How Populations Grow
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
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
Population Growth Immigration – individuals move into an area [IN] Emigration – individuals move out of an area [EXIT]
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
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