Patterns of Evolution

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Patterns of Evolution
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Genetic Drift

• Random change in allele frequency
• In small populations, individuals that carry a
  particular allele may leave more descendants than
  other individuals, by chance
• Over time, these occurrences can cause an allele
  to become common in a population

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Isolating Mechanisms

• As new species evolve, populations become
  reproductively isolated from each other.
• Reproductive
• Behavioral
• Geographic
• Temporal

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Reproductive Isolation

• When the members of two populations cannot
  interbreed and produce fertile offspring.

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Behavioral Isolation

• Occurs when two populations are capable of
  interbreeding but have differences in courtship
  rituals or other reproductive strategies that
  involve behavior

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Geographic Isolation

• Two populations are isolated by geographic
  barriers such as rivers, mountains, or bodies of
  water.

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Temporal Isolation

• Two or more species reproduce at different times.

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Macroevolution

• Refers to large-scale evolutionary patterns and
  processes that occur over long periods of time.

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Extinction

• 99 of all species that have ever lived are
  extinct
• Some mass extinctions have occurred killing off
  entire ecosystems.
• These were believed to have occurred due to a
  collapsing environment.
• These extinctions left room for new species to
  evolve.

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Adaptive Radiation

• Occurs when a single species or a small group of
  species has evolved, through natural selection,
  into diverse forms that live in different ways.
• Ex Darwins finches more than a dozen species
  evolved from a single species.

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Convergent Evolution

• Adaptive radiation can cause the production of
  unrelated organisms that look remarkably similar
• May occur when animals evolve in separate
  locations under similar conditions and they
  develop the need for similar structures.
• Ex swimming animals have a streamline body
  (sharks, fish, dolphins, and penguins)

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Divergent Evolution

• When species that were similar become different.
• Same as adaptive radiation.

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Coevolution

• The process by which two species evolve in
  response to changes in each other over time
• Ex a flower changes color, odor, or scent over
  time, so the pollinator may also change