BISC 313 Lecture Notes - Lecture 6: Metapopulation, Habitat Fragmentation, Logistic Function
1 Nov 2017
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Document Summary
Population size changes as a result of 4 processes: birth, death, immigration, and emigration. Populations exhibit a wide range of growth patterns, including exponential growth, logistic growth, fluctuations, and regular cycles. Exponential growth- increase by a rate continuously rather than reproduction happening at set times--until density-dependent factors regulate its numbers. Logistic growth: some populations reach a stable size that changes little over time. Carrying capacity is dependent on the environment and can change. Population cycles: fluctuations in high and low population numbers at regular intervals. Internal factors such as hormonal or behavioral changes in response to crowding. External factors, such as weather, food supplies, or predators. Delayed density dependence can cause populations to fluctuate in size. Delayed density dependence: time lags over which the carrying capacity of the environment changes. Density dependent factors on one population affects the future generations. Fluctuations in growth rate, n, and change events can affect a population"s risk of extinction.
