Evolution of Australian BiotaPart 1

Evidence for the rearrangement of crustal plates and continental drift indicates that Australia was once part of an ancient super continent

Pangaea was a patchwork supercontinent formed by a series of continental collisions that began in the Late Paleozoic and continued into the early part of the Mesozoic.

The part of Pangaea that lies in the Northern Hemisphere is called Laurasia. It includes most of the present-day North America, Greenland, Europe, and Asia.

Gondwana is the part of Pangaea that lies in the Southern Hemisphere. It includes most of the present-day South America, Africa, India, Australia, and Antarctica.

Pangaea split into the two megacontinents Laurasia and Gondwana beginning in the Late Triassic.

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identify and describe evidence that supports the assertion that Australia was once part of a landmass called Gondwana, including:- matching continental margins- position of mid-ocean ridges- spreading zones between continental plates- fossils in common on Gondwanan continents, including Glossopteris and

Gangamopteris flora, and marsupials- similarities between present-day organisms on Gondwanan continents

- All landforms were originally joined together in a giant landmass called Pangaea

- In the Jurassic, 160 million years ago, Pangaea split into two super continents:

Gondwana and Laurasia

- Gondwana: Australia, Africa, Madagascar, New Zealand, South America, India

- Laurasia: Europe, North America, Asia (except India)

- About 60 million years ago, Australia split from Gondwana

- Evidence that Australia was once part of Gondwana:

Geological evidence:

- The rock strata around continental margins match exactly in many places, eg:

1) South Australia & Australia, 2) West Africa & east South America.

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The breakup of Gondwana

Dolerite is a common rocktype throughout Tasmania. It

is derived from the breakup ofGondwana.

- The Gondwanan landmass started to disperse between 170 - 180 million years ago. The dispersal caused great tension in the Earth’s crust and molten rock intrusion followed as conduits were created in the continental crust, tapping the molten rocks (magma) in the Earth’s mantle. The dolerites that outcrop over extensive parts of central and eastern Tasmania, together with similar igneous rocks in South Africa, South America and Antarctica, are the solidified evidence of the magma from the break up of Gondwana.

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- Mid-ocean ridges are formed where plates are moving apart

- When plates move apart, molten rock rises up and forms new sea floor.

- In these areas, called spreading zones, the new rock that forms is older the

further it is from the ridge

- This proves that the plates have been moving apart steadily for a long time

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Biological evidence:

- The fossil record and present day organisms provide evidence that

Australia was part of Gondwana

- Fossil Evidence:Glossopteris and Gangamopteris are fossil plants found in rocks of the

same age in Australia, Africa, India, South America, Antarctica and

New Zealand

Fossils of marsupials have been found on all the continents that were

part of Gondwana

This is evidence that the continents were once joined

discuss current research into the evolutionary relationships between extinct species, including megafauna and extant Australian species

Extant Organisms:

- Still in existence; not destroyed, lost, or extinct:- The moose is an extant species while the dodo is an extinct species.- In the group of molluscs known as the cephalopods, as of 1987 there

were approximately 600 extant species and 7,500 extinct species

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o Nothofagus, or the southern beech trees, are found in forests of

Australia, New Guinea, New Zealand and South America

o Many plants and animals exist only where the Nothofagus still live; e.g. a

parasitic fungus, a moss and bugs which depend on the moss

o Many groups of animals in Australia have close relatives in South

America, Africa, India and New Zealand, but not in Northern Asia,

Europe or North America

o These animals include: parrots, ratites (flightless birds), marsupial

mammals, chelid turtles, some geckoes, many families of earthworms,

terrestrial molluscs, spiders and insects, and the scorpion genus

Cercophonius

- Megafauna are large animals, such as elephants and whales

- Megafauna are not the ancestors of present animals, eg kangaroos didn’t come

from giant kangaroos, rather they both evolved from a common ancestor.

- Over the last 50k years most of the world’s megafauna have become extinct

- Two theories have been put forward to explain this:

Climate Change: Megafauna were mainly suited to glacial conditions. Their

large bodies enabled them to live in extreme conditions. In Eurasia and North

America, when permafrost was replaced with forest, the megafauna died out

and animals more adapted to forest began to thrive. In Australia, the

temperature changed from cold-dry to warm-dry. As a result, water sources

began to dry up, and many animals lost their habitat and died out.

Human Expansion: The time of the extinction of megafauna matches very

closely the pattern of human migration into these areas. Megafauna are also

large and slow, which makes them susceptible to hunting. In Africa, humans

evolution occurred there, so hunting increased slowly, allowing animals to

adjust. That is why there are still megafauna there. However, in places where

humans arrived as skilled hunters, the most extinction occurred.

- Living fossil (or relict species) are organisms that have changed little or not at all

since ancient times.

- Australia has many examples of living fossils, such as: 1) Stromatolites, 2) The

Wollemi Pine, 3) Crocodiles, 4) Queensland lungfish, and 5) Monotremes.

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Evolutionary relationship refers to how closely one organism is related to another. From this we can draw on how closely related extinct species such as megafauna are to current Australian species. Firstly megafauna as the name suggests are large animals. Current living megafauna include elephants and whales. However over the last 50000 years megafauna have become extinct. Extinction was more than likely due to a number of factors including climatic change and human expansion.

Evolutionary relationships can be shown between megafauna and current Australian species. For example if we compare the diprotodon and the common wombat we can identify many structural similarities. Structural similarities include skull structure, body covering, length and structure of limbs, ears and snout are all similarities between that of the wombat and the diprotodon.

This example illustrates the evolutionary relationships between extinct Australian megafauna and current Australian species. (Other evolutionary relationships include; giant kangaroo vs kangaroo, giant echidna vs echidna and Genyornis vs the emu to name a few.)

Vs

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solve problems to identify the positions of mid-ocean ridges and spreading zones that infer a moving Australian continent

- Mid-ocean ridges occur where continental plates are moving apart

- Spreading zones are the new areas of floor created at ridges where molten rock

rises out from the mantle and solidifies

- There are spreading zones on the southern side of the Indo-Australian plate, and

collision zones on the northern side

- This implies that Australia is moving north

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identify data sources, gather, process and analyse information from secondary sources and use available evidence to illustrate the changing ideas of scientists in the last 200 years about individual species such as the platypus as new information and technologies became available

Technologies contributing to our knowledge of the platypus

The Platypussary

The Platypussary was an innovation developed by Dr. David Fleay, an Australian, in the late 30’s and early 1940’s. It was developed in order to stimulate the platypus’ natural habitat, in the pursuit of breeding a pair. Dr. Fleay’s Platypussary, located at the Healesville Sanctuary just outside Melbourne, consisted of natural settings and a series of tanks and pumps. Though previous attempts had been made at mimicking a stream, such as that by Eadie in the previous century, Fleay’s incorporated a series of flowing pools, filled with gravel and natural items you would expect to find in a typical Australian stream.

The significance of Dr. Fleay’s technology, the Platypussary, was that it gave rise to the first breeding pair of platypuses ever. In 1943, at Healesville, two platypuses gave birth to “Corrie”. The Platypussary had nest boxes and glass panels, making all areas accessible by keepers. The outcome of this was revolutionary research into the breeding habits of the platypus, including gestation, pre-natal and post-natal process.

The most invaluable knowledge of the platypus to date comes from the research of Healesville Platypussary, and, since then, technology has been advanced, creating almost exact replicas of the platypus’ natural environment. The birth at Healesville in 1943 was the only one until 2003.

Taronga Zoo had just established its Wollemi Exhibit, a walk through enclosure mimicking the natural Eastern Australian bushland. The stream running through it, in conjunction with a first class Platypussary, led to the birth of twin Platypuses, and, again, in 2006.

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The simulation of the Platypus’ natural environment was quintessential, and, through an elaborate network of pumps and filters, a life-like flowing stream, monitored closely, enabled the Platypus to be bred in captivity, thus, giving us an in-depth knowledge into the lifestyle and breeding habits of the Platypus. 

 

Electron Microscopy

The first Electron Microscope (left) was built in 1931 by the German engineers, Ruska and Knoll. This technology went on to advance knowledge in just about every field of science, including zoology, where it clarified the mysteries of the platypus.

Up until the 1930’s, the Platypus was observed closing its eyes, ears and nostrils when foraging underwater. This led to the question, “how do they actually find their food?”. 

The Electron Microscope enabled scientists to take a much closer look at the strange bill of the Platypus, which they noticed was vigorously swept from side to side during foraging. What was discovered about the amazing bill of the Platypus was a shock to scientists.

Thousands of ultra-sensitive touch receptors streamed messages back to the brain, helping the Platypus to navigate its way through the streams with its eyes closed. It could also be used to detect prey, if touched.

These Electroreceptors work to detect minute electrical signals, relay the message back to the brain, creating an image of the riverbed and locating prey.

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Not only were these revelations due to the Electron Microscope, but a myriad of others in biology too.

Cells could be delved into in more detail, enabling scientists to examine further biological adaptations of the Platypus, such as increased haemoglobin count, salt retaining kidneys and the nervous network between the bill and the brain.

The Electron Microscope has contributed to many fields of science, in particular biology, and the knowledge about our furry friend, the Platypus –namely at a molecular level- is owed greatly to the invention of the Electron Microscope.

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