Dot point help

[Danoz The Great]

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Hello the many*cough* EES citizens out there, I have an assessment task due on the 4th. It uses two dot points.

"Explain, using at least 2 hypotheses, the recent extinctions of the marsupial, bird, and reptile megafauna in Australia as an example of smaller extinctions involving several large species"
and
"Compare these smaller extinction events with widespread 'catastrophic' events in which entire ecosystems collapse with the extinction of many entire classes and orders".



I know that em_516 got help with the latter dot point before in the one and only pervious thread in here. But I need to link the two dot points together.

So far, I've had loads of trouble finding information. I've found stuff on the KT explosion, but no megafauna that died in that perticular time period.


Any help would be much appreciated!!!

[Cape]

Explain the recent extinction of the marsupial bird and reptile megafauna in australia, as an example of smaler extinction events involving several large species:

The Australian megafauna consisted of land animals weighing more than 100kg. All these mammals; reptiles and flightless birds had become extinct by about 30000 years ago, a relatively short time after the first human settlers arrived. Carbon 14 dating has given a date of extinction of 50000 years. A number of ideas have been proposed for the extinction of australian megafauna:
*Aboriginal use of fire altered and reduced the ecosystem on which the megafauna depended.
*They were hunted to extinction by humans. This is the so-called blitzkrieg hypothesis, which suggests that these animals might have had no fear of humans or that they might have been too slow to escape human hunters.
*At the end of the last glaciation, 18000 years ago organisms could not adapt to the shift from cold, dry to warm, dry conditions.
*Australia is a low relief continent and any changes to soils through fire and drought will alter water retention characteristics as well as dry out inland lakes and rivers. Any change in the food chain has profound consequences throughout the ecosystem.

Compare these smaller extinction events with widespread 'catastrophic' events in which entire ecosystems collapse with the extinction of many entire classes and orders:
The five mass extinction occurred:
*Late cretaceous - 60% of species
*Late triassic - 75% of species
*Late Devonian - 80% of species
*Late ordovician - 85% of species
*Late permian - 95% of species.
Similarities:
- Palaeontologists have not been able to agree entirely on what caused the extinctions.
-Associated with different climatics regime and a different pattern of climate change and consequent habitat change.
Differences:
- Mass extinctions wipe out more than 30% of land and marine life, which smaller extinctions wipe out species from a particular area.
- Mass extinctions occur in a short time, while smaller extinctions are gradual.

Hope it helps

[Danoz The Great]

Thanks heaps Cape!

[Cape]

No probs. If your stuck on anything else just post it up and I'll try and help. Cause I'm constantly going through my ees work for uni cause I'm doing an ees subject at uni.

[dawso]

yeah, for more information, search for sites on riversleigh, thats the fossil site in northern qld that has a heap of megafauna fossils in it, from memory, there is one perfect site that is the first response in anzwers, lol, but ill let u look it up cause i gotta go study for my own half yearlies....

[Danoz The Great]

Cool. Thanks for that

[em_516]

pm me if you're really stuck and no one else has replied..it seems i got to the thread a little late..sorry