Population Growth

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Limiting factors

Population sizes change depending on birth rate, death rate and migration in and out of the population.

These factors are affected by food supply, predation, reproductive abilities and disease. In a stable ecosystem, where these factors stay fairly balanced, the population size remains fairly constant.

Limiting factors = factors that keep a population at a maximum size that can be sustained by the ecosystem (eg. food supply).

Carrying capacity = the population size that can be sustained by an ecosystem.

Environmental resistance = collective term for the limiting factors that keep a population at carrying capacity.

Limiting factors keep the population at the carrying capacity, and the limiting factors which determine it's size are collectively called environmental resistance.

On a population growth curve (graph showing the growth of a population over time) there are usually three clear stages:

  • Lag phase - growth is slow because the population is so small that even doubling…


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