Other Mechanisms of Evolution. Student Expectation (SE) 7F - analyze and evaluate the effects of other evolutionary mechanisms , including genetic drift, gene flow, mutation, and recombination. Darwin’s Theory of Evolution.
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Other Mechanisms of Evolution Student Expectation (SE) 7F - analyze and evaluate the effects of other evolutionary mechanisms, including genetic drift, gene flow, mutation, and recombination.
Darwin’s Theory of Evolution • 1. Darwin’s “On the Origin of Species” presented evolution as a process carried out by means of natural selection. Now we know that natural selection is NOT the only source of evolutionary change. Other mechanisms are: • Genetic Drift • Gene Flow (Migration) • Mutations • Recombination of DNA
a. Genetic Drift • A random change in the frequency of alleles in small populations often due to natural disasters • Examples of Genetic Drift • Bottleneck Effect • Founder Effect
Bottleneck Effect A form of genetic drift that occurs when a population’s size is reduced for at least one generation.
Founders Effect A few individuals from a population start a new population with a different allele frequency than the original population.
Gene Flow: Migration Introduction of new alleles in a population. New individuals enter a population and contribute to the gene pool.
c. Mutation A change in a DNA sequence that affects genetic expression. Mutations only contribute to genetic variation if they occur in the DNA sequence found in gametes.
d. DNA Recombination The process by which genetic material is broken and joined to other genetic material in meiosis and leads to genetic variation (ie crossing over)
The Evolution of Californian Salamanders Watch the video showing the evolution of Ensatina salamanders in California. In a brief paragraph, explain why you think Stebbins concluded that there is only one species of Ensatinain California. http://www.pbs.org/wgbh/nova/evolution/evolution-action-salamanders.html