How Populations Evolve

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Chapter 13 How Populations Evolve
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Why is life on earth so diverse?
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Evolution

• Changes occurring, over time, in a population
  (NOT AN INDIVIDUAL)

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Evolutionary adaptations

• Inherited changes that enhance an organisms
  ability to survive and reproduce in a particular
  environment

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Booby
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Booby adaptations

• Webbed feet propelling birds through the water
  at high speeds
• Streamlined body reduces friction in water
• Wedged shaped tail allows quick stopping in
  water
• Closeable nostrils prevents water from entering
  when diving
• Glands oil for waterproofing and salt
  regulation

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Adaptations are often a trade-off

• Remember, evolutionary adaptations need to allow
  the organism better survival possibilities,
  therefore promoting reproduction
• Boobys big feet Advantage? Disadvantage
• Adaptations that allow an organism to survive
  longer/better will always win

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Most famous evolutionary scientist?
Charles Darwin
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ButDarwin wasnt first

• 500 B.C. Greek philosophers suggested life may
  have arisen from as simple life forms in water
• Aristotle held the belief that species were fixed
  great influence on western culture
• 1700s Fossil evidence lead scientists to
  believe earth is much older than 6,000 years

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And then there was Lamarck

• In the early 1800s Jean Baptiste Lamarck was
  among the first to publicly speculate that there
  was a relationship between fossils and living
  organisms
• Evolution
• Unfortunately, he is mostly remembered for being
  wrong about the mechanism of evolution

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Lamarcks mechanism

• He based his theory on use or disuse
• He though that body parts changed based on their
  use, and that these changes were passed on to
  offspring
• Example Giraffe necks

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Why such a long neck?
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Disadvantages?
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Why was Lamarck important?

• Thought that species changed through their
  interaction with their environment
• Set up the modern concept of evolution
• Paved the way for Darwin to get the mechanism
  right

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Charles Darwin and the voyage of the HMS Beagle
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Galapagos Islands
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Galapagos Islands

• Contain hundreds of species that are found
  nowhere else on earth (endemic)
• Darwin found many uniques species that were
  similar to each other, but had slight variations
  between islands (e.g. Finches)

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More Darwin

• 1840s wrote a long essay on what he found
  (didnt publish)
• 1850s Darwin was sent a summary of George
  Wallaces work
• 1858 Darwin allowed a colleague to present his
  work (along with Wallaces) at a conference
• 1859 Published his book, On the Origins of
  Species by the means of Natural Selection

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Descent with modification

• This is an important area where Darwin differed
  from Lamarck (but he was correct)
• All species are related through a common ancestor
• The descendents moved into diverse environments
• In each environment, the descendents began to
  accumulate changes
• These changes were modifications (adaptations)
  that allowed them to better survive in their
  environment

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Descent with modification

• This is an important area where Darwin differed
  from Lamarck (but he was correct)
• All species are related through a common ancestor
• The descendents moved into diverse environments
• In each environment, the descendents began to
  accumulate changes
• These changes were modifications (adaptations)
  that allowed them to better survive in their
  environment