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Encyclopedia > Macroevolution

Macroevolution refers to evolution that occurs at or above the level of species, in contrast with microevolution,[citation needed] which refers to smaller evolutionary changes (typically described as changes in allele frequencies) within a species or population. The process of speciation may fall within the purview of either, depending on the forces thought to drive it. Paleontology, evolutionary developmental biology, and comparative genomics contribute most of the evidence for the patterns and processes that can be classified as macroevolution. An example of macroevolution is the appearance of feathers during the evolution of birds from one group of dinosaurs. This article is about evolution in biology. ... In biology, a species is one of the basic units of biodiversity. ... Microevolution is the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as change at or below the species level. ... Allele frequency is a term of population genetics that is used in characterizing the genetic diversity of a species population, or equivalently the richness of its gene pool. ... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... Paleontology, palaeontology or palæontology (from Greek: paleo, ancient; ontos, being; and λόγος, logos, knowledge) is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. ... Evolutionary developmental biology (evolution of development or informally, evo-devo) is a field of biology that compares the developmental processes of different animals in an attempt to determine the ancestral relationship between organisms and how developmental processes evolved. ... Comparative genomics is the study of relationships between the genomes of different species or strains. ...


Within the Modern Synthesis school of thought, macroevolution is thought of as the compounded effects of microevolution. Thus, the distinction between micro- and macroevolution is not a fundamental one - the only difference between them is of time and scale. This understanding is disputed by some biologists, who claim that there may be macroevolutionary processes that cannot be described by strictly gradual phenotypic change, of the type studied by classical population genetics. This article or section does not cite any references or sources. ... Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ...


Some creationists have also adopted the term "macroevolution" to describe the form of evolution that they reject. They may accept that evolutionary change is possible within species ("microevolution"), but deny that one species can evolve into another ("macroevolution"). These arguments are rejected by mainstream science, which holds that there is ample evidence that macroevolution has occurred in the past.[1][2] Creationism is generally the belief that the universe was created by a deity, or alternatively by one or more powerful and intelligent beings. ... This article or section does not adequately cite its references or sources. ...

Contents

Research topics

Some examples of subjects whose study falls within the realm of macroevolution:

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. ... Gradualism is the belief that changes occur, or ought to occur, slowly in the form of gradual steps (see also incrementalism) In politics, the concept of gradualism is used to describe the belief that change ought to be modified in small, discrete increments rather than abrubt changes such as revolutions... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... The Dodo, shown here in a 1651 illustration by Jan Savery, is an often-cited[1] example of modern extinction. ... An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... Four of the 13 finch species found on the Galápagos Archipelago, and thought to have evolved by an adaptive radiation that diversified their beak shapes to adapt them to different food sources. ... The Cambrian explosion is the geologically kukko sudden appearance in the fossil record of the ancestors of familiar animals, starting about 542 million years ago (Mya). ... Rainforests are among the most biodiverse ecosystems on earth Biodiversity is the variation of taxonomic life forms within a given ecosystem, biome or for the entire Earth. ... In biology, heterochrony is defined as a developmental change in the timing of events, leading to changes in size and shape. ... // Summary The Evolution of the Genome is a book edited by Dr. T. Ryan Gregory of the University of Guelph, Ontario, Canada, covering a wide range of topics in the study of genome evolution. ... Horizontal gene transfer (HGT), also Lateral gene transfer (LGT), is any process in which an organism transfers genetic material to another cell that is not its offspring. ...

Origin of the Term

Russian Entomologist Yuri Filipchenko (or Philipchenko), depending on the transliteration) first coined the terms "macroevolution" and "microevolution" in 1927 in his German language work, "Variabilität und Variation"[1]. Yuri Filipchenko (sometimes spelled Philipchenko), Russian entomologist and coiner of the terms microevolution and macroevolution. ...


Since the inception of the two two terms, their meanings have been revised several times and even fallen into disfavour amongst scientists who prefer to speak of biological evolution as one process.[1]


History of macroevolution

The debate over the relationship between macroevolution and microevolution has been going on since the 1860s, when evolution first became a widely accepted idea following the publication of Charles Darwin's The Origin of Species. For other people of the same surname, and places and things named after Charles Darwin, see Darwin. ... Charles Darwins Origin of Species (publ. ...


The first theory of macroevolution, Lamarckism, developed by biologist Jean-Baptiste Lamarck, asserted that individuals develop traits they use and lose traits they do not use, and that individuals pass the acquired traits onto their offspring. Lamarck asserted that when environmental changes changed the "needs" of a species, this caused it to develop different traits, leading to the transmutation of species. Lamarckism or Lamarckian evolution is a theory put forward by the French biologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck, based on heritability of acquired characteristics, the once widely accepted idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring. ... Jean-Baptiste Lamarck. ...


Gregor Mendel, a Moravian[3] monk, popularly known as the "father of modern genetics" for his discovery of the laws of genetic variation in his study of natural variation in plants, believed that the laws of inheritance provided no grounds for macroevolution. In a lecture on March 8, 1865, Mendel noted that his research described the mechanism of microevolution, but gave no grounds for belief in macroevolution, saying "No one will seriously maintain that in the open country the development of plants is ruled by other laws than in the garden bed. Here, as there, changes of type must take place if the conditions of life be altered, and the species possesses the capacity of fitting itself to its new environment. [However,] nothing justifies the assumption that the tendency to form varieties increases so extraordinarily that the species speedily lose all stability, and their offspring diverge into an endless series of extremely variable forms." To the contrary, he said, the tendency is toward stability, with variation being the exception, not the rule. (Henig, 141) Gregor Johann Mendel (July 20, 1822[1] – January 6, 1884) was a Moravian[2] Augustinian priest and scientist often called the father of modern genetics for his study of the inheritance of traits in pea plants. ... Flag of Moravia Moravia (Czech and Slovak: Morava; German: ; Hungarian: ; Polish: ) is a historical region in the east of the Czech RepublicCzechia. ... St. ...


Darwin, on the other hand, saw no fundamental difference between microevolution and macroevolution. He asserted that "Certainly no clear line of demarcation has as yet been drawn between species and sub-species — that is, the forms which in the opinion of some naturalists come very near to, but do not quite arrive at, the rank of species: or, again, between subspecies and well-marked varieties, or between lesser varieties and individual differences. These differences blend into each other by an insensible series; and a series impresses the mind with the idea of an actual passage." (Darwin, 77)


Although Mendel's laws of inheritance were published as early as 1866, his theory was generally overlooked until the early twentieth century, in part because it was published in an obscure journal and by someone from outside the mainstream scientific community. Darwin himself never read of Mendel's work, and his own proposed mechanism for inherited traits, pangenesis, was more useful for statisticians of the biometric school than it was for biologists. Darwin had discovered a variation ratio of 2.4:1 in a study of snapdragons which he published in 1868, similar to the 3:1 ratio that led Mendel to discover the laws of genetic variation. However, Darwin was not sure of its ultimate meaning. (Henig, 143) After the rediscovery of Mendel's laws in 1900, the statisticians and biologists argued against each other until they were reconciled by the work of R.A. Fisher in the 1930s. Mendelian inheritance (or Mendelian genetics or Mendelism) is a set of primary tenets relating to the transmission of hereditary characteristics from parent organisms to their children; it underlies much of genetics. ... Pangenesis was Charles Darwins hypothetical mechanism for heredity. ... At Disney World, biometric measurements are taken of the fingers of multi-day pass users to ensure that the pass is used by the same person from day to day. ... Sir Ronald Fisher Sir Ronald Aylmer Fisher, FRS (February 17, 1890–July 29, 1962) was an extraordinarily talented evolutionary biologist, geneticist and statistician. ...


Modern evolutionary synthesis

In the late 1930s, evolutionary biologist Theodosius Dobzhansky devised the Modern evolutionary synthesis. Bringing macroevolution and microevolution to the English language, he wrote "we are compelled at the present level of knowledge reluctantly to put a sign of equality between the mechanisms of macro- and microevolution."[4]. Some have argued that he was reluctant to equate macro- and microevolution because it went against the beliefs of his mentor, Filipchenko, who was an orthogenetist, and of the opinion that micro- and macroevolution were of a different mechanism and calibre (Burian, 1994). From the writings of Dobzhansky, the modern synthesis view of evolution grew to its present prominence. Theodosius Grigorevich Dobzhansky (Russian — Феодосий Григорьевич Добржанский; sometimes anglicized to Theodore Dobzhansky; January 25, 1900 - December 18, 1975) was a noted geneticist and evolutionary biologist. ... This article or section does not cite any references or sources. ... Orthogenesis, orthogenetic evolution or autogenesis, is the hypothesis that life has an innate tendency to move in a unilinear fashion due to some internal or external driving force. The hypothesis is based on Essentialism, finalism and cosmic teleology and proposes an intrinsic drive which slowly transforms species. ...


Welsey Elsberry[5] observes that in 1940, Richard Goldschmidt “proposed that macroevolution refer to the establishment of the good species and higher taxa. Microevolution would then refer to everything below the species level.”[6] Richard Benedict Goldschmidt (April 12, 1878 – April 24, 1958) was a German-born American geneticist. ...


With the discovery of the structure of DNA and genes, genetic mutation gained acceptance as the mechanism of variance in the 1960s. This developing theory of evolution was then called the modern evolutionary synthesis, which remains prominent today. The synthetic model of evolution equated microevolution and macroevolution, asserting that the only difference between them was one of time and scale. This article or section does not cite any references or sources. ...


Non-Darwinian evolutionists

A few non-Darwinian evolutionists remained, however, including Ivan Ivanovich Schmalhausen and Conrad Hal Waddington, who argued that the processes of macroevolution are different from those of microevolution. According to these scientists, macroevolution occurs, but is restricted by such proposed mechanisms as developmental constraints. The concept can be summarized in Schmalhausen's Law," which holds that "When organisms are living within their normal range of environment, perturbations in the conditions of life and most genetic differences between individuals have little or no effect on their manifest physiology and development, but that under severe and unusual general stress conditions even small environmental and genetic differences have major effects." Non-Darwinian evolution points to evidence of great changes in population under conditions of stress; however, it is generally rejected by the scientific community because it provides no mechanism for larger changes at a genetic level under those circumstances[1]. Ivan Ivanovich Schmalhausen (April 23, 1884 – October 7, 1963) was a Russian zoologist and evolutionist. ... Conrad Hal Waddington FRS FRSE (1905 — 1975), known to his friends as Wad, was a developmental biologist, paleontologist, geneticist, embryologist and philosopher. ... Ivan Ivanovich Schmalhausen (April 23, 1884 – October 7, 1963) was a Russian zoologist and evolutionist. ...


Punctuated equilibria

In the late 1970s, Stephen Jay Gould challenged the synthesis model of evolution, and proposed a punctuated equilibrium model, whereby major evolutionary changes took place in limited gene pools after radical climate changes. He said, "I well remember how the synthetic theory [of evolution] beguiled me with its unifying power when I was a graduate student in the mid-1960s. Since then I have been watching it slowly unravel as a universal description of evolution.....I have been reluctant to admit it — since beguiling is often forever — but if Mayr's characterization of the synthetic theory is accurate, then that theory, as a general proposition, is effectively dead, despite its persistence as textbook orthodoxy." (Paleobiology, Vol.6, 1980, p. 120). He also was not proposing additional mechanisms to the modern synthesis but was only maintaining that life's history is not in a constant state of gradual evolving (The Structure of Evolutionary Theory pp 1006-1021) Natural History magazine Stephen Jay Gould (September 10, 1941 – May 20, 2002) was an American paleontologist, evolutionary biologist, and historian of science. ... 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. ... This article has been identified as possibly containing errors. ...


Despite his rejection of the synthetic theory, however, he asserted that "Evolutionary theory is now enjoying this uncommon vigor. Yet amidst all this turmoil no biologist has been led to doubt the fact that evolution occurred; we are debating how it happened. We are all trying to explain the same thing: the tree of evolutionary descent linking all organisms by ties of genealogy. Creationists pervert and caricature this debate by conveniently neglecting the common conviction that underlies it, and by falsely suggesting that evolutionists now doubt the very phenomenon we are struggling to understand."


Criticisms of macroevolution

While details of macroevolution are continuously studied by the scientific community, the overall theory behind macroevolution (i.e. common descent) has been overwhelmingly consistent with empirical data. Predictions of empirical data from the theory of common descent have been so consistent that biologists often refer to it as the "fact of evolution" (Theobald 2004). Nevertheless, macroevolution is sometimes disputed by religious groups. Generally speaking, these groups attempt to differentiate between microevolution and macroevolution, asserting various hypotheses which are considered to have no scientific basis by any mainstream scientific organization, including the American Association for the Advancement of Science[7]. This article or section does not adequately cite its references or sources. ... A group of organisms is said to have common descent if they have a common ancestor. ... The American Association for the Advancement of Science (AAAS) is an organization that promotes cooperation between scientists, defends scientific freedom, encourages scientific responsibility and supports scientific education for the betterment of all humanity. ...


Much of the debate encircling the validity of macroevolution as a distinct evolutionary process involves primarily two factors: (1) species stasis (a pattern in which species show no net morphological change over millions of years) and (2) species selection (selection at the species level where the individuals experiencing differential reproduction or death are species rather than organisms as is typically the case in Neo-Darwinism). Since the discovery of Punctuated Equilibria in the fossil record, it has often been questioned whether these two processes (species stasis and species sorting) require deviation from typical explanations which adhere to Darwinian (or Synthetic) orthodoxy. Recent work on stasis by Eldredge and others has shown, however, that stasis is often the byproduct of species being broken up into several, quasi-autonomous lineages. Clearly, if these lineages (presumably discrete populations) are sufficiently autonomous, then the entire species cannot exhibit morphological change because it does not evolve as a coherent unit. In such instances where each of the populations is effectively evolutionary independent, it would be virtually impossible for the entire species to exhibit net morphological change in the absence of rampant parallelism (a very unlikely proposition since this invokes an almost orthogenetic or teleological perspective).


Species selection, on the other hand, has been a more difficult problem to evaluate empirically because it is a trickier concept to pin down. While Coyne and Orr recently discussed numerous potential and empirical cases of species selection, there has been no consensus over a working definition of species selection in spite of more than 30 years of debate. Some camps (Vrba and Lieberman) insist that selection requires emergent characters while others (Gould and Lloyd) contend that only emergent fitness differences are required for the operation of selection processes. Since Darwin chose not to differentiate between "emergent" or "reducible" characters when describing male adaptations resulting from asymmetrical polyandry where no female behaviors or preferences for such macroscopic traits were evident (a phenomenon now know as "sperm competition"), historical posterity clearly defers to Gould and Lloyd's conception that only fitness differences are important for selection processes. Also, it makes little sense to distinguish between this form of "male-male" competitive sexual selection and other types involving allegedly emergent characters, such as male antlers. Clearly, both male gametocytes and male antlers are properties of males, and to say that these are fundamentally different types of selection based on whether one trait is macroscopic while the other is microscopic (appearing only on individual sex cells) is not the conventional approach. As discussed in greater detail above, Darwin treated selection as an economic process involving evolutionary assets of individuals, regardless of whether these traits were macroscopic vs. microscopic. This conceptual distinction is a recent invention, and so it is likely that Coyne and Orr are correct in asserting that there is strong empirical evidence for the operation of species selection in nature with well over a hundred sister groups analyzed thus far.


See also

Microevolution is the occurrence of small-scale changes in allele frequencies in a population, over a few generations, also known as change at or below the species level. ... Charles Darwins first sketch of an evolutionary tree from his First Notebook on Transmutation of Species (1837) Speciation is the evolutionary process by which new biological species arise. ... A transitional fossil or transitional form is the fossilized remains of a life form that illustrates an evolutionary transition. ... This is a very tentative list of vertebrate transitional fossils (fossil remains of a creature that exhibits primitive traits in comparison with more derived life-forms to which it is related). ...

References

  1. ^ a b c d http://www.talkorigins.org/faqs/macroevolution.html
  2. ^ http://www.talkorigins.org/indexcc/CB/CB901.html
  3. ^ Henig, Robin Marantz (2000). The Monk in the Garden : The Lost and Found Genius of Gregor Mendel, the Father of Genetics. Houghton Mifflin. ISBN 0-395-97765-7. “The article, written by an obscure Moravian monk named Gregor Mendel...” 
  4. ^ Dobzhansky, Theodosius Grigorievich (1937). Genetics and the origin of species. LC QH366 .D6. , p12
  5. ^ http://www.rtis.com/nat/user/elsberry/evobio/evc/wre_arch/wre00123.htm
  6. ^ Goldschmidt, Richard (1940). The material basis of evolution. New Haven, Yale University Press. LC QH366 .G53. 
  7. ^ AAAS press release news-links and resources

External links


  Results from FactBites:
 
Macroevolution - Wikipedia, the free encyclopedia (1347 words)
Macroevolution is largely disputed by many creationism and intelligent design advocates.
The first theory of macroevolution, Lamarckism, developed by biologist Jean-Baptiste Lamarck, asserted that individuals develop traits they use and lose traits they do not use, and that individuals pass the acquired traits onto their offspring.
In bringing macroevolution and microevolution to the English language, wrote "we are compelled at the present level of knowledge reluctantly to put a sign of equality between the mechanisms of macro- and microevolution" (Dobzhansky, 12).
macroevolution - definition of macroevolution in Encyclopedia (1823 words)
Macroevolution is the concept that evolution of species and higher taxa is the result of large-scale changes in gene-frequencies over time.
The first theory of macroevolution, Lamarckism, developed by biologist Jean-Baptiste Pierre Antoine de Monet, Chevalier de Lamarck, asserted that individuals develop traits they use and lose traits they do not use, and that individuals pass the traits the acquired traits onto their offspring.
In bringing macroevolution and microevolution to the English language, wrote "we are compelled at the present level of knowledge reluctantly to put a sign of equality between the mechanisms of macro- and microevolution" (1937, page 12).
  More results at FactBites »

 
 

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