Introduction to evolution: Difference between revisions

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[[File:Age-of-Man-wiki.jpg|thumb|250px|The "Paleontological Tree of the Vertebrates," from the 5th edition of ''The Evolution of Man'' (London, 1910) by [[Ernst Haeckel]]. The evolutionary history of [[species]] has been described as a [[phylogenetic tree|tree]], with many branches arising from a single trunk.]]

{{Evolutionary biology}}

In [[biology]], '''evolution''' is the process of change in all forms of [[life]] over generations, and [[evolutionary biology]] is the study of how [[evolution]] occurs. Change is normally driven by need, however, sometimes Biological [[population]]s evolve through [[genetics|genetic]] changes that correspond to changes in the [[organism]]s' [[phenotypic trait|observable traits]]. Genetic changes include [[mutations]], which are caused by damage or replication errors in organisms' [[DNA]]. As the [[genetic variation]] of a population [[genetic drift|drifts]] randomly over generations, [[natural selection]] gradually leads traits to become more or less common based on the relative [[reproductive success]] of organisms with those traits.

The [[age of the Earth]] is about 4.5 billion years.<ref name="USGS1997">{{cite web |url=http://pubs.usgs.gov/gip/geotime/age.html |title=Age of the Earth |date=July 9, 2007 |publisher=[[United States Geological Survey]] |access-date=2015-05-29}}</ref><ref>{{harvnb|Dalrymple|2001|pp=205–221}}</ref><ref>{{cite journal |last1=Manhesa |first1=Gérard |last2=Allègre |first2=Claude J. |author-link2=Claude Allègre |last3=Dupréa |first3=Bernard |last4=Hamelin |first4=Bruno |date=May 1980 |title=Lead isotope study of basic-ultrabasic layered complexes: Speculations about the age of the earth and primitive mantle characteristics |journal=[[Earth and Planetary Science Letters]] |volume=47 |issue=3 |pages=370–382 |bibcode=1980E&PSL..47..370M |doi=10.1016/0012-821X(80)90024-2}}</ref> The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago.<ref name="Origin1">{{cite journal |last1=Schopf |first1=J. William |author-link1=J. William Schopf |last2=Kudryavtsev |first2=Anatoliy B. |last3=Czaja |first3=Andrew D. |last4=Tripathi |first4=Abhishek B. |date=October 5, 2007 |title=Evidence of Archean life: Stromatolites and microfossils |journal=[[Precambrian Research]] |volume=158 |pages=141–155 |issue=3–4 |doi=10.1016/j.precamres.2007.04.009|bibcode=2007PreR..158..141S }}</ref><ref name="Origin2">{{cite journal |last=Schopf |first=J. William |date=June 29, 2006 |title=Fossil evidence of Archaean life |journal=[[Philosophical Transactions of the Royal Society B]] |volume=361 |issue=1470 |pages=869–885 |doi=10.1098/rstb.2006.1834 |pmid=16754604 |pmc=1578735}}</ref><ref name="RavenJohnson2002">{{harvnb|Raven|Johnson|2002|p=68}}</ref> Evolution does not attempt to explain the origin of life (covered instead by [[abiogenesis]]), but it does explain how early lifeforms evolved into the complex ecosystem that we see today.<ref>{{cite web |url=http://evolution.berkeley.edu/evolibrary/misconceptions_faq.php#a1 |title=Misconceptions about evolution |website=Understanding Evolution |publisher=[[University of California, Berkeley]] |access-date=2015-09-26}}</ref> Based on the similarities between all present-day organisms, all life on [[Earth]] is assumed to have originated through [[common descent]] from a [[last universal ancestor]] from which all known [[species]] have diverged through the process of evolution.<ref>{{harvnb|Futuyma|2005a}}</ref>