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Biol 121- 2010.01.18- Ecology- Community Ecology- Species Richness, Energy Flow (Ch. 53-54).docx

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Department
Biology
Course
BIOL 121
Professor
Carol Pollock
Semester
Winter

Description
Biol 121 225 Freeman 121720 122230Jan 18 10 Species richness is a simple count of how many species are present in a given community Species diversity is a weighted measure that incorporates a species relative abundance as well as its presence or absence hard to do on relatively small study plots Why are some communities more larger patches of habitat contain more species than do smaller patcheslarge species rich than others areas contain more types of niches and therefore support higher number of speciesImmigration and Extinction rates immigration rates should decline as the number of species in an area increasesand the theory of island individuals that arrive are more likely to represent a species already present biogeographyextinction rates should increase as species richness increasesniche overlap and competition becomes more intensethe result is an equilibriumbalance between arrival of new species andextinction of existing onesimmigration rates should be higher on large islands close to mainland because immigrants are more likely to find large islands that are close to shore than small ones that are far awayextinction rates should be highest on small islands far from shore because fewer resources are available to support large populations and because fewer individuals arrive to keep the population goingtherefore species richness should be higher on larger islands than smaller islands and on near shore islands versus remote islands Why is this theory important 3 relevant to wide variety of islandlike habitats like alpine meadows lakes ponds cavesmade specific predictions that could be testedhelp inform decisions about design of natural preserves in general mostspecies rich reserves should be ones that are relatively large and located close to other relatively large habitat areas Why does a strong latitudinal first consider two fundamental principles to solve problem gradient in species diversity existhigher species richness near 1 Causal mechanism must be abiotic because latitude is a physical phenomenon equator and decreasing numbers produced by Earths shape going South or North2 Species diversity of a particular area is the sum of four processes speciation extinction immigration emigration dispersal thus latitudinal gradient must be caused by abiotic factor that affects the rates of these four thingsover 30 hypotheses havebeen proposed to explain latitudinal gradienteg1 High productivity in tropics promotes high diversity by increasing speciation rates and decreasing extinction rates productivity is the total amount of PS per unit area per year idea is that increased biomass production supports more herbivores and thus more
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