Abiogenesis & Evolution

No safe ground for life to stand on during world's largest mass extinction

Imperial College London - No safe ground for life to stand on during world's largest mass extinction: "Many scientists had previously thought that an asteroid hitting the earth or a deep-sea methane release had caused the extinction, which obliterated more than two-thirds of reptile and amphibian families.

However, analysis of a unique set of molecules found in rocks taken from the Dolomites in Italy has enabled scientists to build up a picture of what actually happened. The molecules are the remains of polysaccharides, large sugar-based structures common in plants and soil, and they tell the story of the extinction.

The molecules date from the same time as a major volcanic eruption that caused the greatest ever outpouring of basalt lava over vast swathes of land in present day Siberia.

The researchers believe that the volcanic gases from the eruption, which would have depleted earth's protective ozone layer and acidified the land and sea, killed rooted vegetation. This meant that soil was no longer retained and it washed into the surrounding oceans.

The chemistry of the rocks reveals that although the sugar molecules were found in marine sediments, they derived from land, supporting the theory that massive soil erosion caused them to end up in the sea.

Soil materials in the oceans would have blocked out light and soaked up oxygen. Analysis of rock chemistry suggests that after the soil crisis on land, the marine ecosystem succumbed to the stresses of environmental change and oceanic life faltered, completing a global catastrophe."

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Extinction Events

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ODPTC 5 Biggest Extinction Events

Science & Technology at Scientific American.com: The Woodstock of Evolution -- The World Summit on Evolution, held in the Galapagos Islands, revealed a science rich in history and tradition, data and theory, as well as controversy and debate: "Interestingly, despite the impact of the five biggest mass extinctions (Ordovician 439 Ma, Devonian 367 Ma, Permian 245 Ma, Triassic 208 Ma, Cretaceous 65 Ma), many organism groups passed through all of these extinction episodes safely, such as the cockroach. 'What is amazing is not only the extent of loss, but how fast life bounces back,' Fortey concluded."

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Importance of Mass Extinction Events

The Woodstock of Evolution -- The World Summit on Evolution (ScientificAmerican.com): Richard Fortey from the British Museum of Natural History discussed the evidence of evolution in the Phanerozoic (from 542 Ma, million years ago, till the present). Fortey emphasizing the importance of mass extinction events in resetting the direction of evolution, the importance of evolutionary arms races in driving morphological innovation, the relationship of climate change and changing geography to evolutionary change, and the extent to which evolution can be described as directional. With half a billion years of a solid fossil record, Fortey said we can track the evolutionary periods of creativity and crises.

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