Ecology And Environment

Five Extinctions Mass Extinction Marine Extinction Land Extinction five Major Mass Extinctions



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The Meaning of extinction is the sharp decrease in the diversity and abundance of life. Throughout history there have been numerous extinctions that include many different species of life. Anything can be made extinct, plants, animals and humans alike. All this takes is something to spark the process. This article looks at the five worst extinctions of all time.

The Cretaceous-Tertiary Extinction

This event occurred over 65 million years ago, the event was a large scale mass extinction of both animal and plant species. The event is more commonly known as the K-T extinction, as it is associated with a Geological Signature called the K-T Boundary.

The K-T Boundary is a very fine band of sedimentation only found in certain parts of the world, and it is under these boundaries where Non-Avian Dinosaur fossils are found. Scientists have speculated that these events could have been caused by a massive asteroid impact or a volcanic eruption.

The Triassic-Jurassic Extinction –

This extinction was what separated the Triassic and Jurassic Period. It took place over 199 million years ago, and is one of the largest extinctions known about today. The event caused a mass extinction on both land and in sea, with many species of life completely disappearing.

During this extinction at least half of the species living on earth were wiped out. This is what gave the Dinosaurs the freedom to take the lead as the dominant force during the Jurassic period.

The Permian-Triassic Extinction

This extinction event happened 254 million years ago, and it is more commonly known as the great dying. The event was what created the boundary between the Permian and Triassic periods. It is recorded as earths worst extinction event with over 96% of all marine species destroyed. On top of this 70% of land species were also made extinct, and it was also the only known extinction of all insects.

Again scientists have come to the agreement that it was a multiple impact event caused by asteroids, or a sudden increase in volcanic activity that caused this catastrophic event.

The Late Devonian Extinction

Over 375 Million years ago, this mass extinction wiped out over half of the population of living organisms on the planet. It is not certain as to whether it was two mass extinctions that caused the end of the Devonian era, or if it was a series of smaller extinctions.

By the late Devonian age, the earth had been colonized by plants and insects. A large amount of reefs had been created in the worlds water, so when the extinction occurred, it was mainly marine life that was affected. The cause of the event is also not clear; one theory explains that it was a rise in sea level that could have caused a global cooling.

The Ordovician-Silurian Extinction

This event was the third largest extinction event in the earth's known history, it is more commonly known as Ordovician Extinction. The exact date of the event is not known, but it is thought to have occurred somewhere in-between 440 to 450 million years ago.

At this time all known life was confined to the worlds oceans and over 60% of all known living organisms were made extinct. It is thought that the cause of this mass extinction was a drop in sea level that caused the disruption and elimination the oceans habitats.



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ARTICLE SOURCES AND CITATIONS
  • InfoBoxCallToAction ActionArrowhttp://park.org/Canada/Museum/extinction/cretmass.html
  • InfoBoxCallToAction ActionArrowhttp://palaeo.gly.bris.ac.uk/palaeofiles/triassic/triextict.htm
  • InfoBoxCallToAction ActionArrowhttp://palaeo.gly.bris.ac.uk/palaeofiles/permian/intro.html
  • InfoBoxCallToAction ActionArrowhttp://www.devoniantimes.org/opportunity/massExtinction.html
  • InfoBoxCallToAction ActionArrowhttp://www.bbc.co.uk/nature/extinction_events/Ordovician%E2%80%93Silurian_extinction_event