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Ordovician-Silurian Extinction

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Approximately 66 million years ago, the first, and most recent extinction event of ‘the Big Five’ took place- the Cretaceous-Paleogene (K-Pg) Extinction, also known as the Cretaceous-Tertiary (K-T) Extinction. While this event is known primarily for its involvement in the extinction of dinosaurs, it also had quite the effect on a large majority of other plant and animal species, to the point where no tetrapod (four-legged vertebrae) weighing above 25 kilograms survived. The original trigger is believed to have been a massive comet or an asteroid impact, estimated at about ten kilometers in size, but other theories suggest that volcanic eruptions, climate change, or sea level change played a role was well. Either way, there were catastrophic…show more content…
It was the second largest of the five major events, and its dates correlate with the start and the end of the most severe ice age of the Phanerozoic Era. Almost all of the major taxonomic groups were affected during this event, but marine communities took the brunt of the extinctions, wiping out one third of all brachiopod and bryozoan families (aquatic invertebrates), and groups of conodonts (eels), trilobites, and graptolites. There are several suspected causes for the mass extinction, with a heavy focus on climate change and glaciation driven cooling, in addition to the minor contribution of the elimination of several habitats from sea-level fall, and some volcanism. The specific statistics show that 27% of all families, 57% of all genera and 60% to 70% of all species became extinct during this…show more content…
However, recent speculation has lead many scientists to believe that we are currently in a mass extinction period, one that could not only be bigger than any previous extinction event, but that actually points a finger towards humans as being the main cause. This extinction event is known as The Holocene Extinction, the Sixth Extinction or the Anthropocene Extinction, and whether we like it or not, there is definitely a considerable amount of evidence to prove that this mass extinction is happening, and that the cause is largely due to human activity. Specific research indicates that deforestation, hunting, pollution, the introduction of non-native species into various regions, destruction of vast tracts of land, river systems, and habitats, and the widespread transmission of infectious diseases spread through livestock and crops are having the most drastic effects on most species. Current studies even show that the present rate of extinction may be up to 140,000 species per year, making it the greatest loss of biodiversity since the Cretaceous–Paleogene Extinction. Edward Osborne Wilson, an American biologist, researcher, theorist, naturalist and author, calculated that if the current rate of human disruption of the biosphere continues, one-half of
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