1. How Populations Grow

4. Characteristics of Populations
3 important characteristics of a population: geographic distribution, density, and growth rate
Geographic distribution – range; area inhabited by a population
*Density – number of individuals per unit area
Growth rate – the increase or decrease in numbers of individuals over time

5. Population Growth
3 factors affect population size: number of births, number of deaths, and number of individuals that enter or leave the population
Populations increase or decrease depending on how many individuals are added or taken away

6. Population Growth Immigration – individuals move into an area [IN]
Emigration – individuals move out of an area [EXIT]

7. Exponential Growth
Occurs when individuals in a population reproduce at a constant rate
Increases slowly at first, then as the population becomes larger, it increases faster
“J”-shaped curve on graph
With unlimited resources and ideal conditions… population becomes nearly infinite  does not continue very long

8. Logistic Growth
When a populations growth slows or stops following a period of exponential growth
This happens when resources become less available
“S”-shaped curve on graph
Carrying capacity = the largest number of individuals of a certain species a given environment can support