BIOS 230 Lecture Notes - Lecture 21: Keystone Species, Species Richness, Community Structure
18 Nov 2016
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Document Summary
Community- group of species that occupy a given area, interacting directly or indirectly, a more restrictive definition is a subset of species. Relative abundance- % of each species contributes to total # of individuals. When discussing slope in terms of rank abundance vs relative abundance, it is a measure of evenness. Diversity indices- quantify relationship between species # and relative abundance. Most communities have a small number of common species. Keystone species- disproportionately impacts the community relative to its abundance. Removal of keystone species results in significant biodiversity loss. When 2 species interact through a 3rd species. Predator enhances inferior competitors by reducing abundance of superior competitors. Bottom up control- community is controlled by trophic level below. Top down control- predator populations control abundance of their prey. Community structure varies in time and space. Changes reflect shifting of populations in response to. Successin- gradual change in community structure through time. Grow quickly, smaller size, good dispersers, high population growth.
