KEY CONCEPT New species can arise when populations are isolated'

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KEY CONCEPT New species can arise when
populations are isolated.
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The isolation of populations can lead to
speciation.

• Populations become isolated when there is no gene
  flow.
• Isolated populations adapt to their own
  environments.
• Genetic differences can add up over generations.

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• Reproductive isolation can occur between isolated
  populations.

• members of different populations cannot mate
  successfully
• final step to becoming separate species

• Speciation is the rise of two or more species
  from one existing species.

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Populations can become isolated in several ways.

• Behavioral barriers can cause isolation.
• called behavioral isolation
• includes differences in courtship or mating
  behaviors

• Although not geographically separated,
  reproduction is prevented
• 1) Different mating rituals
• 2) Use of pheromones
• No gene flow differing populations unable to
  reproduce

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• 2. Geographic barriers can cause isolation.

• called geographic isolation
• physical barriers divide population

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Kaibab Squirrel (Grand Canyon)
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Founder Effect 14 Species of Galapagos Finches
A
B
B
D
D
C
C
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• 3. Temporal barriers can cause isolation.
• called temporal isolation
• timing of reproductive periods prevents mating

• Although not geographically separated,
  reproduction is prevented
• 1) Mate at different seasons
• 2) Some noctural
• No gene flow differing populations unable to
  reproduce

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End Result Reproductive Isolation

• Created as a result of behavioral, geographical,
  temporal isolation
• No mating between populations (no gene flow)
• Two groups unable to reproduce
• Sex organs dont match, rituals dont attract,
  physically separated
• Species group of organisms that can interbreed
  and produce fertile offspring