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! === Adaptation === {{further|Adaptation}} [[File:Homology vertebrates-en.svg|thumb|upright=1.35|[[Homology (biology)|Homologous]] bones in the limbs of [[tetrapod]]s. The bones of these animals have the same basic structure, but have been [[adapted]] for specific uses.{{imagefact|date=December 2022}}]] Adaptation is the process that makes organisms better suited to their habitat.<ref>{{harvnb|Mayr|1982|p=483}}: "Adaptation... could no longer be considered a static condition, a product of a creative past and became instead a continuing dynamic process."</ref><ref>The sixth edition of the ''Oxford Dictionary of Science'' (2010) defines ''adaptation'' as "Any change in the structure or functioning of successive generations of a population that makes it better suited to its environment."</ref> Also, the term adaptation may refer to a trait that is important for an organism's survival. For example, the adaptation of horses' teeth to the grinding of grass. By using the term ''adaptation'' for the evolutionary process and ''adaptive trait'' for the product (the bodily part or function), the two senses of the word may be distinguished. Adaptations are produced by natural selection.<ref>{{cite journal |last=Orr |first=H. Allen |date=February 2005 |title=The genetic theory of adaptation: a brief history |journal=Nature Reviews Genetics |volume=6 |issue=2 |pages=119–127 |doi=10.1038/nrg1523 |issn=1471-0056 |pmid=15716908|s2cid=17772950 }}</ref> The following definitions are due to Theodosius Dobzhansky: # ''Adaptation'' is the evolutionary process whereby an organism becomes better able to live in its habitat or habitats.<ref>{{harvnb|Dobzhansky|1968|pp=1–34}}</ref> # ''Adaptedness'' is the state of being adapted: the degree to which an organism is able to live and reproduce in a given set of habitats.<ref>{{harvnb|Dobzhansky|1970|pp=4–6, 79–82, 84–87}}</ref> # An ''adaptive trait'' is an aspect of the developmental pattern of the organism which enables or enhances the probability of that organism surviving and reproducing.<ref>{{cite journal |last=Dobzhansky |first=Theodosius |date=March 1956 |title=Genetics of Natural Populations. XXV. Genetic Changes in Populations of ''Drosophila pseudoobscura'' and ''Drosophila persimilis'' in Some Localities in California |url=https://archive.org/details/sim_evolution_1956-03_10_1/page/82 |journal=Evolution |volume=10 |issue=1 |pages=82–92 |doi=10.2307/2406099 |issn=0014-3820 |jstor=2406099}}</ref> Adaptation may cause either the gain of a new feature, or the loss of an ancestral feature. An example that shows both types of change is bacterial adaptation to antibiotic selection, with genetic changes causing antibiotic resistance by both modifying the target of the drug, or increasing the activity of transporters that pump the drug out of the cell.<ref>{{cite journal |last1=Nakajima |first1=Akira |last2=Sugimoto |first2=Yohko |last3=Yoneyama |first3=Hiroshi |last4=Nakae |first4=Taiji |display-authors=3 |date=June 2002 |title=High-Level Fluoroquinolone Resistance in ''Pseudomonas aeruginosa'' Due to Interplay of the MexAB-OprM Efflux Pump and the DNA Gyrase Mutation |journal=Microbiology and Immunology |volume=46 |issue=6 |pages=391–395 |doi=10.1111/j.1348-0421.2002.tb02711.x |issn=1348-0421 |pmid=12153116|s2cid=22593331 |doi-access=free }}</ref> Other striking examples are the bacteria ''[[Escherichia coli]]'' evolving the ability to use [[citric acid]] as a nutrient in a [[E. coli long-term evolution experiment|long-term laboratory experiment]],<ref>{{cite journal |last1=Blount |first1=Zachary D. |last2=Borland |first2=Christina Z. |last3=Lenski |first3=Richard E. |date=10 June 2008 |title=Inaugural Article: Historical contingency and the evolution of a key innovation in an experimental population of ''Escherichia coli'' |journal=PNAS |volume=105 |issue=23 |pages=7899–7906 |bibcode=2008PNAS..105.7899B |doi=10.1073/pnas.0803151105 |issn=0027-8424 |pmc=2430337 |pmid=18524956|doi-access=free }}</ref> ''[[Flavobacterium]]'' evolving a novel enzyme that allows these bacteria to grow on the by-products of nylon manufacturing,<ref>{{cite journal |last1=Okada |first1=Hirosuke |last2=Negoro |first2=Seiji |last3=Kimura |first3=Hiroyuki |last4=Nakamura |first4=Shunichi |display-authors=3 |s2cid=4364682 |date=10 November 1983 |title=Evolutionary adaptation of plasmid-encoded enzymes for degrading nylon oligomers |journal=Nature |volume=306 |issue=5939 |pages=203–206 |bibcode=1983Natur.306..203O |doi=10.1038/306203a0 |issn=0028-0836 |pmid=6646204}}</ref><ref>{{cite journal |last=Ohno |first=Susumu |author-link=Susumu Ohno |date=April 1984 |title=Birth of a unique enzyme from an alternative reading frame of the preexisted, internally repetitious coding sequence |journal=PNAS |volume=81 |issue=8 |pages=2421–2425 |bibcode=1984PNAS...81.2421O |doi=10.1073/pnas.81.8.2421 |issn=0027-8424 |pmc=345072 |pmid=6585807|doi-access=free }}</ref> and the soil bacterium ''[[Sphingobium]]'' evolving an entirely new [[metabolic pathway]] that degrades the synthetic [[pesticide]] [[pentachlorophenol]].<ref>{{cite journal |last=Copley |first=Shelley D. |date=June 2000 |title=Evolution of a metabolic pathway for degradation of a toxic xenobiotic: the patchwork approach |journal=[[Trends (journals)|Trends in Biochemical Sciences]] |volume=25 |issue=6 |pages=261–265 |doi=10.1016/S0968-0004(00)01562-0 |issn=0968-0004 |pmid=10838562}}</ref><ref>{{cite journal |last1=Crawford |first1=Ronald L. |last2=Jung |first2=Carina M. |last3=Strap |first3=Janice L. |date=October 2007 |title=The recent evolution of pentachlorophenol (PCP)-4-monooxygenase (PcpB) and associated pathways for bacterial degradation of PCP |journal=[[Biodegradation (journal)|Biodegradation]] |volume=18 |issue=5 |pages=525–539 |doi=10.1007/s10532-006-9090-6 |issn=0923-9820 |pmid=17123025|s2cid=8174462 }}</ref> An interesting but still controversial idea is that some adaptations might increase the ability of organisms to generate genetic diversity and adapt by natural selection (increasing organisms' evolvability).<ref>{{harvnb|Altenberg|1995|pp=205–259}}</ref><ref>{{cite journal |last1=Masel |first1=Joanna |author-link=Joanna Masel |last2=Bergman |first2=Aviv |date=July 2003 |title=The evolution of the evolvability properties of the yeast prion [PSI+] |url=https://archive.org/details/sim_evolution_2003-07_57_7/page/1498 |journal=Evolution |volume=57 |issue=7 |pages=1498–1512 |doi=10.1111/j.0014-3820.2003.tb00358.x |pmid=12940355|s2cid=30954684 }}</ref><ref>{{Cite journal |last1=Lancaster |first1=Alex K. |last2=Bardill |first2=J. Patrick |last3=True |first3=Heather L. |last4=Masel |first4=Joanna |date=February 2010 |title=The Spontaneous Appearance Rate of the Yeast Prion [''PSI''+] and Its Implications for the Evolution of the Evolvability Properties of the [''PSI''+] System |journal=Genetics |volume=184 |issue=2 |pages=393–400 |doi=10.1534/genetics.109.110213 |issn=0016-6731 |pmc=2828720 |pmid=19917766}}</ref><ref>{{cite journal |last1=Draghi |first1=Jeremy |last2=Wagner |first2=Günter P. |author-link2=Günter P. Wagner |date=February 2008 |title=Evolution of evolvability in a developmental model |journal=Evolution |volume=62 |issue=2 |pages=301–315 |doi=10.1111/j.1558-5646.2007.00303.x |pmid=18031304 |s2cid=11560256 |doi-access= }}</ref> [[File:Whale skeleton.png|upright=1.35|thumb|left|A [[baleen whale]] skeleton. Letters ''a'' and ''b'' label [[flipper (anatomy)|flipper]] bones, which were adapted from front leg bones, while ''c'' indicates [[vestigial]] leg bones, both suggesting an adaptation from land to sea.<ref name="transformation445">{{cite journal |last1=Bejder |first1=Lars |last2=Hall |first2=Brian K. |s2cid=8448387 |author-link2=Brian K. Hall |date=November 2002 |title=Limbs in whales and limblessness in other vertebrates: mechanisms of evolutionary and developmental transformation and loss |journal=Evolution & Development |volume=4 |issue=6 |pages=445–458 |doi=10.1046/j.1525-142X.2002.02033.x |pmid=12492145}}</ref>]] Adaptation occurs through the gradual modification of existing structures. Consequently, structures with similar internal organisation may have different functions in related organisms. This is the result of a single ancestral structure being adapted to function in different ways. The bones within bat wings, for example, are very similar to those in mice feet and [[primate]] hands, due to the descent of all these structures from a common mammalian ancestor.<ref>{{cite journal |last1=Young |first1=Nathan M. |last2=HallgrÍmsson |first2=Benedikt |s2cid=198156135 |date=December 2005 |title=Serial homology and the evolution of mammalian limb covariation structure |url=https://archive.org/details/sim_evolution_2005-12_59_12/page/2691 |journal=Evolution |volume=59 |issue=12 |pages=2691–2704 |doi=10.1554/05-233.1 |issn=0014-3820 |pmid=16526515}}</ref> However, since all living organisms are related to some extent,<ref name="Penny1999">{{cite journal |last1=Penny |first1=David |last2=Poole |first2=Anthony |date=December 1999 |title=The nature of the last universal common ancestor |journal=Current Opinion in Genetics & Development |volume=9 |issue=6 |pages=672–677 |doi=10.1016/S0959-437X(99)00020-9 |pmid=10607605}}</ref> even organs that appear to have little or no structural similarity, such as [[arthropod]], [[squid]] and [[vertebrate]] eyes, or the limbs and wings of arthropods and vertebrates, can depend on a common set of homologous genes that control their assembly and function; this is called [[deep homology]].<ref>{{cite journal |last=Hall |first=Brian K. |s2cid=22142786 |date=August 2003 |title=Descent with modification: the unity underlying homology and homoplasy as seen through an analysis of development and evolution |url=https://archive.org/details/sim_biological-reviews_2003-08_78_3/page/409 |journal=Biological Reviews |volume=78 |issue=3 |pages=409–433 |doi=10.1017/S1464793102006097 |issn=1464-7931 |pmid=14558591}}</ref><ref>{{cite journal |last1=Shubin |first1=Neil |author-link1=Neil Shubin |last2=Tabin |first2=Clifford J. |author-link2=Clifford Tabin |last3=Carroll |first3=Sean B. |date=12 February 2009 |title=Deep homology and the origins of evolutionary novelty |url=https://archive.org/details/sim_nature-uk_2009-02-12_457_7231/page/818 |journal=Nature |volume=457 |issue=7231 |pages=818–823 |bibcode=2009Natur.457..818S |doi=10.1038/nature07891 |pmid=19212399 |s2cid=205216390 }}</ref> During evolution, some structures may lose their original function and become vestigial structures.<ref name="Fong">{{cite journal |last1=Fong |first1=Daniel F. |last2=Kane |first2=Thomas C. |last3=Culver |first3=David C. |date=November 1995 |title=Vestigialization and Loss of Nonfunctional Characters |journal=[[Annual Review of Ecology and Systematics]] |volume=26 |pages=249–268 |doi=10.1146/annurev.es.26.110195.001341}}</ref> Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely related species. Examples include [[pseudogene]]s,<ref>{{cite journal |author1=ZhaoLei Zhang |last2=Gerstein |first2=Mark |date=August 2004 |title=Large-scale analysis of pseudogenes in the human genome |journal=Current Opinion in Genetics & Development |volume=14 |issue=4 |pages=328–335 |doi=10.1016/j.gde.2004.06.003 |issn=0959-437X |pmid=15261647}}</ref> the non-functional remains of eyes in blind cave-dwelling fish,<ref>{{cite journal |last1=Jeffery |date=May–June 2005 |first1=William R. |title=Adaptive Evolution of Eye Degeneration in the Mexican Blind Cavefish |journal=Journal of Heredity |volume=96 |issue=3 |pages=185–196 |doi=10.1093/jhered/esi028 |pmid=15653557|citeseerx=10.1.1.572.6605}}</ref> wings in flightless birds,<ref>{{cite journal |last1=Maxwell |first1=Erin E. |last2=Larsson |first2=Hans C.E. |date=May 2007 |title=Osteology and myology of the wing of the Emu (''Dromaius novaehollandiae'') and its bearing on the evolution of vestigial structures |journal=[[Journal of Morphology]] |volume=268 |issue=5 |pages=423–441 |doi=10.1002/jmor.10527 |issn=0362-2525 |pmid=17390336|s2cid=12494187 }}</ref> the presence of hip bones in whales and snakes,<ref name="transformation445" /> and sexual traits in organisms that reproduce via asexual reproduction.<ref>{{cite journal |last1=van der Kooi |first1=Casper J. |last2=Schwander |first2=Tanja |date=November 2014 |title=On the fate of sexual traits under asexuality |url=https://www.researchgate.net/publication/259824406 |format=PDF |journal=Biological Reviews |volume=89 |issue=4 |pages=805–819 |doi=10.1111/brv.12078 |issn=1464-7931 |pmid=24443922 |s2cid=33644494 |access-date=5 August 2015 |url-status=live |archive-url=https://web.archive.org/web/20150723175840/http://www.researchgate.net/profile/Tanja_Schwander/publication/259824406_On_the_fate_of_sexual_traits_under_asexuality/links/53ff35a50cf283c3583c85f3.pdf |archive-date=23 July 2015}}</ref> Examples of [[Human vestigiality|vestigial structures in humans]] include [[Wisdom tooth|wisdom teeth]],<ref>{{cite journal |last1=Silvestri | first1=Anthony R. Jr. |last2=Singh |first2=Iqbal |date=April 2003 |title=The unresolved problem of the third molar: Would people be better off without it? |url=http://jada.ada.org/cgi/content/full/134/4/450 |journal=[[Journal of the American Dental Association]] |volume=134 |issue=4 |pages=450–455 |doi=10.14219/jada.archive.2003.0194 |pmid=12733778 |archive-url=https://web.archive.org/web/20140823063158/http://jada.ada.org/content/134/4/450.full |archive-date=23 August 2014 }}</ref> the [[coccyx]],<ref name="Fong" /> the [[vermiform appendix]],<ref name="Fong" /> and other behavioural vestiges such as [[goose bumps]]<ref>{{harvnb|Coyne|2009|p=62}}</ref><ref>{{harvnb|Darwin|1872|pp=101, 103}}</ref> and [[primitive reflexes]].<ref>{{harvnb|Gray|2007|p=66}}</ref><ref>{{harvnb|Coyne|2009|pp=85–86}}</ref><ref>{{harvnb|Stevens|1982|p=87}}</ref> However, many traits that appear to be simple adaptations are in fact [[exaptation]]s: structures originally adapted for one function, but which coincidentally became somewhat useful for some other function in the process.{{sfn|Gould|2002|pp=1235–1236}} One example is the African lizard ''Holaspis guentheri'', which developed an extremely flat head for hiding in crevices, as can be seen by looking at its near relatives. However, in this species, the head has become so flattened that it assists in gliding from tree to tree—an exaptation.{{sfn|Gould|2002|pp=1235–1236}} Within cells, [[molecular machine]]s such as the bacterial [[flagella]]<ref>{{cite journal |last1=Pallen |first1=Mark J. |last2=Matzke |first2=Nicholas J. |date=October 2006 |title=From ''The Origin of Species'' to the origin of bacterial flagella |url=https://www.ocf.berkeley.edu/~matzke/matzke_cv/_pubs/Pallen_Matzke_2006_NRM_origin_flagella.pdf |type=PDF |journal=Nature Reviews Microbiology |volume=4 |issue=10 |pages=784–790 |doi=10.1038/nrmicro1493 |issn=1740-1526 |pmid=16953248 |s2cid=24057949 |access-date=25 December 2014 |archive-url=https://web.archive.org/web/20141226013207/https://www.ocf.berkeley.edu/~matzke/matzke_cv/_pubs/Pallen_Matzke_2006_NRM_origin_flagella.pdf |archive-date=26 December 2014}}</ref> and [[translocase of the inner membrane|protein sorting machinery]]<ref>{{cite journal |last1=Clements |first1=Abigail |last2=Bursac |first2=Dejan |last3=Gatsos |first3=Xenia |last4=Perry |first4=Andrew J. |last5=Civciristov |first5=Srgjan |last6=Celik |first6=Nermin |last7=Likic |first7=Vladimir A. |last8=Poggio |first8=Sebastian |last9=Jacobs-Wagner |first9=Christine |last10=Strugnell |first10=Richard A. |last11=Lithgow |first11=Trevor |date=15 September 2009 |title=The reducible complexity of a mitochondrial molecular machine |journal=PNAS |volume=106 |issue=37 |pages=15791–15795 |bibcode=2009PNAS..10615791C |doi=10.1073/pnas.0908264106 |pmid=19717453 |pmc=2747197 |display-authors=3 |doi-access=free }}</ref> evolved by the recruitment of several pre-existing proteins that previously had different functions.<ref name="ScottEC" /> Another example is the recruitment of enzymes from [[glycolysis]] and [[xenobiotic metabolism]] to serve as structural proteins called [[crystallin]]s within the lenses of organisms' eyes.<ref>{{harvnb|Piatigorsky|Kantorow|Gopal-Srivastava|Tomarev|1994|pp=241–250}}</ref><ref>{{cite journal |last=Wistow |first=Graeme |date=August 1993 |title=Lens crystallins: gene recruitment and evolutionary dynamism |url=https://archive.org/details/sim_trends-in-biochemical-sciences_1993-08_18_8/page/301 |journal=Trends in Biochemical Sciences |volume=18 |issue=8 |pages=301–306 |doi=10.1016/0968-0004(93)90041-K |issn=0968-0004 |pmid=8236445}}</ref> An area of current investigation in evolutionary developmental biology is the developmental basis of adaptations and exaptations.<ref>{{cite journal |last1=Johnson |first1=Norman A. |last2=Porter |first2=Adam H. |s2cid=1651351 |date=November 2001 |title=Toward a new synthesis: population genetics and evolutionary developmental biology |journal=Genetica |volume=112–113 |issue=1 |pages=45–58 |doi=10.1023/A:1013371201773 |issn=0016-6707 |pmid=11838782}}</ref> This research addresses the origin and evolution of [[Embryogenesis|embryonic development]] and how modifications of development and developmental processes produce novel features.<ref>{{cite journal |last1=Baguñà |first1=Jaume |last2=Garcia-Fernàndez |first2=Jordi |year=2003 |title=Evo-Devo: the long and winding road |url=http://www.ijdb.ehu.es/web/paper.php?doi=14756346 |journal=[[The International Journal of Developmental Biology]] |volume=47 |issue=7–8 |pages=705–713 |issn=0214-6282 |pmid=14756346 |url-status=live |archive-url=https://web.archive.org/web/20141128011936/http://www.ijdb.ehu.es/web/paper.php?doi=14756346 |archive-date=28 November 2014}} * {{cite journal |last=Love |first=Alan C. |date=March 2003 |title=Evolutionary Morphology, Innovation and the Synthesis of Evolutionary and Developmental Biology |url=https://archive.org/details/sim_biology-philosophy_2003-03_18_2/page/309 |journal=Biology and Philosophy |volume=18 |issue=2 |pages=309–345 |doi=10.1023/A:1023940220348 |s2cid=82307503 |ref=none}}</ref> These studies have shown that evolution can alter development to produce new structures, such as embryonic bone structures that develop into the jaw in other animals instead forming part of the [[Evolution of mammalian auditory ossicles|middle ear in mammals]].<ref>{{cite journal |last=Allin |first=Edgar F. |date=December 1975 |title=Evolution of the mammalian middle ear |journal=Journal of Morphology |volume=147 |issue=4 |pages=403–437 |doi=10.1002/jmor.1051470404 |issn=0362-2525 |pmid=1202224 |s2cid=25886311 }}</ref> It is also possible for structures that have been lost in evolution to reappear due to changes in developmental genes, such as a mutation in chickens causing embryos to grow teeth similar to those of crocodiles.<ref>{{cite journal |last1=Harris |first1=Matthew P. |last2=Hasso |first2=Sean M. |last3=Ferguson |first3=Mark W.J. |last4=Fallon |first4=John F. |s2cid=15733491 |date=21 February 2006 |title=The Development of Archosaurian First-Generation Teeth in a Chicken Mutant |journal=Current Biology |volume=16 |issue=4 |pages=371–377 |doi=10.1016/j.cub.2005.12.047 |pmid=16488870|doi-access=free |bibcode=2006CBio...16..371H }}</ref> It is now becoming clear that most alterations in the form of organisms are due to changes in a small set of conserved genes.<ref>{{cite journal |last=Carroll |first=Sean B. |date=11 July 2008 |title=Evo-Devo and an Expanding Evolutionary Synthesis: A Genetic Theory of Morphological Evolution |journal=[[Cell (journal)|Cell]] |volume=134 |issue=1 |pages=25–36 |doi=10.1016/j.cell.2008.06.030 |pmid=18614008|s2cid=2513041 |doi-access=free }}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. 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