Evolution of Australian Biota

1. Evolution of Australian Biota Identify and describe evidence that Australia was once part of Gondwana

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

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

4. 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!

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

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

7. 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.

8. 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 include:fossils of the Glossopteris and Gangamopteris plants which are only found on contients of the southern hemisphere.

9. 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.

10. 4.Spreading zones between continental plates: • According to the plate tectonic theory, the Earth’s 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.

11. 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.