1. Ch35: Population Change
Higher Human Biology

2. Population
A population is a group of individuals of the same species which makes up part of the community in an ecosystem.
When a population colonises a new environment the population increases rapidly until it reaches the carrying capacity - the maximum population size that can be maintained by the environmental conditions.

3. Populations terminology
Population density – the number of individuals of the same type present per unit area (or volume) of a habitat.
Birth rate – the number of new individuals produced by a population during a certain time interval.
Death rate – the number of individuals within a population that have died during the same time interval.

4. Population Growth Curve
Exponential growth
Rapid increase in population size
Carrying capacity
Number of Individuals
Birth = Death rate rate
Population colonising a new environment
Time

5. Population Stability
When the population reaches the level that the available environmental recourses can just maintain the population becomes stable.
At this stage it is in a state of dynamic equilibrium (there are very slight changes but overall it is relatively balanced) and the population has reached its carrying capacity and birth rate equals death rate.
Human interference has caused many populations to become unstable or threatened.

6. Population Regulation
The carrying capacity is determined by:
Food
Oxygen
Water
Space
If one is limited it prevents the population increasing
Regulatory Effect
Death by….
Predation
Disease
Pollution by organism’s waste
Population decrease

7. Regulation of population size
factor limited e.g. food, water
Population decrease Death rate increases
Population increase
Population at Carrying capacity
(maximum supported by the environment)
Population decrease
Population increase Birth rate increases
Factor plentiful e.g. food, water

8. Rapid population increase
Human Population Explosion
Humans have overcome causes of mortality (e.g. predation) so have increased our carrying capacity & have increased exponential growth.
Revolutionary changes
Agricultural
Rapid population increase
Industrial

9. Undeveloped Societies
Totally dependent on immediate environment for food, water, shelter.
Live ‘hand to mouth’
No agriculture
No modern technology
Kalahari Bushmen
(Africa)

10. low population density shared society
e.g. Hunter-gatherers
remote locations
low carrying capacity
low population density
shared society
Aborigines
(Australia)
Arctic Inuit (Eskimos)
Population limited by water availability
Population limited by low temperature

11. Influence of modern society on undeveloped societies
Modern societies have introduced:
tools
technology
disease – led to a population decline
Caused problems:
Less land to live off
Traditional cultures are disappearing
Economic & social problems

12. Common in Latin America, Africa & Asia
Subsistence farming
Grow crops on own land to meet the families own needs.
Store excess crop for use during times of shortage
Rarely sell any crops or animals
Use basic tools
Use family labour
Common in Latin America, Africa & Asia

13. Subsistence farming (cont’d)
Low standard of living
Often no electricity or sanitation
Lifestyle similar to 10,000 y.a. at start of agricultural revolution
Population denser than hunter-gatherers

14. Effect of Science on Human Population Growth
Better housing
Immunisation against diseases e.g. smallpox & polio
Modern sanitation
Piped water
Improvements in child care
Efficient food production
Antibiotics

15. Effect of Science on Human Population Growth
Scientific discoveries & Inventions
1650 AD Advances in science
Advances in medicine
Industrial revolution
These advances have contributed to a human population boom by removing limiting factors that in the past regulated the population.

16. Exponential Growth of Human Population
The human population is now growing exponentially due to:
Less child mortality
Increased female fertility
Overcoming predation (due to guns)
Increase in life expectancy

17. Increased food availability
Exponential Growth
Also due to…
Increased food availability
Machinery
Pesticides
Fertilisers

18. Births no longer spaced out
Change in Cultural Habits
Women tend to suckle their young for less time, as ovulation is inhibited during breast-feeding, women are more likely to conceive their next child sooner.
Births no longer spaced out
Birth rate increases

19. Actually the population growth rate is slowing down due to…
Doubling time
… the length of time for the worlds population to double.
Actually the population growth rate is slowing down due to…
In 1980s doubling time was decreasing steadily thus the world population was rapidly increasing
use of contraception
social pressures (e.g. China)
deaths from AIDS

20. World’s wealth is not distributed evenly
The highest population growth is in the poorest nations so 50% of the world population live in poverty!