Patterns%20of%20Evolution

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Patterns of Evolution
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Divergent Evolution

• There is isolation of a population from the main
  gene pool, with first geographical and then
  reproductive barriers, resulting in a new species.

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Adaptive Radiation

• This is the evolution from a common ancestor of
  different forms adapted to different ecological
  niches.
• E.g. Darwins Finches
• when the ancestors of the finches were blown to
  the Galapagos Islands, they found many unoccupied
  niches that in there homeland had been filled by
  other birds.

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Adaptive Radiation

• Lacking competition, the finches spread out and
  filled the vacant niches.
• Natural selection led to selection for different
  adaptations as they did so.
• After enough time, they had so diversified that
  they had formed different species.

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Convergent Evolution

• This is the independent evolution of similar
  adaptive features in originally different
  species.
• It happens because they have adapted to the same
  environment.
• e.g. Dolphins, Ichthyosaurs and Sharks look
  similar because of being adapted to a water
  environment.

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Convergent Evolution

• Plants that live on mountains tend to have small,
  scale-like leaves, often with hairs and closely
  fitted to the stem, and they have a
  close-to-the-ground, compact growth habit,
  forming cushions or mats of vegetation.
• Although they may have originated from different
  species, they start to look alike.

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Parallel Evolution

• This is the evolution of similar features, not
  present in the ancestral form, in 2 or more
  closely related species.
• e.g. the loss of wings on off-shore windy
  islands by some insects and birds.

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Local Case Studies

• Pg 236 240 text book
• Hebes and Molluscs