1. Population Change
Chapter 35

2. Population & Carrying Capacity
Each species have huge reproductive potential
- especially in a new environment
If birth rate exceeds death rate = population growth
But population cannot increase indefinitely
Carrying capacity:
- maximum population that can be supported by an environment
Growth curves show 4 phases
Carrying capacity regulated by LIMITING FACTORS
E.g. food, water, oxygen, & space
Predators, disease, & pollution can also have an effect

3. Human Population Explosion
Humans not controlled by most limiting factors
- no predators, food/water shortage etc.
Effect of agriculture:
Up to 10,000 years ago – all humans were ‘hunter-gatherers’
No food reserves (population was stable)
Agriculture began (crops grown, animals domesticated)
Led to human population ‘spurt’

4. Modern undeveloped societies
Totally dependant on immediate environment for food, water & shelter
Bushmen of Kalahari Desert, Arctic Inuit, Australian Aborigines
– hunter-gatherers
No crops or animals
Environment carrying capacities very limited
Economic & social problems caused by contact with modern cultures
Subsistence farming
– growing crops & rearing animals for own families needs
Common in latin america, Asia & Africa

5. Science on human population growth
Second ‘spurt’ began in 1650AD
Industrial & scientific revolution
Major discoveries & inventions
Advancements in medicine
(e.g. immunisation)
More efficient food production
Improved housing & sanitation
Limiting factors largely removed

6. Factors contributing to human population ‘spurt’
Overcoming predation
- invention of guns & weaponry
Increased food availability
- machinery, fertilisers, pesticides
Reduction of child mortality
- improved hygiene & nutrition, vaccines, antibiotics
Increased life expectancy
- improved health & living conditions, & female fertility
Cultural Habits
- breast feeding
(prolactin inhibits LH = no ovulation)
- shorter suckling period, longer fertile period

7. Doubling time Time it takes for world population to double
Was steadily decreasing
Has slowed recently – contraception use, social pressures, and AIDS have all had an effect
Population increase is most rapid in developing countries
Half the worlds population is in extreme poverty