1. KEY CONCEPT Populations grow in predictable patterns.

2. Changes in a population’s size are determined by immigration, births, emigration, and deaths.
The size of a population is always changing.
Four factors affect the size of a population.
Immigration – the movement of individuals into one population from another.
Births – increase the number of individuals in a population.
Emigration – the movement of individuals out of a population and into another population.
Deaths – decrease the number of individuals in a population.

3. Population growth is based on available resources.
Exponential growth is a rapid population increase due to an abundance of resources.
Fig. In Australia during the early 1900s, the introduced European rabbit population exhibited exponential growth.
Formula for calculating exponential growth:
y=abx
y= population # a= # of females
x= # of years (generations) b= # of offspring/female

4. Logistic growth is due to a population facing limited resources.

5. Carrying capacity is the maximum number of individuals in a population that the environment can support.
A population crash is a dramatic decline in the size of a population over a short period of time.

6. Ecological factors limit population growth.
A limiting factor is something that keeps the size of a population down.
Density-dependent limiting factors are affected by the number of individuals in a given area.
Fig. Taking down prey as large as a moose requires that the members of a pack work together. As many as ten wolves may take hours or even days to wear down this moose.

7. Density-dependent limiting factors are affected by the number of individuals in a given area.
predation
competition
parasitism and disease

8. Density-independent limiting factors limit a population’s growth regardless of the density.
unusual weather
natural disasters
human activities
Fig. The storm surge accompanying a hurricane can cause dangerous flooding.