Population Change Chapter 35

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

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’

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

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

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

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