Fitness_and_Natural_Selection[1]

Fitness_and_Natural_Selection[1] - Measuring Fitness Types...

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Unformatted text preview: Measuring Fitness/ Types of Natural Selection Topics of Today’s Lecture • Gene Flow revisited • Measuring Darwinian ¡tness (w) • Measuring Selection coef¡cients (s) • Different ways in which selection operates Directional Selection Disruptive Selection Stabilizing Selection Balancing Selection • Factors promoting adaptation • Factors leading to loss or preservation of genetic variation GENE FLOW Leads to genetic similarity between populations. Can counteract genetic drift (because it makes populations larger) and, in some cases, natural selection. Isolated populations may diverge genetically due to natural selection or genetic drift Lower rate of gene Fow: Corn, which is wind-pollinated, is unlikely to fertilize individuals more than 50 feet away. Higher rate of gene Fow: Some organisms can distribute their genes much further. For example, fruit ¡ies released in Death Valley were recaptured almost 15 kilometers away from the site of release. Gene Fow keeps populations similar to one another genetically Barriers may prevent gene Fow and allow populations to diverge from one another. Defnitions oF Natural Selection • “Survival oF the fttest” • DiFFerential reproductive success oF diFFerent phenotypes resulting From interaction with the environment and leading to a change in the genetic composition oF a population. Darwinian Fitness (w) • Relative measure compared to other genotypes in a population • Value may vary over time and place with differences in the physical and biotic environment of a species • Most successful variant assigned value of w=1...
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This note was uploaded on 09/23/2011 for the course BIOL 240 taught by Professor Staff during the Spring '11 term at S.F. State.

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Fitness_and_Natural_Selection[1] - Measuring Fitness Types...

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