Australia is a land like no other, with about one million different native species. More than 80 per cent of the country’s flowering plants, mammals, reptiles and frogs are unique to Australia, along with most of its freshwater fish and almost half of its birds. Australia’s marine environment is home to 4000 fish species, 1700 coral species, 50 types of marine mammal and a wide range of seabirds. Most marine species found in southern Australian waters occur nowhere else.

Australia’s geographic isolation has meant that much of its flora and fauna is very different from species in other parts of the world. Most are found nowhere else. However, some closely related species are found on the continents which once made up the ancient southern supercontinent Gondwana. Covered in rainforest and ferns 300 million years ago, Gondwana included South America, Africa, India and Antarctica. Most of Australia’s flora and fauna have their origins in Gondwana, which broke up about 140 million years ago.

Australia separated from Antarctica 50 million years ago. As it drifted away from the southern polar region, its climate became warmer and drier and new species of plants and animals evolved and came to dominate the landscape.

In Australia there are more than 378 species of mammals, 828 species of birds, 300 species of lizards, 140 species of snakes and two species of crocodiles. Of the mammals, almost half are marsupials. The rest are either placental mammals or monotremes. There are more than 140 species of marsupials, including kangaroos, wallabies, koalas, wombats and the Tasmanian Devil, which is now found only in Tasmania.

There are 55 different species of kangaroos and wallabies—macropods—native to Australia. Macropods vary greatly in size and weight, ranging from half a kilogram to 90 kilograms. The main difference between wallabies and kangaroos is in size—wallabies tend to be smaller. Some stand as tall as humans and others are as small as domestic cats. The kangaroo is Australia's largest marsupial. Kangaroos travel by hopping on their long hind legs, using their tail for balance. They can reach speeds of up to 60 kilometres per hour and can jump distances of eight metres and heights of around three metres. Kangaroos live in large packs (or mobs) of around 100. Their diet consists of grasses, leaves and other plants. They thrive wherever a regular water source is available. The introduction of European farming methods has established regular water supplies and allowed the kangaroo population to grow dramatically. It is estimated that there are around fifty million kangaroos in Australia.

The dingo is Australia’s native wild dog and its largest carnivorous mammal. In some pastoral areas, dingoes are also regarded as pests due to the threat they pose to sheep and other farm animals. In an effort to keep fertile south-east Australia relatively free of dingoes, the world’s largest fence was built, spanning 5320 kilometres from Queensland to South Australia.

Australia hosts another unique animal group, the monotremes, which are egg-laying mammals, often referred to as ‘living fossils’. The most distinctive is the platypus, a river-dwelling animal with a duck-like bill, a furry body and webbed feet. There are only two types of monotreme in the world—the platypus and the echidna—and both of them are found in Australia. Platypuses are found all along the eastern coast of Australia, from Tasmania to Far North Queensland. They are small, dark-brown, furry mammals with webbed paws and a duck-like beak. Platypuses live in burrows that they dig into the banks of rivers. They are diving animals, and can stay under water for up to fifteen minutes. Unlike a duck's beak, the platypus' beak is rubbery and flexible. It has hundreds of electroreceptor cells inside it, which can detect the electrical currents that are caused by its prey swimming through the water. Platypuses give birth by laying eggs. The eggs are incubated by the mother in special nesting burrows. When it hatches, the baby platypus feeds on milk secreted from two patches of skin midway along the mother's belly.

Echidnas can be found all over Australia. They are small, round animals with large, clawed feet; a long snout; and a coat covered in sharp, flexible spines. Their diet consists almost exclusively of termites, which is why they are also known as spiny anteaters. A single egg is laid in the female echidna's pouch and hatches in about ten days. The baby echidna (or puggle) lives in its mother's pouch until it begins to develop spines. The echidna's spines are used mainly as a defence mechanism. When threatened, an echidna will either roll itself into a spiky ball or dig itself into the ground until only its spines are exposed.

Of the 828 bird species listed in Australia, about half are found nowhere else. Isolation has also contributed to the development and survival of unusual birds. These range from tiny honeyeaters to the large, flightless emu, which stands nearly two metres tall. In between is a vast array of waterbirds, seabirds and birds that dwell in open woodlands and forests. Some outstanding examples are cassowaries, black swans, fairy penguins, kookaburras, lyrebirds and currawongs. There are 55 species of parrots in Australia. Many of these birds are as numerous as they are colourful, including a spectacular variety of cockatoos, rosellas, lorikeets, cockatiels, parakeets and budgerigars.

Australia has more species of venomous snakes than any other continent (21 of the world’s 25 deadliest snakes). Fear of snake bites is common among people planning to travel in Australia. However, bites are rare and most often occur when a snake is deliberately provoked by a human.

Australia’s diverse oceans support around 4000 of the world’s 22 000 types of fish, as well as 30 of the world’s 58 seagrass species. Australia is also home to the world’s largest coral reef system, the UNESCO World Heritage-listed Great Barrier Reef. Marine species of note include the predatory great white shark, which grows up to six metres in length; the giant filter-feeding whale shark, which can reach lengths of 12 metres; the bluebottle or Portuguese man-of-war, which is a common hazard at many Australian beaches; and the box jellyfish, which is one of the most venomous animals in the world.