Darwin's Theory of Natural Selection and the Evolution of Animals

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Darwin’s theory of natural selection has provided us with the explanations of the processes involved in the changes of species over long periods of time. His theory was based on five major assumptions: VARIATION: When Individuals within a species differ from one another in physical characteristics and in their behaviour. HERITABILITY: Some of the variations amongst the members of species is inherited, meaning that the offspring tend to resemble their parents more than the other members of the species. COMPETITION: Members of most species produce far more offspring than can survive. If there weren’t problems with survival Darwin figured out that a pair of elephants could have about 19 million descendents alive 750 years after birth! However there are those who don’t win competitions for best food and best place to live are the ones who are less likely to reproduce. NATURAL SELECTION: Those who survive the competitions will then go on to breed and these tend to have the characteristics that are better suited to the environment than those who don’t. Thus, there is natural selection or ‘survival of the fittest’. ADAPTATION: Successive generations will tend to be more and more adaptive to their environment and will have characteristics that heighten their abilities to survive, to get food and most importantly to reproduce and all of this is a result of the process of Natural Selection. (Eg. If only fast moving prey survive then that species should evolve over the generations in the direction of becoming on average faster moving.) Darwin believed that the increasing competition for finite resources exerts selective p... ... middle of paper ... ...eacock’s long train attractive, so those with the long trains have more reproductive success than those with short ones, turning this characteristic into an advantage and an adaptive trait. The peppered moth is a good example regarding Darwin’s theory of natural selection this was done by Kettlewell who studied two variants of peppered moth, one which was light and the other one was dark the difference of colour inherited. The moths are eaten by birds who rely on their sight to find them, he observed them on light and dark coloured lichen trees (trees were in polluted area) and found that the light coloured moths survived best on the light lichen trees and the dark ones on the dark lichen trees. According to Darwin’s theory, the number of darker moths should increase if the proportion of dark tress also increase.

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