01:119:115 Lecture Notes - Lecture 20: Ecological Footprint, Demographic Transition, Negative Feedback
15 Mar 2016
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Document Summary
Limited amount of resources may lead to trade-offs between survival and reproduction. Parent bird survival depends on size of brood. Ecologists try to understand adaptive consequences of life history traits at different population densities. Density-independent population: birth and death rate do not change with population density, affected by abiotic factors (e. g. weather, pollution, fire) Density-dependent population: birth rates fall and death rate rise with population density. Many factors that regulate population growth are density dependent. Negative feedback system that regulates population growth. Typically involve biotic factors including (but not limited to): competition for resources, predation, parasitism/disease. All populations show fluctuation in size across time and space: population dynamics. Immigration and emigration (not just birth and death) can also contribute to population dynamics. Metapopulations: groups of populations of a species linked by immigration and emigration. Occur because heterogeneity in environment (patches of different resource quality, elevation, moisture, etc. ) Source habitats/populations: areas where local reproductive success is > than mortality.
