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Topic: Punctuated equilibrium

Related Topics

Peripatric speciation

Gradualism

Theory of evolution

Stephen Jay Gould

Catastrophism

The Blind Watchmaker

Mutagenesis

Cycle facilities at roundabouts

Hypermutation

Kin selection

Zarathustra

Ronald Fisher

Utilitarianism

DNA ligase

Polymerase chain reaction

	Punctuated equilibrium - Wikipedia, the free encyclopedia
		Punctuated equilibrium (or punctuated equilibria) is a theory in evolutionary biology which states that most sexually reproducing species will show little to no evolutionary change throughout their history.
		Punctuated equilibrium is commonly contrasted against the theory of phyletic gradualism, which hypothesizes that most evolution occurs uniformly and by the steady and gradual transformation of whole lineages (anagenesis).
		Punctuated equilibrium differed from Mayr simply in that Eldredge and Gould had placed considerably greater emphasis on stasis, whereas Mayr was generally concerned with explaining the morphological discontinuity (or punctuational patterns) found in the fossil record.
	en.wikipedia.org /wiki/Punctuated_equilibrium (1633 words)

	Punctuated Equilibrium
		Punctuated equilibrium, also called punctuated equilibria or the punctuational model, holds that genetic change occurs relatively rapidly on a geological timescale, and these shorter periods of evolution are sandwiched between longer periods of “stasis,”
		Proponents of the punctuational model have relied heavily upon the work of mathematician Sewall Wright, who observed that novel variation was more likely to become fixed in small populations which were reproductively isolated (often due to geographic factors) from the main population.
		One primary difference between the punctuational and gradualistic models of evolution is thus that under the gradualistic model, the entire parent population slowly morphs into the descendant species.
	www.iscid.org /encyclopedia/Punctuated_Equilibrium (703 words)

	Punctuated equilibrium
		Punctuated equilibrium is a theory of evolution which postulates that changes such as speciation can occur very quickly, with long periods of little change (equilibria) in between.
		The theory of punctuated equilibrium was proposed by Niles Eldredge and Stephen Jay Gould in the 1970s.
		The theory of punctuated equilibrium is often misstated as being an explanation for purported "gaps in the fossil record", i.e.
	www.guajara.com /wiki/en/wikipedia/p/pu/punctuated_equilibrium_1.html (303 words)

	Punctuated equilibria - EvoWiki
		Creationists commonly advance punctuated equilibrium as concession on the part of the paleontological community that evolution is not borne out by the fossil record, largely due to the way in which S. Gould presented it.
		Punctuated equilibrium as advanced by Stanley (1975, 1981, 1982), Gould and Eldredge (1972, 1977), Eldredge (1984, 1985), Eldredge and Stanley (1984) and Gould (1980, 1982) and most vociferously espoused by Gould throughout the latter portion of his career, has come under significant criticism by a number of evolutionary biologists.
		Carroll (1987; 1997) has emphasized that the defense of punctuated equilibrium using operational taxonomic units, per the method of Stanley (1981), is inherently flawed due to the limitations of the Linnean terminological infrastructure employed by taxonomic science, and emphasized that attention to anatomical detail and not taxonomic convention, precludes creating punctuated equilibria where none exist.
	wiki.cotch.net /wiki.phtml?title=Punctuated_equilibria (600 words)

	Evolution: Library: Punctuated Equilibrium
		The concept of punctuated equilibrium was, to some, a radical new idea when it was first proposed by Stephen Jay Gould and Niles Eldredge in 1972.
		The relative importance of punctuated and gradual patterns of evolution is a subject of debate and research.
		This leisurely pace is "punctuated" by a rapid burst of change that results in a new species and that leaves few fossils behind.
	www.pbs.org /wgbh/evolution/library/03/5/l_035_01.html (687 words)

	Punctuated Equilibrium
		Punctuated equilibrium is a model of speciation as uncoupled from selection.
		Punctuated equilibrium (Eldredge and Gould, 1972) is a theory about evolution which describes speciation as a intermittent and drastic process rather than a continuous and gradual one.
		Punctuated equilibrium is considered non-Darwinian because one of its central tenets is that adaptation and speciation are uncoupled: separate and unrelated processes.
	www.wsbd.net /research/evolution/macroev.html (4769 words)

	Equilibrium - Wikipedia, the free encyclopedia
		Chemical equilibrium, when a chemical reaction proceeds at the same rate as its reverse reaction, with no change in the amount of each compound
		Mechanical equilibrium, when the sum of the forces and moments on each particle of a system is zero
		Punctuated equilibrium, a part of evolutionary theory that states that speciation occurs relatively quickly with long periods of little change in between.
	en.wikipedia.org /wiki/Equilibrium (254 words)

	Punctuated Equilibria
		In this matter, the person attempting to come to a better understanding of punctuated equilibria will find that he or she may be hampered by the popular writings of those same authors rather than helped.
		This pattern includes the characteristically abrupt appearance of new species, the relative stability of morphology in widespread species, the distribution of transitional fossils when those are found, the apparent differences in morphology between ancestral and daughter species, and the pattern of extinction of species.
		Punctuated equilibria: the tempo and mode of evolution reconsidered.
	www.talkorigins.org /faqs/punc-eq.html (3019 words)

	Evolution And 'Punctuated Equilibrium'
		Second, it is false because punctuated equilibrium is not an attempt to explain a lack of proof, but an attempt to explain the picture which arises of evolutionary time lines as the proof mentioned previously has accumulated.
		Punctuated equilibrium is intended to explain an absence of transitional varieties between species; and discussion of the theory has drawn attention to gaps in the fossil record.
		You view of punctuated equilibrium is common, but it is a distortion, and it is a distortion fostered by people like Denton.
	jmm.aaa.net.au /articles/874.htm (1063 words)

	B16: The History of Life: Source Book (Site not responding. Last check: 2007-10-07)
		The most exciting direct extensions of punctuated equilibrium now involve the study of correlated punctuational events across taxa, and the ecological and environmental sources of such cohesion.
		Punctuated equilibrium surely exists in abundance, but validation of the general hypothesis requires a relative frequency sufficiently high to impart the predominant motif and signal to life's history.
		A good test of punctuated equilibrium requires (in addition to the obvious need for documented rapidity in an interval known to be sufficiently short) both a phyletic hypothesis to assert sister-group relationship of the taxa involved, and survival of putative ancestors to affirm an event of true branching rather than rapid phyletic transformation.
	www.sjgarchive.org /library/text/b16/p0181.htm (617 words)

	Stephen Jay Gould, "Opus 200," 1991
		Punctuated equilibrium gains its rationale from the ideal also a standard component of the allopatric speciation theory, that most peripherally isolated populations are relatively small and undergo their characteristic changes at a rate that translates into geological time as an instant.
		(Punctuated equilibrium, on the other hand, is a different theory of intermediacy for evolutionary trends—pushing a ball up an inclined plane for gradualism, climbing a staircase for punctuated equilibrium.) Some of our colleagues, in an all too common and literally perverse reaction, blamed us for this mayhem upon our theory.
		Punctuated equilibrium has provided a new context for the most important phenomenon of paleontology—evolutionary trends (larger size in horses, more complex sutures in ammonites, bigger brains in humans).
	www.stephenjaygould.org /library/gould_opus200.html (3653 words)

	Evolution - A-Z - Punctuated equilibrium (Site not responding. Last check: 2007-10-07)
		Punctuated equilibrium is the theory put forward by Eldredge and Gould to explain the fact that the fossil record does not show smooth evolutionary transitions.
		According to the theory of punctuated equilibrium, evolution proceeds relatively rapidly during speciation: between speciation events the population remains relatively constant in a condition called stasis.
		Punctuated equilibrium can be contrasted with evolution by phyletic gradualism in which evolution occurs at a constant rate.
	www.blackwellpublishing.com /ridley/a-z/Punctuated_equilibrium.asp (176 words)

	Punctuated Equilibrium
		Punctuated equilibrium is not saltationism, a defunct theory that states that speciations occur in single large steps.
		Punctuated equilibrium should not be confused with saltationism, a theory in which a new species may arise in single generation through a macromutation.
		Punctuated equilibrium predicts that the fossil record will display long gaps during which species change little or not at all, and that is exactly what the fossils do show (Ridley 1993, 513).
	www.geocities.com /CapeCanaveral/Lab/1366/pe.html (2053 words)

	B16: The History of Life: Source Book (Site not responding. Last check: 2007-10-07)
		Elegant cases don't make punctuated equilibrium any more than a swallow makes a summer, but there are a growing number of reports documenting an overwhelming relative frequency (often an exclusivity) for punctuated equilibrium in entire groups or faunas.
		Distinct evolutionary modes yield disparate patterns as results; punctuated equilibrium might therefore be tested by studying the morphological and taxonomic distributions of organisms, including living faunas.
		The pattern of punctuated equilibrium exists (at predominant relative frequency, we would argue) and is robust.
	www.sjgarchive.org /library/text/b16/p0182.htm (1127 words)

	PUNCTUATED EQUILIBRIUM: AN ORGANIC MODEL FOR THE LEARNING ORGANISATION (Site not responding. Last check: 2007-10-07)
		We explain here the concept of punctuated equilibrium, as derived from geology and biology, and why it is important for managers to understand.
		The punctuated equilibrium theory, applied to organisational evolution explains why entrepreneurship works, and incidentally why some organisations are unable to sustain excellence in the long term (see above on IBM case).
		The Punctuated Equilibrium theory of biological evolution was first formulated by Niles Eldredge and Stephen Jay Gould in 1972 [ Schopf T.J.M. Models in Palaeobiology, Freeman Couper and Co. p32].
	members.aol.com /ifprice/peqforum.html (3404 words)

	Conclusions -- Mass Extinction Events
		In 1972, Eldredge and Gould introduced the idea of punctuated equilibrium; in contrast to phyletic gradualism, this theory states that long periods of evolutionary stasis are interrupted, or punctuated, by times of rapid evolution and speciation.
		The extinction record itself is similar to the punctuated equilibrium pattern in that long stretches of low extinction rates (background rate) are interspersed with mass extincion events, which are analagous to Eldredge and Gould's rapid speciative bursts.
		Thus, not only do punctuated equilibrium and the extinction record share a similar pattern, they are causitively related as well; that is speciation record could be seen almost as a time-lagged response to extinction.
	www.earth.rochester.edu /ees207/Mass_Ext/higgins_mass5.html (462 words)

	Hopeful Monsters and Evolution; Punctuated Equilibrium Examined (by Bert Thompson, Ph. D.) (Site not responding. Last check: 2007-10-07)
		Evidence for punctuated equilibrium is identical to the evidence for creation, namely, the abrupt appearance of all major categories of organisms, with nothing connecting them directly to any other groups.
		Hayward mentions, concerning punctuated equilibrium, that it "cannot explain how species could arise so suddenly," he provides us with a kernel of truth that should be explored further.
		Punctuated equilibrium is ultimately dependent upon genetic changes—changes derived from mutations.
	www.markehrlich.com /authors/BThmepee.html (3327 words)

	[No title]
		The newly created institutions result in long-term equilibrium in their policy area because the newly created institutions structure the participation of policy actors in complex systems of mutually non-interfering policy monopolies.
		Whether and when a policy equilibrium is punctuated depends on how the issues are portrayed, what symbols are used, and which institutions have jurisdiction over an issue.
		Punctuations in the equilibrium occur when policy image changes and institutional changes combine to produce.
	www.neiu.edu /~ourgift/media/FOR_DAY_THREE_Punctuated_Equilibrium_Theory_Primer.doc (1365 words)

	Punctuated Equilibrium and Patterns from the Fossil Record
		By reducing the numerical size of the transitional population and the number of years for which it exists, punctuated equilibrium greatly limits the number of organisms bearing transitional characteristics.
		Yet punctuated equilibrium denies evolutionary change both these advantages as it compress the vast majority of origin of macroevolutionary change and biological novelty into the vast minority of the time, and small populations.
		Punctuated equilibrium accepts the conventional idea that species form over hundreds or thousands of generations and through a series of intermediate stages.
	www.ideacenter.org /contentmgr/showdetails.php/id/1232 (4326 words)

	Punctuated equilibrium: come of age?
		The fossil record is characterised by long periods of stasis, or equilibrium, where species are clearly identifiable and stable, punctuated on occasions by the sudden, or ‘rapid’, appearance of new species.
		At one level punctuated equilibrium (PE) is merely a description of the fossil record (assuming geologic time, of course).
		In their recent review of punctuated equilibrium, they wrote with pride of these actions, speaking of creationism as ‘this philistine scourge’.
	www.answersingenesis.org /tj/v8/i2/punct.asp (4050 words)

	The Natural Limits to Biological Change
		Introduced in 1972 by Niles Eldredge and Stephen Gould as a description of the pattern in the fossil record, punctuated equilibrium centers on the claims of stasis and sudden appearance.
		Another tricky aspect of the claims of punctuated equilibrium is that a new species of fossil can only be recognized because of observable differences, usually in the skeletal structure.
		What we see is that beyond punctuated equilibrium's ability to describe the fossil record, it is of little use to evolutionary biologists because they cannot imagine a way to make it work with real organisms.
	www.leaderu.com /orgs/probe/docs/natlim.html (2780 words)

	Stephen Jay Gould - MSN Encarta
		In 1972 Gould and American paleontologist Niles Eldredge of the American Museum of Natural History in New York City originated the punctuated equilibria theory of evolution.
		From these observations Gould and Eldredge proposed that the evolution of a species results from rapid changes to an isolated population, caused by such natural phenomena as major climate change, followed by long periods of evolutionary stability.
		This theory of punctuated equilibria spurred debate among evolutionary biologists that continues today because it contrasts with the gradualist theory of evolution, which suggests that species evolve gradually over long periods of time.
	encarta.msn.com /encyclopedia_761573648/Gould_Stephen_Jay.html (390 words)

	Galactic Interactions » Blog Archive » Punctuated Equilibrium
		This notion is misguided, however; punctuated equilibrium is a modification of evolution that still fits entirely within the random mutation / natural selection paradigm.
		The fact that many call evolution “Darwinism” obscures the way science works; Darwin wasn’t a prophet whose words we must accept in their entirety if we are to accept any of it, he was a scientist who made some observations and posited a theory that has proven to have tremendous explanatory value.
		Here is an essay by one of the people who first proposed punctuated equilibrium about this topic.
	brahms.phy.vanderbilt.edu /~rknop/blog?p=23 (351 words)

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