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Published byRoderick Warner Modified over 9 years ago
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Natural Selection Darwin compiled his notes from his voyage and came to the following conclusion. – Traits are inherited from the parents – Traits can be selected for through selective breeding Confirmed in domestic animals in what became known as artificial selection – Selected traits based on human desire and not the natural environment
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Natural Selection causes Evolution Darwin stated in the absence of artificial selection, Nature provides the selective pressure to drive evolution – Natural selection is driven by competition among members of a community for resources
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Survival of the Fittest According to Malthus’s calculations, the world would quickly run out of resources if the birth rate or organisms wasn’t tied to competition. – Each species struggles to find its niche Creates a struggle for existence (inter species competition) – Fitness is tied to reproductive success The organism that can out compete individuals within its species and those outside their species will leave the most offspring
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Descent with Modification Infers that ALL organisms that are similar are related by a common ancestor – Changes were the result of natural selection Intra-species selection Inter-species selection Availability of resources Presence of resources Catastrophes – Changes are gradual and take a long time Inferred based on the gradual changes to our planet Verified using the fossil record
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Other Evidence of Natural Selection Homologous structures – Similar structure but different function within different species Provides evidence of common ancestor
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Other Evidence of Natural Selection Vestigial Organs – Evidence of similarity of structure but with loss of function Provides evidence of relatedness
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Other Evidence of Natural Selection Similar Embryonic stages (development)
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Summation of Darwin’s Theory Individuals differ due to heritable traits Organisms produce more offspring than are supposed to survive – Creates competition Each type of organism will seek to exploit its advantages in a community The species that we see today are here because they could best exploit their niche
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