Flora and fauna
Flora is a word that refers to plants, while fauna is a word that refers to animals. The flora and fauna of a place, therefore, are the plants and animals that live there. Australia's flora and fauna are unique. They are very different from the plants and animals found on other continents. This is because Australia is relatively isolated from other places.
About 80 percent of Australian plant species are only found on, or endemic to, the Australian continent. These native plants include plants such as eucalypts, acacias, casuarinas, hummock grasses and flowering plants, including banksias and kangaroo paw.
Eucalypts, also known as gumtrees, are the most common plant on the Australian continent. Of the 700 eucalypt species found in Australia, only twelve of them are not endemic. These trees have thin, sickle-shaped leaves that are arranged alternately on a branch. They reproduce by flowering. No other part of the world is as dominated by the same type of vegetation as Australia is dominated by eucalypts. See image 1
Eucalypts, along with other Australian trees like acacias (also called wattles) and tea trees, are sclerophylls, which means they have hard, woody leaves as an adaptation to low-nutrient soils and dry conditions. Sclerophyll forests are the most common type of forest in Australia and they can be separated into two main types: wet sclerophyll forests and dry sclerophyll forests. Wet sclerophyll forests are common in areas with high rainfall. They are characterised by rapidly growing trees and a closed canopy, which means that not much light reaches the forest floor. Dry sclerophyll forests are found in areas with lower rainfall and they have a broken canopy, which means that light reaches the forest floor at some points. These types of forest are all adapted to regenerate after fires. Some even require fire as part of their seed germination processes. Other trees found in Australia include casuarinas, which grow on riverbanks, and mulgas, which are found in areas that have unreliable rainfall.
Australia also has a number of other native and endemic plants. Endemic grassland plants that grow in arid and semi-arid places include hummock grasses such as spinifex and porcupine grasses. These plants can grow on their own, or they can help form an understorey where sclerophyll trees grow. Flowering plants native to Australia include the Geraldton waxflower, the kangaroo paw and the banksia. See image 2
Australia has some spectacularly unique animals. Of the native Australian animal species, 71 percent of mammal and bird species, 88 percent of reptile species and 94 percent of amphibian species are endemic.
There are three types of Australian mammals, which are animals that usually give birth to live young and feed their young with milk: monotremes, marsupials and placental mammals. Monotremes are the most unusual and primitive of these mammals. Instead of giving birth to live young, monotremes lay eggs. Two of the world's three species of monotremes are found only in Australia, the duck-billed platypus and the short-beaked echidna. The third species, the long-beaked echidna, can only be found in Papua New Guinea. See image 3
Marsupials are mammals that give birth to largely-undeveloped young. These babies are not able to fend for themselves, so they live in a pouch in their mothers' bellies, where they feed on milk and grow until they can survive outside. Most of the mammals in Australia are marsupials. Of the 238 species of mammals living in Australia, 144 are marsupials, and 90 percent of these are endemic to Australia. Some common examples of Australian marsupials are kangaroos and possums. See image 4
Placental mammals are more 'standard' mammals. Placental mammal mothers incubate their young within their bodies and give birth to fully-formed infants. Examples of Australian placental mammals are rodents and bats. See image 5
Australia is also home to many endemic reptiles. In one square kilometre of land in the centre of Australia, more reptile species can be found than in a square kilometre in any other place in the world. Reptiles are common in Australia because they are well suited to the hot, dry conditions found in the centre of the continent. They range from estuarine crocodiles to poisonous snakes to skinks and geckoes.
Australia is home to many unique amphibians that have adapted to conditions in dry climates. Australian frogs are adapted to living in the dry centre of the continent. Some burrow underground and aestivate (become dormant), waiting for rainfall. Others raise their young in their stomachs. Australian birds are also adapted to dry conditions. Many of these birds are nomadic, travelling from place to place following favourable conditions. Some examples of Australian birds include black swans, kookaburras, galahs and cockatoos.
The Australian continent is located on the Indo-Australian Plate, which includes the surrounding Indian Ocean and the Indian subcontinent. The Indo-Australian Plate was originally connected to Gondwanaland before it began to drift north some 96 million years ago. As the Australian continent drifted north it developed unique flora and fauna. There are three basic reasons for Australia's diverse organisms. Firstly, since the temperatures on the continent remained constant for such a long period of time, plants and animals were able to evolve and adapt to particular ecological conditions. Secondly, the continent was so isolated that it was impossible for outside species to arrive, allowing native forms to develop unimpeded. And thirdly, even though the continent is very old, there are areas of high fertility. Some species have remained more or less unchanged for 90 million years. A number of these ancient species can be found in the Great Dividing Range. Many of the animals found here in Australia are very similar to the animals that were found long ago on Gondwanaland.