المعرفة

تعادل دقيق

(تم التحويل من Punctuated equilibrium)
هذا المقال هو عن the theory in evolutionary biology. إذا كنت تريد the theory of social change، انظر Punctuated equilibrium in social theory.

التعادل الدقيق Punctuated equilibrium، نموذج لتكوين أنواع جديدة (تنوع)، حيث تكتسب السلالة الجديدة (النوع الجديد) صفاتها المورفولوجية المميزة خلال فترة زمنية قصيرة، هذه الفترة الزمنية القصيرة التي يحدث أثناءها التغير السريع تفصل (تضع نقطا) Punctuate فترات زمنية أطول، تظل أثناءها الصفات المميزة للنوع ثابتة (أي في حالة اتزان).[1]

The punctuated equilibrium model (top) consists of morphological stability followed by rare bursts of evolutionary change via rapid cladogenesis – vertical equilibrium states separated by horizontal "jump" phases. In contrast, phyletic gradualism (below), is a more gradual, continuous model of evolution – with accumulation of small incremental changes represented by slanted bars that split at branch-points, where two separate modes of life are feasible but of which, each prospers best with divergent specializations.
التعادل الدقيق، إلى الأسفل، يتكون من اتزان شكلي وزخات نادرة من التغير التطوري.

Punctuated equilibrium is commonly contrasted with phyletic gradualism, the idea that evolution generally occurs uniformly by the steady and gradual transformation of whole lineages (anagenesis).[2]

In 1972, paleontologists Niles Eldredge and Stephen Jay Gould published a landmark paper developing their theory and called it punctuated equilibria.[3] Their paper built upon Ernst Mayr's model of geographic speciation,[4] I. M. Lerner's theories of developmental and genetic homeostasis,[5] and their own empirical research.[6][7] Eldredge and Gould proposed that the degree of gradualism commonly attributed to Charles Darwin[8] is virtually nonexistent in the fossil record, and that stasis dominates the history of most fossil species.

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التاريخ

Punctuated equilibrium originated as a logical consequence of Ernst Mayr's concept of genetic revolutions by allopatric and especially peripatric speciation as applied to the fossil record. Although the sudden appearance of species and its relationship to speciation was proposed and identified by Mayr in 1954,[4] historians of science generally recognize the 1972 Eldredge and Gould paper as the basis of the new paleobiological research program.[9][10][11][12] Punctuated equilibrium differs from Mayr's ideas mainly in that Eldredge and Gould placed considerably greater emphasis on stasis, whereas Mayr was concerned with explaining the morphological discontinuity (or "sudden jumps")[13] found in the fossil record.[9] Mayr later complimented Eldredge and Gould's paper, stating that evolutionary stasis had been "unexpected by most evolutionary biologists" and that punctuated equilibrium "had a major impact on paleontology and evolutionary biology."[9]

A year before their 1972 Eldredge and Gould paper, Niles Eldredge published a paper in the journal Evolution which suggested that gradual evolution was seldom seen in the fossil record and argued that Ernst Mayr's standard mechanism of allopatric speciation might suggest a possible resolution.[6]

The Eldredge and Gould paper was presented at the Annual Meeting of the Geological Society of America in 1971.[3] The symposium focused its attention on how modern microevolutionary studies could revitalize various aspects of paleontology and macroevolution. Tom Schopf, who organized that year's meeting, assigned Gould the topic of speciation. Gould recalls that "Eldredge's 1971 publication [on Paleozoic trilobites] had presented the only new and interesting ideas on the paleontological implications of the subject—so I asked Schopf if we could present the paper jointly."[14] According to Gould "the ideas came mostly from Niles, with yours truly acting as a sounding board and eventual scribe. I coined the term punctuated equilibrium and wrote most of our 1972 paper, but Niles is the proper first author in our pairing of Eldredge and Gould."[15] In his book Time Frames Eldredge recalls that after much discussion the pair "each wrote roughly half. Some of the parts that would seem obviously the work of one of us were actually first penned by the other—I remember for example, writing the section on Gould's snails. Other parts are harder to reconstruct. Gould edited the entire manuscript for better consistency. We sent it in, and Schopf reacted strongly against it—thus signaling the tenor of the reaction it has engendered, though for shifting reasons, down to the present day."[16]

John Wilkins and Gareth Nelson have argued that French architect Pierre Trémaux proposed an "anticipation of the theory of punctuated equilibrium of Gould and Eldredge."[17]


أدلة من السجل الأحفوري

المقالة الرئيسية: معدل التطور

The fossil record includes well documented examples of both phyletic gradualism and punctuational evolution.[18] As such, much debate persists over the prominence of stasis in the fossil record.[19][20] Before punctuated equilibrium, most evolutionists considered stasis to be rare or unimportant.[9][21][22] The paleontologist George Gaylord Simpson, for example, believed that phyletic gradual evolution (called horotely in his terminology) comprised 90% of evolution.[23] More modern studies,[24][25][26] including a meta-analysis examining 58 published studies on speciation patterns in the fossil record showed that 71% of species exhibited stasis,[27] and 63% were associated with punctuated patterns of evolutionary change.[28] According to Michael Benton, "it seems clear then that stasis is common, and that had not been predicted from modern genetic studies."[18] A paramount example of evolutionary stasis is the fern Osmunda claytoniana. Based on paleontological evidence it has remained unchanged, even at the level of fossilized nuclei and chromosomes, for at least 180 million years.[29]

الآليات النظرية

Punctuational change

When Eldredge and Gould published their 1972 paper, allopatric speciation was considered the "standard" model of speciation.[3] This model was popularized by Ernst Mayr in his 1954 paper "Change of genetic environment and evolution,"[4] and his classic volume Animal Species and Evolution (1963).[30]


مايتعلق بنظريات داروين

تكميلية وسائل التطور السريع

انظر أيضاً: وسائط تطور سريعة

التعادل الدقيق في النظرية الاجتماعية

انظر أيضاً: النظرية الاجتماعية في التعادل الدقيق

التعادل الدقيق في العلاقات الدولية

في تغيير اللغة

انظر أيضا

المصادر

  1. ^ عبد الجليل هويدي، محمد أحمد هيكل (2004). أساسيات الجيولوجيا التاريخية. مكتبة الدار العربية للكتب.
  2. ^ Gould, S.J. (15 April 1982). "Punctuated equilibrium — a different way of seeing". New Scientist. Vol. 94. pp. 137–139 – via Google Books.
  3. ^ أ ب ت خطأ استشهاد: وسم <ref> غير صحيح؛ لا نص تم توفيره للمراجع المسماة pe1972
  4. ^ أ ب ت Mayr, Ernst (1954). "Change of genetic environment and evolution". In Huxley, J.; Hardy, A.C.; Ford, E.B. (eds.). Evolution as a Process. London, UK: Allen and Unwin. pp. 157–180 – via Blackwell Publishing.
  5. ^ Lerner, I.M. (1954). Genetic Homeostasis. New York, NY: John Wiley.
  6. ^ أ ب Eldredge, Niles (1971). "The allopatric model and phylogeny in Paleozoic invertebrates". Evolution. 25 (1): 156–167. doi:10.2307/2406508. hdl:2246/6568. JSTOR 2406508. PMID 28562952.
  7. ^ Gould, S.J. (1969). "An evolutionary microcosm: Pleistocene and recent history of the land snail P. (Poecilozonites) in Bermuda". Bull. Mus. Comp. Zool. 138: 407–532.
  8. ^ Rhodes, F.H.T. (1983). "Gradualism, punctuated equilibrium and the Origin of Species". Nature. 305 (5932): 269–272. Bibcode:1983Natur.305..269R. doi:10.1038/305269a0. PMID 6353241. S2CID 32953263.
  9. ^ أ ب ت ث Mayr, Ernst (1992). "Speciational Evolution or Punctuated Equilibria." In Albert Somit and Steven Peterson The Dynamics of Evolution. New York: Cornell University Press, pp. 21-48.
  10. ^ Shermer, Michael (2001). The Borderlands of Science. New York: Oxford University Press, pp. 97-116.
  11. ^ Geary, Dana (2008). "The Legacy of Punctuated equilibrium." In Warren D. Allmon et al. Stephen Jay Gould: Reflections on His View of Life. Oxford: Oxford University Press, pp. 127-145.
  12. ^ Prothero, D. (2007). "Punk eek, Transitional Formsand Quote Miners." In Evolution: what the fossils say and why it matters. New York: Columbia University Press, pp. 78–85.
  13. ^ Schindewolf, Otto (1936). Paldontologie, Entwicklungslehre und Genetik. Berlin: Borntraeger.
  14. ^ Gould, S. J. (2002). The Structure of Evolutionary Theory. Cambridge, Massachusetts: The Belknap Press of Harvard University Press. p. 775. ISBN 978-0-674-00613-3.
  15. ^ S. J. Gould (1991). "Opus 200" Natural History 100 (August): 12-18.
  16. ^ Eldredge, Niles (1985) Time Frames: The evolution of punctuated equilibria. Princeton: Princeton University Press, p. 120.
  17. ^ Wilkins, John S.; Nelson, G. J. (2008). "Trémaux on species: A theory of allopatric speciation (and punctuated equilibrium) before Wagner" (PDF). History and Philosophy of the Life Sciences. 30 (2): 179–206. PMID 19203015.
  18. ^ أ ب Benton, Michael and David Harper (2009) Introduction to Paleobiology and the Fossil Record New York: John Wiley & Sons, pp. 123-124.
  19. ^ خطأ استشهاد: وسم <ref> غير صحيح؛ لا نص تم توفيره للمراجع المسماة Futuyma86
  20. ^ Erwin, D. H. and R. L. Anstey (1995) New approaches to speciation in the fossil record. New York : Columbia University Press.
  21. ^ S. J. Gould 2002. The Structure of Evolutionary Theory. Cambridge MA: Harvard University Press, p. 875.
  22. ^ Wake, David B.; Roth, G.; Wake, M. H. (1983). "On the problem of stasis in organismal evolution". Journal of Theoretical Biology. 101 (2): 212. Bibcode:1983JThBi.101..211W. doi:10.1016/0022-5193(83)90335-1.
  23. ^ Simpson, G. G. (1944). Tempo and Mode in Evolution. Columbia University Press. New York, p. 203.
  24. ^ Campbell, N.A. (1990) Biology p. 450–451, 487–490, 499–501. Redwood City CA: Benjamin Cummings Publishing Company.
  25. ^ S. J. Gould, & Eldredge, Niles (1977). "Punctuated equilibria: the tempo and mode of evolution reconsidered." Archived 2018-05-08 at the Wayback Machine Paleobiology 3 (2): 115-151. (p.145)
  26. ^ McCarthy, T. & Rubridge, B. (2005) The Story of Earth and Life. Cape Town: Struik Publishers. ISBN 1-77007-148-2.
  27. ^ de Brito Neto, S. G.; Fernando Alves, E.; Cavalcante e Almeida Sá, Mariana (2017). "Speciation in real time and historical-archaeological and its absence in geological time". Academia Journal of Scientific Research. doi:10.15413/ajsr.2017.0413 (inactive 31 December 2022). ISSN 2315-7712.{{cite journal}}: CS1 maint: DOI inactive as of ديسمبر 2022 (link)
  28. ^ Erwin, D. H. and Anstey, R. L (1995). "Speciation in the fossil record." In Erwin, D. H. & Anstey, R. L. (eds). New Approaches to Speciation in the Fossil Record. Columbia University Press, New York, pp. 11–39.
  29. ^ Bomfleur, B.; McLoughlin, S.; Vajda, V. (March 2014). "Fossilized nuclei and chromosomes reveal 180 million years of genomic stasis in royal ferns". Science. 343 (6177): 1376–1377. Bibcode:2014Sci...343.1376B. doi:10.1126/science.1249884. PMID 24653037. S2CID 38248823.
  30. ^ Mayr, Ernst (1963). Animal Species and Evolution. Cambridge, MA: Harvard University Press.

قراءات للإستزادة


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وصلات خارجية

قالب:Speciation

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