Why does Australia have different living things to other continents?

Answer 1

First of all, if you're a creationist, ask your local representative of whichever divine being you believe in. Ignore the rest of this post, as creationists will consider it heresy.

It has to do with genetic drift - the foundation of evolution. Australia is a very isolated continent, lacking any land bridge to another continent. It is thus isolated. Furthermore, the climate of Australia differs significantly from the other 6 (for that matter, the other 6 also have unique climates), meaning adaptations in Australia need to solve a different set of problems. When a population of a species is isolated from the rest of that species, as those of Australia were whenever continental drift separated Australia from what was left of Pangea (the megacontinent from when all of the continents were connected), its genetic traits slowly begin to differ from the original species - this is called genetic drift. Eventually, instead of 2 separated populations of a single species, we have 2 separate species. One of these species is in Australia, the other in the Pangea remenant (probably just Eurasia at that point).

Why they are so radically different in Australia than in most other continent combinations is primarily due to the amount of time since Australia separated from Pangea. South America and Africa split fairly recently. The geological evidence has not yet eroded away, and is easily identified by geologists. Furthermore, the genetic differentiation has not been enough to make a significant difference between Jaguars and Leopards (well, from a layman's perspective). Just going from the amount of genetic drift, I'd suggest that Australia split from the other continents fairly early in the disintegration of Pangea, perhaps even the first significant land mass to split off (other than possibly Antarctica, which is barely relevant in a discussion of evolutionary diversity.

Answer 2

Australia has unique wildlife due to its geographical isolation. Over millions of years, the continent's isolation allowed for the evolution of distinct species adapted to its specific environments. Additionally, Australia's diverse range of habitats, from deserts to rainforests, contributes to the variety of living things found there.