mass extinction


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mass extinction

n.
The extinction of a large number of species within a relatively short period of time, as between the Cretaceous and Tertiary Periods when three-quarters of all species on earth, including most dinosaurs, became extinct.

mass extinction

A massive (>15%) and relatively abrupt reduction in the diversity and number of microbes, algae, fungi, protists, plants and animals on the planet.

Seven mass extinctions have have been identified according to the fossil record; the largest occurred in the Early Cambrian period (±500 million years ago) when there was ± 68% reduction in taxa.

mass extinction

any of the several episodes which have occurred throughout the evolution of biological organisms where there has been a period when organisms have disappeared from the fossil record relatively quickly and at a much greater rate than the background extinction. Such mass extinctions may well have resulted from several causes. The demise of the DINOSAURS at the end of the Cretacious (K/T boundary) was probably brought about by the earth being struck by an asteroid, the subsequent effects leading to the extinction of several groups of organisms. Climatic changes (some possibly caused by asteroid/comet impacts) also probably initiated some mass extinctions.
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The probability of mass extinction occurring after an asteroid that could hit a random location on the Earth's surface was approximately 13 percent when the Chicxulub-scale asteroid hit the Earth.
As scientists have noted, a mass extinction was achieved when the natural carbon cycle failed to compensate for such discarding.
But is the claim that we are undergoing mass extinction event to rank alongside the five major wipeouts of the last half-billion years justifiable?
The preferential removal of the largest animals from the modern oceans, unprecedented in the history of animal life, may disrupt ecosystems for millions of years even at levels of taxonomic loss far below those of previous mass extinctions," the authors wrote.
Scientists have long suspected that an ocean acidification event occurred during the greatest mass extinction of all time, but direct evidence has been lacking until now," said Matthew Clarkson, of the University of Edinburgh's School of GeoSciences, who coordinated the study.
Millions of years from now, the planet will be inhabited only by the descendants of those creatures that survive this new mass extinction.
It probably indicates a significant mass extinction of the conodont fauna in the middle Telychian.
Alien forces aren't always at play in mass extinctions.
Lead author Yadong Sun, who is based in Leeds while completing a joint PhD in geology, says: "Global warming has long been linked to the end-Permian mass extinction, but this study is the first to show extreme temperatures kept life from re-starting in Equatorial latitudes for millions of years.
FOR five million years after the worst mass extinction in Earth history, much of the planet was simply too hot for anything to survive, scientists have learned.
But thanks to overhunting, deforestation, pollution, the spread of non-native species and now climate change, we are likely in the midst of the sixth mass extinction in the geologic history of the world.