Australia became and island around 50 million years ago. It had broken off from Gondwanaland and had been pushed north. In doing so, it had been separated from all other land masses, and had become an isolated area for flora and fauna evolution. It is because of this that the plant and animal species found in Australia today are so unique, and so incredibly different from all other plants and animals found anywhere else in the world. It is not surprising to think how shocked European sailors would have been when they arrived in this harsh barren land inhabited by creatures unlike anything they had ever seen before.

Fauna

Probably the most obvious species of animals that this isolated island has produced is the marsupial. Marsupials are thought to have reached Australia from South America across the Antarctic land connection. For the early part of Gondwana's separation, most marsupials were small herbivorous tree dwellers, as they were stalked by numerous predators if on ground. After the disappearance of the great lizards that once walked the earth, the marsupials quickly evolved into land roaming creatures by making the move out of the trees and onto the ground. This is believed to come from the possum who feeds both on the bottom of the forest as well as the canopy.

Several species of marsupials are unable to walk using their hind legs, as the hind legs move together - this creates the appearance of bouncing. This is thought to be how kangaroos came into existence. The kangaroos began to expand as the continent became drier and grasslands more abundant. They moved out of the forests and into the open planes, taking advantage of the large amounts of grass available. The tree kangaroo on the other hand saw the little amount of competition for food in the trees and adapted to tree climbing in order to find food. As kangaroo populations flourished, competition for food and a mate increased. It became a battle of survival of the fittest, a great ground for natural selection. The kangaroos developed an incredibly powerful tail - a "Prehensile" tail, meaning that it acts as an extra limb. Other marsupial also have this advantage of an extra limb, which is helpful for holding on to branches of trees.

Monotremes, such as the echidna, have been part of Australia for about as long as marsupials. They have been able to evolve on this isolated island tens of millions of years. They are found naturally only in Australia and New Guinea. The only monotremes found in the world today are the short beaked echidna (Tachyglossus aculeatus), the long-beaked echidna (Zaglossus bruijnii), and the platypus (Ornithorhynchus anatinus). Both long-beaked and short-beaked echidnas can be found in New Guinea. The short-beaked echidna and the platypus can be found in Australia, but it is thought that the long-beaked echidna was once found in Australia, but was unable to survive the change of climate. These animals are so unique that European scientists were unable to make sense of them when first encountered. Upon examination, English biologist George Shaw concluded that the platypus was a hoax and was just the remains of several animals sewn together by an explorer.

Over the last 20 million years, throughout the period that Australia has been an island, many different species of mammals have migrated to the island from various surrounding land masses. It has only been in these last 15-20 million years that Australia has been close enough to New Guinea for mammals to migrate. Fifteen million years ago, bats flew across from Asia, and since then have evolved into the 150 different species that are native to Australia. 50 species of rodents are now found in Australia, after they migrated on drifting logs or mats of vegetation 4.5 million years ago from Asia.

Australia's range of animals is unlike no other in the world. The species found on this great island are so unique, simply because they have been able to evolve with no interference from surrounding continents.

Flora

Over the last 30 million years, Australian flora has developed in isolation which little influence from migrants, even once Australia became close enough to South-East Asia for significant migration to occur.
As Australia separated from Gondwana, many changes in flora came about. The most obvious change was that of the appearance of flowering plants. These first flowering plants (angiosperms) started to appear as the continent dried out, and by the Cretaceous period, they were fairly well defined.

Depressions around Australia including what is now Victoria, were caused by a rise in sea levels during the Lower Cretaceous period. Consequently, large sediment deposits were found in these areas and are now exposed as the Otway and Strzelecki Ranges. In this area, the fossil evidence indicates predominantly near-coastal freshwater conditions of deposition. Because of these unique conditions, along with the climate, and the isolation of the continent, the flora of Australia has developed into a unique and highly diverse array of flora. In fact, eighty percent of Australia's plant species are endemic to Australia, as are thirty percent of genera found in Australia.

Probably the most recognised plant-life in Australia is that of the Eucalypts. Largely associated with the koala, the Ecalypt is greatly unique to Australia, and is unlike any plant-life found around the world. It occupies large areas of woodland and plays a large role in the ecosystems it is part of.

One distinctive characteristic of Australian plants is there adaptation to have leathery, hard, spiny or reduced leaves. This is due to the changing environment that has caused them to adapt in order to survive. This form of adaptation is called scleromorphy. Apart from small amounts of rain forest, and high altitude forests, the majority of vegetation is of dry sclerophyll type. This adaptation is due to water reduction and conservation, and also low-nutrient-status soils.

Another adaptation the flora of Australia has had to make is one in order to withstand regular and easily spread fires which are common around the island. Within the areas of thick damp rain forests, lightning strikes were quite limited in their effects. There is such a moist atmosphere, and such little litter of plant life on the ground, that it is difficult for a strong fire to start in these areas. This is clearly contrasted in open woodland areas, where dry bark and lots of dry litter can be found. In such areas, fire is common, and can wipe out large numbers of trees, especially when they come into contact with very tall, highly flammable Eucalypts. Because of such events, woodland flora in Australia has adapted in order to survive such occurrences. Even in the Eocene period, 50 million years ago, adaptations had been made by the banksias in order to survive fires. They had produced woody seeds which became an advantage when fires were frequent. Other adaptations such as thick, insulated bark to prevent the tree from over-heating; the development of 'lignotubers' in shrubs which are capable of withstanding the hottest fires, and produce new branches when the ashes have cooled; as well as thick woody seeds, which can not only withstand strong blazes, but may require heat from ashes in order to germinate; these adaptations allow Australia unique flora to survive Australia's unique climate.

Now, millions of years after the separation from Gondwana, Australia's flora has adapted in order to survive the changing soils, arid regimes, and frequent fire, in order to give Australia plant-life unlike no other in the world.
 

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