an Overview of Australian outdoor environments before humans 3.1.1 an Overview of Australian outdoor environments before humans

From the study design Key Knowledge: an overview of Australian outdoor environments before humans, including characteristics of biological isolation, geological stability, and climatic variations. Key Skills: describe the characteristics of the Australian environment before humans.

3 Main phases Precambrian, 4,300 - 600 Million years ago: The forming of the earth. Gondwana, 180 Million years ago: Major splitting of northern and southern continents from the supercontinent - Pangea. Australia - Isolation, 65 Million years ago: Separates from all other continents to become an isolated landmass of its own.

Precambrian 4300 - 600 Million years ago. Three pieces of continental crust formed during this phase. This phase was the beginning of life, bacteria and other single celled organisms began to form. During the late Precambrian phase, multicellular of bodied animals such as jellyfish arose.

Gondwana Approx. 180 Million years ago - the once ‘super-continent’ Pangea (all of the known continents) broke into two large continental masses. The southern continents of Australia, South America, Africa and Antarctica (along with India) formed ‘Gondwana’. The northern continents formed ‘Eurasia’. During this phase, the earth began to get warmer, crocodiles, dinosaurs and mammals developed.

Australia - Isolation Approx. 65 Million years ago. Australia separated from other land masses (NZ and Antarctica). During this phase, Australia remained warm and humid with rainforest vegetation. Australia has continued to move gradually towards the northern hemisphere since this time due to continental drift. The unique development of all Australian characteristics began here.

continental drift Theory Continental drift is the theory that all of the earth’s continents are continuously moving. Plates move as ‘convection currents’ underneath the earth’s continental plates cause movement as magma from the earth’s mantle heats up and creates pressure. The layout of the earth’s continents and physical features such as mountain ranges, mid-ocean ridges and volcanoes are all attributed to this.

Evidence of drift

Australian characteristics Key Concept Australian characteristics

Unique Australian Environment The unique Australian environment has been shaped by three factors: Biological Isolation Geological Stability Climatic Variations Each of these factors explain why the unique Australian environment, its flora and fauna, are the way they are.

biological isolation As Australia is an island continent (isolated from other continents), Australian flora and fauna have adapted to the Australian conditions in isolation, making them unique to anywhere else in the world.

A high percentage of endemic species (found nowhere else in the world) are found in Australia. E.g. 85% of the worlds mammals, 12/19 known flowering plants. Example: Australian marsupials, such as Kangaroos, developed an energy saving reproduction method… in their pouch, to save energy in the hot Australian environment.

Geological stability As Australia lies in the middle of a continental plate and has had no recent volcanic activity, the landscape has been shaped by outdoor forces such as erosion , for thousands of years. The state of soil - dry and low in nutrients, is a result of this.

Example: The Koala has a tiny brain which requires little energy, as the leaves they eat have little nutritional value. Example: Australia has high levels of biodiversity, as flora species have adapted to the low nutrients due to no species being able to dominate.

climatic variations Australia experiences a relative erratic climate in comparison to other continents of the world. There are two extremes; the El Nino years (long, lean droughts) and the La Nina years (flooding rains). These periods can last from 1-10 years, this unpredictability has had an impact on the adaptability and diversity of flora and fauna. Water storage strategies have been adapted by flora and fauna. Example: Mountain Ash trees have adapted to regular bushfires and aboriginal fire-stick farming by needing fire to germinate its seed pods.

Example: Due to extended dry periods, the eucalyptus tree has developed improved water retention strategies. Their leaves hang down, are thinner and have high oil content to conserve water.

Flora species adaption Eucalyptus (also known as the Gumtree) Over 700 species found in Australia Have adapted to many environments e.g. coastal, alpine Oily leaves reduce water loss Have deep root systems to access underground water Fire travels up tree through lack of bark, germinating seed pods which burst open and start growing

Eucalypts in the Bogong High Plains Eucalypts at Wilsons Promontory

Fauna adaptation Kangaroo Raise baby in pouch to save energy Have four special pairs of teeth for chewing tough leaves Fur reflects 30% of heat from the sun Hopping pushes air into lungs by compressing diaphragm, saving energy Fauna adaptation