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What we have now

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Evolution is the change in the inherited traits of a population of organisms through successive generations.[1] After a population splits into smaller groups, these groups evolve independently and may eventually diversify into new species. Ultimately, life is descended from a common ancestry through a long series of these speciation events, stretching back in a tree of life that has grown over the 3.5 billion years of life on Earth.[2][3][4][5] This is visible in anatomical, genetic and other likenesses between groups of organisms, geographical distribution of related species, the fossil record and the recorded genetic changes in living organisms over many generations. To distinguish from other uses of the word evolution, it is sometimes termed biological evolution, genetic evolution or organic evolution.[6][7]

Evolution is the product of two opposing forces: processes that constantly introduce variation in traits, and processes that make particular variants become more common or rare. A trait is a particular characteristic, such as eye color, height, or a behavior, that is expressed when an organism's genes interact with its environment. Genes vary within populations, so organisms show heritable differences (variation) in their traits. The main cause of variation is mutation, which changes the sequence of a gene. Altered genes, or alleles, are then inherited by offspring. There can sometimes also be transfer of genes between species.[8][9]

Two main processes cause variants to become more common or rare in a population. One is natural selection, through which traits that aid survival and reproduction become more common, while traits that hinder survival and reproduction become more rare.[1][10] Natural selection occurs because only a few individuals in each generation will survive, since resources are limited and organisms produce many more offspring than their environment can support. Over many generations, mutations produce successive, small, random changes in traits, which are then filtered by natural selection and the beneficial changes retained. This adjusts traits so they become suited to an organism's environment: these adjustments are called adaptations.[11] Not every trait, however, is an adaptation. Another cause of evolution is genetic drift, which produces entirely random changes in how common traits are in a population. Genetic drift comes from the role that chance plays in whether a trait will be passed on to the next generation.[12][13]

Evolutionary biologists document the fact that evolution occurs, and also develop and test theories that explain its causes. The study of evolutionary biology began in the mid-nineteenth century, when research into the fossil record and the diversity of living organisms convinced most scientists that species changed over time.[14][15] The mechanism driving these changes remained unclear until the theories of natural selection were independently proposed by Charles Darwin and Alfred Wallace. In 1859, Darwin's seminal work On the Origin of Species brought the new theories of evolution by natural selection to a wide audience,[16] leading to the overwhelming acceptance of evolution among scientists.[17][18][19][20] In the 1930s, Darwinian natural selection became understood in combination with Mendelian inheritance, forming the modern evolutionary synthesis,[21] which connected the units of evolution (genes) and the mechanism of evolution (natural selection). This powerful explanatory and predictive theory has become the central organizing principle of modern biology, directing research and providing a unifying explanation for the history and diversity of life on Earth.[18][19][22] Evolution is therefore applied and studied in fields as diverse as agriculture, anthropology, conservation biology, ecology, medicine, paleontology, philosophy, and psychology along with other specific topics in the previous listed fields.

My redraft

[edit]

Evolution is the change in the inherited traits of a population of organisms through successive generations.[1] This change is the product of two opposing forces: processes that constantly introduce variation in traits, and processes that make particular variants become more common or rare. A trait is a particular characteristic, such as eye color, height, or a behavior, that is expressed when an organism's genes interact with its environment. To distinguish from other uses of the word evolution, it is sometimes termed biological evolution, genetic evolution or organic evolution.[6][23]

The main source of variation is mutation, which changes the base pair sequences of genes. These altered genes can be passed on through reproduction, and give rise to alternative varieties, or alleles, of traits in organisms. Another source of variation is genetic recombination which shuffles the genes into new combinations that can result in organisms exhibiting different traits. Under certain circumstances, variation can also be increased by the transfer of genes between species.[8][24]

Two main processes cause variants to become more common or rare in a population. One is natural selection, through which traits that aid survival and reproduction become more common, while traits that hinder survival and reproduction become more rare. Natural selection occurs because only a few individuals in each generation will survive, since resources are limited and organisms produce many more offspring than their environment can support. Over many generations, the mutations that produce small, random changes in traits, are filtered by natural selection and the beneficial changes successively retained. This iterative process adjusts traits so they become better suited to an organism's environment: these adjustments are called adaptations.[11]

However, not all change is adaptive. Another cause of evolution is genetic drift, which leads to random changes in how common traits are in a population. Genetic drift is most important when traits do not strongly influence survival, particularly so in small populations where chance plays a disproportionate role in the frequency of traits passed on to the next generation.[25][26]

A key process in evolution is speciation, in which a single ancestral species splits and diversifies into multiple new species, and there are several modes through which this occurs. Ultimately, all living (and extinct) species are descended from a common ancestor via a long series of speciation events. These events stretch back in a diverse "tree of life" that has grown over the 3.5 billion years in which life has existed on Earth.[27][28][4][29] This is visible in anatomical, genetic and other similarities between groups of organisms, geographical distribution of related species, the fossil record and the recorded genetic changes in living organisms over many generations.

Evolutionary biologists document the fact that evolution occurs, and also develop and test theories that explain its causes. The study of evolutionary biology began in the mid-nineteenth century, when research into the fossil record and the diversity of living organisms convinced most scientists that species changed over time.[14][15] The mechanism driving these changes remained unclear until the theory of natural selection was independently proposed by Charles Darwin and Alfred Wallace. In 1859, Darwin's seminal work On the Origin of Species brought the new theory of evolution by natural selection to a wide audience,[16] leading to the overwhelming acceptance of evolution among scientists.[17][18][19][20] In the 1930s, Darwinian natural selection became understood in combination with Mendelian inheritance, forming the modern evolutionary synthesis,[21] which connected the substrate of evolution (inherited genetics) and the mechanism of evolution (natural selection). This powerful explanatory and predictive theory has become the central organizing principle of modern biology, directing research and providing a unifying explanation for the history and diversity of life on Earth.[18][19][22] Evolution is therefore applied and studied in fields as diverse as agriculture, anthropology, conservation biology, ecology, medicine, paleontology, philosophy, and psychology along with other specific topics in the previous listed fields.

My redraft, v2

[edit]

Evolution (also known as biological evolution, genetic evolution and organic evolution)[6][30] is the change in the inherited traits of a population of organisms through successive generations.[1] This change results from interactions between processes which introduce variation into a population, and other processes which remove it. As a result, variants with particular traits become more, or less, common. A trait is a particular characteristic, anatomical, biochemical or behavioural, that is the result of gene–environment interaction.

The main source of variation is mutation, which changes the base pair sequences of genes. These altered genes can be passed on through reproduction, and give rise to alternative varieties, or alleles, of traits in organisms. Another source of variation is genetic recombination which shuffles the genes into new combinations that can result in organisms exhibiting different traits. Under certain circumstances, variation can also be increased by the transfer of genes between species,[8][31] and by the extremely rare, but significant, wholesale incorporation of genomes through endosymbiosis.[32][33]

Two main processes cause variants to become more common or rare in a population. One is natural selection, through which traits that aid survival and reproduction become more common, while traits that hinder survival and reproduction become more rare. Natural selection occurs because only a small proportion of individuals in each generation will survive and reproduce, since resources are limited and organisms produce many more offspring than their environment can support. Over many generations, heritable variation in traits is filtered by natural selection and the beneficial changes are successively retained through differential survival and reproduction. This iterative process adjusts traits so they become better suited to an organism's environment: these adjustments are called adaptations.[11]

However, not all change is adaptive. Another cause of evolution is genetic drift, which leads to random changes in how common traits are in a population. Genetic drift is most important when traits do not strongly influence survival, particularly so in small populations where chance plays a disproportionate role in the frequency of traits passed on to the next generation.[34][35] Genetic drift is important in the neutral theory of molecular evolution, and plays a role in the molecular clocks that are used in phylogenetic studies.

A key process in evolution is speciation, in which a single ancestral species splits and diversifies into multiple new species, and there are several modes through which this occurs. Ultimately, all living (and extinct) species are descended from a common ancestor via a long series of speciation events. These events stretch back in a diverse "tree of life" that has grown over the 3.5 billion years in which life has existed on Earth.[36][37][4][38] This is visible in anatomical, genetic and other similarities between groups of organisms, geographical distribution of related species, the fossil record and the recorded genetic changes in living organisms over many generations.

Evolutionary biologists document the fact that evolution occurs, and also develop and test theories that explain its causes. The study of evolutionary biology began in the mid-nineteenth century, when research into the fossil record and the diversity of living organisms convinced most scientists that species changed over time.[14][15] The mechanism driving these changes remained unclear until the theory of natural selection was independently proposed by Charles Darwin and Alfred Wallace. In 1859, Darwin's seminal work On the Origin of Species brought the new theory of evolution by natural selection to a wide audience,[16] leading to the overwhelming acceptance of evolution among scientists.[17][18][19][20] In the 1930s, Darwinian natural selection became understood in combination with Mendelian inheritance, forming the modern evolutionary synthesis,[21] which connected the substrate of evolution (inherited genetics) and the mechanism of evolution (natural selection). This powerful explanatory and predictive theory has become the central organizing principle of modern biology, directing research and providing a unifying explanation for the history and diversity of life on Earth.[18][19][22] Evolution is applied and studied in fields as diverse as agriculture, anthropology, conservation biology, ecology, medicine, paleontology, philosophy, and psychology along with other specific topics in the previous listed fields.

References

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  1. ^ a b c d Futuyma, Douglas J. (2005). Evolution. Sunderland, Massachusetts: Sinauer Associates, Inc. ISBN 0-87893-187-2.
  2. ^ Schopf, J.W. (1999). Cradle of life: the discovery of Earth's earliest fossils. Princeton.
  3. ^ Woese, C. (1998). "The Universal Ancestor". PNAS. 95 (12): 6854–6859. doi:10.1073/pnas.95.12.6854. PMC 22660. PMID 9618502.
  4. ^ a b c Theobald, D.L. (2010). "A formal test of the theory of universal common ancestry". Nature. 465 (7295): 219–222. doi:10.1038/nature09014. PMID 20463738.
  5. ^ Doolittle, W.F. (February, 2000). "Uprooting the tree of life" (PDF). Scientific American. 282 (2): 90–95. doi:10.1038/scientificamerican0200-90. PMID 10710791. {{cite journal}}: Check date values in: |date= (help)
  6. ^ a b c Cite error: The named reference GeneticEvolution was invoked but never defined (see the help page).
  7. ^ Kottak, Conrad Phillip (2005). Window on Humanity: A Concise Introduction to Anthropology. The McGraw–Hill Companies, Inc, New York.
  8. ^ a b c Jain, R.; Rivera, M.C.; Lake, J.A. (1999), "Horizontal gene transfer among genomes: the complexity hypothesis.", Proc Natl Acad Sci U S A, 96 (7): 3801–6, doi:10.1073/pnas.96.7.3801, PMC 22375, PMID 10097118.
  9. ^ Richardson, Aaron O. and Jeffrey D. Palmer (January 2007). "Horizontal gene transfer in plants" (PDF). Journal of Experimental Botany. 58 (1): 1–9. doi:10.1093/jxb/erl148. PMID 17030541. Retrieved 2007-03-18.{{cite journal}}: CS1 maint: date and year (link)
  10. ^ Lande R, Arnold SJ (1983). "The measurement of selection on correlated characters". Evolution. 37 (6): 1210–26. doi:10.2307/2408842. JSTOR 2408842.
  11. ^ a b c Ayala FJ (2007). "Darwin's greatest discovery: design without designer". Proc. Natl. Acad. Sci. U.S.A. 104 (Suppl 1): 8567–73. doi:10.1073/pnas.0701072104. PMC 1876431. PMID 17494753.
  12. ^ Evolution 101:Sampling Error and Evolution and Effects of Genetic Drift from the Understanding Evolution University of California at Berkeley
  13. ^ Evolution 101: Peripatric Speciation from the Understanding Evolution webpages made by the University of California at Berkeley
  14. ^ a b c Ian C. Johnston (1999). "History of Science: Early Modern Geology". Malaspina University-College. Retrieved 2008-01-15.
  15. ^ a b c Bowler, Peter J. (2003). Evolution:The History of an Idea. University of California Press. ISBN 0-52023693-9.
  16. ^ a b c Darwin, Charles (1859). On the Origin of Species (1st ed.). London: John Murray. p. 1. ISBN 0801413192.. Related earlier ideas were acknowledged in Darwin, Charles (1861). On the Origin of Species (3rd ed.). London: John Murray. xiii. ISBN 0801413192.
  17. ^ a b c AAAS Council (December 26, 1922). "AAAS Resolution: Present Scientific Status of the Theory of Evolution". American Association for the Advancement of Science.
  18. ^ a b c d e f "IAP Statement on the Teaching of Evolution" (PDF). The Interacademy Panel on International Issues. 2006. Retrieved 2007-04-25. Joint statement issued by the national science academies of 67 countries, including the United Kingdom's Royal Society
  19. ^ a b c d e f Board of Directors, American Association for the Advancement of Science (2006-02-16). "Statement on the Teaching of Evolution" (PDF). American Association for the Advancement of Science. from the world's largest general scientific society
  20. ^ a b c "Statements from Scientific and Scholarly Organizations". National Center for Science Education.
  21. ^ a b c Cite error: The named reference Kutschera was invoked but never defined (see the help page).
  22. ^ a b c "Special report on evolution". New Scientist. 2008-01-19.
  23. ^ Kottak, Conrad Phillip (2005). Window on Humanity: A Concise Introduction to Anthropology. The McGraw–Hill Companies, Inc, New York.
  24. ^ Richardson, Aaron O. and Jeffrey D. Palmer (January 2007). "Horizontal gene transfer in plants" (PDF). Journal of Experimental Botany. 58 (1): 1–9. doi:10.1093/jxb/erl148. PMID 17030541. Retrieved 2007-03-18.{{cite journal}}: CS1 maint: date and year (link)
  25. ^ Evolution 101:Sampling Error and Evolution and Effects of Genetic Drift from the Understanding Evolution University of California at Berkeley
  26. ^ Evolution 101: Peripatric Speciation from the Understanding Evolution webpages made by the University of California at Berkeley
  27. ^ Schopf, J.W. (1999). Cradle of life: the discovery of Earth's earliest fossils. Princeton.
  28. ^ Woese, C. (1998). "The Universal Ancestor". PNAS. 95 (12): 6854–6859. doi:10.1073/pnas.95.12.6854. PMC 22660. PMID 9618502.
  29. ^ Doolittle, W.F. (February, 2000). "Uprooting the tree of life" (PDF). Scientific American. 282 (2): 90–95. doi:10.1038/scientificamerican0200-90. PMID 10710791. {{cite journal}}: Check date values in: |date= (help)
  30. ^ Kottak, Conrad Phillip (2005). Window on Humanity: A Concise Introduction to Anthropology. The McGraw–Hill Companies, Inc, New York.
  31. ^ Richardson, Aaron O. and Jeffrey D. Palmer (January 2007). "Horizontal gene transfer in plants" (PDF). Journal of Experimental Botany. 58 (1): 1–9. doi:10.1093/jxb/erl148. PMID 17030541. Retrieved 2007-03-18.{{cite journal}}: CS1 maint: date and year (link)
  32. ^ Margulis, Lynn (1998). The symbiotic planet: a new look at evolution. Weidenfeld & Nicolson, London.
  33. ^ Sapp, J. (1994). Evolution by association: a history of symbiosis. Oxford University Press, UK.
  34. ^ Evolution 101:Sampling Error and Evolution and Effects of Genetic Drift from the Understanding Evolution University of California at Berkeley
  35. ^ Evolution 101: Peripatric Speciation from the Understanding Evolution webpages made by the University of California at Berkeley
  36. ^ Schopf, J.W. (1999). Cradle of life: the discovery of Earth's earliest fossils. Princeton.
  37. ^ Woese, C. (1998). "The Universal Ancestor". PNAS. 95 (12): 6854–6859. doi:10.1073/pnas.95.12.6854. PMC 22660. PMID 9618502.
  38. ^ Doolittle, W.F. (February, 2000). "Uprooting the tree of life" (PDF). Scientific American. 282 (2): 90–95. doi:10.1038/scientificamerican0200-90. PMID 10710791. {{cite journal}}: Check date values in: |date= (help)
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