Biology Research Assignment

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St Aloysius College

Evolution of Australian Biota Preliminary CourseResearch Assignment

Daniel McAdams 8/8/2012

Question 1: A timeline is drawn with at least four significant stages and their geographical period indicated At each stage identify and describe evidence of changing environments in Australia over millions of years At each stage identify changes in the distribution of Australian species, as rainforest contracted to sclerophyll communities and grasslands spread, as indicated

Changes in the Environment: The environment of Australia was very different during the Triassic as the developing super continent Gondwana just split off from Pangaea. As Australia was connected to South America, India, Antarctica and Africa, they shared similar environment. As there was no Polar Regions as Australia was situated near the equator its climate was generally hot and dry. Due to the absence of polar ice caps sea levels rose which flooded parts of Australia. Australia was generally a dry and desolate place, although with brief periods of heavy rain. The evidence of environmental change during the Triassic support Wegnerss theory of continental drift, as Gondwana slowly drifted away from Laurasia.

13.7 Billion years ago

Change in the distribution of Australian Species: Gymnosperms dominated all areas of the Triassic, which was due to the lack of nutrients Gymnosperms needed to survive. Early stages of the Triassic made it difficult for plant life to prosper. Due to the over abundance of carbon dioxide, caused the temperatures to rise and killing of most dry plants. Plants were not able to grow metres in length. Seed ferns like the Glossopteris dominated all parts of Australia, as they were seed sporing plants, which was perfect for reproduction in arid conditions. This is represented in the earliest Australian fossils of the Glossopteris. Gymnosperms were able to survive in these harsh conditions as they reproduce rapidly, which fore grounded many native Australian species in millions of years to come.

Triassic Period 250-200 million years ago

Changes in the Environment: Australias environment during the Jurassic Period was warm and wet and finally gave way to flourishing plant life. As we were drifting further south of the equator Australia slowly started to decrease in temperature and due to that the dry arid plains of the north and west opened up basins for successive accumulations of shale, limestone and sedimentary rocks. Carbon dioxide levels were raising, but did not affect the majority of Australia due to the slowly drifting movement of the tectonic plates.

Jurassic Period 200-145 million years ago

Change in the Distribution of Australian Species: Dinosaurs roamed all parts of Australia, which is represented in fossil records along the coast and inland Australia. In order for the Dinosaurs to survive plant life had to grower taller and gain more nutrients to match the energy consumptions needed for dinosaurs. This was aided by the wetter and warmer country Australia was becoming. Horsetail ferns were the most dominate plants during this period as they quickly reproduced and varied in size which aided all types of dinosaurs. During the late Jurassic period flowering plants started to evolve, which would change vegetation across Australia.

Change in the Environment: As Australia separated from Gondwana and still connected to Antarctica, it drifted rapidly south. Due to its position climate was huge problem, as North Australia experienced hot tropical weather and the southern end of Australia experienced cool weather. Tasmania was covered by sees due to the sea level rising, as the ice caps started to form on the southern end o f Antarctica. This is evident in Carbon Dating as some Ice caps date back toward the Cretaceous Period.

Cretaceous Period 144-65 million years ago

Change in the Distribution of Australian Species: The Cretaceous period was the start of flowering plants. These flowering plants are the thresh hold to the origin of Australian Plants today. Rainforest ecosystems also started to form on the coast of Australia, which was shared with Antarctica. This is evident in fossil record as it shows that Antarctica and Australia shared Northofagus ferns. The domination of fern plants started around the late Cretacean period, which started the adaptive lifestyle of the evolution of Australian Plants. As Australia started to move further south while Antarctica moving towards the south pole, the split. This starts more tropical plants In Australia, as it reaches a climate that is suitable in a cycle of different climates all year round.

Change in the Environment: As Australia is finally isolated from all other continents, it receives a stable hot and dry climate, which is mostly inflicted on Central Australia making it arid and un-inhabitable. All landscapes and geographical significance that we see today relates to this period. The northern part of Australia has become mountainous, due to tectonic plate collision. Now Australia is slowly drifting north towards the equator which will make all parts of Australia.

Quaternary Period 2.5million years ago - Present Day

Change in the Distribution of Australian Species: As Australia continued to drift north conditions of Australia slowly changed, as soil became poorer rainforest started to die out, which started the domination of sclerophyll plants. As fire commonly started by lightning strikes, which is indicated by carbon particles in fossil records, Plants started to adapt in ways which allow them to survive in fire. About 40,000 years ago, the fire frequency increased further, as indicated by carbon deposits. This results for all Australian plants to be Fire Resistant due to Natural Selection. Now Civilization has cleared all wide spread forest, which now they only situate on the coast of Australia.

Present Day

Question 2: Two Australian sites are named and a description is made of significant fossils found at each site Dor each named site, explain how these fossils contribute to our understanding of Australias evolution

(ii) Lightning Ridge The Lightning Ridge fossil site is quintessentially significant to the origins of Australians mammals, as it contains the oldest fossilised mammal in Australia. Although Lightning ridge is a notorious opal mine, the age and characteristics of their fossils, is what separates them from other Australian fossil sites. The fossils at lightning ridge are a lot different than other fossils in Australia as they have 2 types of fossils, normal bone fossils and opalised fossils. The significant opal fossils occur as when the organism dies and starts fossilising, it is also in the right conditions and area for opal formation. This causes the outside of the fossil to be coated in a thick lair of copal, which not only preserves the outside but the inside as well, as the bone structures silica liquid is preserved by opal formation. Due to Opal formation not only is lightning ridges fossils aesthetically pleasing, older fossils are preserved much better than fossils that undertake normal fossilisation. The abundance of Opal fossils, show 2 things for the evolution of Australia. Due to the preservation of Opal fossils, Lightning ridge has evidence of the oldest dinosaurs in Australia, as the Opal formation rejuvenates and maintains the clarity and condition of prehistoric fossils. The significance of evidence of Dinosaurs in Australia shows that once we had conditions that suited and aided the abundance and survival of Dinosaurs, as no dinosaurs are able to survive in our dry landscape. This means that there was an abundance of nutritious plantation and lots of surrounding bodies of water, as water is now regarded to be the main survival source of all dinosaurs. The evidence of Dinosaurs in Australia is one of the most significant findings in Australia, as the mystery to Australias past is slightly opened through the jigsaw to what is the History of Australia.

Opalised Dinosaur Claw Fossil

Another significant discovery at lightening ridge is the oldest living mammal in Australia. The Steropodon galmani is the oldest fossil found in Australia, which dates back 150 million years ago in the early cretaceous period. The discovery of this fossil is at most significance to the evolution of Australia, as this shows that Australian Biota started its evolution over 100 million years ago. This being the first mammal, shows the origin of most current Australian mammals, The Steropodon is most likely an ancestor the platypus, which Steropodon galmani lower jaw bone describes the existence of monotremes in the early development of Australia. The significance of this fossil is indescribable as it foregrounds the discovery and knowledge of the evolution of Australia.

(ii) Riversleigh Fossil Fields The dry plains of Riversleigh north western Queens land is home to some of the most scientific acclaimed fossils, in the southern hemisphere. Riversleigh has been used over years to decipher Australias past and be able to understand the flora and faunas that existed over a hundred thousand years ago. Not only does it provide evidence of Ancient Australian Biota, we are able to understand the evolution of Australias environment. The Riversleigh fossil sight provides the best example of the evolution of Australias vertebra as it shows 100s of different fossils living in the same area. The most scientifically acclaimed fossil at Riversleigh is the whole skeleton of the ancient megafauna, the Diprotodon. In one small site dozens of these giant wombats have been discovered which shows us the dominance of herbivores over thousands of years ago. Supporting this discovery is the findings of the skull of an Ancient Bandicoot and the skull of the ancient kangaroo. All 3 of these significant