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Unformatted text preview: Samantha Levine BIO 171 Test 2 Ch 53 pgs 1070-1073- Community Structure o Clements- Gleason Dichotomy o 1936- Clements hypothesized that biological communities are stable, integrated, and orderly entities with a highly predictable composition. Species interactions are so extensive and coevolution is so important that communities have become highly integrated and interdependent units in nature. Species within a community cannot live without each other. o Climax community= stable, doesn’t change, developmental progression ends in this. o Gleason Thought that community found in a particular area is neither stable nor predictable. Plant and animal communities are ephemeral associations of species that just happen to share similar climatic requirements. Largely a matter of chance whether a similar community develops in the same area after a disturbance occurs. Downplayed the role of biotic factors. o Predictions of the Clements- Gleason Theory If community structure is predictable, then each pond should develop the same community of species once the chlorine vaporized and made the water habitable. If community structure is unpredictable, then each pond should develop a different community. o Mapping current and Past Species’ Distributions If communities are predictable assemblages, then the ranges of species that make up a particular community should be congruent- meaning that the same group of species should almost always be found growing together. Species can be independent Clemon’s point was too extreme and that Gleason’s view is closer to correction. Chance and history play a large role- Keystone Species Communicating Presence of certain consumers can have an impact on species present Structure of an entire community can change dramatically if a single species of predator or herbivore is removed from a community or added to it.- Community Dynamics o Disturbance and Ecological Changes Disturbance: is any event that removes biomass from a community. Impact of a disturbance: • Type of disturbance • Frequency • Intensity • Characteristic type of disturbance- predictable Disturbance Regime: Characteristic type of disturbance • Determine this by extrapolating data • Reconstructing the history of the site Ecosystems Ch. 54 - Ecosyste m: species pres ent, along with abiotic co mpon ents are linked by flows of en ergy and nutrients. o When you change the sp ecies that are pres ent of the abiotic e nviron m ent, you change the ecosyste m.- How does e n ergy flow through ecosyste ms? o Primary Producer = autotroph- an organis m that can synthesize its own food from inorganic sources....
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This note was uploaded on 02/19/2011 for the course BIO 171 taught by Professor Josephinekurdziel during the Spring '08 term at University of Michigan.
- Spring '08