SPECIATION

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SPECIATION
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• What makes a species?
• Organisms that can breed and create fertile
  offspring in nature

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Examples

• Ducks from the same species
• reproduce to make baby ducks that can breed
• Horses and donkeys are different species
  (different number of chromosomes)
• A horse and a donkey make a mule that is sterile

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• SPECIATION
• The emergence of a new species from pre-existing
  species due to Natural selection and Reproductive
  Isolation
• What is reproductive isolation
• Anything that keeps a species from reproducing

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Types of Reproductive isolation

• Geographic isolation
• physical separation of individuals in a species
• Ecological isolation
• two individuals live in different habitats
• Behavioral isolation
• two individuals have different mating patterns

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• Geographic isolation
• (physical separation)
• leads to..
• Reproductive isolation
• (cant mate together anymore)
• leads to..
• Speciation
• (The two parts of the population can no longer
  interbreed with each other because of genetic or
  physical differences)
• They are now different species!

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• Variation in most populations results in a bell
  curve

Average
Above average
Below average
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Types of Selection

• 1- Stabilizing Selection Natural selection
  pressures favor the average trait

The average trait is favored so the peak of the
curve becomes higher and narrower
This will not result in speciation
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• 2- Directional Selection Natural selection
  pressures favor one extreme or the other

In this population, the above average trait was
favored
This could result in speciationas the ones with
the average trait die out and the whole
population shifts, it will become a new species,
different from the species it once was
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• 3- Disruptive Selection Natural selection
  pressures favor both extremes

In this population, both above average and
below average traits were favored the average
trait was selected against
This will eventually lead to speciation because
the two extremes will become too different from
each other to interbreed
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• Reproductive isolation and Speciation
• leads to more diversity of life on earth
• greater biodiversity
• Example
• Blue jays and
  Stellers jays
• seen east
• of Rocky Mtns.
• seen west
• of Rocky Mtns.

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• These were most likely one species at one time, a
  long time ago
• When the Rocky Mountains arose 65 million years
  ago, the single species became separated by the
  mountain range
• This happened very very slowly!!!

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Speciation in Canada Geese

• There are 11 different races of Canada Geese
• They are currently all the same species and could
  interbreed
• Due to their behavior, they stay separated from
  each other
• They all have separate flyways and separate
  breeding grounds

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• Eventually, they will become different enough due
  to isolation from each other that they will no
  longer be considered the same species

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Types of EvolutionGradualism Punctuated
Equilibrium

• Gradualism species originate through a gradual
  change of adaptations
• slow and steady change over time
• Punctuated Equilibrium speciation occurs
  quickly, in rapid bursts, with long periods of
  equilibrium in between
• environmental changes lead to rapid changes in a
  small populations gene pool that is
  reproductively isolated from the main population
• Speciation happens much more quickly

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Speciation in Elephants
Fossil record supports the view that several
elephant species may have evolved from an
ancestral population in a short time
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Adaptive Radiation

• Occurs when a species lands in a new area
• Individuals spread out into new habitats and
  specialize, eventually becoming different
  species
• This is a type of divergent evolution

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Honey Creepers
The founder species landed on Hawaii about 5
million years ago and settled into the diverse
Hawaiian niches