Population Growth
Population Ecology - the study of the number of individuals of a particular species that are found in an area and how and why those numbers change over time
Population Growth cont’d
Population Density - the number of individuals of a population per unit of habitat area - e.g., the number of Grassquits per hectare - e.g., the number of snapper per litre of sea water
Population Growth cont’d
Population Size - the number of individuals making up a population Population size changes due to: • births • deaths • immigration • emigration
Population Growth cont’d
Birth Rate (b) - also called crude birth rate - number of births per 1,000 individuals in a population in a given year Death Rate (d) - also called crude death rate - number of deaths per 1,000 individuals in a population in a given year
Fertility Rate
- The number of children born to a woman - Jamaica’s fertility rate is 2.41
Replacement Fertility Rate
- The fertility rate that is high enough to replace an area's population.
- In Industrialised countries it is 2.1
Population Growth cont’d
Immigration (i) - movement of individuals into a population
Emigration (e) - movement of individuals out of a population
Population Growth cont’d
Growth Rate (r) - also called annual rate of natural population change r= b–d r = (b + i) – (d + e) Biotic Potential - maximum rate at which a population can increase when there are no limits on its growth
Population Growth cont’d
Exponential Growth - growth in population size increases by a fixed percentage of the whole in a given time period
Population Growth cont’d
Environmental Resistance - all the factors jointly acting to limit the growth of a population Carrying Capacity - number of individuals of a given species that can be sustained indefinitely in a given area
S-shaped Growth Curve
Carrying Capacity
Number of Individual Organisms
A population grows exponentially until it is acted on by limiting factors that cause the growth to level off at the carrying capacity. Time
Regulation of Population Size
Density Dependent Checks on Population Growth - where some limiting factors become more
influential as a population’s density increases - examples: • competition for resources • predation • parasitism • disease
Regulation of Population Size
Density Independent Checks on Population Growth - exert their effects on population regardless of population density - examples: • floods • hurricanes • severe droughts • fire • temperature
Overpopulation
- occurs when people exceed the carrying capacity of an area - more people than can live on Earth or a geographic region in comfort, health & happiness - also called environmental unsustainability - leaves the planet or region unfit for future generations
Overpopulation cont’d
There are 2 types of overpopulation: 1. People Overpopulation 2. Consumption Overpopulation
Factors Affecting Population Growth
- Migration - Birth Rate
- Economic Rewards/Penalties - religion, culture - Empowering Women - average marriage age - Family Planning - children as part of labour force
- Death Rate
- AIDS - Crime - better nutrition - availability of good health care
- Economic Development
Population Distribution: Urban Living
Urbanisation - process in which people increasingly move from rural areas to densely populated cities
- Increased density of settlement and/or businesses and other activities over time
Population Distribution: Urban Living
Urbanisation (Cont’d) - Approximately 50% of the world's population
live in urban areas
- Cities are the main centres for new jobs, education, innovation, culture & trade
Push Factors
Unemployment Mechanised agriculture
- Government policies / lack of investments
Effects of Urbanisation include:
• Vegetation Loss • Urban Microclimate • Water Demands, Increased Runoff & Flooding • Solid Waste and Pollution • Noise Pollution • Land Conversion & Social Disruption
Improving Urban Life (Some Solutions)
• reduce population growth • increase investments & social services in rural areas • repair and revitalise existing cities • grow food in abandoned lots & community garden plots
Economic Development/ Demographic Transition
- hypothesis that countries, as they become industrialised, have declines in death rates followed by declines in birth rates - the transition takes place in 4 stages 1. Pre-Industrial 2. Transitional 3. Industrial 4. Post-Industrial
1) Pre-Industrial Stage
- harsh living conditions - high birth rate - high death rate 2) Transitional Stage - industrialisation begins - death rate drops - birth rate remains high
3) Industrial Stage
- birth rate drops - birth rate approaches death rate - population growth slows 4) Post-Industrial Stage - birth rate equals death rate - zero population growth
Age Structure Diagram
- a diagram representing the percentage (or number of people) of the population at each age level in a population - plots the percentage or numbers of males & females in the total population
Pre-Industrial Stage – Little Population Growth
Transitional Stage – Rapid Population Growth
Industrial Stage – Population Growth Slows
Post-Industrial Stage – Negative Population Growth
2001 Population Data For Selected Countries
Country Population Births Deaths Per 1000 Per 1000 Pop. Pop. Net Migration Per 1000 Pop. Population Aids Deaths Change in 1999 Per 1000 Pop. Per 1000 Pop. (Adult prevalence)
Botswana Haiti Jamaica Barbados United States Germany
Source:
2004 Population Data For Selected Countries
Country Population Births Deaths Per 1000 Per 1000 Pop. Pop. Net Migration Per 1000 Pop. Population Aids Deaths Change in 2003 Per 1000 Pop. Per 1000 Pop. (Adult prevalence)
Botswana Haiti Jamaica Barbados United States Germany
Source:
2006 Population Data For Selected Countries
Country Population Births Deaths Per 1000 Per 1000 Pop. Pop. Net Migration Per 1000 Pop. Population Aids Deaths Change in 2003 Per 1000 Pop. Per 1000 Pop. (Adult prevalence)
Botswana Haiti Jamaica Barbados United States Germany
Source:
2009 Population Data For Selected Countries
Country Population Births Deaths Per 1000 Per 1000 Pop. Pop. Net Migration Per 1000 Pop. Population Aids Deaths Change in 2007 Per 1000 Pop. (People living with (Fert) AIDS)
Botswana Haiti Jamaica Barbados United States Germany
Source: