Free VCE Outdoor and Environmental Studies Flashcard Review

The separation of Australia's landmass from other continents by ocean for tens of millions of years, so its plants and animals evolved with little genetic exchange. The result is very high endemism (marsupials, monotremes, eucalypts, acacias), unusual evolutionary lines with no close overseas relatives, and species that never faced placental predators or hard-hoofed grazers.

Australia has sat in the middle of its tectonic plate for a very long time, so it has had almost no recent mountain-building, volcanism or continental glaciation. The consequences are low relief (the flattest inhabited continent), ancient deeply weathered rock, thin and highly leached soils, and slow-flowing, low-gradient rivers.

Australia's climate varies enormously across space (tropical north, arid centre, temperate and alpine south-east) and, crucially, over time — long droughts broken by flooding rains, driven largely by ENSO. Ecosystems evolved to boom-and-bust rather than to reliable annual rainfall, so many species breed opportunistically after rain.

The ancient southern supercontinent that included Australia, Antarctica, South America, Africa, India and New Zealand. Its progressive break-up set up Australia's biological isolation, and Gondwanan lineages survive in Australia today in groups such as Nothofagus (Antarctic beech) rainforest and southern conifers.

The proportion of species in a place that occur naturally nowhere else. Australia's endemism is exceptionally high because of long isolation — most native mammals, and the great majority of reptiles, frogs and flowering plants, are found only here. In an exam answer, use endemism as the key evidence of biological isolation.

Around 45 million years ago. Once the gap opened, the Antarctic Circumpolar Current formed and Antarctica cooled and iced over, while Australia drifted north into lower latitudes. This drove long-term drying of the continent and the replacement of widespread rainforest with sclerophyll eucalypt and acacia vegetation.

Because of geological stability. Without recent uplift, volcanism or glaciation to expose and grind fresh rock, the same ancient land surface has been weathered and leached by rainfall for millions of years, stripping out phosphorus and nitrogen. Fertile exceptions occur where there was recent volcanism, such as the basalt soils of Victoria's Western District.

(1) Very low relief and low mountains — Mt Kosciuszko, the highest peak, is only 2228 m, and the Great Dividing Range is heavily eroded rather than sharp and young. (2) Extremely old, deeply weathered surfaces and soils, plus the near absence of active volcanoes and of large destructive earthquakes compared with plate-margin continents.

Egg-laying mammals — the platypus and the short-beaked echidna — that survive only in Australia and New Guinea. They are the standard exam example of biological isolation preserving an evolutionary lineage that disappeared elsewhere.

Marsupials were present before Australia's isolation was complete, and once the continent separated, placental mammals (apart from bats and later rodents) could not arrive to compete with them. In isolation, marsupials radiated to fill grazing, browsing, burrowing and predatory roles taken by placentals on other continents.

Very large animals that lived in Australia during the Pleistocene, including Diprotodon (a rhino-sized herbivorous marsupial), the marsupial lion Thylacoleo, the giant short-faced kangaroo Procoptodon and the flightless bird Genyornis. They died out tens of thousands of years ago; debate continues over the relative roles of climatic drying and human arrival.

Vegetation dominated by plants with hard, tough, often small leaves rich in lignin and low in nutrients — typically eucalypts, acacias, banksias and heath species. Sclerophylly is an adaptation to nutrient-poor soils, drought and fire, and it is the characteristic vegetation type of much of southern Australia.

Dormant buds sitting beneath the bark of eucalypts that shoot after fire scorches the canopy, allowing the tree to refoliate along the trunk and branches within weeks. Evidence that Australian environments experienced recurrent fire long before humans arrived.

A woody swelling at or below ground level, packed with dormant buds and stored starch, from which a plant resprouts after its top is burnt, grazed or cut. Common in mallee eucalypts, and a key fire-survival adaptation of Australian flora.

The retention of seed in woody fruits or cones on the plant, released only when triggered — usually by the heat of fire. Banksias and hakeas are classic examples: mass seed release onto a nutrient-rich, competition-free ashbed maximises germination.

A coupled ocean-atmosphere cycle in the Pacific that swings between El Nino, La Nina and neutral phases over roughly two to seven years. ENSO is the single biggest driver of Australia's year-to-year rainfall variability, and therefore of the drought-flood-fire cycles that shaped Australian ecosystems before humans arrived.

The ENSO phase in which the central and eastern Pacific warms and the Walker circulation weakens, shifting rainfall away from Australia. Typical Australian effects: below-average rainfall in the east, hotter days, reduced streamflow and elevated bushfire risk.

The ENSO phase in which the western Pacific near Australia is unusually warm and trade winds strengthen, pushing moisture over the continent. Typical effects: above-average rainfall in eastern Australia, widespread flooding, cooler daytime temperatures and strong vegetation growth that can later become fire fuel.

The long-term drying trend over roughly the last 15 million years as Australia drifted north and global climate cooled. Rainforest contracted to coastal and mountain refuges, the arid centre expanded, and drought- and fire-tolerant eucalypt, acacia, spinifex and chenopod communities spread — producing the continent humans first encountered.

Around 20,000 years ago conditions were colder, windier and much drier than today. Sea level was roughly 120 m lower, small glaciers formed in the Snowy Mountains, dunefields expanded across the interior, forests contracted to refuges, and Tasmania and New Guinea were joined to the mainland by dry land.