Further evidence such as the lack of remains to support that the northern hemisphere was once covered in ice as the southern hemisphere once was also supports Wegener’s theory that the continents have moved. Lack of evidence to support that ice once covered the northern hemisphere suggests that the northern hemisphere was once at a more equatorial region 300 million years ago and experienced a more tropical climate. Evidence of tropical plant remains found in the form of coal also supports this. This is also supported by fossil remains found in the centre of Australia that suggest that the area was once lush tropical rainforest that supported many tropical species.
Question 2:
Australian Flora and Fauna:
Flora species: Proteaceae Grevillea
The Grevillea species from the Proteaceae family is an example of a species of flora that has evolved to suit its environment; the Australian bush. Particular evolutionary traits have arisen as a result of Australia’s isolation and increasing aridity.
Plants from the Proteaceae family exist in nearly all continents in the southern hemisphere and Australia has the greatest abundance of species. However when Australia separated from the great landmass ‘Gondwana’ about 100 million years ago, species of the Proteaceae family continued to evolve. As a result of its isolation the Grevillea species developed its own characteristics and features independent from other Proteaceae species in the southern hemisphere.
Different patterns of evolution can be seen even within Australia. Increasing aridity and a change in sea levels that occurred during the early Tertiary Period, between 12 and 5 million years ago, effectively divided Australia’s flora between east and west. Species that had been widespread across Australia became restricted to non-arid sections in the north, south, west and east. Thus these isolated plants evolved independently from each other, becoming distinct species. Further the gradual drying of the continent over the last few million years has reduced the habitats of certain Proteaceae species reducing the abundance of species in certain areas. The Grevillea demonstrates certain evolutionarily traits associated with these two factors, that is it has distinct features that are both different and similar to other Proteaceae species in Australia.
Figure A: Typical Proteaceae Grevillea
Fauna species: The Australian Red Kangaroo
The Australian Red Kangaroo is an example of an Australian species of fauna that has evolved over time to suit its environment. As the species has evolved certain characteristics have developed as a response to the animals arid and isolated environment.
The Australian Red Kangaroo came into existence around 25 million years ago, about 10 million years after Australia split from Antarctica, and preferred rainforest type environments. As a result of Australia’s split from Gondwana, about 100 million years ago and later Antarctica, the kangaroo evolved independently in an isolated environment, this is why kangaroo existence is solely limited to areas within Australia.
This original kangaroo was tree dwelling and much smaller that today’s kangaroos. These kangaroos had opposable digits to suit the trees in which they lived. As Australia became drier and woodlands slowly replaced rainforests around 15 million years ago, the kangaroo was forced to develop into a larger carnivorous animal living in open woodland environments.
About 5 to 2 million years ago, Australia’s arid areas increased, resulting in the extinction of some species of kangaroo that were unable to adapt to the climate change. Around 20,000 years ago today’s Red Kangaroo came into existence, with adaptations allowing it to live in Australia’s dry environment. These adaptation that’s have developed over that last 25 million years include that ability to have offspring when the environmental conditions are correct and very specialised methods of water balance.
Figure B: The Australian Red Kangaroo
Question 3:
Fossils and Modern Species:
Table 1: Comparison of Early and Modern Day Life Forms
As shown in the Table 1 above, features of early and modern day species have been compared. From these differences and similarities many assumptions can be made. These comparisons provide clues as to the appearance, diet and behaviour of early life forms and also how they have developed to today’s species.
With reference to the Riversleigh Platypus and the Modern platypus, a possible explanation for the difference features may be that the early platypus had a different or greater diet, possibly consisting of meat or harder materials, and was therefore greater in size. Thus it can be hypothesised that their may have been a change in the diet of the platypus, to softer or less food, which can also explain a decrease in size.
The short-faced kangaroo was also larger than the modern day kangaroo, and had much more versatile arms and a larger, more rounded face. The change in these features can be possibly explained by again a change in diet or behaviour. The early kangaroo may have need its arms in order to collect food and as a result was able to eat a greater variety of food, explaining its large size. Whereas today’s kangaroo does not need its arms in order to collect food, thus the animal is smaller in size.
As shown above the Diprotodon had a much more rounded skull and had short bulky claws, while the modern kangaroo has a flattened skull for burrowing and long, wide claws for digging. Here it can be hypothesised that over time the habitat of the wombat has changed and therefore the need for claws for digging and skull shaped for burrowing was needed.
By closely examining species from the past and the present it is easy to find similarities between certain species. This comparison can provide clues to scientists about the evolution of the animals diet, appearance and behaviour over time.
Question 4:
Adaptations of Australian Plants:
Bird/Mammal Pollination:
Plants that reproduce through this method include Grevillea and Banksia species. The flowers have features that attract birds and small mammals to the plant. These features include bright, vibrant, conspicuous, coloured flower petals. Some species are fragrant and nectar so that it will attach to the bird or mammal when they eat the nectar and then be passed onto another plant.
Insect Pollination:
Plants that pollinate this way include the Bottle Bush and others in the myrtaceae family. The flowers of these plants have usually inconspicuous flowers but are lightly scented and some contain nectar. The insects that pollinate the plants include the native and European Bee and other flying insects. These spread the pollen by flying from one plant to another dispersing pollen.
Wind Pollination:
The plants pollinate through this method include the Casuarina or Sheeoak. These plants use their anthers that are attached to long filaments that extend into the air the release pollen. These features allow the pollen to be easily blown away. These plants have no nectar or scent and have very small or no petals. The male plant has a feathery stigma to accept the pollen.
Bibliography:
Internet Websites:
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