This is a big topic to condense into a few words. It is truly mind blowing.
Here we go, the earths crust is constantly moving and all land is moving in mega slow motion all the time, quite literally taking millions of years to move. At some points in time there is more land and at other times it diminished.
At one time millions of years ago, there was one huge continent Gondwana (just to confuse matters there were several supercontinents over the millennia with different names).
This you tube clip gives a good idea of what happened to the land masses.
“Continental Drift: 3.3 Billion Years”
https://youtu.be/UwWWuttntio
Gondwana had prehistoric life such as primitive plants and dinosaurs. As the land moved, Australia and New Zealand broke away. They moved so far from the other land masses that, the evolution of life was quite different. Some of it appears have stayed pretty much as it was for example the ferns and ancient trees, probably because the climate in some regions has not changed much. Some creatures became very different, for example marsupials. They are mammals but have pouches in which to rear their young. There are a few marsupials in South America too but not as many as in Australia.
Although there are no dinosaurs now, there are some pretty big lizards including the salt water crocodile which inhabits most of Northern Australia’s Coastal regions.
The photo was not taken by me, it’s a free picture.
How did I do?
The Travelling Bee 