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Evolution - From The Beginning
The Australian outback - with
its vast expanses of flat land, dry grasses and kangaroos - is usually
the image people have when they think about the world's largest
island. But this was not always so. The Red Centre was once covered
in broad-leafed forest between 20 million and 60 million years ago!
 Australia
was once part of a much larger land mass called Gondwana which included
the modern continents of Africa, South America, Antarctica and India.
Proof of this was provided when many of the same ancient plants
and animals were unearthed in fossil beds some were discovered dispersed
throughout parts of all these present day continents.
About 120 million years ago, Gondwana began to
break up. Connections between Africa and South America were broken
about 100 million years ago. About 80 million years ago, New Zealand
and New Caledonia broke away from the eastern edge of the Australian
plate. Finally, about 50 million years ago, Australia separated
from Antarctica and began moving northwards. For 35 million years
it was totally isolated from all other land masses until it collided
with the Asian plate.
Although Australia contains less than one-thousandth
of the world's tropical rainforests, these forests are some of the
most signifricant ecosystems on earth. They are relics of vegetation
types which were once much more widespread (fossil pollens indicating
that most of Australia was covered by closed forests some 50 to
100 million years ago). The Wet Tropics now contains most of the
world's plant relics of those ancient forests. All of Australia's
unique marsupials and most of its other animals originated in rainforest
ecosystems, of which the Wet Tropics is the closest surviving remnant.
 The
Wet Tropics provides a living record of the ecological and evolutionary
process that shaped Australian plants and animals over the past
415 million years. The ongoing processes of speciation, extinction
and adaptation have been determined by a complex history, particularly
continental drift and cycles of climate change. These changes
occurred slowly, allowing species to adapt, to change, and ultimately
for speciation to occur. |
Some interesting sites
have been devoted to evolution and pre-history, especially concerning
the Age of Dinosaurs. You might want to have a look at these:
Thanks are extended to the Flecker Botanic
Gardens slide library for the use of photos copyrighted by D.Warmington,
P. Shanahan and G. Sankowski.
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