Population Size


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•  Discussion of the effect of natality, mortality, immigration and emigration on population size

The change in the size of a population over time is determined by four key factors:

•  Natality:  Increases to population size through reproduction (births)

•  Immigration:  Increases to population size from external populations

•  Mortality:  Decreases to population size as a result of death

•  Emigration:  Decreases to population size due to loss to external populations

The role of these factors in determining population size can be summarised by the following equation:

  • Population Size = (Immigration + Natality) – (Mortality + Emigration)

Population Size Equation

population size