Biology 2483A Lecture : Ecology Notes
23 Nov 2012
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Document Summary
Population dynamics are the ways in which populations change in abundance over time. Population size changes as a result of four processes birth, death, immigration, and emigration. Nt+1 = nt+b-d+i-e, where nt is population size at time t. Patterns of population growth: populations exhibit a wide range of growth patterns, including exponential growth, logistic growth, fluctuations, and regular cycles. A single population can experience each of them at different times. Exponential growth: the population increases by a constant proportion at each point in time. When conditions are favourable, a population can increase exponentially for a limited time. When a species reaches a new area, exponential growth can occur if conditions are favourable. The population may grow exponentially until density-dependent factors regulate its numbers. Species such as the cattle egret colonize new regions by long-distance or jump dispersal events. Local populations then expand by short-distance dispersal events.
