Different patterns of evolution




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2.7 Discuss Darwin’s observations of Australian flora and fauna and relate these to his theory of evolution. P272 BIF

Charles Darwin landed in Sydney in 1836. It was during his visit to Australia, that he collected much of the information that went to forming his theory of natural selection.

Darwin not only observed the uniqueness of the Australia biota such as species of monotremes and marsupials, but he also observed similarities between flora and fauna here in Australia with flora and fauna in other parts of the world that he had visited. For example, he observed the similarities between unrelated organisms, such as marsupials (isolated in Australia) and placentals form other parts of the world. Marsupials and placentals that live in similar environments and have similar ways of life (similar niches) resemble each other structurally and physiologically. This similarity in unrelated species supports Darwin’s theory of evolution.

Different patterns of evolution:



Adaptive radiation:

When many related species evolve from a single common ancestor. This occurs as organisms spread into new habitats and evolve over millions of years, adapting to the environments they inhabit.



Divergent evolution:

This is a consequence of adaptive radiation and relates to the process where 2 or more related species gradually become more different.



Convergent evolution:

When species living in similar environments evolve similarities in appearance. For example, the shark, penguin and dolphin (a fish, bird and mammal) all have similar streamlined body shapes to move through the water easily.



Darwin’s observations of Australian flora and fauna provided him with many examples of:





Using the article http://www.sl.nsw.gov.au/events/exhibitions/2009/darwin/images/2.html, summarise Darwin’s’ visit to Australia.

Sample answer:

Australia provided some important insights for Darwin in the development of his theory of natural selection. Darwin saw a number of platypuses cavorting and Brown shot one.

The platypus behaved very much like a European water-rat and it was adapted to its environment in similar ways. But it was clearly a different species. Would the Creator, mused Darwin, create an entirely different species in the antipodes with similar adaptations?

Why not just place the water-rat in Australia? A similar thought occurred about the potoroo, which acted very much like a rabbit.
Darwin had kept notes on the geology of the areas visited. Back in Sydney, Covington had been busy collecting zoological specimens and Darwin also did some collecting in Sydney.
In Hobart , Darwin climbed Mount Wellington with Syms Covington, which took five and a half hours:

... tree-ferns flourished in an extraordinary manner ...

the foliage of these trees, forming so many most elegant

parasols created a shade approaching to darkness.



(Rattus fuscipes ) captured by Darwin at Albany from Charles Darwin.



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