Evolution of Australian Biota

Part 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.

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

-AlllandformswereoriginallyjoinedtogetherinagiantlandmasscalledPangaea

-IntheJurassic,160millionyearsago,Pangaeasplitintotwosupercontinents:GondwanaandLaurasia

-Gondwana:Australia,Africa,Madagascar,NewZealand,SouthAmerica,India

-Laurasia:Europe,NorthAmerica,Asia(exceptIndia)

-About60millionyearsago,AustraliasplitfromGondwana

-EvidencethatAustraliawasoncepartofGondwana:

Geologicalevidence:

-Therockstrataaroundcontinentalmarginsmatchexactlyinmanyplaces,eg:1)SouthAustraliaAustralia,2)WestAfricaeastSouthAmerica.

The breakup of Gondwana

Dolerite is a common rock
type throughout Tasmania. It
is derived from the breakup of
Gondwana.

-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.

-Mid-oceanridgesareformedwhereplatesaremovingapart

-Whenplatesmoveapart,moltenrockrisesupandformsnewseafloor.

-Intheseareas,calledspreadingzones,thenewrockthatformsisolderthefurtheritisfromtheridge

-Thisprovesthattheplateshavebeenmovingapartsteadily foralongtime

Biologicalevidence:

-The fossil record and present day organisms provide evidence thatAustraliawaspartofGondwana

-FossilEvidence:

GlossopterisandGangamopterisarefossilplantsfoundinrocksofthesameageinAustralia,Africa,India,SouthAmerica,AntarcticaandNewZealand
FossilsofmarsupialshavebeenfoundonallthecontinentsthatwerepartofGondwana
Thisisevidencethatthecontinentswereoncejoined

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

ExtantOrganisms:

-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[update] there were approximately 600 extant species and 7,500 extinct species

Nothofagus,orthesouthernbeechtrees,arefoundinforestsofAustralia,NewGuinea,NewZealandandSouthAmerica
Manyplantsandanimalsexistonly wheretheNothofagusstilllive;e.g.aparasiticfungus,amossandbugswhichdependonthemoss
ManygroupsofanimalsinAustraliahavecloserelativesinSouthAmerica,Africa,IndiaandNewZealand,butnotinNorthernAsia,

EuropeorNorthAmerica

Theseanimalsinclude:parrots,ratites(flightlessbirds),marsupialmammals,chelidturtles,somegeckoes,manyfamiliesofearthworms,terrestrialmolluscs,spidersandinsects,andthescorpiongenusCercophonius

-Megafaunaarelargeanimals,suchaselephantsandwhales

-Megafaunaarenottheancestorsofpresentanimals,egkangaroosdidn’tcome

fromgiantkangaroos,rathertheybothevolvedfromacommonancestor.

-Overthelast50kyearsmostoftheworld’smegafaunahavebecomeextinct

-Twotheorieshavebeenputforwardtoexplainthis:

ClimateChange:Megafaunaweremainlysuitedtoglacialconditions.Theirlargebodiesenabledthemtoliveinextremeconditions.InEurasiaandNorthAmerica,whenpermafrostwasreplacedwithforest,themegafaunadiedoutandanimalsmoreadaptedtoforestbegantothrive.InAustralia,thetemperaturechangedfromcold-drytowarm-dry.Asaresult,watersourcesbegantodry up,andmanyanimalslosttheirhabitatanddiedout.

HumanExpansion:Thetimeoftheextinctionofmegafaunamatchesverycloselythepatternofhumanmigrationintotheseareas.Megafaunaarealsolargeandslow,whichmakesthemsusceptibletohunting.InAfrica,humansevolutionoccurredthere,sohuntingincreasedslowly,allowinganimalstoadjust.Thatiswhytherearestillmegafaunathere.However,inplaceswherehumansarrivedasskilledhunters,themostextinctionoccurred.

-Livingfossil(orrelictspecies)areorganismsthathavechangedlittleornotatallsinceancienttimes.

-Australiahasmanyexamplesoflivingfossils,suchas:1)Stromatolites,2)TheWollemiPine,3)Crocodiles,4)Queenslandlungfish,and5)Monotremes.

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 Genyornisvs the emu to name a few.)

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

-Mid-oceanridgesoccurwherecontinentalplatesaremovingapart

-Spreadingzonesarethenewareasoffloorcreatedatridgeswheremoltenrockrisesoutfromthemantleandsolidifies

-TherearespreadingzonesonthesouthernsideoftheIndo-Australianplate,andcollisionzonesonthenorthernside

-ThisimpliesthatAustraliaismovingnorth

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’sPlatypussary, 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.

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 sideduring 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.

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.