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How many major mass extinctions have there been in Earth's history?
Wiki User
∙ 11y ago
There have been at least five mass extinctions in earths history. The Permo-Triassic extinction, about 250 million years ago, was the worst. paleontologists estimate that 70% of land species and 90% of marine species went extinct at that time. Although there are many there are many theories, scientists still do not know the exact cause. The Cretaceous-Teritartiary extinction occured 65 million years ago and killed off dinosaurs.
Wiki User
∙ 11y ago
Wiki User
∙ 11y agoThere have been at least five mass extinctions in earths history. The Permo-Triassic extinction, about 250 million years ago, was the worst. paleontologists estimate that 70% of land species and 90% of marine species went extinct at that time. Although there are many there are many theories, scientists still do not know the exact cause. The Cretaceous-Teritartiary extinction occured 65 million years ago and killed off dinosaurs.
Wiki User
∙ 8y agoThere have been at least five mass extinctions in earths history. The Permo-Triassic extinction, about 250 million years ago, was the worst. paleontologists estimate that 70% of land species and 90% of marine species went extinct at that time. Although there are many there are many theories, scientists still do not know the exact cause. The Cretaceous-Teritartiary extinction occured 65 million years ago and killed off dinosaurs.
Read more: How_many_mass_extinctions_have_there_been
Wiki User
∙ 10y agoThere have been 5 Mass Extinction events in Earth's history.
They are.
1.Cretaceous-Tertiary extinction event (End Cretaceous or K-T extinction): 65.5 Ma at the Cretaceous.Maastrichtian-Paleogene.Dania… transition interval. The K-T event is now called the Cretaceous-Paleogene (or K-Pg) extinction event by many researchers. About 17% of all families, 50% of all genera and 75% of species became extinct. In the seas it reduced the percentage of sessile animals to about 33%. The majority of non-avian dinosaurs became extinct during that time. The boundary event was severe with a significant amount of variability in the rate of extinction between and among different clades. Mammals and birds emerged as dominant land vertebrates in the age of new life.
2.Triassic-Jurassic extinction event (End Triassic): 205 Ma at the Triassic-Jurassic transition. About 23% of all families and 48% of all genera (20% of marine families and 55% of marine genera) went extinct. Most non-dinosaurian archosaurs, most therapsids, and most of the large amphibians were eliminated, leaving dinosaurs with little terrestrial competition. Non-dinosaurian archosaurs continued to dominate aquatic environments, while non-archosaurian diapsids continued to dominate marine environments. The Temnospondyl lineage of large amphibians also survived until the Cretaceous in Australia (e.g., Koolasuchus).
3.Permian-Triassic extinction event (End Permian): 251 Ma at the Permian-Triassic transition. Earth's largest extinction killed 57% of all families and 83% of all genera (53% of marine families, 84% of marine genera, about 96% of all marine species and an estimated 70% of land species) including insects.The evidence of plants is less clear, but new taxa became dominant after the extinction. The "Great Dying" had enormous evolutionary significance: on land, it ended the primacy of mammal-like reptiles. The recovery of vertebrates took 30 million years,but the vacant niches created the opportunity for archosaurs to become ascendant. In the seas, the percentage of animals that were sessile dropped from 67% to 50%. The whole late Permian was a difficult time for at least marine life, even before the "Great Dying".
4.Late Devonian extinction: 360-375 Ma near the Devonian-Carboniferous transition. At the end of the Frasnian Age in the later part(s) of the Devonian Period, a prolonged series of extinctions eliminated about 19% of all families, 50% of all genera and 70% of all species. This extinction event lasted perhaps as long as 20 Ma, and there is evidence for a series of extinction pulses within this period.
5.Ordovician-Silurian extinction event (End Ordovician or O-S): 440-450 Ma at the Ordovician-Silurian transition. Two events occurred that killed off 27% of all families and 57% of all genera. Together they are ranked by many scientists as the second largest of the five major extinctions in Earth's history in terms of percentage of genera that went extinct.
Source(s):http://en.wikipedia.org/wiki/Extinction_…Wiki User
∙ 11y ago5
Kailani Barajas
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