learner-sheet-10thin-layer-chromatography-forphotosynthetic-pigments
Textbook/Publications
Key concepts
v2.1 5Y02
Practical booklet 8
Cambridge International AS & A Level Biology (9700) – from 2016
158
Learning objectives
Suggested teaching activities
Learning resources
King p.113-114
Siddiqui p.90-91
Observation and experiment
Past Papers
Paper 41, Nov 2011, Q10 (b)
Paper 51, Nov 2011, Q1 (c)(d)(e)
Paper 53, Nov 2011, Q1 (d)(ii)
13.1.f
describe the light dependent stage as
the photoactivation of chlorophyll
resulting in the photolysis of water and
the transfer of energy to ATP and
reduced NADP (cyclic and non-cyclic
photophosphorylation should be
described in outline only)
Key concepts
Biochemical processes
v2.1 5Y02
Use a diagram to ask learners questions about what happens in a photosystem
(13.1.c).
o Ensure learners know that excitation of energetic electrons results in a transfer
to an acceptor.
o Explain that the absorption of light energy in PII also triggers the photolysis of
water by an enzyme (termed the oxygen evolving complex, closely located to the
reaction centre). (W) (Basic)
With verbal prompts, learners build up the ‘Z-scheme’ to produce an outline of noncyclic photophosphorylation and include explanations.
o Sketch a ‘rising’ letter ‘N’, then add PII, then PI (represent energy
levels).
o Add circles for the electron transport chain carriers (or label ETC)
and add arrows to show the electron pathway.
o Add arrows to show the production of ATP as electrons flow down the ETC.
o Show the photolysis of water, with electrons replacing the gap in PII, oxygen
evolved.
o Show the electrons accepted by NADP to produced reduced NADP.
o Add the title non-cyclic photophosphorylation (noted for 13.1.a later). (I) (Basic)
Learners repeat the construction of the Z-scheme and add explanatory notes without
help. (F)
o Describe cyclic photophosphorylation.
o Learners suggest why only ATP can be synthesised.
o Learners add this in a different colour to their Z-scheme. (I) (Basic)
Learners revise work on chemiosmosis (Unit 9) to give an account of ATP synthesis
at the thylakoid membrane. A partially labelled diagram showing a section through
the thylakoid membrane with electron carriers of the ETC and the ATP synthase
complex can be used as stimulus. (H) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://cnx.org/content/m48011/latest/
http://www.life.illinois.edu/govindjee/tex
tzsch.htm
http://www.johnkyrk.com/photosynthesi
s.html
Textbook/Publications
Bio Factsheet 02: The essential guide
to photosynthesis.
Bio Factsheet 153: The Light
Dependent Stage of Photosynthesis
Past Papers
Paper 43, Nov 2013, Q7 (a)
159
Learning objectives
Suggested teaching activities
Learning resources
12.1.e (ii)
explain that the synthesis of ATP is
associated with the electron
transport chain on the membranes
of mitochondria and chloroplasts
(see 12.2.g)
Only part of this learning objective is included here: explain that the synthesis of ATP
is associated with the electron transport chain on the membranes of chloroplasts (see
12.2.g)
Learners complete a short written test to remind them of previous work
o Chloroplasts are cellular structures where ATP is formed.
o ATP is an energy transfer molecule.
o The initial energy input for chloroplasts is light energy and for mitochondria,
energy-containing organic compounds.
o The ETC involves thylakoid membrane proteins capable of accepting and
donating electrons. (F)
Online
http://www.ncbi.nlm.nih.gov/books/NB
K21063/
Key concepts
Cells as the units of life,
Biochemical processes
13.1.a
explain that energy transferred as ATP
and reduced NADP from the light
dependent stage is used during the
light independent stage (Calvin cycle)
of photosynthesis to produce complex
organic molecules
Key concepts
Biochemical processes,
Organisms in their environment
In groups learners construct a large, poster-sized concept map / spider diagram with
photosynthesis as a topic. (G) (Basic)
Discuss and agree as a class the main points and improve ideas to A Level
standard. Learners then make notes in diagrammatic or bullet-point form.
o An overall equation for photosynthesis (word equation changed to chemical
formulae, balanced).
o Two main stages, occurring in the chloroplasts of mesophyll cells and both
involving enzymes.
o In the light dependent stage, light energy is transferred to ATP and the reduced
coenzyme, NADP.
o Oxygen (waste product) from this stage can be used for aerobic respiration (in
plant or released into the atmosphere to other organisms).
o In the light independent stage (also termed the Calvin cycle), carbon dioxide,
ATP and NADPH are used for the production of complex organic molecules,
such as glucose and starch. (W) (I) (Challenging)
Note
Learners should understand the terms ‘autotroph’, ‘photoautotroph’ and ‘producer’.
Avoid using the terms ‘light reaction’ and ‘dark reaction’.
13.1.g
outline the three main stages of the
Calvin cycle:
fixation of carbon dioxide by
combination with ribulose
bisphosphate (RuBP), a 5C
v2.1 5Y02
Discuss why the light dependent stage of photosynthesis needs to occur when no
glucose has yet been made (allows the transfer of light energy to ATP and reduced
NADP).
o Learners write out the overall equation of photosynthesis to spot that carbon
dioxide has not yet been involved (sets the scene for the Calvin cycle). (W)
(Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Textbook/Publications
Bio Factsheet 153: The Light
Dependent Stage of Photosynthesis
Past papers
Paper 41, June 2013, Q10 (b)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/134-photosynthesisa-survival-guide-teaching-resources
http://photoscience.la.asu.edu/photosy
n/study.html
http://www.johnkyrk.com/photosynthesi
sdark.html
http://www.biologymad.com/master.ht
ml?http://www.biologymad.com/a2bio
logy.htm
http://staff.jccc.net/pdecell/photosyn/ph
otoframe.html
http://faculty.fmcc.suny.edu/mcdarby/A
nimals&PlantsBook/Plants/01Photosynthesis.htm
Past papers
Paper 43, Nov 2013, Q7 (b)
Online
http://www.science.smith.edu/departm
ents/Biology/Bio231/calvin.html
http://www.wiley.com/college/boyer/04
70003790/animations/photosynthesis
/photosynthesis.htm
160
Learning objectives
Suggested teaching activities
Learning resources
compound, to yield two molecules of
GP (PGA), a 3C compound
the reduction of GP to triose
phosphate (TP) involving ATP and
reduced NADP
the regeneration of ribulose
bisphosphate (RuBP) using ATP
Learners link together a set of statements, based around the ideas in the learning
objectives and including rubisco, to describe the Calvin cycle.
o Provide curved arrows, so that they can create a cycle with their statements. (P)
(I) (Challenging)
Discuss their cycles.
o Emphasise the roles of reduced NADP and ATP (include the concept of
recycling to the light dependent stage).
o Explain that the steps are catalysed by enzymes.
o Show how 6 carbon dioxide molecules are required to produce 1 glucose
molecule, so that the overall equation for photosynthesis makes sense.
o Learners then produce their own annotated Calvin cycle. (W) (I) (Challenging)
Background: learners investigate the experiments carried out by Calvin and his
colleagues using the ‘lollipop’ apparatus. (I) (Challenging)
Learners annotate fully a skeleton outline of the Calvin cycle (provide a variety so
that each contains different information – could be differentiated). (F) (Basic)
(Challenging)
http://nobelprize.org/nobel_prizes/che
mistry/laureates/1961/calvinlecture.pdf
Key concepts
Biochemical processes
Textbooks/Publications
Bio Factsheet 02: The essential guide
to photosynthesis.
Bio Factsheet 227: RuBP carboxylase
– the most important enzyme on the
planet?
Past Papers
Paper 41, June 2011, Q10 (b)
Paper 43, June 2011, Q10 (b)
Note
For ‘error-free learning’, use only the syllabus names and abbreviations:
o GP (glycerate 3-phosphate) or PGA (3PG / 3-phosphoglycerate /
3-phosphoglyceric acid)
o TP (triose phosphate). Avoid other common names: glyceraldehyde 3-phosphate
(GALP); 3-phosphoglyceraldehyde (PGAL)
o Explain that other acceptable names are used.
No names of enzymes, other than rubisco, are required.
13.1.h
describe, in outline, the conversion of
Calvin cycle intermediates to
carbohydrates, lipids and amino acids
and their uses in the plant cell
Key concepts
Biochemical processes
v2.1 5Y02
Agree that GP is the raw material for producing carbohydrates, lipids and amino
acids (no details of pathways required).
o Learners add this information to their Calvin cycle. (I) (Basic)
Briefly discuss how two molecules of GP can produce a hexose sugar. (W) (Basic)
Discuss, using question and answer, the use of hexose sugars (glucose and
fructose, Unit 1), including:
o Immediate use to release energy as respiratory substrates.
o Synthesis of sucrose for transport to sinks (revise plant transport, Unit 4).
o Conversion to starch or lipid for energy storage.
o Production of structural compounds (cellulose).
o Learners suggest what else is required to synthesise amino acids for proteins
Cambridge International AS & A Level Biology (9700) – from 2016
161
Learning objectives
Suggested teaching activities
Learning resources
(uptake of nitrate and sulfate ions in the roots). (W) (Basic)
Learners produce an outline set of notes from the discussion. (I) (Basic)
13.3.a
describe the relationship between
structure and function in the
chloroplast using diagrams and
electron micrographs
Key concepts
Cells as the units of life,
Biochemical processes
Place the chloroplast into context as a summary.
o Learners identify: the photosynthetic organism (plant); the organ of
photosynthesis (leaf); the main photosynthetic tissue (palisade mesophyll); the
organelle of photosynthesis (chloroplast); the structures of the chloroplast. (W)
(Basic)
Learners draw a labelled diagram of a chloroplast, annotating (or write a summary)
to show how the chloroplast is adapted for photosynthesis.
o Note the requirement for membranes and intermembrane spaces to generate
ATP as electrons pass along a chain of electron carriers.
o Note the locations of the light dependent stage and the light independent stage.
(I) (Challenging)
Learners interpret photomicrographs and electron micrographs of chloroplasts,
drawing labelled diagrams. (I) (Basic)
Online
http://www.vcbio.science.ru.nl/en/imag
e-gallery/show/PL0130/
http://www.vcbio.science.ru.nl/en/fese
m/applets/chloroplast/
http://www.biologie.uni-hamburg.de/bonline/e05/r21.htm
http://faculty.uca.edu/johnc/Chloroplast
_and_microbodies.jpg
Textbook/Publications
Bio Factsheet 198: Chloroplasts –
structure and function
Bio Factsheet 61: Chloroplasts and
mitochondria
Past Papers
Paper 41, Nov 2011, Q10 (a)
13.2.a
explain the term limiting factor in
relation to photosynthesis
Key concepts
Biochemical processes,
Organisms in their environment
13.2.b
explain the effects of changes in light
intensity, carbon dioxide concentration
and temperature on the rate of
photosynthesis
Key concepts
v2.1 5Y02
Show learners a number of definitions of the term limiting factor. As a group produce
an explanation to note down that is in the context of photosynthesis. (W) (I) (Basic)
Learners draw a generalised graph showing the rate of photosynthesis on the y-axis
and the factor on the x-axis.
o Label the graph with the regions where the factor directly affects the rate of
photosynthesis and those where other factors become limiting. (I) (Basic)
Online
http://www.rsc.org/learnchemistry/content/filerepository/CMP/
00/001/068/Rate%20of%20photosynt
hesis%20limiting%20factors.pdf
Learners suggest the factors that may affect the rate of photosynthesis, and discuss
ways in which the rate could be measured. (W) (Basic)
Learners suggest the parts of the photosynthetic process that involve enzymes, and
hence affect photosynthetic rate.
o Light dependent stage: photolysis of water; synthesis of ATP (ATP synthase);
transfer of electrons to NADP for reduction.
o Light independent stage: each of the steps of the Calvin cycle (the bulk of
Online
http://www.biology4all.com/resources_l
ibrary/details.asp?ResourceID=43
http://resources.teachnet.ie/foneill/exp
er.htm
http://www.assessnet.org.uk/elearning/
Cambridge International AS & A Level Biology (9700) – from 2016
162
Learning objectives
Suggested teaching activities
Learning resources
Biochemical processes,
Organisms in their environment,
Observation and experiment
enzyme-catalysed reactions occur here).
Learners use their notes on chloroplast pigments and the two stages of
photosynthesis to suggest how changes in carbon dioxide concentration and light
intensity will affect the rate of photosynthesis.
o Include an explanation as to why the light independent stage will not operate
when there is no light. (I) (Basic) (Challenging)
To link back to 13.2.a learners interpret graphs showing the effects of limiting
factors, explaining why the rate of photosynthesis changes and using extracted date
to support their answer. (I) (Challenging)
Textbook/Publications
King p.115-117, 149
Siddiqui p.86-89, 94
Bio Factsheet 136: Practical
Investigations for Photosynthesis
Bio Factsheet 25: Tackling data
interpretation questions II:
photosynthesis (limiting factors)
Past Papers
Paper 41, June 2012, Q8 (a)(b)
13.2.c
explain how an understanding of
limiting factors is used to increase crop
yields in protected environments, such
as glasshouses
Key concepts
Biochemical processes,
Observation and experiment
13.2.d
carry out an investigation to determine
the effect of light intensity or light
wavelength on the rate of
photosynthesis using a redox indicator
(e.g. DCPIP) and a suspension of
chloroplasts (the Hill reaction)
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Explain that knowledge of limiting factors can be used to control the growing
conditions of commercial crops, especially in protected environments. (W) (Basic)
Brainstorm ideas as to what growers can do to increase crop yields in glasshouses.
Include:
o Artificial light (photosynthesis for more hours of the day; increase light intensity
on days with little sunlight).
o Use of paraffin lamps (carbon dioxide and heat). (W) (Basic)
o Learners make notes and explain how these will improve yield. (F)
Online
http://www.bbc.co.uk/schools/gcsebite
size/science/add_aqa/photosynthesis
/photosynthesisrev3.shtml
http://www.omafra.gov.on.ca/english/cr
ops/facts/00-077.htm
From 13.2.b learners will know that the production of oxygen can be used to
measure the rate of photosynthesis.
o Learners suggest why the rate of production of NADP in the light dependent
stage correlates with the rate of photosynthesis.
o Explain that a way of measuring this could be to use a different electron
acceptor, DCPIP, which can be visualised (blue dye that becomes colourless
when reduced). (W) (Basic)
o Learners suggest how DCPIP can be used to measure rate. (W) (Challenging)
Learners carry out a version of the Hill reaction practical or watch it demonstrated
and then explain a set of results. Ensure that both investigations, light intensity and
light wavelength, are covered. (P) (I) (H) (Challenging)
Discuss the findings of the original investigation performed by Robin Hill: oxygen is
evolved in the absence of carbon dioxide; the electrons transferred to the electron
acceptor originate from water. (W) (Challenging)
Practical booklet 9
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://www.nuffieldfoundation.org/practi
cal-biology/investigating-lightdependent-reaction-photosynthesis
http://www.saps.org.uk/secondary/teac
hing-resources/157-measuring-therate-of-photosynthesis
http://www.hansatechinstruments.com/forum/uploads/david
_walker/whose.pdf
Textbook/Publications
163
Learning objectives
13.2.e
carry out investigations on the effects
of light intensity, carbon dioxide and
temperature on the rate of
photosynthesis using whole plants,
e.g. aquatic plants such as Elodea and
Cabomba
Key concepts
Observation and experiment
13.3.b
explain how the anatomy and
physiology of the leaves of C4 plants,
such as maize or sorghum, are
adapted for high rates of carbon
fixation at high temperatures in terms
of:
the spatial separation of initial
carbon fixation from the light
dependent stage (biochemical
details of the C4 pathway are
required in outline only)
the high optimum temperatures of
the enzymes involved
Key concepts
Biochemical processes,
Natural selection,
Organisms in their environment
v2.1 5Y02
Suggested teaching activities
Learning resources
Practical booklet 9 (Hill reaction) uses melting point tubes as reaction vessels and
does not use a centrifuge. Learners can investigate the effect of both light
wavelength and light intensity on the rate of photosynthesis. Pooled data for analysis
may be collected as preparation for Paper 5. Learners can also use the technique to
devise plans that can be peer reviewed (see 12.2.h and 12.2.m).
Siddiqui p.93-93
Practical: learners investigate the effect of light intensity, light wavelength, carbon
dioxide concentration and temperature on the rate of photosynthesis.
o Learners design and carry out at least one investigation of their own, once a
technique has been shown to them. (I) (Challenging)
o Learners explain how the plan can be modified to investigate the effect of limiting
factors. (I) (Challenging)
Online
http://www.saps.org.uk/secondary/teac
hing-resources/190-using-pondweedto-experiment-with-photosynthesishttp://www.saps.org.uk/secondary/teac
hing-resources/284-investigatingphotosynthesis-with-leaf-discs
http://www.saps.org.uk/secondary/teac
hing-resources/285-learner-sheet-20starch-production-in-plants-duringphotosynthesis
Note
Carbon dioxide concentration can be varied by using an aquatic (water) plant in
varying concentrations of solutions containing sodium hydrogen carbonate (sodium
bicarbonate).
Learners review C3 photosynthesis by completing worksheets with gaps or by
rearranging cards describing stages and then suggest why the term C3 plant is
used. (W) (P) (I) (F) (Basic)
Explain that rubisco can also catalyse the oxygenation of RuBP.
o Use diagrams, and remind learners of enzyme inhibition (AS Level) to prompt
them to suggest why the reaction is favoured in high oxygen concentrations.
o Learners suggest the conditions when oxygen concentrations will be high (high
light intensity and high temperatures increase rate of light dependent stage). (W)
(Basic)
o Learners write an explanation of photorespiration. (I) (Basic) (Challenging)
Explain that C4 plants are traditionally from hotter environments. (W) (Basic)
Describe, using diagrams, the structural and functional features of maize or sorghum
as examples of C4 plants. (W) (Challenging)
o Learners suggest how the features adapt the plants to reduce the effects of
photorespiration and allow high rates of carbon fixation.
o Learners label and annotate a diagram of a section through the leaf of a C4
plant.
o Learners produce a comparison table of C3 (see 13.3.a) and C4 leaf structure.
(W) (I) (Challenging)
Cambridge International AS & A Level Biology (9700) – from 2016
Past paper
Paper 53, Nov 2011, Q1 (a)(b)(c)
Online
http://www.icrisat.org/cropsorghum.htm
http://en.wikipedia.org/wiki/Sorghum
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/C/C4plants.html
http://www.marietta.edu/~biol/biomes/p
hotosynthesis.htm
www.biologymad.com/resources/Crop
%20Plants.pps
Past Papers
Paper 43, June 2011, Q4
164
Learning objectives
Suggested teaching activities
Learning resources
Discuss the effect of higher temperatures on C3 enzymes versus C4 enzymes. (W)
(Basic)
o Learners use their graph(s) from 13.2.b (temperature v rate of photosynthesis),
to sketch in a curve for a C4 plant. (I) (Basic)
Extension: learners consider the effects of global warming on the distribution of C4
plants. (I) (Challenging)
15.2.a
describe the rapid response of the
Venus fly trap to stimulation of hairs on
the lobes of modified leaves and
explain how the closure of the trap is
achieved
Key concepts
Cells as the units of life,
Organisms in their environment
v2.1 5Y02
Display photographs of the Venus fly trap plant and its modified leaves.
o Leaners brainstorm uses of nitrogen in plants.
o Discuss the need for a source of nitrogen in addition to the products of
photosynthesis.
o Explain that the plant requires supplemental nitrogen owing to low levels of
nitrogen in the bog habitats where it is found. (W) (Basic)
Explain to learners that the equivalent of an action potential occurs to cause the
snapping shut of the trap to catch insects.
o Briefly review learner understanding of stimulus, receptor and action potential
(Unit 10). (W) (Basic)
Learners sequence a set of statements as the basis to make notes. Ideas to include:
o Stimulus = insect movement (mechanical).
o Receptors = hair cells (upper leaf surface).
o Touching two times in succession, i.e. the presence of an insect, results in
depolarisation of the hair cell membrane (owing to an influx of positive ions).
o If the depolarisation is large enough, action potentials spread across from
receptor cells to reach cells on the outside surface.
o One possible mechanism of closure of the trap:
H+ is pumped out of cells on the outside surface into the cell walls
The low pH causes cell wall loosening and movement out of H+ leads to
influx of Ca2+
Water follows osmotically and the cells swell to snap the trap shut. (I)
(Challenging)
Background: learners investigate how carnivorous plants like the Venus flytrap
digest and absorb their insect catch. (I) (Basic)
Cambridge International AS & A Level Biology (9700) – from 2016
Online
http://plantsinmotion.bio.indiana.edu/pl
antmotion/movements/nastic/nastic.ht
ml
http://www.botany.org/Carnivorous_Pla
nts/venus_flytrap.php
165
Learning objectives
Suggested teaching activities
Learning resources
14.2.a
explain that stomata have daily
rhythms of opening and closing and
also respond to changes in
environmental conditions to allow
diffusion of carbon dioxide and
regulate water loss by transpiration
Learners link stomatal opening and closure to transpiration (Unit 4) and
photosynthesis.
o Discuss the environmental stimuli for opening and closure (learners recall factors
affecting transpiration rate).
o Explain the ‘internal clock’ of guard cells and the daily rhythm of opening during
the day and closing during the night. (W) (Basic)
Provide graphs showing daily rhythms of opening and closing, with the effects of
changing environmental conditions on particular days.
o Learners describe and explain the graph, using this as the basis of their notes.
(I) (Challenging)
Online
http://www.tiem.utk.edu/~gross/bioed/
webmodules/circadianrhythm.html
Key concepts
Cells as the units of life,
Organisms in their environment
14.2.b
describe the structure and function of
guard cells and explain the mechanism
by which they open and close stomata
Key concepts
Cells as the units of life,
Biochemical processes
14.2.c
describe the role of abscisic acid in the
closure of stomata during times of
water stress (the role of calcium ions
as a second messenger should be
emphasised)
Key concepts
Biochemical processes,
v2.1 5Y02
Note
Mention the term circadian rhythm (not required learning).
Very high wind speeds may also cause stomatal closure – some books do not show
this on typical graphs.
Learners draw and label a diagram of guard cells, making a note of their function. (I)
(Basic)
Learners use an outline diagram of the events occurring for stomatal opening and
complete a worksheet to describe and explain the mechanism involved (uses much
knowledge from AS Level). (I) (Challenging)
Learners use knowledge of the mechanism of stomatal opening to write out and
explain the sequence of events occurring for stomatal closure. (F)
Learners use prepared slides (see 7.2.e, Unit 4) to observe guard cells and stomata.
(I) (Basic)
Learners observe stomatal opening and closure in temporary slides made of
epidermal strips in solutions of different water potential. (I) (Basic)
Online
http://www.phschool.com/science/biolo
gy_place/labbench/lab9/stomamov.ht
ml
http://www.saps.org.uk/secondary/teac
hing-resources/104-stomata-functionguard-cells-and-transpiration
Describe the role of abscisic acid (ABA) as a 'stress hormone' to help plants survive
difficult environmental conditions such as drought. (W) (Basic)
Explain to learners that calcium ions are important in plant cell signalling. (W)
(Basic)
Learners make summary bullet-point notes based on the following ideas:
o Guard cells have receptors for ABA: the presence of ABA results in high
concentrations of calcium ions within the cytoplasm.
o ABA can inhibit the proton pump used to pump out protons, preventing the
inward flux of potassium ions.
Online
http://labs.biology.ucsd.edu/schroeder/
clickablegc.html#figure1
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/A/ABA.html
http://www.planthormones.info/abscisicacid.htm
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
166
Learning objectives
Organisms in their environment
Suggested teaching activities
o The presence of both ABA and calcium ions leads to changes in the membrane
that causes the opening of potassium ion channels.
o The calcium ions, therefore, can be considered as a second messenger.
o Movement out of potassium ions from the cell will cause stomatal closure (see
14.2.b). (I) (Challenging)
Note
Not all the details of ABA and calcium ion involvement in stomatal closure are
known: it is worth checking for updates.
The changes in the membrane are depolarisation as a result of activation of anion
channels in the membrane (details not required).
As abscisic acid can enter cells, receptors could be membrane-bound or internally
located.
15.2.b
explain the role of auxin in elongation
growth by stimulating proton pumping
to acidify cell walls
Key concepts
Cells as the units of life,
Biochemical processes
Discuss how cell division and cell elongation will lead to plant growth and stem
elongation.
o Explain that auxin is a plant hormone involved in cell elongation. (W) (Basic)
Discuss details of cell wall structure before outlining the sequence of events that
occur (learners recall AS Level knowledge). Learners make notes to include:
o Auxin increases the activity of proton pumps (ATP required) and protons are
pumped out of the cell into the cell wall.
o The decrease in pH activates expansins (proteins) involved in loosening cell wall
structure.
o Water moves in by osmosis, increasing turgor and allowing cells to elongate. (W)
(I) (Challenging)
Learning resources
Bio Factsheet 48: Tackling exam
questions: plant growth substances
Bio Factsheet 111: Plant Growth
Substances
Past Papers
Paper 43, June 2011, Q11 (a)
Online
http://bcs.whfreeman.com/thelifewire/c
ontent/chp38/3802003.html
http://croptechnology.unl.edu/pages/inf
ormationmodule.php?idinformationm
odule=998688536&topicorder=6&ma
xto=11&minto=1
http://home.earthlink.net/~dayvdanls/pl
ant_grow.htm
http://www.personal.psu.edu/fsl/ExpCe
ntral/
Note
Auxins are a class of hormones, rather than one particular plant hormone. At this
level the use of ‘auxin’ is acceptable. The same applies to gibberellins.
15.2.c
describe the role of gibberellin in the
germination of wheat or barley
Key concepts
Biochemical processes,
Observation and experiment
v2.1 5Y02
Introduce gibberellin as a hormone that promotes germination by breaking seed
dormancy.
o Agree what is meant by ‘germination’. (W) (Basic)
Learners annotate a diagram of a section through a wheat or barley grain, showing
the sequential events occurring once water is imbibed. Use questioning and include:
o Diffusion, e.g. of gibberellin from embryo to aleurone layer;
o Transcription and translation (in aleurone layer cells for production of digestive
hormones);
Cambridge International AS & A Level Biology (9700) – from 2016
Practical booklet 10
Online
http://www.indiana.edu/~oso/animation
s/barley.html
Textbooks/Publications
King p.240-241
167
Learning objectives
Suggested teaching activities
o Hydrolysis of starch and protein (by digestive enzymes) and use of products for
respiration and growth of seedling. (I) (Challenging)
Learners organise a set of statements to show the correct sequence of events in
seed germination. (F)
Practical booklet 10: learners carry out practical to investigate the effect of different
concentrations of gibberellic acid on stimulating amylase activity in germinating
seeds.
o The results can be analysed using the t-test (see 17.1.c). (P) (I) (Basic)
15.2.d
explain the role of gibberellin in stem
elongation including the role of the
dominant allele, Le, that codes for a
functioning enzyme in the gibberellin
synthesis pathway, and the recessive
allele, le, that codes for a nonfunctional enzyme
Key concepts
Cells as the units of life,
DNA, the molecule of heredity
16.3.d
explain how gibberellin activates genes
by causing the breakdown of DELLA
protein repressors, which normally
inhibit factors that promote
transcription
Key concepts
Biochemical processes,
DNA, the molecule of heredity,
v2.1 5Y02
Learning resources
Past Papers
Paper 43, June 2011, Q11 (b)
Paper 41, Nov 2013, Q9
Remind learners of 15.2.b and explain that in stem elongation, gibberellin causes
both cell division and cell elongation. (I) (Basic)
Learners recall basic points: the definition of an allele (Unit 3); genes code for
polypeptides / proteins; enzymes are proteins; the definitions of dominant and
recessive (alleles). (W) (Basic)
Explain that there is a gene responsible for expressing an enzyme that is important
in the synthesis of active gibberellin.
o State that there is a dominant allele for the functioning enzyme and a recessive
allele for a non-functioning enzyme. (W) (Basic)
Learners use knowledge of genetics and of the role of gibberellin to explain how
plants that are LeLe and Lele will have tall stems, whereas plants that are lele will
have short stems. (F)
Learners carry out practical work to investigate the effect of gibberellic acid on stem
(hypocotyl) elongation and on seed germination (barley) (see 15.2.c).
Online
http://www.tutorvista.com/content/biolo
gy/biology-iv/plant-growthmovements/gibberellins.php
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/G/Gibberellins.html
http://www.plant-hormones.info/
Note
This could be amalgamated with 16.3.d.
Past Papers
Paper 43, Nov 2012, Q10 (b)
Explain that DELLA proteins are regulators of growth: they bind to transcription
factors necessary for expression of genes coding for growth proteins.
o Learners explain how the DELLA proteins can be considered repressors. (W)
(Basic)
Explain that gibberellin can bind to intracellular receptor proteins (GID1) and that this
leads to a complex with DELLA proteins, making them susceptible to degradation by
the cell.
o Learners suggest the consequences of this breakdown. (W) (Challenging)
Learners describe the sequence of events that lead to an event such as stem
elongation in the presence of gibberellins. (I) (Challenging)
Practical booklet 10
Cambridge International AS & A Level Biology (9700) – from 2016
Textbooks/Publications
King p.244
Bio Factsheet 118: Germination
Bio Factsheet 133: Comparing
Chemical Communication in Plants
and Animals
Online
http://users.rcn.com/jkimball.ma.ultran
et/BiologyPages/G/Gibberellins.html
168
Learning objectives
Observation and experiment
Suggested teaching activities
Learning resources
Note
Learners could be directed to use this information on the mode of action of
gibberellins in their interpretations of results from practical booklet 10 (see 15.2.c).
© Cambridge International Examinations 2014
v2.1 5Y02
Cambridge International AS & A Level Biology (9700) – from 2016
169
