chapter 37 ~ community and ecosystems
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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……. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 37 ~ Community and Ecosystems
Where’s 3?
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0011 0010 1010 1101 0001 0100 1011Community 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
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0011 0010 1010 1101 0001 0100 1011Interactions
• Interspecific (interactions between populations of different species within a community):
•Predation - including parasitism; may involve a keystone species/predator •Competition•Commensalism•Mutualism
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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
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0011 0010 1010 1101 0001 0100 1011Competition: a closer look
• Competitive Exclusion Principle
G.F. Gause - Russian2 species with similar needs for the same limiting resources cannot coexist in the same place
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Competition evidence• 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
Ex: Anolis lizard sp. perching sites in the Dominican Republic
Ex: Darwin’s finch beak size on the Galapagos Islands
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0011 0010 1010 1101 0001 0100 1011The 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
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0011 0010 1010 1101 0001 0100 1011Succession
• 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
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0011 0010 1010 1101 0001 0100 1011Trophic Structure
• Food chain shows transfer of energy up trophic levels.
• Food web is a network of interconnecting food chains.
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0011 0010 1010 1101 0001 0100 1011Species 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