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paper1_final - Youngjoo Ha October 18, 2007 BIOLOGY 121:...

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October 18, 2007 BIOLOGY 121: Evolution of Animal form Paper 1 – Draft 3 Charles Darwin and Natural Selection In On the Origin of Species , Charles Darwin claims that natural selection is the primary mechanism of change in evolution. Natural selection preserves favorable variations and eliminates harmful variations at the level of an individual. There are three essential components to natural selection: variations shown in individuals, hereditary transmission of variations, and an increase in fitness shown in the progeny. Variation in individuals is necessary for a change in evolution to occur, because differences in phenotypes provide raw material for on which natural selection to work. As shown in Darwin’s theory of population growth, more individuals are produced that can survive, so competition among individuals, in the same and different species, takes place. All species would increase their numbers at a geometric rate if there were no external influences that would limit the rate of growth. Some of the influences that limit the rate are climate and interactions with other competitors. Therefore, because individuals are engaged in a struggle for existence constantly, it would be difficult for a species to grow, if all the individuals in the species had the same trait that were not profitable to the individual. If there were many variations among different individuals in a species, there would be greater amount of raw material for natural selection to take place. Natural selection would act on individuals to preserve favorable variations and eliminate harmful variations, so the individuals with profitable variations would be more likely to produce offspring, and pass on the variations. An accumulation of modified variations would result in a formation of a new species.
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This note was uploaded on 04/07/2008 for the course BIOLOGY 121 taught by Professor Mcshea during the Fall '07 term at Duke.

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paper1_final - Youngjoo Ha October 18, 2007 BIOLOGY 121:...

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