Marsupial diversification in Australia and the absence of other mammals reflect Australia’s long isolation. Australia has an abundance of endemic species—species found nowhere else—which is typical of islands whose isolation by expanses of water prevents species from migrating.
I believe that adaptation has also played a part in this as endemic species adapt to this type of climate and environment secluded from other parts.
appendages. Over time, evolution led to changes in the bones' shapes and sizes in different species, but they have maintained the same overall layout. Scientists call these synonymous parts homologous structures.
Appendages are body parts that extend such as limbs, tails. In plants these can be branches or leaves. This is a very interesting concept as I have never heard of homologous structures and how they can tell a lot about evolution.