Application:
• 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
