How Does Evolution Happen?

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How Does Evolution Happen?

• After making observations and analyzing evidence,
  Charles Darwin concluded that natural selection
  is the mechanism of evolution.

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Early Ideas on Evolution

• The first person to do so was the French
  naturalist
• Jean Baptiste de Lamarck propose how species
  change.
• De Lamarck proposed that during their lifetime,
  organisms change in response to their
  environment.
• Ex. Giraffes had long necks because their
  ancestors had stretched their necks while
  reaching for leaves high in a tree.
• Useful acquired traits were passed on,
  unbeneficial traits were
• not.
• This is how de Lamarck suggested that a
  reasonable
• explanation for how evolution occurs.

3
Charles Darwin

• Charles Darwin served as the naturalist, a
  scientist who studies nature, on the HMS Beagle.
• Darwins observations during his trips on the
  Beagle helped Darwin develop his theory on
  evolution

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Darwins Journey
The HMS Beagle
Charles Darwin
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Darwins Journey

1. Darwin observed plants and animals on the
   Galapagos Islands located west of Ecuador, a
   country in South America

6
Darwins Finches

1. Darwin observed that plants and animals were on
   Galapagos islands were the same as those in
   Ecuador, but werent identical and differed from
   island to island.
2. Darwin noticed that the shape of finches beaks
   differed based upon their food.

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Darwins Finches
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Darwins Thinking

• Darwin proposed that the Galapagos finches came
  from South America
• Darwin suggested that the finches evolved
  adaptations over many generations
• Example Finches with different beak shapes
  related to their food

9
Ideas about Breeding

• Artificial or Selective breeding is the practice
  by which humans select plants or animals for
  breeding based upon desired traits
• Traits are inherited characteristics
• Certain traits can spread thorough populations
• Selective breeding in dogs has produced over 150
  breeds

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Ideas About Population

1. Darwin was influenced by Thomas Malthus. He
   realized that populations of all species are
   limited by starvation,disease, competition and
   predation.
2. Traits that help organisms survive in their
   environment and are passed on to offspring

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Ideas About Earths History

1. Darwin was also influenced by Charles Lydell, who
   believed that Earth changed slowly over time.
2. Darwin believed that organisms had time to slowly
   change.

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Darwins Theory of Natural Selection

• Darwin struggled with his theory for 20 years.
• Alfred Russel Wallace came to same conclusion
  about evolution as Darwin.
• 1859, Darwin published his book On the Origin of
  Species by Means of Natural Selection

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Darwins Theory of Natural Selection
The Origin of Species
Charles Darwin
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Natural Selection

• Four Steps process by which organisms are better
  adapted to their environment.
• Overpopulation
• Genetic Variation
• Adaptation (inherit beneficial traits)
• Selection (successful reproduction)

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Genetics and Evolution

1. Darwin knew organisms inherited traits to create
   variation but not how traits were inherited.
2. We now know that organisms that inherit genes
   that increase their survival are more likely
   passed on to their offspring (heredity and
   genetics)