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Published byHarold Stevenson Modified over 9 years ago
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Twelfth lecture
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Biodiversity
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Population level Genetic diversity Hierarchy of Biodiversity Community level Species diversity Ecosystem level Functional group diversity Landscape level Spatial heterogeneity Biome level Biosphere level
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Defining and quantifying species diversity Species diversity: –Species richness: # of different species –Species evenness: relative abundance of species Diversity indices –There are many! –“Shannon-Wiener index” takes into account both richness and evenness H’ = diversity Pi = proportion of the ith species (e.g. 0.5 means that species i represents 50% of total) S = number of species in the community –e.g. two ecosystems, each has 5 species and 25 individuals #1: 21 of one species, 1 each of other 4H’ = 0.662 #2: 5 of each speciesH’ = 1.610 H’ = - Pi log e Pi i = 1 s
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Functional group diversity Functional group: –e.g. Coniferous vs. deciduous –e.g. Warm blooded herbivores –e.g. Nitrogen fixers –e.g. Organisms at a given trophic level Two types 1. Within group diversity (# species/group) e.g. “Trophic breadth” Provide “Functional redundancy” 2. Diversity of groups (# groups/ecosystem) e.g. “Trophic depth”
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Species vs. functional group diversity Key questions –Which one is important? –How are they important? –(We will come back to these…..)
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Anthropogenic loss of biodiversity Land use change (habitat loss & fragmentation) Over-harvesting Introduction of exotic species Eutrophication and other changes in biogeochemical cycles Pollution (water, land, atmospheric) Climate change Synergistic effects –e.g. (Fragmentation + climate change)
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Value of biodiversity To humans –Direct market value as genetic repository for crops and pharmaceuticals –Recreation, aesthetics, spirituality –Ecosystem services To biological and ecological systems –Adaptation –Function
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