Measuring Populations Growth Rate- the amount by which a population’s size changes over time. –Birth, death, immigration, and emigration Immigration- how many individuals move into a population. Emigrating- when an individual leaves a population.

Birth rate - death rate = growth rate

Exponential Growth

Logistic Model

Population Regulation There are two limiting factors which control population size –Density dependant factors – ex water, food –Density independent factors – ex weather, floods, fires

Predator Prey Relationships

Perils of Small Population Small populations are vulnerable to extinction. With small populations there is often increased likelihood of inbreeding Inbreeding causes a decrease in genetic variation an thus the population would be less likely to be able to adapt to the environment.