15.2 Theories of Evolution

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15.2 Theories of Evolution

• Evolution is the change of populations of
  organisms over time.

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Lamarks Explanation

• First to publish a hypothesis explaining where
  all the species came from.
• His explanation used the idea of a common
  ancestor, and related the fossil record to living
  organisms.
• Main problem with Lamarks hypothesis was that he
  said that Acquired traits were passed to the
  offspring.

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Modern Evolutionary Thought

• Darwin and Wallace both proposed the idea of
  Natural Selection.
• Natural Selection the organisms best suited for
  to the environment reproduce more successfully.
• The favorable traits increase in a population
• Populations are all the individuals of a species
  that are able to interbreed.

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Charles Darwin

• Born 1809, started medical school, then clergy,
  finally taking job as Naturalist on the HMS
  Beagle.
• Sailed on the Beagle for five years on a mapping
  and specimen collecting mission.
• As naturalist he was required to collect
  specimens and keep very careful records.

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Beagle Voyage

• Darwin read about Uniformitarianism which said
  that the earths formations were made from
  processes that are still going.
• Darwin saw many land forms that he realized were
  very different environments than they once were.
• Darwin found ocean fossils in mountain areas.

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• Darwin reasoned that the changes that he observed
  were VERY slow.
• Any organisms that lived in these areas would
  need to change to survive or die.

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Darwins finches

• Darwin collected 13 different finches from an
  group of islands called Galapos.
• A bird expert found that although the birds were
  all similar they were different species
• Each finch species had a specialized beak for its
  food source.
• Explained this by saying that a small goup of
  birds had adapted to life on the islands.

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The Origin of Species

• Darwin had reservations about publishing his
  book.
• In 1858 Wallace asked Darwin for his help with
  his own theory of evolution.
• Even though both hypothesizes came out at the
  same time Darwins had been a work of 21 years,
  and was better documented.

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Darwins theory

• Darwins first theory was descent with
  modification which said that all the fossils that
  appear are simple modifications of the earlier
  organisms.
• Explained by the fact that organisms give rise to
  others similar to themselves but not exactly the
  same.

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Natural Selection

• Modification by natural selection states how
  evolution occurs.
• Organism are influenced by their environment.
• Not every organism is the same, some traits help
  an organism survive.
• Traits that help an organism survive are
  therefore passed down to its offspring.

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Natural Selection

• A population adapts as its genes change
• Fitness refers to how well an organisms genes
  help it survive
• Adaptive advantage is the ability of an organism
  to survive is its environment quickly changes.