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This article is written based on the consensus of the mainstream science community. Go here for the conflict between creationists and scientists.

In biology, evolution (also called organic evolution to distinguish from chemical evolution) refers to a natural process whereby living organisms change in their biological characteristics over successive generations.^{[1][2][3][4][5]} As the result of evolution, an organism becomes able to adopt best with the environment in which it lives.^[2] Dobzhansky, Ayala, Stebbins and Valentine defines evolution in the following way:^[6]

"Organic evolution is a series of partial or complete and irreversible transformations of the genetic compositions of populations, based principally upon altered interactions with their environment. It consists chiefly of adaptive radiations into new environments, adjustment to environmental changes that take place in a particular habitat, and the origin of new ways for exploiting existing habitats. These adaptive changes occasionally give rise to greater complexity of developmental pattern, of physiological reactions, and of interactions between populations and their environment."

When a population of organisms consisting of a single species splits into several smaller groups, these splinter groups independently evolve into new species. Anatomical similarities, geographical distribution of similar species and the fossil record indicate that all extinct and living organisms are descended from a common ancestor through a long series of these divergence events, stretching back in a tree of life that has grown over the 3,500 million years of life on Earth.^[7]

Contents 1 Mechanism 1.1 Natural selection 1.2 Genetic drift 2 Religious reaction 3 Evolution beyond the organism 4 References 5 External links

Mechanism

Evolution occurs through four mechanisms - natural selection, genetic drift, mutation and migration.^[8]

Natural selection

Natural selection is the process by which heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations. The "FAO Corporate Document Repository" maintained by the Food and Agriculture Organization (FAO) defines natural selection as "the differential survival and reproduction of organisms because of differences in characteristics that affect their ability to utilize environmental resources."^[9] Allendorf and Luikart define natural selection as "differential contribution of genotypes to the next generation due to differences in survival and reproduction."^[10] According to the National Institute of Food and Agriculture (NIFA), "genes which produce characteristics that are more favorable in a particular environment will be more abundant in the next generation."^[11] Through natural selection, the genotypes in a population which are best adapted to the environment, increase in frequency relative to the less well-adapted genotypes over successive generations.^[12] Natural selection favors genes that aid survival and reproduction.

Genetic drift

Genetic drift is random change in the frequency of alleles, caused by the random sampling of a generation's genes during reproduction. The relative importance of natural selection and genetic drift in a population varies depending on the strength of the selection and the effective population size, which is the number of individuals capable of breeding.

Religious reaction

There is overwhelming scientific consensus supporting the validity of evolution by natural selection; however because of its potential implications for the origins of humankind, evolutionary theory has been opposed by religious organizations since the time of its inception. Particularly in the United States, there is an organized "creationist movement" which expresses a biblical view in favor of evolution. No mainstream scientific organization accepts the arguments of creationists as valid.

Evolution beyond the organism

In The Selfish Gene biologist Richard Dawkins proposed the name Meme for a heritable unit of information that behaves analogously to a gene.^[13] A Meme is any idea that is passed along with replication and variation that affects fitness. Ideas following the same basic evolutionary algorithm as genes will inevitable tend towards increased fitness in their environment. In a capitalistic society this experimentation and variable success of small businesses drives an incredible array of business models and products to success where as a controlled economy is incapable of the experimentation that leads to progress.

References

1. ↑ Michael Allaby, Oxford Dictionary of Zoology, Oxford University Press, ISBN 0195669940, p. 198. "Change, with continuity in successive generations of organism (i.e. 'descent with modification' as Darwin called it). The phenomenon is amply demonstrated by the fossil record, for the changes over geological time are sufficient to recognize distinct eras, for the most part with very different plants and animals."
2. ↑ ^{2.0 2.1} K. C. Ghosh and B. Manna, Fundamentals of Zoology, New Central Book Agency, ISBN 8173814325, p. 807. "Evolution is a process by which an organism changes itself to adopt best with the environment."
3. ↑ Korak Kanti Chaki, Gautam Kundu, Supriti Sarkar, Introduction to General Zoology, vol 1, New Central Book Agency, ISBN 8173814805, p. 421.
4. ↑ An introduction to evolution Understanding Evolution, University of California Museum of Paleontology and the National Center for Science Education.
5. ↑ Futuyma, Douglas J. (2005). Evolution. Sunderland, Massachusetts: Sinauer Associates, Inc. ISBN 0-87893-187-2. 
6. ↑ Dobzhansky, Th., F.J. Ayala, G.L. Stebbins & J.W. Valentine. 1977. Evolution. W.H. Freeman, San Francisco.
7. ↑ Thomas Cavalier-Smith (2006), Cell evolution and Earth history: stasis and revolution Philos Trans R Soc Lond B Biol Sci, pp. 969–1006.
8. ↑ Natural selection Understanding Evolutuion
9. ↑ [1]
10. ↑ Allendorf, F.W., and G. Luikart (2007), Conservation and the Genetics of Populations, Blackwell Publishing, pp. 642.
11. ↑ Glossary of Biotechnology Terms National Institute of Food and Agriculture (NIFA)
12. ↑ Bio-glossary European Commission
13. ↑ Dawkins, 2006. The Selfish Gene, 30th Anniversary edition. Ch. 11.

External links

• Evolution entry in Stanford Encyclopedia of Philosophy
• Understanding Evolution A site explaining evolution maintained by the University of California