Theory of Evolution

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Theory of Evolution
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Charles Darwin

• Charles Robert Darwin
• Born February 12 1809   April 19 1882)
• He was an English Naturalist
• He published his theory of evolution with
  evidence In his 1859 book On the Origin of
  Species.

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The voyage of the Beagle

• In December 1831, the British ship HMS Beagle set
  sail from England on a five year trip around the
  world.
• Darwin was on board as a naturalist
• His job was to learn as much as possible about
  the living things he saw on the voyage.
• Darwin's observations led him to develop one of
  the most important scientific theories of all
  time the theory of evolution by natural
  selection.

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Darwins voyage
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Darwins Observations

• Darwin made many observations along his stops on
  the Beagle
• Darwin's observations included the diversity of
  living things, the remains of ancient organisms,
  and the characteristics of organisms on the
  Galapagos Islands.
• Darwin was amazed by the tremendous diversity of
  living things. Scientists now have identified
  more than 1.7 million species of organisms.
• A species is a group of similar organisms that
  can mate with each other and produce fertile
  offspring.

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The Galapagos Islands

• In 1835 the Beagle reached the Galapagos Islands,
  where Darwin observed many unusual life forms on
  these small islands such as giant tortoises and
  giant iguanas.
• When Darwin returned to England, he compared
  organisms to organisms that lived elsewhere. He
  also compared organisms on different islands in
  the Galapagos group.
• He was surprised by some of the similarities and
  differences he saw.

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• Darwin found many similarities between Galapagos
  organisms and those in South America. However,
  there were important differences.
• The Iguanas on the Islands had large claws that
  allowed them to grip slippery rocks while the
  iguanas on the mainland had smaller claws to
  climb trees.

• From his observations, Darwin hypothesized that a
  small number of plants and animals had come to
  the islands from the mainland.
• Once they reached the islands, the reproduced.
  Eventually their offspring became different from
  their mainland relatives.

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Adaptations

• Like the tortoises, the finches on the Galapagos
  Islands were noticeably different from one island
  to the next.
• The most obvious difference on the Finches was
  their beak size and shape.
• Darwin proposed that each species of finch had a
  different size and shaped beak to suit its
  environment. This is an example of an Adaptation.
• An Adaptation is a trait that helps an organism
  survive and reproduce.

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Evolution

• Darwin wanted to understand the different
  adaptations of organisms on the Galapagos
  Islands.
• He hypothesized that the species gradually
  changed over many generations and became better
  adapted to the new conditions.
• The gradual change in species over time is called
  EVOLUTION.

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Natural Selection

• In 1858, Darwin and Alfred Russell Wallace, each
  proposed an explanation for how evolution could
  occur in nature.
• Darwin proposed that evolution could happen by
  natural selection.
• Natural selection is the process by which
  individuals that are better adapted to their
  environment are more likely to survive and
  reproduce than other members of the same species.

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• Darwin identified factors that affect Natural
  Selection
• 1. Overproduction Most species produce many more
  offspring that can possible survive.
• 2. Variations any difference between individuals
  of the same species.
• 3. Competition because resources are limited,
  members of a species must compete with each other
  to survive.

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• 4. Selection Darwin proposed that over a long
  time, natural selection can lead to change.
  Helpful variations may gradually accumulate in a
  species while the unfavorable ones disappear.
• 5. Environmental change A change in the
  environment can affect the organisms ability to
  survive.

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