Evidence of Evolution

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Evidence of Evolution

• Direct Evidence
• Indirect Evidence

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Direct Evidence

• Visible evidence that organisms have changed over
  time
• Ex. Fossils

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Fossils

• Paleontologists are scientists who collect and
  study fossils.
• The fossil record provides incomplete information
  about the history of life.
• Over 99 of all species that have lived on Earth
  have become extinct, which means that the species
  has died out.

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How Fossils Form
Fossil Formation

• Fossil Formation

Water carries small rock particles to lakes and
seas.
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How Fossils Form
Dead organisms are buried by layers of sediment,
which forms new rock.
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How Fossils Form
The preserved remains may be later discovered and
studied.
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Dating Fossils

• Relative Dating
• In relative dating, the age of a fossil is
  determined by comparing its placement with that
  of fossils in other layers of rock.
• Rock layers form in order by agethe oldest on
  the bottom, with more recent layers on top.

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Relative Dating
Relative dating allows paleontologists to
estimate a fossil's age compared with that of
other fossils.
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Dating Fossils

• Radioactive dating
• Some elements are radioactive and steadily break
  down into nonradioactive elements.
• Radioactive dating is the use of half-lives to
  determine the age of a sample.
• A half-life is the length of time required for
  half of the radioactive atoms in a sample to
  decay.

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Half-life of Radioactive Isotopes

• C-14 breaks down into N-14 at a fixed rate.
• The half life of C-14 is 5,760 years.
• When an organism dies, the C-14 in the organism
  starts to change into N-14.
• Knowing the half-life, you can compare the amount
  of C-14 to N-14 to determine the age of the fossil

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Radioactive Dating

• Lets say the fossil we are dating shows 50 C-14
  and 50 N-14.
• The fossil should be 5,760 years old.
• If another 5,760 years passed, what would be the
  ratio of C-14 to N-14?
• Right!!.........C-14 25 to N-14 75
• Potassium 40 is an isotope with a half-life of
  1.2 billion years!!

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Potassium 40
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Indirect Evidence of Evolution

• Evidence we can look at today that suggests we
  may have a common ancestry with other organisms.
• Embryological Similarities

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Indirect Evidence of Evolution

• 2. Comparative Morphology
• (Homologous Structures)

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Indirect Evidence of Evolution

• 3. Similarities in Biochemistry
• DNA similarities (98 of our DNA is the same as a
  chimpanzee)
• Protein in all organisms is composed of the same
  20 amino acids!!

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Evidence of Evolution

• Direct Evidence something we can look at that
  takes us back in time.
• Ex. Fossils
• Indirect Evidence something we can look at that
  show some kind of evolutionary connection between
  organisms.
• Ex. Embryological similarities, Homologous
  structures, Biochemistry similarities

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• Darwins explanation of evolution is called
  Natural Selection.
• What does the term Artificial Selection mean?
  Discuss this with a neighbour.
• Artificial Selection