Chapter 10: Natural Selection

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Chapter 10Natural Selection

• Section 10-2
• Darwins Solution

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Darwins Findings

• Most of the specimens Darwin gathered in the
  Galapagos turned out to be endemic species they
  are indigenous to that region
• Species on Galapagos looked similar to mainland
  species, but were different
• Darwin believed species changed gradually over
  time

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Darwins Findings

• Darwin published On the Origin of Species By
  Means of Natural Selection in 1859 (30 years
  after the Beagle)
• Rushed publication to beat out Alfred Russel
  Wallace, who had identical ideas
• Darwins book described the huge amount of
  evidence to support evolution and gave a
  hypothesis as to how and why it occurs

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Of Farmers and Pigeons

• Darwin incorporated observations from local farm
  animals and crops
• Argued that farmers had changed living things by
  domesticating them
• No two individuals are exactly alike, and
  variation is inheritable
• Farmers used this variation in selective breeding

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Artificial Selection

• Farmers chose best characteristics
• Nature provided variation, humans controlled the
  breeding
• This is called artificial selection
• Has resulted in a wide range of plants and
  animals that are very different from their
  ancestors

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Selection in Nature

• Darwin observed selection in nature as well
• Inheritable variation exists in nature but what
  mimicked the farmer in nature?
• Think back to Malthus high birth rates and a
  shortage of lifes basic needs forced organisms
  into a constant struggle for survival

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Selection in Nature

• Because each organism is slightly different, each
  has slightly different advantages and
  disadvantages
• Some individuals are more fit than others (better
  suited to survive and reproduce, or survival of
  the fittest)

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Selection in Nature

• Generation after generation, the struggle for
  existence selects the fittest individuals to
  survive and reproduce
• Species in general become better suited to their
  environments as they respond to selection
  pressures

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Common Descent

• Living things have slowly changed over time
• Each living species descended from other species
  over time
• Principle of common descent all living things
  share common ancestors
• From a scientific perspective, the evidence for
  evolution is undeniable the how and why are the
  hangups