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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References in periodicals archive ?
Earth has so far gone through five mass extinction events -- scientists are worried we're on course to trigger a sixth -- and the deadliest one happened 252 million years ago at the end of the Permian geologic period.
SchwEngerl argues that the category of animals the study focuses on -- land vertebrates -- is too narrow to back up the claim that a major mass extinction event is already underway.
However, recent faunal studies, especially on conodonts, suggest the extinction event transcends the formational boundaries, and place the Permian-Triassic boundary within the basal or middle part of the Kathwai Member of the Mianwali Formation (see Pakistani-Japanese Research Group,1985; Wardlawand Mei, 1999).
We tend to focus so much on the extinction event, not so much the recovery," Maher said, "but the recovery is also a really important piece that sets the stage for what happens in the next interval of life.
At first glance, they don't appear to record any major fossil changes indicative of a large-scale extinction event, Lucas said.
A primeval volcanic range in western India known as the Deccan Traps, which were once three times larger than France, began its main phase of eruptions roughly 250,000 years before the Cretaceous-Paleogene, or K-Pg, extinction event, the researchers report in the journal Science.
Some corporate leaders have been wondering whether they're facing the same extinction event that hit Borders, Kodak, HMV, Blockbuster and others.
However, it's the impending sixth extinction that has Kolbert and others most concerned, for it is an extinction event totally caused by humans.
Final chapters deal with the great K-T extinction event and a short introduction to the allure of paleontology itself.
It's up to residents of Cyprus to ensure that this Mass Extinction Event occurs now.
The problem is getting worse and we were going to be facing an extinction event of actually losing potentially three or four clubs - not to administration, but to liquidation.