15.1 - History of Evolutionary Thought

Chapter 15

The Idea of EvolutionEvolution - the change in the gene frequencies of a population over generational time.

Section 1 History of Evolutionary Thought

Chapter 15Section 1 History of Evolutionary Thought

The Definition of Evolution, explainedGene Frequency - The measure of the occurrence of an allele in relation to that of other alleles of the same gene in a population.

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Chapter 15Section 1 History of Evolutionary Thought

The Definition of Evolution, explained

PopulationA group of organisms that are able to interbreed.

What natural barriers would prohibit an organism from interbreeding?

Example: Kodiak Bear

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Chapter 15Section 1 History of Evolutionary Thought

The Definition of Evolution, explainedGenerational TimeFrom one generation to the next. (Not within the same generation!)

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Chapter 15Section 1 History of Evolutionary Thought

The Definition of Evolution, explainedGenerational TimeLamarck’s Flawed Theoryhttp://my.hrw.com/sh/hm6_0030367514/student/media/flash/60262.swf

Chapter 15Section 1 History of Evolutionary ThoughtCharles

Darwin’s Contribution

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Chapter 15Section 1 History of Evolutionary Thought

Darwin’s IdeasDescent with ModificationDarwin wrote On the Origin of Species, in which he argued that 1descent with modification occurs, 2that all species descended from common ancestors, and 3that natural selection is the mechanism for evolution.

Chapter 15Section 1 History of Evolutionary Thought

Darwin’s Ideas, continuedNatural SelectionOrganisms in a population adapt to their environment as the proportion of individuals with genes for favorable traits increases. Those individuals that pass on more genes are considered to have greater fitness.

Natural Selection

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Adaptation

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Fitness