Open main menu
Home
Random
Recent changes
Special pages
Community portal
Preferences
About Wikipedia
Disclaimers
Incubator escapee wiki
Search
User menu
Talk
Dark mode
Contributions
Create account
Log in
Editing
Exaptation
(section)
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!
==Examples== [[File:Red feather pigments.jpg|thumb|Bird feathers of various colors]] Exaptations include the co-option of [[feathers]], which initially evolved for heat regulation, for display, and later for use in bird flight. Another example is the lungs of many [[Basal (phylogenetics)|basal]] [[fish]], which evolved into the lungs of terrestrial vertebrates but also underwent exaptation to become the [[gas bladder]], a buoyancy control organ, in derived fish.<ref>{{cite journal |author=Colleen Farmer |year=1997 |title=Did Lungs and the Intracardiac Shunt Evolve to Oxygenate the Heart in Vertebrates? |journal=Paleobiology |volume=23 |pages=358–372 |jstor=2401109|issue=3 |doi=10.1017/S0094837300019734 |bibcode=1997Pbio...23..358F |s2cid=87285937 }}</ref> A third is the [[Evolution of mammalian auditory ossicles|repurposing of two of the three bones in the amniote jaw]] to become the malleus and incus of the mammalian ear, leaving the mammalian jaw with just one hinge.<ref>{{cite web|title=Jaws to ears in the ancestors of mammals|url=https://evolution.berkeley.edu/evolibrary/article/evograms_05|publisher=UC Berkeley|access-date=20 January 2018}}</ref> [[Arthropod]]s provide the earliest identifiable fossils of land animals, from about {{ma|419}} in the Late [[Silurian]], and terrestrial tracks from about {{ma|450}} appear to have been made by arthropods.<ref>{{Cite journal | author=Pisani, D., Laura L. Poling, L.L., Lyons-Weiler M., and Hedges, S.B. | title=The colonization of land by animals: molecular phylogeny and divergence times among arthropods | journal=BMC Biology | year=2004 | volume=2 | doi=10.1186/1741-7007-2-1 | pmid=14731304 | page=1 | pmc=333434 | doi-access=free }}</ref> Arthropods were well pre-adapted to colonize land, because their existing jointed [[exoskeleton]]s provided support against gravity and mechanical components that could interact to provide levers, columns and other means of locomotion that did not depend on submergence in water.<ref name="CowenHistLifeEd3P126">{{cite book |author=Cowen, R. |title=History of Life |edition=3rd |publisher=Blackwell Science |isbn=978-0-632-04444-3 |page=126|date=2000-04-14 }}</ref> [[Metabolism]] can be considered an important part of exaptation. As one of the oldest biological systems and being central to life on the Earth, studies have shown that metabolism may be able to use exaptation in order to increase fitness, given some new set of conditions or environment.<ref>[http://www.zora.uzh.ch/88311/5/Barve_Nature_2013.pdf A Latent Capacity for Evolutionary Innovation through Exaptation in Metabolic Systems]</ref> Studies have shown that up to 44 carbon sources are viable for metabolism to successfully take place and that any one adaptation in these specific metabolic systems is due to multiple exaptations.<ref>{{Cite journal |last1=Barve |first1=Aditya |last2=Wagner |first2=Andreas |date=2013 |title=A latent capacity for evolutionary innovation through exaptation in metabolic systems |journal=Nature |volume=500 |issue=7461 |pages=203–206 |doi=10.1038/nature12301 |pmid=23851393|url=https://www.zora.uzh.ch/id/eprint/88311/5/Barve_Nature_2013.pdf |bibcode=2013Natur.500..203B |s2cid=4419972 }}</ref> Taking this perspective, exaptations are important in the origination of adaptations in general. A recent example comes from [[Richard Lenski]]'s [[E. coli long-term evolution experiment|''E. coli'' long-term evolution experiment]], in which aerobic growth on [[Citric acid|citrate]] arose in one of twelve populations after 31,000 generations of evolution.<ref>{{Cite journal |last1=Blount |first1=Zachary D. |last2=Borland |first2=Christina Z. |last3=Lenski |first3=Richard E. |date=2008 |title=Historical contingency and the evolution of a key innovation in an experimental population of Escherichia coli |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=105 |issue=23 |pages=7899–7906 |doi=10.1073/pnas.0803151105 |issn=1091-6490 |pmc=2430337 |pmid=18524956 |bibcode=2008PNAS..105.7899B|doi-access=free }}</ref> Genomic analysis by [[Zachary Blount|Blount]] and colleagues showed that this novel trait was due to a [[gene duplication]] that caused a citrate [[Transport protein|transporter]] that is normally expressed only under anoxic conditions to be expressed under [[oxic]] conditions, thus exapting it for aerobic use.<ref>{{Cite journal |last1=Blount |first1=Zachary D. |last2=Barrick |first2=Jeffrey E. |last3=Davidson |first3=Carla J. |last4=Lenski |first4=Richard E. |title=Genomic analysis of a key innovation in an experimental Escherichia coli population|journal=Nature |volume=489 |issue=7417 |pages=513–518 |doi=10.1038/nature11514 |pmc=3461117|pmid=22992527|year=2012 |bibcode=2012Natur.489..513B }}</ref> Gould and [[Jürgen Brosius|Brosius]] took the concept of exaptation to the genetic level. It is possible to look at a [[retroposon]], originally thought to be simply junk DNA, and deduce that it may have gained a new function to be termed as an exaptation.<ref>{{cite journal |last1=Brosius |first1=Jürgen |title=Retroposons--seeds of evolution |journal=Science |date=1991 |volume=251 |issue=4995 |pages=753 |pmid=1990437 |doi=10.1126/science.1990437|bibcode=1991Sci...251..753B }}</ref><ref>{{cite journal |last1=Brosius |first1=Jürgen |last2=Gould |first2=Stephen Jay |title=On "genomenclature": a comprehensive (and respectful) taxonomy for pseudogenes and other "junk DNA" |journal=Proc Natl Acad Sci U S A |date=1992 |volume=89 |issue=22 |pages=10706–10 |pmid=1279691 |pmc=50410 |doi=10.1073/pnas.89.22.10706|bibcode=1992PNAS...8910706B |doi-access=free }}</ref><ref>{{cite journal |last1=Okada |first1=Norihiro |title=Emergence of mammals by emergency: exaptation |journal=Genes to Cells |date=14 July 2010 |volume=15 |issue=8 |pages=801–812 |doi=10.1111/j.1365-2443.2010.01429.x |pmid=20633052 |s2cid=8687487 |doi-access=free }}</ref> Given an emergency situation in the past, a species may have co-opted junk DNA for a useful purpose. This may have occurred with [[mammal]]ian ancestors when confronted with the [[Permian–Triassic extinction event]] about 250 million years ago and substantial increase in the level of oxygen in Earth's atmosphere. More than 100 [[Locus (genetics)|loci]] have been found to be [[Conserved sequence|conserved]] only among mammalian genomes and are thought to have essential roles in the generation of features such as the [[placenta]], [[Thoracic diaphragm|diaphragm]], [[mammary gland]]s, [[neocortex]], and auditory ossicles. It is believed that as a result of exaptation, or making previously "useless" DNA into DNA that could be used in order to increase survival chance, mammals were able to generate new brain structures as well as behavior to better survive the mass extinction and adapt to new environments. Similarly, [[virus]]es and their components have been repeatedly exapted for host functions. The functions of exapted viruses typically involve either defense from other viruses or cellular competitors or transfer of nucleic acids between cells, or storage functions. [[Koonin]] and Krupovic suggested that virus exaptation can reach different depths, from recruitment of a fully functional virus to exploitation of defective, partially degraded viruses, to utilization of individual virus proteins.<ref>{{cite journal |last1=Koonin |first1=EV |last2=Krupovic |first2=M |title=The depths of virus exaptation |journal=Current Opinion in Virology |date=2018 |volume=31 |pages=1–8 |doi=10.1016/j.coviro.2018.07.011 |pmid=30071360|s2cid=51906158 |url=https://hal-pasteur.archives-ouvertes.fr/pasteur-01977329/file/Koonin_Krupovic_COiV2018_V2.pdf }}</ref>
Edit summary
(Briefly describe your changes)
By publishing changes, you agree to the
Terms of Use
, and you irrevocably agree to release your contribution under the
CC BY-SA 4.0 License
and the
GFDL
. You agree that a hyperlink or URL is sufficient attribution under the Creative Commons license.
Cancel
Editing help
(opens in new window)