Extinction Of Species
A known species has gone extinct if no member of the species is found anywhere on Earth. This is known as biological extinction and is irreversible.
- Before a species goes biologically extinct, it goes through two other stages:
LOCAL EXTINCTION
- Species is no longer found in the area it once inhabited, though it is present elsewhere in the world.
ECOLOGICAL EXTINCTION
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So few members of the species are left that it can no longer play its normal ecological role in the community.
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Background Extinction is a process of natural and low-level extinction that goes on continuously due to changes in the environmental conditions; such changes may be small or big, gradual or sudden. When such changes occur, the local species must adapt itself, move to a more favorable area or become extinct.
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The background extinction has always been happening and biologists say that 99.9% of all species that ever lived are extinct.
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The rate of background extinction has been generally uniform over long geological periods. At some points in time, however, mass extinctions have occurred on earth.
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A mass extinction is a global, catastrophic event with more than 65% of all species becoming extinct.
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There have been 5 mass extinctions over the past 500 million years and in each case there was a huge loss of biodiversity.
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Both environmental and biological factors have led to mass extinctions. The suggested causes include global cooling, falling sea levels, predation and competition.
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Our planet is now in the midst of its sixth mass extinction of plants and animals — the sixth wave of extinctions in the past half-billion years.
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We’re currently experiencing the worst spate of species die-offs since the loss of the dinosaurs 65 million years ago. Although extinction is a natural phenomenon, it occurs at a natural “background” rate of about one to five species per year. Scientists estimate we’re now losing species at up to 1,000 times the background rate, with literally dozens going extinct every day.