From a study of the history of life on earth through fossil records, we learn that large-scale loss of species like the one we are currently witnessing have also happened earlier, even before humans appeared on the scene. During the long period (> 3 billion years) since the origin and diversification of life on earth there were five episodes of mass extinction of species. How is the 'Sixth Extinction' presently in progress different from the previous episodes? The difference is in the rates; the current species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and our activities are responsible for the faster rates. Ecologists warn that if the present trends continue, nearly half of all the species on earth might be wiped out within the next 100 years.
The Sixth Extinction differs from previous mass extinctions in the rate at which species are disappearing—100 to 1,000 times faster than pre-human times due to human activities. Students commonly confuse this with earlier extinctions by thinking the number of species lost is what makes it unique, rather than the speed of extinction. The key point NTA tests is that anthropogenic (human-caused) activities are directly responsible for the accelerated extinction rate, not natural causes. Remember: the distinction is about rate of extinction, not total numbers, and human activity is the driving factor that separates the Sixth Extinction from all previous mass extinction events.
Since the origin and diversification of life on Earth, there have been five episodes of mass extinction. How is the sixth extinction, in progress, different from the previous episodes?
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