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KEY CONCEPT Populations grow in predictable patterns.

KEY CONCEPT Populations grow in predictable patterns. 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.

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KEY CONCEPT Populations grow in predictable patterns.

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

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

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