How do new species arise? -- Speciation --

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How do new species arise?-- Speciation --

• Species group of organisms that can interbreed
  and produce fertile offspring
• Speciation the process by which genetically
  distinct species arise.
• Speciation Formation of new species
• As adaptations and differences accumulate, the
  organisms become so different that they cannot
  interbreed (reproduce) anymore

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Speciation Formation of New Species

• If a population becomes separated, or a group of
  individuals becomes isolated, they may change
  over time.
• They may change so much that they cannot
  interbreed anymore with the members of the
  original population. Reproductive Isolation.
• Reproductive Isolation is the first step towards
  the formation of a new species
• What influences reproductive isolation
• Geographic Isolation (Allopatric Speciation)
• Behavioral Isolation (Sympatric Speciation)
• Temporal Isolation (Sympatric Speciaton)

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1. Geographic Isolation

• A physical barrier separates (splits) the
  original population
• As time passes, the environment may selects for
  different traits and the 2 populations become
  genetically different AND cant reproduce
• Barriers Rivers, mountains, bodies of water

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Kaibab and Abert Squirrels

• - The Kaibab squirrel (Sciurus aberti
  kaibabensis) became geographically isolated from
  the common ancestor about 10,000 years ago.
• Its closest relative is the Abert squirrel
  (Sciurus aberti aberti)
• - They live in opposite sides of the Grand Canyon

Kaibab
Abert
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Wrasses Original population split up when the
isthmus of Panama was formed- 2 species now,
one on each side of Central America
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2. Temporal Isolation (Time of Reproduction)

• Groups of individuals reproduce at different
  times. The genes of the 2 groups do not mix.
• It is happening now with some of the migratory
  birds that decide not to migrate.
• The birds that do not migrate start mating before
  the migratory ones come back.
• Eventually they might become different enough
  that they may not recognize each other.

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Robins usually migrate south to warmer climates.
Some are not migrating. They reproduce before
the migrating individuals return.
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3. Behavioral Isolation(Reproductive Behavior
changes)

• If 2 populations have different courtship
  behaviors, they will not be able to interbreed
• Different songs (birds) or mating calls (frogs)
• Different scents (smells)
• A simple mutation can cause a change

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Types of Speciation

• Allopatric the evolution of geographically
  isolated populations into distinct species.
• Sympatric - the process through which new species
  evolve from a single ancestral species while
  inhabiting the same geographic region