Derived trait: Difference between revisions
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In [[phylogenetics]], a trait is '''derived''' if it is present in an organism, but was absent in the last common ancestor of the group being considered. |
In [[phylogenetics]], a trait is '''derived''' if it is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to characters that are not present in an organism, but were present in its ancestors, ''i.e.'' traits that have undergone secondary loss. |
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For the sake of precision, the term "derived" is preferred to "advanced," a term which may inaccurately imply superiority. Simplicity is often secondarily derived |
For the sake of precision, the term "derived" is preferred to "advanced," a term which may inaccurately imply superiority. Simplicity is often secondarily derived.<ref name=Clark1999>{{citation | last = Clark | first = C.G. | year = 1999 | title = The Effect of Secondary Loss on Our Views of Eukaryotic Evolution | journal = The Biological Bulletin | volume = 196 | issue = 3 | pages = 385–388 | doi = 10.2307/1542976 | url = http://www.biolbull.org/cgi/reprint/196/3/385.pdf}}</ref> For example, the absence of [[mitochondria]] in the anaerobic [[protist]] ''[[Entamoeba histolytica]]'' is a result of their secondary loss, and when considered in the context of eukaryotes as a whole, is a derived trait.<ref>{{cite journal |author=Clark CG, Roger AJ |title=Direct evidence for secondary loss of mitochondria in Entamoeba histolytica |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=92 |issue=14 |pages=6518–21 |year=1995 |month=July |pmid=7604025 |pmc=41549 |doi= |url=http://www.pnas.org/cgi/pmidlookup?view=long&pmid=7604025}}</ref> Likewise, the primitive character state for birds (i.e. the state possessed by their last common ancestor) is flight, which was secondarily lost by penguins and dodos. |
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Whether or not a trait is considered derived depends on the group in question. For example, among the (crown group) tetrapods, having five fingers is the primitive trait - as their last common ancestor bore a five-digit hand.{{Fact|date=January 2009}} However, amongst the vertebrates, five fingers is a derived trait, as the last common ancestor to the vertebrates did not even bear fingers. |
Whether or not a trait is considered derived depends on the group in question. For example, among the (crown group) tetrapods, having five fingers is the primitive trait - as their last common ancestor bore a five-digit hand.{{Fact|date=January 2009}} However, amongst the vertebrates, five fingers is a derived trait, as the last common ancestor to the vertebrates did not even bear fingers. |
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==References== |
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{{reflist]] |
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==References== |
==References== |
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Revision as of 20:01, 13 February 2009
In phylogenetics, a trait is derived if it is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to characters that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary loss.
For the sake of precision, the term "derived" is preferred to "advanced," a term which may inaccurately imply superiority. Simplicity is often secondarily derived.[1] For example, the absence of mitochondria in the anaerobic protist Entamoeba histolytica is a result of their secondary loss, and when considered in the context of eukaryotes as a whole, is a derived trait.[2] Likewise, the primitive character state for birds (i.e. the state possessed by their last common ancestor) is flight, which was secondarily lost by penguins and dodos.
Whether or not a trait is considered derived depends on the group in question. For example, among the (crown group) tetrapods, having five fingers is the primitive trait - as their last common ancestor bore a five-digit hand.[citation needed] However, amongst the vertebrates, five fingers is a derived trait, as the last common ancestor to the vertebrates did not even bear fingers.
References
{{reflist]]
References
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- ^ Clark, C.G. (1999), "The Effect of Secondary Loss on Our Views of Eukaryotic Evolution" (PDF), The Biological Bulletin, 196 (3): 385–388, doi:10.2307/1542976
- ^ Clark CG, Roger AJ (1995). "Direct evidence for secondary loss of mitochondria in Entamoeba histolytica". Proc. Natl. Acad. Sci. U.S.A. 92 (14): 6518–21. PMC 41549. PMID 7604025.
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