Why is the flora and fauna of Australia so unique?
Evolution is ultimately an unpredictable process. Although it can be predicted in the short term through knowledge of natural selection and inheritance, long term evolution is randomly altered by the interaction of highly variable factors. Such factors include the randomness of genetic diversity within a species and the process of natural selection acting upon this. Also significantly altering evolution is the unpredictable movement of tectonic plates which often leads to the isolation of large areas of land, such as Australia. Stemming from this arises various other substantial factors such as a lack of competition and predation and considerable changes in climate and ecosystems. The interaction of these forces (the unpredictable changes) is exactly what happened to Australia and as a consequence, drove the native Australian animals onto a very unique evolutionary path different from any other area land- no matter how similar their environments. It is widely accepted that between 260-180 million years ago, all of the Earth’s land was a part of one single large landmass called ‘Pangaea’. However, 180 million years ago Pangaea is believed to have split into two smaller ‘supercontinents’, with the land we call Australia connected to the southern landmass of ‘Gondwana’. This came as a result of the random movement of tectonic plates; the outer crust of the Earth consists of about 12 of these plates which are able to move due to convection currents in the mantle. As a result of this continual plate movement, Australia completely rifted from the last Gondwanan continent of Antarctica approximately 45 million years ago. Since then, up until 5 million years ago, Australia remained as a completely isolated continent. This 40 million-year period of isolation drove Australia’s plants and animals into a unique evolutionary path. Due to Australia’s isolation, fauna from other continents were unable to travel across to Australia. As a result of this, there was a significant lack of competition for Australian species for a very long time. Natural selection in the absence of competition enabled them to evolve in very unique ways. Natural selection is the evolutionary process whereby heritable traits that enable organisms to more effectively live and reproduce become more prominent within the population. Thus, they increase an organism’s chance of survival. Natural selection is based upon genetic variability producing these favourable traits. Moreover, biotic and abiotic features in the environment such as competition, predation, disease and environmental change impact upon an organism’s need to adapt. Thus, Australia’s isolation led to an organism’s genetic variation and adaptation becoming more focused on adapting to the environment rather than avoiding predation. As this unique natural selection continued, Australian flora and fauna were precisely adapting to their niche environments; they were adapting to their adaptations. For example, the Koala has many adaptations for its environment but it has limited adaptations for predation; its large paws and claws are adapted for climbing trees and its stomach has adapted to digest the abundant food source of eucalyptus leaves. However, this slow moving marsupial would not be able to withstand any competition or depletion of its food source or predation. If the Koala and most other Australian organisms were subject to more competition, evolution would have been ‘balanced’ in Australia such as it is in other continents around the world. Its impact on natural selection would have caused adaptations to predators and not just solely to their environmental conditions. In effect Australia’s isolation removed a significant variable from the process of natural selection. Thus, they were able to adapt precisely to their uncontended niche environments.. One example of this is the monotreme, the platypus. It has adapted so precisely to its...
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