5.3.1 Outline factors affecting population size

Natality (birth rate / reproduction) and Immigration (movement of individuals into an area) both increase population size.

Mortality (death rate) and Emigration (movement of individuals out of an area) both decrease population size.

If Natality and Immigration are greater than Mortality and Emigration then population size will increase overall.

If Natality and Immigration are less than Mortality and Emigration then population size will decrease overall.