Community

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• Chapter 53
• Community
• Ecology

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Community structure

• Richness (number of species) abundance.
• Species diversity
• Hypotheses
• Individualistic chance assemblage with similar
  abiotic requirements Interactive
  assemblage locked into association by mandatory
  biotic interactions

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Interactions

• Interspecific (interactions between populations
  of different species within a community)
  Predation (-/) including parasitism may
  involve a keystone species/predator
  Competition (-/-)
• compete for limited resource
• 2 species cannot coexist in a community if their
  niches are identical

• Mutualism (/)
• both species benefit
• lichens (algae fungus)
• Commensalism (/0)
• one species benefits while the other is not
  harmed
• barnacles that attach to a whale

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The Niche

• Ecological niche the sum total of an organisms
  use of biotic and abiotic resources in its
  environment its ecological role
• v fundamental the set of resources a population
  is theoretically capable of using under ideal
  conditions
• v realized the resources a population actually
  uses
• Thus, 2 species cannot coexist in a
  community if their niches are identical

Ex Barnacle sp. on the coast of Scotland
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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 (microhabitats)
Ex Darwins finch beak size on the Galapagos
Islands
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Predation defense

• Cryptic (camouflage) coloration
• Aposematic (warning) coloration
• Mimicry superficial resemblance to another
  species
• v Batesian palatable/ harmless species mimics
  an unpalatable/ harmful model
• v Mullerian 2 or more unpalatable,
  aposematically colored species resemble each other

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Voilá!
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