Yo!

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Yo!

• Please get out your Natural Selection outline you
  made from the textbook were going to add to
  it.
• Didnt do it? Get out a piece of paper.
• Everyone please read the board.
• Please pass back the permission slip!

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Armand Bayou Nature Center
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Natural Selection
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Natural Selection

• Process by which organisms best suited to their
  environmental conditions are most likely to
  survive and reproduce
• Its HOW evolution works!

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Three conditions that must be true for natural
selection to occur

• Natural variation of a trait in a population
• Trait must be heritable
• Trait must lead to differential reproduction
  (must make you more likely to reproduce)

• Some male peacocks have more vibrant tail
  displays than others
• Tail and display behavior is encoded in DNA
• Males with more vibrant displays are more likely
  to mate.

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Natural selection leads to adaptations

• Adaptation a structure or behavior that helps
  an organism survive in their environment.

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Through natural selection, adaptations are
encoded in DNA.

• An INDIVIDUAL cannot change their adaptations.
• POPULATIONS undergo natural selection and over
  many generations, can experience a change in
  adaptations.
• Some people confuse adaptation with acclimation!

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Coevolution

• Read the excerpt from the text, then draw a
  cartoon of the steps of coevolution.

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Speciation
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Speciation

• How do new species evolve?
• Divergent selection in ancestral species,
  variation provides ability to survive in
  different environments.
• If different groups of the species become
  physically isolated, they can continue to adapt
  to separate environments (microevolution)
• Eventually, they may be so different that they
  cannot successfully mate new species.

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Geographic Isolation
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So what if an entire species cant change quickly
enough to deal with changing conditions?
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For each individual, either it survives to
reproduce or it dies

• So what if an entire species cant change quickly
  enough to deal with changing conditions?

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Extinction

• Background extinction rate about 1 to 5
  species/ year
• Mass extinction the loss of many species in a
  sudden event.

• Current extinction rate 1,000 to 10,000 times
  the natural background rate (dozens a day).

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Legal/scientific designations

• Healthy
• Threatened
• Endangered
• Extinct

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Grizzlies and Polar Bears diverged about 150,000
yrs ago.
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Check for understanding!

• Why cant an individual change its adaptations
  in its lifetime?
• What is the better word for an inidividual
  getting used to a new situation?
• What happens to populations in which no
  individual is able to survive?