Life 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! == Development == {{align|right|{{Life timeline}}}} === Origin of life === {{Main|Abiogenesis}} The [[age of Earth]] is about 4.54 [[Bya|billion years]].<ref>{{cite journal |last=Dalrymple |first=G. Brent |title=The age of the Earth in the twentieth century: a problem (mostly) solved |journal=Special Publications, Geological Society of London |year=2001 |volume=190 |issue=1 |pages=205–221 |doi=10.1144/GSL.SP.2001.190.01.14 |bibcode=2001GSLSP.190..205D|s2cid=130092094 }}</ref> Life on Earth has existed for at least 3.5 billion years,<ref name="PNAS-20151014-pdf">{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnike |first2=Patrick |last3=Harrison |first3=T. Mark |last4=Mao |first4=Wendy L. |date=19 October 2015 |title=Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon |url=http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf |journal=PNAS |doi=10.1073/pnas.1517557112 |pmid=26483481 |pmc=4664351 |volume=112 |issue=47 |pages=14518–14521 |bibcode=2015PNAS..11214518B |url-status=live |archive-url=https://web.archive.org/web/20151106021508/http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf |archive-date=6 November 2015 |doi-access=free }}</ref><ref>{{Cite journal |title=Fossil evidence of Archaean life |journal=Philos. Trans. R. Soc. Lond. B Biol. Sci. |volume=361 |issue=1470 |pmc=1578735|doi=10.1098/rstb.2006.1834 |pmid=16754604 |date=June 2006 |pages=869–885 | last1 = Schopf | first1 = J.W.}}</ref><ref name="RavenJohnson2002">{{cite book |first1=Peter |last1=Hamilton Raven |first2=George |last2=Brooks Johnson |title=Biology |url=https://archive.org/details/biologyrave00rave |url-access=registration |date=2002 |publisher=McGraw-Hill Education |isbn=978-0-07-112261-0 |page=[https://archive.org/details/biologyrave00rave/page/68 68] |access-date=7 July 2013 }}</ref><ref>{{cite book |first1=Clare |last1=Milsom |first2=Sue |last2=Rigby |author2-link=Sue Rigby |title=Fossils at a Glance |edition=2nd |publisher=John Wiley & Sons |date=2009 |isbn=978-1-4051-9336-8 |page=134 |url=https://books.google.com/books?id=OdrCdxr7QdgC&pg=PA134 |access-date=10 August 2023 |archive-date=13 April 2023 |archive-url=https://web.archive.org/web/20230413194758/https://books.google.com/books?id=OdrCdxr7QdgC&pg=PA134 |url-status=live }}</ref> with the oldest physical [[Trace fossil|traces]] of life dating back 3.7 billion years.<ref name="NG-20131208">{{cite journal |first1=Yoko |last1=Ohtomo |first2=Takeshi |last2=Kakegawa |first3=Akizumi |last3=Ishida |first4=Toshiro |last4=Nagase |first5=Minik T. |last5=Rosing |title=Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks |journal=[[Nature Geoscience]] |doi=10.1038/ngeo2025 |date=8 December 2013 |volume=7 |issue=1 |pages=25–28 |bibcode=2014NatGe...7...25O}}</ref><ref name="AST-20131108">{{cite journal |last1=Noffke |first1=Nora |author-link=Nora Noffke |last2=Christian |first2=Daniel |last3=Wacey |first3=David |last4=Hazen |first4=Robert M. |title=Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia |date=8 November 2013 |journal=[[Astrobiology (journal)|Astrobiology]] |volume=13 |issue=12 |pages=1103–1124 |doi=10.1089/ast.2013.1030 |bibcode=2013AsBio..13.1103N |pmid=24205812 |pmc=3870916}}</ref> Estimates from molecular clocks, as summarized in the [[TimeTree]] public database, place the origin of life around 4.0 billion years ago.<ref>{{cite book |last=Hedges |first=S. B. Hedges |chapter=Life |pages=89–98 |title=The Timetree of Life |editor1=S. B. Hedges |editor2=S. Kumar |publisher=Oxford University Press |year=2009 |isbn=978-0-1995-3503-3}}</ref> Hypotheses on the origin of life attempt to explain the formation of a [[universal common ancestor]] from simple [[organic molecule]]s via pre-cellular life to [[protocell]]s and metabolism.<ref>{{cite web |url=http://phoenix.lpl.arizona.edu/mars145.php |title=Habitability and Biology: What are the Properties of Life? |access-date=6 June 2013 |website=Phoenix Mars Mission |publisher=The University of Arizona |url-status=live |archive-url=https://web.archive.org/web/20140417155949/http://phoenix.lpl.arizona.edu/mars145.php |archive-date=17 April 2014 }}</ref> In 2016, a set of 355 [[gene]]s from the [[last universal common ancestor]] was tentatively identified.<ref name="NYT-20160725">{{cite news |last=Wade |first=Nicholas |author-link=Nicholas Wade |title=Meet Luca, the Ancestor of All Living Things |url=https://www.nytimes.com/2016/07/26/science/last-universal-ancestor.html |date=25 July 2016 |work=[[The New York Times]] |access-date=25 July 2016 |url-status=live |archive-url=https://web.archive.org/web/20160728053822/http://www.nytimes.com/2016/07/26/science/last-universal-ancestor.html |archive-date=28 July 2016 }}</ref> The biosphere is postulated to have developed, from the origin of life onwards, at least some 3.5 billion years ago.<ref name="Campbell 2006">{{cite book |last=Campbell |first=Neil A. |author2=Brad Williamson |author3=Robin J. Heyden |title=Biology: Exploring Life |publisher=Pearson Prentice Hall |year=2006 |location=Boston, Massachusetts |url=http://www.phschool.com/el_marketing.html |isbn=978-0-13-250882-7 |url-status=dead |archive-url=https://web.archive.org/web/20141102041816/http://www.phschool.com/el_marketing.html |archive-date=2 November 2014 |access-date=15 June 2016 }}</ref> The earliest evidence for life on Earth includes [[Biogenic substance|biogenic]] [[graphite]] found in 3.7 billion-year-old [[Metasediment|metasedimentary rocks]] from [[Western Greenland]]<ref name="NG-20131208"/> and [[microbial mat]] [[fossils]] found in 3.48 billion-year-old [[sandstone]] from [[Western Australia]].<ref name="AST-20131108"/> More recently, in 2015, "remains of [[Biotic material|biotic life]]" were found in 4.1 billion-year-old rocks in Western Australia.<ref name="PNAS-20151014-pdf"/> In 2017, putative fossilised [[microorganism]]s (or [[Micropaleontology#Microfossils|microfossils]]) were announced to have been discovered in [[hydrothermal vent|hydrothermal vent precipitates]] in the [[Nuvvuagittuq Greenstone Belt|Nuvvuagittuq Belt]] of Quebec, Canada that were as old as 4.28 billion years, the oldest record of life on Earth, suggesting "an almost instantaneous emergence of life" after [[Origin of water on Earth#History of water on Earth|ocean formation 4.4 billion years ago]], and not long after the [[Age of the Earth|formation of the Earth]] 4.54 billion years ago.<ref name="NAT-20170301">{{cite journal |last1=Dodd |first1=Matthew S. |last2=Papineau |first2=Dominic |last3=Grenne |first3=Tor |last4=Slack |first4=John F. |last5=Rittner |first5=Martin |last6=Pirajno |first6=Franco |last7=O'Neil |first7=Jonathan |last8=Little |first8=Crispin T.S. |title=Evidence for early life in Earth's oldest hydrothermal vent precipitates |url=http://eprints.whiterose.ac.uk/112179/ |journal=[[Nature (journal)|Nature]] |date=1 March 2017 |volume=543 |issue=7643 |pages=60–64 |doi=10.1038/nature21377 |pmid=28252057 |access-date=2 March 2017 |bibcode=2017Natur.543...60D |url-status=live |archive-url=https://web.archive.org/web/20170908201821/http://eprints.whiterose.ac.uk/112179/ |archive-date=8 September 2017 |doi-access=free }}</ref> === Evolution === {{main|Evolution}} [[Evolution]] is the change in [[heritable]] [[Phenotypic trait|characteristics]] of biological populations over successive generations. It results in the appearance of new species and often the disappearance of old ones.<ref>{{cite book |last1=Hall |first1=Brian K. |author-link1=Brian K. Hall |last2=Hallgrímsson |first2=Benedikt |title=Strickberger's Evolution |url=https://archive.org/details/strickbergersevo0000hall |url-access=registration |year=2008 |edition=4th |location=Sudbury, Massachusetts |publisher=Jones and Bartlett Publishers |isbn=978-0-7637-0066-9 |lccn=2007008981 |oclc=85814089 |pages=[https://books.google.com/books?id=jrDD3cyA09kC&pg=PA4 4–6]}}</ref><ref>{{cite web |title=Evolution Resources |location=Washington, DC |publisher=[[National Academies of Sciences, Engineering, and Medicine]] |year=2016 |url=http://www.nas.edu/evolution/index.html |url-status=live |archive-url=https://web.archive.org/web/20160603230514/http://www.nas.edu/evolution/index.html |archive-date=3 June 2016}}</ref> Evolution occurs when evolutionary processes such as [[natural selection]] (including [[sexual selection]]) and [[genetic drift]] act on genetic variation, resulting in certain characteristics increasing or decreasing in frequency within a population over successive generations.<ref name="Scott-Phillips">{{cite journal |last1=Scott-Phillips |first1=Thomas C. |last2=Laland |first2=Kevin N. |author2-link=Kevin Laland |last3=Shuker |first3=David M. |last4=Dickins |first4=Thomas E. |last5=West |first5=Stuart A. |author-link5=Stuart West |date=May 2014 |title=The Niche Construction Perspective: A Critical Appraisal |journal=[[Evolution (journal)|Evolution]] |volume=68 |issue=5 |pages=1231–1243 |doi=10.1111/evo.12332 |pmid=24325256 |pmc=4261998 |quote=Evolutionary processes are generally thought of as processes by which these changes occur. Four such processes are widely recognized: natural selection (in the broad sense, to include sexual selection), genetic drift, mutation, and migration (Fisher 1930; Haldane 1932). The latter two generate variation; the first two sort it.}}</ref> The process of evolution has given rise to [[biodiversity]] at every level of [[biological organisation]].<ref>{{harvnb|Hall|Hallgrímsson|2008|pp=3–5}}</ref><ref name="Voet2016a">{{cite book |last1=Voet |first1=Donald |author-link1=Donald Voet |last2=Voet |first2=Judith G. |author-link2=Judith G. Voet|last3=Pratt |first3=Charlotte W. |author-link3=Charlotte W. Pratt|year=2016 |title=Fundamentals of Biochemistry: Life at the Molecular Level |edition=Fifth |location=[[Hoboken, New Jersey]] |publisher=[[Wiley (publisher)|John Wiley & Sons]] |isbn=978-1-118-91840-1 |lccn=2016002847 |oclc=939245154 |at=Chapter 1: Introduction to the Chemistry of Life, pp. 1–22}}</ref> === Fossils === {{main|Fossils}} Fossils are the preserved remains or [[trace fossil|traces]] of organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in layers ([[stratum|strata]]) of [[sedimentary rock]] is known as the ''fossil record''. A preserved specimen is called a fossil if it is older than the arbitrary date of 10,000 years ago.<ref>{{cite web|url=http://www.sdnhm.org/science/paleontology/resources/frequent/|title=Frequently Asked Questions|publisher=San Diego Natural History Museum|access-date=25 May 2012|url-status=dead|archive-url=https://web.archive.org/web/20120510101706/http://sdnhm.org/science/paleontology/resources/frequent/|archive-date=10 May 2012}}</ref> Hence, fossils range in age from the youngest at the start of the [[Holocene]] Epoch to the oldest from the [[Archean|Archaean]] Eon, up to 3.4 [[1000000000 (number)|billion]] years old.<ref>{{cite news |first1=Brian |last1=Vastag |title=Oldest 'microfossils' raise hopes for life on Mars |date=21 August 2011 |url=https://www.washingtonpost.com/national/health-science/oldest-microfossils-hail-from-34-billion-years-ago-raise-hopes-for-life-on-mars/2011/08/19/gIQAHK8UUJ_story.html?hpid=z3 |newspaper=The Washington Post |access-date=21 August 2011 |url-status=live |archive-url=https://web.archive.org/web/20111019000458/http://www.washingtonpost.com/national/health-science/oldest-microfossils-hail-from-34-billion-years-ago-raise-hopes-for-life-on-mars/2011/08/19/gIQAHK8UUJ_story.html?hpid=z3 |archive-date=19 October 2011 }}</ref><ref>{{cite news |first=Nicholas |last=Wade |title=Geological Team Lays Claim to Oldest Known Fossils |date=21 August 2011 |url=https://www.nytimes.com/2011/08/22/science/earth/22fossil.html?_r=1&partner=rss&emc=rss&src=ig |work=The New York Times |access-date=21 August 2011 |url-status=live |archive-url=https://web.archive.org/web/20130501085118/http://www.nytimes.com/2011/08/22/science/earth/22fossil.html?_r=1&partner=rss&emc=rss&src=ig |archive-date=1 May 2013 }}</ref> === Extinction === {{Main|Extinction}} Extinction is the process by which a [[species]] dies out.<ref>{{cite encyclopedia |title=Extinction – definition |url=http://encarta.msn.com/dictionary_1861609974/extinction.html |archive-url=https://web.archive.org/web/20090926011523/http://encarta.msn.com/dictionary_1861609974/extinction.html |archive-date=26 September 2009 |url-status=dead}}</ref> The moment of extinction is the death of the last individual of that species. Because a species' potential [[range (biology)|range]] may be very large, determining this moment is difficult, and is usually done retrospectively after a period of apparent absence. Species become extinct when they are no longer able to survive in changing [[habitat]] or against superior competition. Over 99% of all the species that have ever lived are now extinct.<ref>{{cite web |url=http://palaeo.gly.bris.ac.uk/Palaeofiles/Triassic/extinction.htm |title=What is an extinction? |website=Late Triassic |publisher=Bristol University |access-date=27 June 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120901011807/http://palaeo.gly.bris.ac.uk/palaeofiles/triassic/extinction.htm |archive-date=1 September 2012 }}</ref><ref name="Book-Biology">{{cite book |editor1=Kunin, W.E. |editor2=Gaston, Kevin |author=McKinney, Michael L. |chapter=How do rare species avoid extinction? A paleontological view |title=The Biology of Rarity: Causes and consequences of rare—common differences |chapter-url=https://books.google.com/books?id=4LHnCAAAQBAJ&pg=PA110 |date=1996 |publisher=Springer |isbn=978-0-412-63380-5 |access-date=26 May 2015 |archive-date=3 February 2023 |archive-url=https://web.archive.org/web/20230203051637/https://books.google.com/books?id=4LHnCAAAQBAJ&pg=PA110 |url-status=live }}</ref><ref name="StearnsStearns2000">{{cite book |last1=Stearns |first1=Beverly Peterson |last2=Stearns |first2=Stephen C. |title=Watching, from the Edge of Extinction |url=https://books.google.com/books?id=0BHeC-tXIB4C&q=99+percent |year=2000 |publisher=[[Yale University Press]] |isbn=978-0-300-08469-6 |page=x |access-date=30 May 2017 |archive-date=5 November 2023 |archive-url=https://web.archive.org/web/20231105190204/https://books.google.com/books?id=0BHeC-tXIB4C&q=99+percent#v=snippet&q=99%20percent&f=false |url-status=live }}</ref><ref name="NYT-20141108-MJN">{{cite news |last=Novacek |first=Michael J. |title=Prehistory's Brilliant Future |url=https://www.nytimes.com/2014/11/09/opinion/sunday/prehistorys-brilliant-future.html |date=8 November 2014 |work=[[The New York Times]] |access-date=25 December 2014 |url-status=live |archive-url=https://web.archive.org/web/20141229225657/http://www.nytimes.com/2014/11/09/opinion/sunday/prehistorys-brilliant-future.html |archive-date=29 December 2014 }}</ref> [[Mass extinction]]s may have accelerated evolution by providing opportunities for new groups of organisms to diversify.<ref>{{Cite journal |last=Van Valkenburgh |first=B. |author-link=Blaire Van Valkenburgh |year=1999 |title=Major patterns in the history of carnivorous mammals |journal=Annual Review of Earth and Planetary Sciences |volume=27 |pages=463–493 |doi=10.1146/annurev.earth.27.1.463 |bibcode=1999AREPS..27..463V |url=https://zenodo.org/record/890156 |access-date=29 June 2019 |archive-date=29 February 2020 |archive-url=https://web.archive.org/web/20200229201201/https://zenodo.org/record/890156 |url-status=live }}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. 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