Mechanisms of Evolution

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Mechanismsof Evolution
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Mechanisms of Evolution

• There are several
• Natural Selection
• Gene Flow
• Genetic drift
• Mutations
• Non-random mating

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1. Natural Selection

• Variation exists within a population
• More offspring are born than can survive
• Phenotypic differences result in differential
  reproductive success
• Individuals that do survive, pass heritable
  traits on to offspring
• Over time (many generations) this could lead to
  changes in the population

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Natural Selection
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2. Gene Flow

• Is the movement of alleles into or out of a
  population (immigration or emigration).
• Gene flow can introduce new alleles into a gene
  pool or can change allele frequencies.
• Example
• Plant pollen being blown into a new area

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Gene Flow
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3. Genetic Drift

• The change in allele frequencies as a result of
  random chance.
• Affects small populations.

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Examples of Genetic Drift

• B) Population Bottleneck
• Occurs when a population undergoes an event in
  which a significant percentage of a population or
  species is killed or otherwise prevented from
  reproducing.

• The event may eliminate alleles entirely or also
  cause other alleles to be over-represented in a
  gene pool.

EX. Cheetahs
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4. Mutations

• Are inheritable changes in the genotype.
• Provide the variation that can be acted upon by
  natural selection.
• Mutations provide the raw material on which
  natural selection can act.

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5. Non-Random Mating

• In animals, non-random mating can change allele
  frequencies as the choice of mates is often an
  important part of behavior.
• Dog Breeders

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• Mimicry Coral snakes (venomous) and king snakes
  (non-venomous) The harmless king snake mimics the
  poisonous coral snake, causing would-bepredators
  to avoid them. http//3.bp.blogspot.com Monarchs
  (toxic to predators) and viceroys (non-toxic) The
  viceroys mimics the coloration and pattern of the
  unpalatable monarch, also avoiding
  would-be-predators. http//fish.mongabay.com
  Camouflage A flounder will be less conspicuous
  to predators and to would-be prey if it blends in
  with its environment. http//conservationreport.fi
  les.wordpress.comCompare/contrast mimicry and
  camouflage. Pick an organism and explain the
  benefit of that animal or pl