Carrying Capacity 2.4-2.7
Abiotic and Biotic Factors Work Together to Influence Population Size • The growth of individuals and increase in size of populations is regulated by available resources. • Resources are limited. • Competition for food or other resources may take a toll on populations.
Environmental stress, such as heat or cold, will also limit population size. • The greatest number of individuals that a space can support is called its carrying capacity. • The carrying capacity determines the population’s maximum size.
Homeostasis is the tendency for a population to remain stable. • Populations will remain between the upper and lower limits that are defined by mortality, birthrate, and population movements.
Population Density May Fluctuate • The interaction of the population’s growth rate with the environment determines the density of the surviving population. • If you measure the density of a population at different times during the year, you will seldom find any two consecutive measurements that are the same.
Populations May Spread to Neighboring Areas • The ability of populations of living things to spread from a central place into others is called dispersal. • This can be either active or passive. • Organisms must be able to survive and reproduce in the new location.
Barriers Can Prevent Dispersal • Most species have a limited geographic range. • Physical barriers such as mountains and water prevent dispersal. • An increase in a population of organisms that can move encourages emigration to less populated areas that my have resources.