BIOB50H3 Lecture Notes - Lecture 9: Allele, Genetic Drift, Cooperative Breeding
18 Oct 2016
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Lecture 9 october 4 population iii (population growth and regulation) Population size can be determined by density-dependent and density-independent factors. Density-independent factors: effects on birth and death rates that are independent of the number of individuals in the populations (ex. weather conditions, catastrophes) Andrewartha showed that a type of flower (thirps imagines) can be accurately predicted from temperature and rainfall. Density-dependent factors: birth, death, and dispersal rates change as the density of the population changes. As density increases, birth rates often decrease, death rates increase, and dispersal (emigration) increases. When birth, death, or dispersal rates show density dependence, population growth rates may decline as densities increase. If densities become high enough to cause lambda to equal one or r equals zero, the population stops growing; if lambda is less than one or r is less than 0, the population declines.
