Evolution Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! === Extinction === {{Further|Extinction}} [[File:Palais de la Decouverte Tyrannosaurus rex p1050042.jpg|thumb|left|''[[Tyrannosaurus rex]]''. Non-[[bird|avian]] dinosaurs died out in the [[Cretaceous–Paleogene extinction event]] at the end of the [[Cretaceous]] period.]] Extinction is the disappearance of an entire species. Extinction is not an unusual event, as species regularly appear through speciation and disappear through extinction.<ref>{{cite journal |last1=Benton |first1=Michael J. |author-link=Michael Benton |date=7 April 1995 |title=Diversification and extinction in the history of life |url=https://archive.org/details/sim_science_1995-04-07_268_5207/page/52 |journal=Science |volume=268 |issue=5207 |pages=52–58 |bibcode=1995Sci...268...52B |doi=10.1126/science.7701342 |issn=0036-8075 |pmid=7701342}}</ref> Nearly all animal and plant species that have lived on Earth are now extinct,<ref>{{cite journal |last=Raup |first=David M. |s2cid=23012011 |author-link=David M. Raup |date=28 March 1986 |title=Biological extinction in Earth history |journal=Science |volume=231 |issue=4745 |pages=1528–1533 |bibcode=1986Sci...231.1528R |doi=10.1126/science.11542058 |pmid=11542058}}</ref> and extinction appears to be the ultimate fate of all species.<ref>{{cite journal |last1=Avise |first1=John C. |last2=Hubbell |first2=Stephen P. |author-link2=Stephen P. Hubbell |last3=Ayala |first3=Francisco J. |date=12 August 2008 |title=In the light of evolution II: Biodiversity and extinction |journal=PNAS |volume=105 |issue=Suppl. 1 |pages=11453–11457 |bibcode=2008PNAS..10511453A |doi=10.1073/pnas.0802504105 |pmc=2556414 |pmid=18695213|doi-access=free }}</ref> These extinctions have happened continuously throughout the history of life, although the rate of extinction spikes in occasional mass [[extinction event]]s.<ref name="Raup_1994">{{cite journal |last=Raup |first=David M. |date=19 July 1994 |title=The role of extinction in evolution |journal=PNAS |volume=91 |issue=15 |pages=6758–6763 |bibcode=1994PNAS...91.6758R |doi=10.1073/pnas.91.15.6758 |pmc=44280 |pmid=8041694|doi-access=free }}</ref> The [[Cretaceous–Paleogene extinction event]], during which the non-avian dinosaurs became extinct, is the most well-known, but the earlier [[Permian–Triassic extinction event]] was even more severe, with approximately 96% of all marine species driven to extinction.<ref name="Raup_1994" /> The [[Holocene extinction|Holocene extinction event]] is an ongoing mass extinction associated with humanity's expansion across the globe over the past few thousand years. Present-day extinction rates are 100–1000 times greater than the background rate and up to 30% of current species may be extinct by the mid 21st century.<ref>{{cite journal |last1=Novacek |first1=Michael J. |last2=Cleland |first2=Elsa E. |date=8 May 2001 |title=The current biodiversity extinction event: scenarios for mitigation and recovery |doi=10.1073/pnas.091093698 |journal=PNAS |volume=98 |issue=10 |pages=5466–5470 |bibcode=2001PNAS...98.5466N |issn=0027-8424 |pmc=33235 |pmid=11344295|doi-access=free }}</ref> Human activities are now the primary cause of the ongoing extinction event;<ref>{{cite journal |last1=Pimm |first1=Stuart |author-link1=Stuart Pimm |last2=Raven |first2=Peter |author-link2=Peter H. Raven |last3=Peterson |first3=Alan |last4=Şekercioğlu |first4=Çağan H. |last5=Ehrlich |first5=Paul R. |author-link5=Paul R. Ehrlich |date=18 July 2006 |title=Human impacts on the rates of recent, present and future bird extinctions |journal=PNAS |volume=103 |issue=29 |pages=10941–10946 |bibcode=2006PNAS..10310941P |doi=10.1073/pnas.0604181103 |issn=0027-8424 |pmc=1544153 |pmid=16829570 |display-authors=3|doi-access=free }}</ref><ref>{{cite journal |last1=Barnosky |first1=Anthony D. |author-link1=Anthony David Barnosky|last2=Koch |first2=Paul L. |last3=Feranec |first3=Robert S. |last4=Wing |first4=Scott L. |last5=Shabel |first5=Alan B. |date=1 October 2004 |title=Assessing the Causes of Late Pleistocene Extinctions on the Continents |journal=Science |volume=306 |issue=5693 |pages=70–75 |bibcode=2004Sci...306...70B |doi=10.1126/science.1101476 |issn=0036-8075 |pmid=15459379 |display-authors=3|citeseerx=10.1.1.574.332|s2cid=36156087 }}</ref> [[global warming]] may further accelerate it in the future.<ref>{{cite journal |last1=Lewis |first1=Owen T. |date=29 January 2006 |title=Climate change, species–area curves and the extinction crisis |journal=Philosophical Transactions of the Royal Society B |volume=361 |issue=1465 |pages=163–171 |doi=10.1098/rstb.2005.1712 |issn=0962-8436 |pmc=1831839 |pmid=16553315}}</ref> Despite the estimated extinction of more than 99% of all species that ever lived on Earth,<ref name="StearnsStearns1999">{{harvnb|Stearns|Stearns|1999|p=[https://books.google.com/books?id=0BHeC-tXIB4C&q=99%20percent X]}}</ref><ref name="NYT-20141108-MJN" /> about 1 trillion species are estimated to be on Earth currently with only one-thousandth of 1% described.<ref name="NSF-2016002">{{cite web |url=https://www.nsf.gov/news/news_summ.jsp?cntn_id=138446 |title=Researchers find that Earth may be home to 1 trillion species |author=<!--Not stated--> |date=2 May 2016 |website=[[National Science Foundation]] |location=Arlington County, Virginia |access-date=6 May 2016 |url-status=live |archive-url=https://web.archive.org/web/20160504111108/https://www.nsf.gov/news/news_summ.jsp?cntn_id=138446 |archive-date=4 May 2016}}</ref> The role of extinction in evolution is not very well understood and may depend on which type of extinction is considered.<ref name="Raup_1994" /> The causes of the continuous "low-level" extinction events, which form the majority of extinctions, may be the result of competition between species for limited resources (the [[competitive exclusion principle]]).<ref name="Kutschera" /> If one species can out-compete another, this could produce species selection, with the fitter species surviving and the other species being driven to extinction.<ref name="Gould" /> The intermittent mass extinctions are also important, but instead of acting as a selective force, they drastically reduce diversity in a nonspecific manner and promote bursts of rapid evolution and speciation in survivors.<ref>{{cite journal |last=Jablonski |first=David |date=8 May 2001 |title=Lessons from the past: Evolutionary impacts of mass extinctions |journal=PNAS |volume=98 |issue=10 |pages=5393–5398 |bibcode=2001PNAS...98.5393J |doi=10.1073/pnas.101092598 |pmc=33224 |pmid=11344284 |doi-access=free }}</ref> {{Clear}} Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. 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