Module 9S2 Changes in Populations

4.9.1S2 page 3

Lesson Summary

The four determining factors of population size are natality, mortality, immigration, and emigration. Natality and immigration increase population size; mortality and emigration decrease population size. Population size is represented as N.

Change in a population is symbolized as delta N (∆N). The formula for change in population size is ∆N = (natality + immigration) – (mortality + emigration)