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Chapter 37 ~ Community and Ecosystems

Chapter 37 ~ Community and Ecosystems. Where’s 3?. Community structure. What is a community? Community ~ an assemblage of populations living close enough together for potential interaction. Differ by.. Species richness (number of species) & abundance…….

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Chapter 37 ~ Community and Ecosystems

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  1. Chapter 37 ~ Community and Ecosystems Where’s 3?

  2. Community structure • What is a community? • Community~ an assemblage of populations living close enough together for potential interaction. Differ by.. • Species richness (number of species) & abundance……. • Why are certain species found together? • Hypotheses: •Individualistic~ chance assemblage with similar abiotic requirements •Interactive~ assemblage linked by mandatory biotic interactions

  3. Interactions • Interspecific (interactions between populations of different species within a community): •Predation - including parasitism; may involve a keystone species/predator •Competition •Commensalism •Mutualism

  4. Predation defense • Cryptic (camouflage) coloration • Aposematic (warning) coloration • Mimicry~ superficial resemblance to another species √ Batesian~ palatable mimics an unpalatable species √ Mullerian~ 2 or more unpalatable, resemble each other

  5. Competition: a closer look • Competitive Exclusion Principle G.F. Gause - Russian 2 species with similar needs for the same limiting resources cannot coexist in the same place

  6. Resource partitioning~ sympatric species consume slightly different foods or use other resources in slightly different ways Character displacement~ sympatric species tend to diverge in those characteristics that overlap Competition evidence Ex: Anolis lizard sp. perching sites in the Dominican Republic Ex: Darwin’s finch beak size on the Galapagos Islands

  7. The Niche • Ecological niche~ the sum total of an organism’s use of biotic and abiotic resources in its environment; its “ecological role” • 2 species cannot coexist in a community if their niches are identical Ex: Barnacle sp. on the coast of Scotland

  8. Succession • Ecological succession~ transition in species composition over ecological time • Primary~ begun in lifeless area; no soil, perhaps volcanic activity or retreating glacier • Secondary~ an existing community has been cleared by some disturbance that leaves the soil intact

  9. Trophic Structure • Food chain shows transfer of energy up trophic levels. • Food web is a network of interconnecting food chains.

  10. Species diversity • Species diversity is composed of; species richness - number of different species in a community, and.. relative abundance – number of species in a community. • Keystone species exert control over community composition. • http://www.youtube.com/watch?v=Ng6CNn6XnBg

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