Australian Saltwater fish species Pictures
CONTRARY TO POPULAR BELIEF, there aren't a lot of fish in the sea, researchers say.
Despite covering 70 per cent of the Earth's surface, marine environments contain only 20 per cent of all its species.
In the new study, scientists made the surprising discovery that freshwater rivers and lakes contain more fish species than salty oceans. Yet freshwater environments occupy only two per cent of the Earth's surface. It could be evidence of life re-inventing itself after mass extinctions long ago, the experts believe.
Evolution after mass extinction of fish
The findings suggest that most marine fish alive today are descended from freshwater ancestors, even though life is thought to have first evolved in the oceans.
A marine apocalypse may have been followed by a re-emergence of life in watery environments on land.
A team led by Dr John Wiens, from Stony Brook University in New York, USA, studied the biodiversity of ray-finned fish, which make up 96 per cent of all fish species. The scientists created evolutionary trees based on molecular data and fossils, and a large database of fish habitats.
More fish in lakes, rivers than in the sea
"There are more fish species in freshwater than in saltwater habitats, despite the much greater area and volume of the oceans, " says John. "More remarkably, our results suggest that most marine fish alive today are descended from freshwater ancestors."
"Our results suggest that ancient extinctions in the marine environment may have wiped out the earliest ray-finned fishes living in the oceans, that the oceans were then recolonised from freshwater habitats, and that most marine fish species living today are descended from that recolonisation, " he says. "This pattern of ancient extinction and more recent recolonisation may help explain why the oceans are now so species-poor, even for fish."
The findings are published online in the journal .
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Assur abolished cannibalism2013-02-08 09:04:59 by balladromic
Humans are a predatory species. We are the top predators on this planet. We prey on plants. We prey on animals. We prey on fish, mammals, mollusks, and on the other predators in the seas. Although humans dont generally eat a lot of insects, we prey on insect products like honey and silk, and the shells of beetles that we use for dyes.
We prey on everything including other humans. How widely cannibalism was practiced amongst our ancestors isn't clearly known, but the abolition of cannibalism was one of Assur's legendary deeds. Cannibalism has been universally suppressed so we don't eat other people, but we still prey upon their products, their labor, their lands, and their resources.
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