How the continents were formed
Up until about 250 millions of years ago the world had just one huge super-continent called Pangaea. Animals and plants intermix with one another on this huge single landmass.
About 200 million years ago this super-continent broke up into two continents — Laurasia and Gondwana. When this separation took place monotremes an marsupials were the predominate mammals of the Gondwana region and placental mammals in Laurasia.
Then about 60 million years ago Gondwana broke up into what became South America, Africa, Antarctica, India and Australia.
Australia and Antarctica slowly drifted southwards,far away from all the other continents, and became completed isolated from the rest of the world by vast oceans. The other continents however stayed relatively close to each other and over time collided or joined parts of the old Laurasia landmass. When these landmasses came together monotremes and marsupials were unable to compete with the more advanced placental mammals and became mostly extinct. In Africa and India marsupials became completely extinct. When South America joined North America almost all the marsupials there also vanished, to be replaced by placental mammals.
Australia, meanwhile, drifted in a vast ocean, isolated from the rest of the world. The animals and plants which were originally on the Australian landmass no longer had contact with creatures from other parts of the world and continued to evolve independently. The climate also became drier and more arid. Monotremes and marsupials were more suitable for this new environment and became the dominate animals in Australia.
This separate evolution has resulted in some unusual and odd Australian animals. This is why Australian native animals are so different from those found elsewhere in the world.
Australia's long isolation from the rest of the world has allowed Australian animals to evolve separately from those in other parts of the world, but to fill similar niches in the environment. For example the Echidna is an Australian Anteater. The Tasmanian Tiger (now extinct) was a marsupial wolf. The existence of similar animals in different parts of the world is referred to as "Parallel Evolution".
Monotremes first appeared between 145–99 million years ago and are the oldest type of Australian mammals. Two out of the five known species of monotremes in the world live in Australia. These are the Echidna and Platypus.
Marsupials appeared about 64-65 million years ago and are the second oldest type of mammal found in Australia. They occupy every niche of the Australian habitat and range from the large Red Kangaroo to marsupials of the smaller than a mouse.
Placental Mammals in Australia today are relatively recent arrivals, bats were the first to arrive getting here about 23 million years ago. Rodents arrived about 5-10 million years ago. These animals reached Australia by flying and crossing the seas that separated Australian from Asia when Australia slowly stated drifting closer to Asia making crossings to the continent possible. These placental mammals make up a very small percentage of the total mammalian population. Humans introduced a number of animals. The Dingo was the first of these, coming here about 5000 years ago.
Megapods such as the Mallee fowl, trace their ancestry as far back as Gondwanan time. These birds are stocky birds which look somewhat like chickens. They have small heads and large feet (that's why the name "megapod" meaning big-feet).
Other birds such as Kookaburras are the world's largest kingfishers.
Australian Amphibians and Reptiles Australia has many amphibians and reptiles found nowhere else in the world.
Lizards – There are over 700 species unique to Australia alone.
Snakes – Australia has more poisonous snakes than non-poisonous ones. The Red-bellied Black Snake is one.
Frogs – Four families of native frogs inhabit the continent.
Crocodiles – Australia has two species of crocodile. The Saltwater Crocodile is the world's largest and can grow to 1,000 kilos and is known to attack humans. Fresh water crocodiles are much smaller and do not attack humans.
Turtles – There are 35 species of freshwater turtles.
Six species of sea turtle also visit the coastlines.
|DID YOU KNOW|
|Australia does not have any native land tortoises, monkeys and apes. This is another example of its isolations from other continents.|
Marsupials and Monotremes are Better Suited for the Australian Environment
Originally, while all the continents were joined together, there were primitive mammals of all sorts in Australia.
When Australia broke off from Gondwana and started drifting off to the south, the environment started to get drier and sparser. Monotremes and marsupial mammals were well suited for the new harsher environment than the placental mammals. Then, about 34 million years ago, there was a huge world-wide extinction event, possibly caused by large scale bombardment of the earth by objects from outer space such as meteors. This seems to have affected the placental mammals more than it did other creatures. From then onwards monotremes and marsupial mammals seem to have thrived in Australia and placental mammals slowly became extinct.
It is believed that these animals were better suited for Australia's harsh arid environment because of their lower metabolic rate and less demanding reproductive system.
Marsupials and monotremes became the dominant mammals of Australia.
Marsupials mammals got their
name from the Latin word “marsupium” which means pouch. All
marsupials have an external pouch located on their mother’s abdomen
(tummy) in which they carry their young.
Marsupials differ for other mammals in that they give birth to very small underdeveloped babies who must make a dangerous journey from the mother’s birth canal at the bottom to the pouch located on her abdomen. They do this by crawling up the mother's tummy to the pouch. This is the most dangerous time of a young marsupial's life as these babies could easily fall off and die.
Once safely in the mother’s pouch the baby, called a Joey, attaches itself to a milk teat where it feeds and grows into a baby animal. A baby kangaroo may live in its mothers pouch for as long as 6 months.
Marsupials of Australia, may have originated in modern day China (East Laurasia). They probably arrived in Australia around 50 million years ago via North America, South America and through the Antarctica.
Once Australia separated from the other continents and started to drift southward the marsupials stranded on it didn't have any competition from more placental mammals. Without competition the marsupials diverged into over 140 different species found in Australia today. Some descendants of those original marsupials even almost hopped their way back towards China reaching as far as Indonesia and Papua New Guinea. Unfortunately the original marsupials in other parts of the world couldn't compete with placental mammals and became mostly extinct.
|DID YOU KNOW|
|A few marsupials still survive in other parts of the world. In America these are known as Opossums.|
A monotreme is a primitive mammal that lays eggs like a bird or reptile but feeds its babies milk like a mammal. Monotremes are warm blooded but have a slightly lower metabolic and heart rate than other mammals. This means they need less energy than equivalent sized mammals. Monotremes have fur but no teeth.
There are only two types of monotremes in the world, both are found in Australia. These are the Echidna and the Platypus. Monotremes lays tiny leathery eggs. The babies lick milk from the fur on their mother's abdomen.
|DID YOU KNOW|
|Monotreme means "one hole". This is because these animals have only opening for their anus, urinary and reproductive tracts. This is similar to birds and reptiles.|
Introduced Animals in Australia
Humans deliberately brought various animals into Australia
The first animals to be introduced into Australia was the Dingo a wild Australian dog. It was brought here by sea-farers over 5000 years ago.
Other introduced animals were brought here for agricultural purposes (cattle and sheep), for transportation (camel and horse), for sport (rabbit and fox), for pleasure (myna bird and house sparrow) and for pest control ( Cane Toad). Some of these creatures have been disastrous to the Australian ecology.
Here are a few animals that have been ecological disasters:
|Australia Didn't Have Hoofed Animals and Mice until Europeans Arrived|
Until Europeans came in 1788, there
were no hoofed animals (like horses, cattle, goats, deer etc.) in
Many native animals of Australia are close to extinction
According to the Australian Department of the Environment's Endangered Australian Animals List many Australian native animals are endangered and threatened with extinction. For example; even the cuddly Koala is listed as vulnerable, the Cassowary and Night Parrot are listed as endangered and the Gouldin Finch as critical. Below is a list of endangered native Australian animals.
Many native animals of Australia became extinct since humans arrived
Since the arrival of European settlers in 1776 Australia has lost:
7 of the 700 known species of
19 of the known species of mammals
The Tasmanian Tiger is an example of a recently extinct Australian animal. It was hunted into extinction.
The last Tasmanian Tiger died in captivity in 1927.
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