Extinction is the loss of an organism whether it is a group of organisms or it is an entire species. Throughout the history of the Earth, more than 90 percent of organisms that have lived on Earth have gone extinct  . Some of the causes of extinction include: destruction, overexploitation and pollution. During Earth’s history there have been five mass extinctions. Scientists believe we are currently going through the Sixth Mass Extinction.
- 1 Mass extinctions through history
- 2 Current mass extinction
- 3 See also
- 4 References
- 5 External links
Mass extinctions through history
Throughout the history of the Earth, there have been Five Mass Extinctions that have occurred. Scientists argue that today we are experiencing the Sixth Mass Extinction.
The Ordovician-Silurian Extinction
The second largest of the five mass extinction events that have taken place, the Ordovician-Silurian extinction took place between 447-443 million years ago. At this time, 25 percent of marine families and 60 percent of marine generea were lost because of sea levels dropping, which was caused by the formation of glaciers .
The Devonian Extinction
The Devonian extinction took place about 364 million years ago. The cause of this extinction is unknown. Marine species that thrived in warm water were devastated during this time, which has lead scientists to believe that during this time Earth was experiencing a time of global cooling. What caused the global cooling is unknown; some speculate that meteorite impacts may have played part.
The Permian-Triassic Extinction. The cause of this extinction remains unknown. While no concrete evidence has been found to support ideas, scientists speculate that either an extra-terrestrial impact had occurred during this time or that there was a volcanic eruption that had coated much of the land with lava.
The End Triassic Extinction
About 199 to 214 million years ago, the End Triassic extinction took place. During this time, about 22 percent of marine families, 52 percent of marine genera and an unknown percentage of vertebrate deaths had resulted from massive floods of lava. These volcanoes ranged in the central area of the Atlantic Ocean. The eruption of these volcanoes is thought to have led to deadly levels of global warming and the breaking up of Pangaea .
The Cretaceous-Tertiary ExtinctionThe most famous of the extinctions, the Cretaceous-Tertiary extinction occurred about 65 million years ago and is most notable because of the extinction of dinosaurs during this time. There is much debate about what had caused this extinction. Some scientists believe that there were asteroid impacts located by the Yucatan Peninsula while other scientists argue that this mass extinction was caused by flood-like volcanic eruptions that influenced climate change.
Current mass extinction
Sixth Mass Extinction
Researchers claim that we are currently in the middle of a mass extinction that is happening at a faster rate than the Cretaceous-Tertiary extinction . Animals are going extinct 100 to 10,000 times faster than the ‘normal’ extinction time – this being about 10 to 25 species a year . While scientists are alarmed about the rates in which species are going extinct, the main concern is what is causing these extinctions. Earth has lost about half of its wildlife in the past 40 years which science has come to blame on human actions. Human activity has been rapidly expanding, destroying habitats in order to provide room for roads and cities. The growing human population has caused a large demand of fossil fuels .
Many people question if human activity is really to blame for loss of species. In a study conducted by the University of Maryland’s Department of Geographical Sciences, researchers assessed the potential impact of future land-use scenarios. What researchers found was that impacts from human activity would contribute to global warming and a loss of habitable areas known as ‘biodiversity hotspots’. The loss of these biodiversity hotspots plays a role in extinction of species .
Global warming and extinction. . Because humans dominate the planet, humans are contributing to the change that is taking place on Earth. Ice sheets are melting in Antarctica; Alaska's permafrost is melting causing towns to sink and resulting inhabitants to be relocated. In Greenland, ice sheets are gone which has created climate conditions that are bringing species close to extinction. Mountains without glaciers in Patagonia and the Alps are reducing the ability for these regions to store water that is needed for consumption. All of these habitats are being destructed and are causing a loss of biodiversity. The reason that this extinction is so different than the others that have happened is because human activity is the main cause .
Other closely related articles in this wiki include:
- Mass Extinction, Mass Die-Off Information, Prehistoric Facts -- National Geographic. (n.d.). Retrieved October 14, 2015, from http://science.nationalgeographic.com/science/prehistoric-world/mass-extinction/, Accessed October 29, 2015
- Endangered Species International. (n.d.). Retrieved October 25, 2015, from http://www.endangeredspeciesinternational.org/overview.html, Accessed October 29, 2015
- Wikipedia. Retrieved November 9, 2015, from https://en.wikipedia.org/wiki/Dalmanitidae#/media/File:Dalmanites_limulurus_trilobite_silurian.jpg, Accessed November 9, 2015
- Flickr. Retrieved November 9, 2015, from https://www.flickr.com/photos/arkhangellohim/8547209420, Accessed November 9, 2015
- Ehrlich, P., & Ehrlich. (2015, September 12). How humans cause mass extinctions | Jordan Times. Retrieved September 18, 2015, from http://www.jordantimes.com/opinion/project-syndicate/how-humans-cause-mass- extinctions, Accessed October 29, 2015
- Roberts, A. (2015, Spetember). Study links climate policy to extinction trends. Retrieved September18, 2015, from http://phys.org/news/2015-09-links-climate-policy-extinction-trends.html, Accessed October 29, 2015
- Flickr. Retrieved November 9, 2015, from https://www.flickr.com/photos/tenderliving/3867554898, Accessed November 9, 2015
- Climate change endangering diversity, abundance of marine species - Green - News – Catholic Online. (n.d.). Retrieved October 19, 2015, from http://www.catholic.org/news/green/story.php?id=64747, Accessed October 29, 2015
- WikiMedia. Retrieved November 9, 2015, from https://upload.wikimedia.org/wikipedia/commons/thumb/e/ec/Polar_Bear_2004-11-15.jpg/1280px-Polar_Bear_2004-11-15.jpg, Accessed November 9, 2015
- Chichilnisky, G. (2015, October 13). Avoiding extinction: What next? | BLOUIN BEAT: Science & Health. Retrieved October 19, 2015, from http://blogs.blouinnews.com/blouinbeatsciencehealth/2015/10/13/avoiding-extinction-what-next/, Accessed October 29, 2015
Relevant external links include: