Stacie%20Daer

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CHAPTER 10

• Stacie Daer

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• Are all features of living organisms adaptations?
  How could you determine if a trait in an organism
  is a product of evolution by natural selection?

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• An adaptation is a trait that is favored by
  natural selection and increases an individuals
  fitness in a particular environment.
• Fitness is the relative survival and reproduction
  of one variant compared to others in the same
  population.
• Natural Selection is the process by which
  individuals with certain traits have greater
  survival and reproduction than individuals who
  lack these traits, resulting in an increase in
  the frequency of successful alleles and a
  decrease in the frequency of unsuccessful ones.

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• Adaptations can take many forms a behavior that
  allows better evasion of predators, a protein
  that functions better at body temperature, or an
  anatomical feature that allows the organism to
  access a valuable new resource all of these
  might be adaptations. Many of the things that
  impress us most in nature are thought to be
  adaptations.

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Not all features are adaptations!

• Biologists find it difficult to be certain
  whether any particular structure of an organism
  arose by selection and hence can be called
  adaptive or whether it arose by chance and is
  selectively neutral. ( Hair color)
• Sometimes there is no obvious reason for the
  presence of a certain trait. This can be because
  the utility of a trait is lost and does not
  appear adaptive now, the function of a trait is
  unknown, or the trait is a result of another
  trait that is adaptive.

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Linked Genes

• Genes are located on the same chromosome.
• One gene is passed on as a result of natural
  selection, and the linked gene is also passed on
  even though it isnt an adaptation.
• Example) red hair and light skin

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Vestigial Structures

• Vestigial structures are features that were
  adaptations for an organisms ancestor, but now
  have evolved to serve no function because the
  environment changed.

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• While not all evolutionary changes are a result
  of adaptation, all adaptations can be explained
  by natural selection.

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Other Mechanisms of Evolution

• Genetic Drift (luck)
• Change in allele frequency that occurs as a
  result of chance.
• Gene Flow (migration)
• Spread of an allele throughout a species gene
  pool.