Earth's major plates, modern

6.          Today, many scientists think the evidence indicates a sixth mass extinction is under way. The blame for this one, perhaps the fastest in Earth's history, falls firmly on the shoulders of humans. By the year 2100, human activities such as pollution, land clearing, and over fishing may have driven more than half of the world's marine and land species to extinction.

 

65 million years ago, Cretaceous

5.         Cretaceous–Paleogene extinction event (End Cretaceous, K-T extinction, or K-Pg extinction): 65.5 Ma at theCretaceous.Maastrichtian-Paleogene.Danian transition interval.[5] The K–T event is now officially called the Cretaceous–Paleogene (or K–Pg) extinction event in place of Cretaceous-Tertiary. About 17% of all families, 50% of all genera[6] and 75% of all species became extinct.[7] In the seas it reduced the percentage of sessile animals to about 33%. The majority of non-avian dinosaurs became extinct during that time.[8] The boundary event was severe with a significant amount of variability in the rate of extinction between and among different cladesMammals andbirds emerged as dominant land vertebrates in the age of new life.

 

135 million years ago Jurassic, 

 

200 milion years ago, Triassic, 

4.         Triassic–Jurassic extinction event (End Triassic): 200 Ma at the Triassic-Jurassic transition. About 23% of all families, 48% of all genera (20% of marine families and 55% of marine genera) and 70% to 75% of all species went extinct.[6] 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 Temnospondyllineage of large amphibians also survived until the Cretaceous in Australia (e.g., Koolasuchus).

 

225 million years ago, Permian, Earth's largest extinction

3.          Permian–Triassic extinction event (End Permian): 251 Ma at the Permian-Triassic transition. Earth's largest extinction killed 57% of all families, 83% of all genera and 90% to 96% of all species.[6] (53% of marine families, 84% of marine genera, about 96% of all marine species and an estimated 70% of land species, including insects[9]The evidence of plants is less clear, but new taxa became dominant after the extinction.[10] 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,[11] 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".

 

2.          Late Devonian extinction: 375–360 Ma near the Devonian-Carboniferous transition. At the end of the Frasnian Agein the later part(s) of the Devonian Period, a prolonged series of extinctions eliminated about 19% of all families, 50% of all genera[6] and 70% of all species.[citation needed] This extinction event lasted perhaps as long as 20 Ma, and there is evidence for a series of extinction pulses within this period.

 

450-440 Ma. Ordovician-Silurian Extinction. Second largest extinction

1.         Ordovician–Silurian extinction event (End Ordovician or O-S): 450–440 Ma at the Ordovician-Silurian transition. Two events occurred that killed off 27% of all families, 57% of all genera and 60% to 70% of all species.[6] 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.

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Replies to This Discussion

Enjoyed that Joan - very educational.

It would be a good idea to add the probable cause of the extinction to this.  Those causes are very interesting.

Luara, that is a good idea. Thanks! That will be a fun project. 

Thanks for the summary. Over half of Earth's species extinct by 2100 - sounds about right for business as usual.

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