Population Growth Curves

1 Exponential Stage

Limiting factors are not restricting the growth of a population

• with low or reduced limiting factors, the population expands exponentially into the habitat

• both the number of individuals and the rate of growth increases rapidly

2 Transition Phase

The increase in number begins to slow as well as the rate of growth

• this is because the limiting factors begin to affect the population and restrict its growth

  • increased competition, predators, rate of disease and mortality

3 Plateau Phase

Limiting factors restrict the population to its carrying capacity

• changes in limiting factors cause populations to fluctuate (increase and decrease) around the carrying capacity

Population growth curves

Populations are affected by four main factors:

(+) Natality - increases the population size through reproduction

(+) Immigration - increases the population size from external populations

(-) Mortality - decreases the population size as a result of deaths

(-) Emigration - decreased the population size as a result of loss to external populations

Population Size = (Natality + Immigration) - (Mortality + Emigration)

Population Growth: I + N > E + M

Population Stability: I + N = E + M

Population Decline: I + N < E + M