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St Aloysius College
Evolution of Australian Biota Preliminary Course Research Assignment
Daniel McAdams 8/8/2012
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 Wegners’s theory of continental drift,
as Gondwana slowly drifted away from Laurasia. 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.
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
13.7 Billion years ago
Triassic Period 250-200
million years ago
Changes in the Environment:
Australia’s 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.
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.
Jurassic Period 200-145
million years ago
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.
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.
Cretaceous Period 144-65
million years ago
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.
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
Quaternary Period 2.5million
years ago - Present Day
Opalised Dinosaur Claw Fossil
Steropodon galmani lower jaw bone
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
Australia’s 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 Australia’s past is slightly opened through
the jigsaw to what is the History of Australia.
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
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.
Skeleton of the Megafauna
Diprotodon
Nimbadon Skull,
found at Riversleigh
fossil fields
(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
Australia’s 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 Australia’s environment.
The Riversleigh fossil sight provides the best example of the
evolution of Australia’s vertebra as it shows 100’s 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 fossils recovered from Riversleigh all show us
the variety of Herbivores roaming Australia. Although all these 3
organisms would have died at different time periods, this proves
evolutionary pattern shows that Herbivores were the most
successful in surviving in these arid and desolate environments. This tells us that the evolution of
Australia’s organism were advantageous to herbivorous, as now most of Australia’s species being
herbivorous., it shows the climate and conditions that Australia underwent over thousand s of years
ago. Found inside the fossilised stomachs of the Ekaldata (rat kangaroo) are salt bust, which
indicates the dependency of low nutrient plant life to most organisms. It has been speculated that
animals consumed these dehydrated plants in desperation, as Australia regularly experienced
droughts, which killed off all the luscious and nutritious plant life.
The fossil of the Nimbadon Skulls (Ancient Koala’s) provides 2 pieces of evidence
towards the evolution of Australia. The Nimbadon were considered megafauna, as
they are much bigger and scientifically related to the current Australian Koala, this
shows that in order to survive the Nimbadon had to be smaller to wider its range
of diet and consume less food to survive. In doing this the smaller Nimbadon’s
survived and that’s how the Koala has evolved to the current organism. The
decreasing of size of the koala is also supported by all types of megafauna, as now
their ancestors are much smaller. Also the recovering of the Nimbadon skull
shows the evolution of Australia’s plants. Ancient Koala fossils indicates how its
dietary habits have changed overtime, from eating variety of rainforest plants, to
currently dry eucalypt leaves. This shows the drastic changes over time, as Australia
has continuously become more arid and dry which affected our diversity of plant life.
This fossil sight has contributed to Australia’s evolution as it gives copious amounts
of evidence towards the variety of organism that roamed Australia before human civilization and
shows, as it signifies the link between ancient Australian mammals and current Australian mammals,
and also shows us the vegetation and climate Australia experienced before human record.
Question 3:
Two different Australian examples are provided for species that has (i) evolved and survived
and (ii) bas become extinct
Propose a number of reason for each of two scenarios
(i)
Name: Lyrebird (Menura novaehollandiae)
Distribution: East Coast of Australia & Tasmania
Habitat: Rain Forest throughout Australia
Different Species: Superb Lyrebird, Albert’s Lyrebird
Size: 80-98 centimetres (3rd largest Song Bird)
Diet: Invertebrates
Fossils: Dated back to 15 million years ago
The Australian Lyrebird has been around for millions of years, with fossils of
the creature being dating back to 15 million years ago. Lyrebirds have been able
to survive for all this time due to ideal habitat of the rainforest. Over 50 million
years ago Gondwana was dominated by rainforest, which covered Australia
during its separation of the supercontinent, which was where the Lyrebird was
able to thrive in its natural habitat. But, over time the Rainforest has gradually
decreased in size, due to climate changes from its separation. This caused for
lyrebirds to strictly live on the east coast of Australia and parts of Tasmania,
where all of Australia’s rainforest situate today.
The Lyrebird are native Australian animals and have continued to evolve and survive due to its
unique abilities in warding off predators and attracting females for reproduction. Over time the
Lyrebird has been sought after by predators due to its vulnerability, as they can easily be spotted,
due to its large and magnificent tail feathers. Lyrebirds are known as the best animals of mimicry as
they have a large repertoire of sounds they are able to mimic exactly. Lyrebirds have been spotted
mimicking sounds like other birds, crickets, gun-shots, car alarms, humans talking, chainsaws
(deforestation), camera shutters and most importantly the sounds of their predators. The
Lyrebird’s unique ability of mimicry has grown over time due to natural selection, as the ones that
were able to mimic better were able to survive longer.
There Long Vibrant feathers has also adapted to be able to attract females for reproduction, which
continues the evolution of the lyre bird. Not only does it aid the chance of further variation. The
Lyrebirds feathers are designed lure its prey, so it doesn’t have to hunt. Also its tails are adapted to
ward off predators with its bright and abstract pattern.
The Lyrebird is a highly adapted creature, which overtime has gained variants so it is able to
reproduce offspring that is subjected to needs of Natural Selection.
(ii)
Name: Marsupial Lion (Thylacoleo carnifex)
Distribution: South Australia
Habitat: Australian Plains
Size: 150cm (head to tail)
Diet: Meat
Fossils: Pleistocene-Modern (2 million-40,000 years ago)
The Marsupial Lion was an elite predator with key adaptations that allow it to survive and evolve in
its own environment. It had retractable claws to change purposes from running to hunting, It had
large frontal canine teeth to easily rip and tear up its prey and was incredibly fast so it is easily able
escape its fellow competitors such as the megalania (giant goanna) for food. The Marsupial Lion also
had a wider range of diet compared to most megafauna at the time. The Marsupial lion was adapted
to any possible threat or extinction, so how what caused the extinction of this highly evolved
organism.
Overtime Geologists, Palaeontologists and Scientist have tried to pinpoint the reason for the
extinction, as these highly evolved creatures suddenly disappeared over 40,000 years ago. This topic
has been highly debated and is now narrowed down to 2 main theories to high the extinction of the
Megafauna occurred.
Human Impact:
The impact of humans on the megafauna is currently the widest excepted theory for their
extinction, as humans and megafauna co-existed for about a 5’000 year period. Due to extinctive
behaviour, humans are designed to try and slay the biggest creatures as they reap the largest
reward. Due to primitive knowledge at the time, humans were not able to make sufficient
weapons to hunt these massive creatures, so different measures were taken in hunting the
mega beast. Techniques such as Fire Stick farming was commonly used by indigenous tribes as
they were able to slowly decimate the numbers of megafauna. The Fire Stick Farming had
detrimental effect on our vegetation, killing off most of the diet of the megafauna; this caused
the herbivores to die due to lack of food to maintain their massive diet. Than carnivores such as
Thylacoleo suffered as their main food resource died out as well. Evidence of humans feeding off
animals such as the Thylacoleo is seen in Cuddle Springs as dismembered parts of its bodies and
Flames, are fossilised in this area proves that humans may have had an impact on the
Megafauna’s survival. Other examples of human impact on mega fauna, was the hunting off
their young offspring. Due to the sheer size and abilities of megafauna such as the Thylacoleo
humans hunted down and killed their babies as they were easily vulnerable to predators. In
Naracoote South Australia, several fossilised infant Thylacoleos’s and other megafauna has been
found injured in similar areas of the skeleton. The Humans impact on the megafauna such as the
Thylacoleo has been backed up by scientific evidence that due to its brief period of co-existence
and history shows a strong reason to the extinction of these highly evolved creatures.
The Last Ice Age
The Last Ice age has been noted to be a reason for the extinction of megafauna, in not just in
Australia but across most continents. When an ice age occurs, much of the earth’s water is
trapped in poles, allowing the sea level to drop significantly. The sea level lowering has a
significant effect on our environment making it colder and drier, as rainfall rapidly decreases.
The centre of Australia being dry already, created a drier and arid landscape as much vegetation
and organisms started to die out. This caused the larger animals to die out first (megafauna) and
the smaller animals to sustain their diet and survive. Megafauna could have died out due to the
ice age, as they are so big they have larger dietary needs and a very narrow diet. This means that
they needed a lot of food to survive, but they had a smaller range of food they were able to
digest. Although the thylacoleo was adapted to this problems, there problem was not access of
food, it was the reliance on other organism to survive so they were able to feed on them to
sustain their own dietary needs. Although this theory is very highly regarded as the most
scientific reason for the extinction but, through fossil examinations there are speculators against
this theory. Due to the sheer size of these creatures, they had very large food reserves which
allowed them to survive for long periods of time, surviving on previous meals and the limited
food supply they had left, which is estimated to be just as long as an Ice Age. Although the
controversy on this theory, due to Scientifics and examination of the megafauna the, Ice Age is a
very viable reason to the extinction of the megafauna.
Nectophrynoides asperginis,
Kihansi spray toad. Africa’s most
endangered Frog
Question 4:
Provide one example of a current effort to monitor biodiversity
Describe how this effort Is made
Explain the need to maintain biodiversity
The Amphibians specialist group are monitoring the conditions of frog’s world wide as an effort to
monitor Frog biodiversity. The ASG conserve the biologically values of frogs by preserving the
habitats of frogs worldwide, so they are able to repopulate after a mass extinction. It is estimated
that one third of the world’s frog population is on the brink of extinction, due to the impurities of
our ecosystems. By conserving and protecting these frogs environment we are able to monitor and
see the state our ecosystem is in, without fear of the extinction of the world’s frogs.
During the 20th century scientist has become alarmed at
the decline of amphibian populations, as they noticed a
widespread of the death of frogs throughout the world.
Many people speculated an essence of coincidence of all
the deaths, but scientists were able to provide link
between the copious numbers of amphibious related
deaths. As Frogs breathe through their skin they are very
subjected towards impurities and toxins in our atmosphere,
and as our environment deteriorates so does the frogs, as
they are heavily affected by even the slightest change in
our ecosystem. So scientist now uses frogs as an indicator
towards the health of our own ecosystem. This is a common
example of biodiversity as they are monitoring the death of frogs
towards scientific and environment purposes. Although they are
monitoring the deaths of frogs they are no way inflicting or aiding
the deaths, for the method to be monitoring biodiversity they have
to allow there research to be purely natural, or else finding s are illegitimate and invalid. By first
conserving and protecting these frogs, are able to allow the frog species to reach population levels
that our suitable for survival and natural repopulation, from there they are able to monitor deaths
and locations which lets us know the current state of our own environment. This method of
Biodiversity is very successful as it is the best indicator of the health of our ecosystem and due to the
upheaval of frog species we are able to see the advantages of biodiversity in our society.
Biodiversity is the variety of species of all organisms inside an environment. The diversity of animal
and plant species in an environment is very important to a scientist, as they need a large variety of
species to continue scientific research for the own reasons. Scientist constant exploit and use
animals plants, as they only keep them around for their own gain. Without a wide diversity of
species in the world this would put them out of a business as they are not able to continue research
without the specimen. Although Biodiversity is not all for the wrong reasons, most importantly the
core reasons for biodiversity is to allow the potential for evolution species so that they are able to
strive in this very dangerous environment. Maintain biodiversity is very important as it allows the
benefits to both the species, as it allows it to evolve and hence survive, and also to use humans, as it
benefits us with scientific research and varied resource of scientific exploitation.
Bibliography
1. M.H. Monroe, 2010, Australia: The Land Where Time Began
Viewed: 31/07/2012
<http://austhrutime.com/australia_drifting_changes.htm>
2. N/A (Author), 2012, Preserving a record of Evolution in Australia
Viewed: 2/08/2012
<http://www.australianwildlife.com.au/riversleigh.htm>
3. Anathony Grayling, 2008, Amazing Vocals Skills of the Lyrebird (evolutionistrue.com)
Viewed: 2/08/2012
Online Article
4. Selina Haefina, 2012, Australia once had 70kg, tree-dwelling, wombat-like marsupials, (Cosmos Magazine)
Viewed: 2/08/2012
Online Article
5. Australian Museum, 2012, Fossils in Lightening Ridge NSW,
Viewed: 2/08/2012
<http://australianmuseum.net.au/Lightning-Ridge>
6. N/A (author), 2003, Dinosaurs and Plants
Viewed: 3/08/2012
<http://www.enchantedlearning.com/subjects/dinosaurs/plants/>