Chapter 53 outline - A community is any assemblage of...

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A community is any assemblage of populations in an area or habitat. Species richness- the number of species contained within a community Relative abundance- a measure of how common or rare a species is in a community
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Contrasting views of communities are rooted in the individualistic and interactive hypotheses Two views on the question of how to account for species found together as members of a community emerged in the 1920s and 30s based on observation of plant distribution An individualistic hypothesis of community structure was proposed by H.A. Gleason it asserts that members of a community are found together simply because they share similar abiotic requirements such as temperature, amount of rainfall and type of soil The Interactive hypothesis was advocated by F.E. Clements who insisted that a community was a closely intertwined group of individuals who were linked by mandatory biotic interactions that cause the community to work together as a unit
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The individualistic hypothesis predicts that communities should generally lack discrete geographic boundaries because each species will be distributed according to its tolerance ranges for abiotic factors, and communities should change continuously with the addition or subtraction of any particular specie The interactive hypothesis predicts that species should be clustered into discrete communities with noticeable boundaries due to the presence of one species greatly influencing the presence of another species
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The Rivet Model Proposed by Paul and Anne Ehrlich ,the rivet model of communities is an extension of the interactive model , it suggests that most of the species in a community are associated tightly with other species in a web of life. Species are analogous to rivets because not all the rivets are required to hold the wing together, but if someone started removing rivets, we’d be concerned with the welfare of the next flight.
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The Redundancy Model According to this model, most of the species in a community are not tightly associated, the web of life is loose. An increase or decrease in one species has little effect
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This note was uploaded on 12/02/2009 for the course SCI 90210 taught by Professor Durkka during the Spring '09 term at École Normale Supérieure.

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Chapter 53 outline - A community is any assemblage of...

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