More Evolution: who, what, how

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• More Evolutionwho, what, how
• Exam key posted on class webpage
• Check out Bonuses on class webpage

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Evolution A species genetic component changes
as the individuals reproduce. These changes are
based on how the DNA changes and who reproduces.
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Reproductive success evolutionary success
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Evolution can occur via several processes. One
common process isNatural Selection Individuals
that are most successful at reproducing will pass
on more of their genetic information.
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Natural Selection can only occur when both of
these conditions are met

• Genetic diversity gives rise to individuals with
  different traits
• and
• Not all individuals can reproduce equally

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Evolution A species genetic component changes
as the individuals reproduce. These changes are
based on how the DNA changes and who reproduces.
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Individuals are selected
But species evolve via changes in DNA during
reproduction.
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Fig 24.6
Who evolves?Species.
A. leucurus
A. harrisi

• A population that can produce fertile offspring
• A population that does reproduce
• A population sharing genetic information

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X
Horse
Donkey

Mule
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X
Horse
Donkey
Sohorses and donkeys are not the same species.

Mule (sterile)
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Fig 24.6
Who evolves?Species.
A. leucurus
A. harrisi

• A population that can produce fertile offspring
• A population that does reproduce
• A population sharing genetic information

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Fig 22.19
How does evolution occur?
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Fig 22.19
Divergent Evolution
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Fig 22.20
Convergent Evolution
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Evolution has no goal...no ultimate life form
wrong right
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Natural Selection

• Individuals that are most successful at
  reproducing will pass on more of their genetic
  information.

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Environmental changes drive evolution.
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250 mya
180 mya
Fig 25.13


Plate Tectonics
65 mya
135 mya
current
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The environment is in constant flux
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Fig 24.5
Changing environment can separate populations and
lead to new species
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Fig 24.9
Separation does not need to be geographic
Flies raised in different environments prefer to
mate with individuals from the same environment...
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Flies raised in different environments prefer to
mate with individuals from the same environment...
Fig 24.9
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Three basic types of selection

• Directional
• Stabilizing
• Disruptive

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• Next even more EvolutionTypes of Selection and
  Randomness
• Exam key posted on class webpage
• Check out Bonuses on class webpage