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Vestigiality

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Vestigiality

In humans the vermiform appendix is a vestigial structure; it has lost much of its ancestral function.

Vestigiality refers to genetically determined structures or attributes that have apparently lost most or all of their ancestral function in a given species, but have been retained during the process of evolution.[1] Assessment of the vestigiality must generally rely on comparison with homologous features in related species. The emergence of vestigiality occurs by normal evolutionary processes, typically by loss of function of a feature that is no longer subject to positive selection pressures when it loses its value in a changing environment. The feature may be selected against more urgently when its function becomes definitively harmful. Typical examples of both types occur in the loss of flying capability in island-dwelling species.

Contents

  • Overview 1
  • History 2
  • Common descent and evolutionary theory 3
  • Examples 4
    • Animals 4.1
    • Humans 4.2
    • Plants 4.3
  • See also 5
  • References 6
  • External links 7

Overview

Vestigial features may take various forms; for example they may be patterns of behavior, anatomical structures, or biochemical processes. Like most other physical features, however functional, vestigial features in a given species may successively appear, develop, and persist or disappear at various stages within the embryonic development to late adulthood.

Vestigiality, biologically speaking, refers to organisms retaining organs, which have seemingly lost the entirety of the original function. The issue is controversial and not without dispute; nonetheless, vestigial organs are common, evolutionary knowledge.[2] In addition, the term vestigiality is useful in referring to many genetically determined features, either morphological, behavioral, or physiological; in any such context however, it need not follow that a vestigial feature must be completely useless. A classic example at the level of gross anatomy is the human vermiform appendix — though vestigial in the sense of retaining no significant digestive function, the appendix still has immunological roles and is useful in maintaining gut flora.

Similar concepts apply at the molecular level — some nucleic acid sequences in eukaryotic genomes have no known biological function; some of them may be "junk DNA", but it is a difficult matter to demonstrate that a particular sequence in a particular region of a given genome is truly nonfunctional. The simple fact that it is noncoding DNA does not establish that it is functionless. Furthermore, even if an extant DNA sequence is functionless, it does not follow that it has descended from an ancestral sequence of functional DNA. Logically such DNA would not be vestigial in the sense of being the vestige of a functional structure. In contrast pseudogenes have lost their protein-coding ability or are otherwise no longer expressed in the cell. Whether they have any extant function or not, they have lost their former function and in that sense they do fit the definition of vestigiality.

Vestigial structures are often called vestigial organs, although many of them are not actually

External links

  1. ^ Bernard Delahousse; Martin Meganck (2009). Engineering in Context. Academica. p. 270.  
  2. ^ Christiansen, Delahousse, Meganic (2009). "Engineering in Context". 
  3. ^ Lawrence, Eleanor (2005) Henderson's Dictionary of Biology. Pearson, Prentice Hall. ISBN 0-13-127384-1
  4. ^ Muller, G. B. (2002) "Vestigial Organs and Structures." in Encyclopedia of Evolution. Mark Pagel, editor in chief, New York: Oxford University Press. pp 1131-1133
  5. ^ Aristotle."History of Animals" (Book 1, Chapter 9)
  6. ^ St. Hilaire, Geoffroy (1798). "Observations sur l'aile de l'Autruche, par le citoyen Geoffroy", La Decade Egyptienne, Journal Litteraire et D'Economie Politique 1 (pp. 46–51).
  7. ^ Lamarck, Jean-Baptiste (1809). Philosophie zoologique ou exposition des considérations relatives à l'histoire naturelle des animaux.
  8. ^ a b c Darwin, Charles (1859). On the Origin of Species by Means of Natural Selection. John Murray: London.
  9. ^ Darwin, 1859, pp. 134–139. Barrett P. H. et al. 1981, A concordance to Darwin's Origin of Species first edition, Cornaell, Ithaca and London, lists only four mentions of the phrase "use and disuse".
  10. ^
  11. ^ Darwin (1872) The Origin of Species, 6th Edn., p. 421
  12. ^  
  13. ^ Darrow, Clarence and William J. Bryan. (1997). The World’s Most Famous Court Trial: The Tennessee Evolution Case Pub. The Lawbook Exchange, Ltd. p. 268
  14. ^ Reeder, Alex (29 December 1997). "Evolution: Evidence from Living Organisms". Bioweb. Retrieved 2008-10-16. 
  15. ^  
  16. ^ Sober, E. (1993). Philosophy of Biology. Boulder: Westview Press. p. 84. 
  17. ^ CJ van der Kooi & T Schwander 2014. On the fate of sexual traits under asexuality Biological Reviews 89:805-819
  18. ^ Justine J-L, Rahmouni C, Gey D, Schoelinck C, Hoberg EP (2013). "The Monogenean which lost its clamps". PLOS ONE 8 (11): e79155.  
  19. ^ Morgan, Thomas Hunt and Bridges, Calvin B. Sex-linked Inheritance in Drosophila. Carnegie Institution of Washington, publication 237, 1916. 
  20. ^ Snustad, D. Peter. & Simmons, Michael J. Principles of Genetics. Publisher: Wiley, 2008. ISBN 978-0470388259
  21. ^ Darwin, Charles (1871). The Descent of Man, and Selection in Relation to Sex. John Murray: London.
  22. ^ "Purpose of appendix believed found".  
  23. ^ Bollinger, RR; Barbas, AS; Bush, EL; et al. (2007). "Biofilms in the large bowel suggest an apparent function of the human vermiform appendix". Journal of Theoretical Biology 249 (4): 826–831.  
  24. ^ "The old curiosity shop".  
  25. ^ Saraga-Babić M, Lehtonen E, Svajger A, Wartiovaara J (1994). "Morphological and immunohistochemical characteristics of axial structures in the transitory human tail". Ann. Anat. 176 (3): 277–86.  
  26. ^ Foye, Patrick (2014). "Coccyx". Medscape. 
  27. ^ Hobson, David W. (1991). Dermal and Ocular Toxicology: Fundamentals and Methods. CRC Press. p. 485.  
  28. ^ Bhamrah, H.S.; Juneja, Kavita (1998). Cytology and evolution: For Students Taking a First Course in Cell Biology at Undergraduate and Medical Student Level. Anmol Publications PVT. LTD.  
  29. ^ Saladin, Kenneth S. (2003). 3rd, ed. Anatomy & Physiology: The Unity of Form and Function. McGraw-Hill. pp. 286–287. 
  30. ^ Darwin, Charles. (1872) The Expression of the Emotions in Man and Animals John Murray, London.
  31. ^ Torkamani, Rufaut, Jones, Sinclair (2006). "Beyond Goosebumps: Does the ARrector Pili Muscle Have a Role in Hair Loss". National Center for Biotechnology Information. 
  32. ^ Murphy, L. B. (1964). "Some Aspects of the First Relationship". International Journal of Psycho-Analysis (45): 31–43. 
  33. ^ Nishikimi M, Fukuyama R, Minoshima S, Shimizu N, Yagi K (May 6, 1994). "Cloning and chromosomal mapping of the human nonfunctional gene for L-gulono-gamma-lactone oxidase, the enzyme for L-ascorbic acid biosynthesis missing in man". J. Biol. Chem. 269 (18): 13685–8.  
  34. ^ Knobloch, I. (1951) "Are There Vestigial Structures in Plants?" Science New Series, Vol. 113: 465
  35. ^ R Ornduff (1969) Reproductive Biology in Relation to Systematics Taxon 18:121-133
  36. ^ CG Eckert (2002) The loss of sex in clonal plants Evolutionary Ecology 45:501-520

References

See also

Plants also have vestigial parts, including functionless stipules and carpels, leaf reduction of Equisetum, paraphyses of Fungi.[34] Well known examples are the reductions in floral display, leading to smaller and/or paler flowers, in plants that reproduce without outcrossing, for example via selfing or obligate clonal reproduction.[35][36]

Plants

There are also vestigial molecular structures in humans, which are no longer in use but may indicate common ancestry with other species. One example of this is a gene that is functional in most other mammals and which produces L-gulonolactone oxidase, an enzyme that can make vitamin C. A documented mutation deactivated the gene in an ancestor of the modern infraorder of monkeys and apes, and it now remains in their genomes, including the human genome, as a vestigial sequence called a pseudogene.[33]

Infants will instinctively grasp any object which touches the palm, in some cases strongly enough to support their own weight.[32] This is known as the palmar grasp reflex.

Humans also bear some vestigial behaviors and reflexes. The formation of goose bumps in humans under stress is a vestigial reflex;[30] its function in human ancestors was to raise the body's hair, making the ancestor appear larger and scaring off predators. The arrector pili muscle, which is a band of smooth muscle that connects the hair follicle to connective tissue, contracts and creates the goose bumps on skin.[31]

Other structures that are vestigial include the occipitofrontalis muscle) have lost their original functions (keep the head from falling) but are still useful for other purposes (facial expression).[29]

[26] or tailbone, though a vestige of the tail of some primate ancestors, is functional as an anchor for certain pelvic muscles including: the levator ani muscle and the largest gluteal muscle, the gluteus maximus.[25],coccyx The [24] Human vestigiality is related to

The muscles connected to the ears of a human do not develop enough to have the same mobility allowed to many animals.

Humans

In the foregoing examples the vestigiality is generally the (sometimes incidental) result of adaptive evolution. However, there are many examples of vestigiality as the product of drastic mutation, and such vestigiality is usually harmful or counter-adaptive. One of the earliest documented examples was that of vestigial wings in Drosophila.[19] Many examples in many other contexts have emerged since.[20]

[18] A case of vestigial organs was described in

Vestigial attachement clamps in various genera of protomicrocotylids. Accessory sclerites (black) are present in normal clamps but absent in simplified clamps. Lethacotyle (right) has no clamp at all.

Boas and pythons have vestigial pelvis remnants, which are externally visible as two small pelvic spurs on each side of the cloaca. These spurs are sometimes used in copulation, but are not essential, as no colubroid snake (the vast majority of species) possesses these remnants. Furthermore, in most snakes the left lung is greatly reduced or absent. Amphisbaenians, which independently evolved limblessness, also retain vestiges of the pelvis as well as the pectoral girdle, and have lost their right lung.

The wings of asexual reproduction) generally lose their sexual traits, such as the ability to locate/recognize the opposite sex and copulation behavior.[17]

Vestigial characters are present throughout the animal kingdom, and an almost endless list could be given. Darwin said that "it would be impossible to name one of the higher animals in which some part or other is not in a rudimentary condition."[8]

Letter c in the picture indicates the undeveloped hind legs of a baleen whale.

Animals

Examples

Vestigial traits can still be considered adaptations. This is because an adaptation is often defined as a trait that has been favored by natural selection. Adaptations, therefore, need not be adaptive, as long as they were at some point.[16]

[15] antecedents.Old Norse or Latin words can only be explained by their English has stated that vestigial structures make no sense without evolution, just as spelling and usage of many modern Douglas Futuyma [14] The vestigial versions of the structure can be compared to the original version of the structure in other species in order to determine the homology of a vestigial structure. Homologous structures indicate

Vestigial structures are often horses, which stand on a single toe, are still evident in a vestigial form and may become evident, although rarely, from time to time in individuals.

Common descent and evolutionary theory

In 1893, Scopes Trial that "There are, according to Wiedersheim, no less than 180 vestigial structures in the human body, sufficient to make of a man a veritable walking museum of antiquities."[13]

In the first edition of On the Origin of Species, Darwin briefly mentioned inheritance of acquired characters under the heading "Effects of Use and Disuse", expressing little doubt that use "strengthens and enlarges certain parts, and disuse diminishes them; and that such modifications are inherited".[9] In later editions he expanded his thoughts on this,[10] and in the final chapter of the 6th edition concluded that species have been modified "chiefly through the natural selection of numerous successive, slight, favourable variations; aided in an important manner by the inherited effects of the use and disuse of parts".[11]

[8]

His colleague, [7]

Vestigial structures have been noticed since ancient times, and the reason for their existence was long speculated upon before Darwinian evolution provided a widely accepted explanation. In the 4th century BC, Aristotle was one of the earliest writers to comment, in his History of Animals, on the vestigial eyes of moles, calling them "stunted in development" due to the fact that moles can scarcely see.[5] However, only in recent centuries have anatomical vestiges become a subject of serious study. In 1798, Étienne Geoffroy Saint-Hilaire noted on vestigial structures:

The blind mole rat (Spalax typhlus) has tiny eyes completely covered by a layer of skin.

History

Vestigial characters range from detrimental through neutral to favorable in terms of selection. Some may be of some limited utility to an organism but still degenerate over time if they do not confer a significant enough advantage in terms of fitness to avoid the effects of genetic drift or competing selective pressures. Vestigiality in its various forms presents many examples of evidence for biological evolution.

It is important to avoid confusion of the concept of vestigiality with that of ostrich uses its wings in displays and temperature control, though they are undoubtedly vestigial as structures for flight.

[4]

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