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Study of our ecosystem for dummies.




Unit-2 Ecosystem
§2.1 Concept of Ecosystem (= Biotic + Abiotic)
• An ecosystem is a biotic
assemblage of plants, animals,
microbes and its interactions.
• Eco = environment, System = coordinated units.
• Ecology→study of ecosystems
• The first law of ecology is that everything is related to
everything else -Barry Commoner.
• Ecology deals with the study of organisms with the surrounding.

§2.2 Ecosystem Structure
§2.2.1 Biotic Structure (plants, animals & microorganism)
• In an ecosystem the biological cycling of materials is
maintained by three groups viz. producers, consumers and


• •

• • ••• • • •
• •• • •• ••
• •




Animal can’t synthesis food depend on plant→Plant can’t synthesis food depend
Abiotic→ Sun, carbon dioxide, minerals etc in the environment.


• Nature is capable of sustaining the producer-consumerdecomposer cycle indefinitely.
• Producers: Green plants→ synthesize their food by
photosynthesis (Chlorophyll+CO2).
• Consumers: 1. Herbivores: (Plant eaters) eg. Rabbit, man,
2. Carnivors: (meat eaters) eg. Dependence on
the consumers
(secondary consumers).
3. Omniovers: (plant and meat eaters) Human,
fox, many birds
4. Detritivores: (dead organism eaters) ants,
crabs, earthworms.
• Decomposers:
Various bacteria and
fungi→ decompose the
complex organic
• In some conditions,
producers dominates
(forest), consumer
predominates (ocean)

§2.2.2 Abiotic Structure
(plants, animals &
• Climatic factors,
geographical factors,
energy, toxic
substances etc.
• Physcial factors:
Sunlight, temperature,


soil type, water availability etc influence the ecosystem. (eg.
Desert and rain forest)
• Chemical factors: Carbon, nitrogen, phosphorus, potassium,
oxygen, sulphur and toxic substances

§2.3. Function of ecosystem:
• Ecosystem perform under natural conditions continuously
• Energy receive from Sun (water+nutrients+air) and pass
through various biotic components → so life is the flow of
• Following are the major functionalities

Food chain & food webs
Energy & Nutrient flow
Cycling of nutrients (biogeochemical cycles)
Primary and secondary production
Ecosystem development & regulation

§2.3.a Food chain & Food Webs:
• Food Chain:
o It is a path way/cycle of food from and back to producer
o or sequence of eating and being eaten in ecosystem.
o Eg.1: grass→grasshopper→mouse→snake→hawk
(Grassland ecosystem)
o Eg.2: Phytoplantons (algaes) →water fleas→small
fish→Tuna (carnivorous fish)
(Pond ecosystem)
o Eg.3: Dead Organic matter→fungi→bacteria
(Forest ecosystem)
• Food web:
o Combination/interconnection of different Food Chains
o There are number of options of eating and being eaten at
different levels.
Food Chain→Food Web→Trophic structure (Ecosystem)



Toad (pre frog)

Preying Mantis (carnivore)


Example-1: (Food-Chain)

Example-2: (Food Web, Many food chains)


§2.3.b Energy & Nutrient Flow:






Energy and Nutrient too move through the food chain & ultimately
reached to dead organic matter (decomposition by micro-organisms)

• Plant system having highest form of energy and decreases with
increase in the path of the food-chain.
• Energy can flow in one direction only.
• Ecological Pyramids: Graphical representation of structure
and an ecosystem, starting with producer at the bottom and
each successive level forming the apex is know as ecological


pyramid. (See the picture: Trend is same for energy system
also (producer to recycler))
• Energy laws:
Ist law: Energy can neither be created nor be destroyed,
but it can be transformed from one form to another.
2nd law: Energy transformation involves degradation or
dissipation (distribution) of energy from a concentrated
form (not directly transformed). (Roughly ~10% of energy
is transformed to one to another system, rest are heat
energy only).
• Sun as the prim source of energy:
To do photosynthesis and oxidation reduction reactions
occurs in plants etc.

§2.3.c Nutrient Cycling:
• Carbon, nitrogen, sulphur, oxygen, hydrogen, phosphorus etc
move in circular paths through biotic and abiotic components →
biogeochemical cycles.

• Water cycle→ hydrological cycle
• Carbon cycle:
o Carbon dioxide is the prim
source for the carbon.\
o It is a gaseous cycle.
o All organic compounds contain
large amount of carbon source
(carbohydrate, protein, amino


o Main steps:
o Green plant: Photosynthesis (CO2+light →
o Plants were eaten by Human and Animals (carbohydrate
o Risperation of Biotic systems (O2→ CO2) liberates CO2
o Combustion of organic matters, dead plants, animals &
Coal release CO2
o Volcanic eruptions also release large CO2
o The cycle goes continuous with loss.

• Oxygen (O2) Cycle:
o Oxygen is vital for life in the biosphere
o Photosynthesis is the prim source of
systems for the O2 production from the
Carbon dioxide (CO2).


• Nitrogen (N2) Cycle:
o 78% of nitrogen gas present in the atmosphere.
o Nitrogen is taken by plant and used in metabolism for
biosynthesis of amino acids, proteins, vitamins etc.
o After death of plants and animals→ ammonifying &
nitrifying bacterias convert them in to ammonia (NH3),
nitrite (NO2-) and nitrate (NO3-), which again used by

Amino acid,
proteins, vitamins

• Phosphorus Cycle
o Phosphorus is an essential nutrient for plants and animals
in the form of ions PO43- and HPO42-.
o Source of phosphorus lies in the rocks, fossils (dead
animal and plant have hardened into rock)


o Formers use the phosphate→run off→ river→ocean/settle
in deep sediments (difficult to regenerates)
o Sea fish→Sea bird→ land


§2.3.d(i) Primary Production:
• Rate at which radiant energy is converted into organic
substances (eg. Carbohydrate) by photosynthesis or chemicalsynthesis by primary producers. (Net power of chemical energy
• Net primary production (NPP) = Overall production (or Gross
Primary production, GPP) –
Respiratory loss (R).
GPP = CO2 + light+(Photosynthesis) → Carbohydrate (100%) + O2
R = Carbohydrate (x) + O2 → energy + CO2
NPP = 100 - x
• NPP depends on

Deserts based
Open Oceans
Moist Temperature Forests
Wet tropical forest

(1) Solar radiations
(2) Availability of Water
(3) Nutrients
(4) Nature and type of Plant with
chlorophyll content.

Gross Primary Production (GPP)
K Cal/m2/yr


§2.3.d(ii) Secondary Production
• Net Energy production (in the forms of chemicals, eg.
Carbohydrate) in Herbivores or carnivores by using primary
producer (plant) (after respiratory loss).

§2.3.e Ecosystem Regulation
• Ecosystems regulate themselves and maintain themselves
under set of environmental condition (Reversible) [or regulates
its internal environment so as to maintain a stable]
• Ecosytems tries to resist the change and maintain equilibrium
with the environment due to the property known as



Death or


Death or

Stress condition

• The shows tolerance within certain extent→ some counteract
(deviation) know as with negative feed back (mechanism) →
bring back to original stage.
• To intense stress leads to positive feed back (mechanism,
irreversible) mechanism → tends to away from optimal
condition → death or collapse


§2.4. Ecological Succession
• Changes in an ecological system due to the external change.
• The progressive replacement of one community (group of
plants & animals living in an area) by another till the
development of stable community in that particular area
• Stages of Ecological Succession:
o (a) Pioneer community: First group of micro-organism,
which establish their community in the area.
o (b) Seres (or) Seral Stage: Various development stages
of a community.
• Type of Ecological Succession: (Environmental basis such a
terrestrial (living land), fresh water or marine etc)
o Primary Succession: (Drastic change): Eg. at Island,
sand, silt bed (river opening), new volcanic flow etc.
When community begins to develop
on a site previously unoccupied
by living organisms.
(see below)

o The sere development involved with the process called


o Secondary Succession: (normal change/time): When
an existing community is disrupted and a new one
subsequently develops at the site.
Eg. at: Some natural catastrophe (sudden event
that causes very great trouble or destruction) such
as fire or landslide, flooding, deforestation, mining.
(see below stages):

Following picture is an example for primary and secondary
successions stages.

(Horiculture- study about gardening)


§2.x. Ecological Pyramids: (It is a graphical representation of
structure and function)
Eg.: Food chain process
Producer→ consumer →decomposer (recycler)
There will be regular increase in the properties (energy,
biomass and no. of organisms)
• Type of Ecological Pyramids:
o 1. Pyramid of Numbers
o 2. Pyramid of Energy
o 3. Pyramid of Biomass

§2.x.1. (1) Pyramid of Numbers:
o Representation of individual organism present in each
tropic level. Eg. A grassland Ecosystem.
 3rd tropic level: (carnivores) less than the herbivores
 2nd tropic level: (herbivores), less compared to the
 1st tropic level: grass small in size larger in number
o (2) Pyramid of Energy: Amount of energy present differ
from different levels.


o (3) Pyramid of Biomass: Total weight/volume of the dry
matter present in different tropical systems (eg. tree→
* Inverted pyramid in an aquatic
system (fish→ plant):
Carnivore: Big fishes 12 gm/m2
Herbivores: 8 gm/m2
Producer: 4 gm/m2

§2.5. Major Ecosystems (some)
§2.5.1. Forest Ecosystem
• Rich is trees interspersed (irregular mixing)with herbs, shrubs
(round shaped flowers), climbers, lichens, algae, variety of
animals and birds etc (rich biodiversity) → in undisturbed and
stable climate condition




§2.5.1.A Tropical Rain forest:
• Evergreen forest found near the
• Always with high temperature, high
humidity and high rainfall→favor for
fast trees growth
• Different types of layers or plants and
animals in the tropical Rain forest :>
o Emergent Layer: Top most
o Canopy: below the Emergent.
Layer. Bright (umbrella like
tree cover), Birds, insects here
o Understory: below canopy,
Receive very low
sunlight→dark leaves(high
chlorophyll) (wood climbers, same kind of orchids which
are attached to branch of trees)
o Floor: Lowest layer. Receives very low sunlight

§2.5.1.B Tropical deciduous forest:
• Not ever green, loses its leaves in autumn
and grows new ones in the spring.
• Little away from the equator (warm
climate round the year, Rain only in the
monsoon), Many timings the climate is
dry only.
§2.5.1.C Tropical scrub forest:
• Where the dry season is longer
• Here small deciduous trees and shrubs only


§2.5.1.D Temperature Rain forest:
• Found in temperature area with adequate rain in forest.
• Dominated by coniferous trees (evergreen tree which produce
fruit in the form of cones)

§2.5.1.E Temperature deciduous forest:
• Found in moderate temperature
• Seanson: Long summer & cold but not too
severe winter, moderate rain. (contains
large oak trees)
§2.5.1.F Temperature coniferous forest:
• Fond in the arctic area (tundra)
• Winter is so long, cold and dry (sunlight for
few hours only)
• Available trees: pines, fir, cedar, spruce
etc (which are tinny, needle shaped with
waxy coating→to withstand cold)
• Soil get frozen during winter, few species
can survey
• Soils are acidic, prevent for further plant
• Species diversity is very low

§2.5.2. Grassland Ecosystem
• Dominated with Grass species (few trees
& shrubs)
• Rain fall in average but erratic
• Limited grazing helps to improve the
primary production of grassland,
overgrazing leads desertification.


§2.5.2.A Tropical grassland
• Occur near the border of tropical rain forest (high average
temperature and low moderate rainfall)
• Wide variety of animals and shrubs here

§2.5.2.B Temperature grassland
• Where the place winter very cold and
summer very hot.
• Usually found on flat, gentle sloped hills.
• Soil are quite fertile can be useful for
agriculture also

§2.5.2.C Polar grassland (Arctic Tundra)
• Very cold and strong winds with ice and snow → creates harsh
condition to grow plants

§2.5.3. Desert Ecosystem
• Where evaporation exceeds
precipitation (rainfall, snow etc)
• 1/3 rd of world’s land area
• Little species diversity consist of
drought resistant plants
• Atmosphere is very dry (insulator)

§2.5.3.A Tropical desert
• Like Sahara (Africa) and Thar (India)
• Driest

§2.5.3.B Temperature desert
• Mojave in Southern California


• Day time temperature high in summer, but cool in winter

§2.5.3.C Cold desert
• Like Gobi desert in China
• Cold winter and warm summer

§2.5.4. Aquatic ecosystem
• Water bodies. Biotic communities present in either fresh water
or in marine. In further of standing type (lentic) like ponds or
free-flowing type (lotic) like rivers.
• Pond ecosystem (stagnant):
o Receiving water in rainy season , playing key role in
o Contain several types of algae, aquatic plants, insects,
fishes and birds.
o Often exposed to tremendous anthropogenic (humangenerated) pressures. (swimming, bathing, cloth washing
& drinking etc)→ get polluted
• Lake ecosystem (big freshwater bodies with standing water):
o There are several zone under the lake ecosystems
 Littoral zone: Shallow zone (not deep), where
effective penetration of sun light
 Limnetic zone: Open zone, light penetration
 Profundal zone: Deep bottom area, where light
penetration is negligible.

Rooted plants
Littoral zone
Limnetic zone
Profundal zone


o Contains several organisms, fishes, snails and various
type of plants etc.
o Stratification: (Arrangement of different parts/diff.
 During summer, top waters become warmer than
the bottom water →top layer only circulate without
affecting inner layer (viscous)→distinct zone

o Type of lakes:
o Highly Nutrient (NPK) concentration type, due to
agriculture run-off and municipal discharge. Eg. Dal lake
o Low pH, high humic acid and brown waters. Eg. Bog lake
o Deep lake: Ancient one; polluted
o Desert Salt lake: In arid area.
o Volcanic lake: Due to after volcanic eruption
o Artificial lake: Created due to construction of dams
• River ecosystem:
o Ist phase: high slope (mountain): Cold and clear water
rushing downward from mountain and flowing through the
plains falls in to the sea →rich in dissolved oxygen
o 2nd phase: Gentle slope : support rich growth of plants.
Less dissolved oxygen content.
o 3rd phase: Reaching sea: Bring them lot of salt and
nutrient to sea.
• Ocean ecosystem:
o Note: 70% of earth surface covered with ocean water
only. >2,50,000 marine species→serving food and drug to
humans→ also provides minerals such as iron,
phosphorus, magnesium and oil & natural gas etc
o Oceans have two major life zones


 i. Coastal zone (land close to sea): Relatively
warm, nutrient rich and good sunlight→good for
primary production
 ii. Open sea: Deepest part of the see;
• Abundant sunlight area, good photo-synthesis
activity, sea plants here
• Dim light area
• Dark zone: ~3000 meters (3 km) deep. No
• Estuary (place where river joins with sea):
o Fresh and salty water meet. Also know as transition zone.
o Strongly affected by tidal (wave) action
o Large nutrient available in that area, good for primary
o Organism growing in that place (Eurythermal) has high
tolerance to temperature and salinity.
o Rich in biodiversity. Many migratory species (fishes). Half
time in sea and half in fresh water. They also get
abundant food→high productivity.
o But, Need to protect from pollution!.

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