Evolution of Australian Biota

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Evolution of Australian Biota

• Identify and describe evidence that Australia was
  once part of Gondwana

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• Together with New Guinea, it is the only place
  where monotremes (egg laying mammals) can be
  found.

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• There are more species of plants to be found in
  the heaths of south western Australia than all of
  Europe.
• Why is Australias wildlife so peculiar?

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• When the platypus was first discovered and
  reported in England, scientists thought the
  description of a an egg laying mammal, with bill
  like a duck, and a tail like a beaver had to be a
  hoax!

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Intro Gondwana

• Alfred Wegner suggested the theory of
  continental drift and that Australia was once
  part of the land mass Gondwana

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• His idea was that the continents were once a
  single land mass, at then drifted apart from each
  other.

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Evidence that supports that Australia was once
part of Gondwana

• Matching continental margins
• The continents do not fit neatly together, as
  they have been affected by erosion.
• Computer models of continents including their
  continental shelves resulted in a good match.

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• 2.Fossil evidence
• Fossils of some extinct plants and Animals have
  only been found in Australia, Antarctica, South
  America, Africa and India.
• This shows that organisms once existed on
  continents which are now separated by oceans.
• Some example includefossils of the Glossopteris
  and Gangamopteris plants which are only found on
  contients of the southern hemisphere.

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• 3.Similarities between present-day organisms on
  Gondwana continents
• The distribution of organisms is consistent with
  continental drift.
• -Marsupial are only found in Australia, New
  Guinea and south America (handout).
• -There are three similar lung fish found in
  Australia, South America and Africa.

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• 4.Spreading zones between continental plates
• According to the plate tectonic theory, the
  Earths crust is made up of huge plates of
  continental crust and ocean crust.
• As continents are part of the plates they drift
  with the plates
• The plates float on the Earths mantle. Due to
  slow convection currents below the crust the
  plates move. These movements cause Earthquakes
  and Volcanoes.
• Plates can be spreading,subduction or colliding.

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• 5.Position of mid ocean ridges
• A line of ridges extends through the worlds
  oceans floors. These are known as mid-ocean
  ridges.
• On each side of the mid-ocean ridges geologist
  noticed that the pattern of magnetism in the
  rocks were identical.

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