evolution of populations

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Evolution of Populations. Other Mechanisms of Genetic Change. Gene Flow. Movement of Alleles From One Population To Another Increases Genetic Variation Of The Receiving Population Less Gene Flow More Differences Between Populations - PowerPoint PPT Presentation


  • Evolution of PopulationsOther Mechanisms of Genetic Change

  • Gene FlowMovement of AllelesFrom One PopulationTo AnotherIncreases Genetic Variation Of The Receiving PopulationLess Gene Flow More Differences Between PopulationsIncreases Probability of Each Population Becoming Separate Species.

  • Genetic DriftNatural Selection Is Not The Only Source of Evolutionary ChangeIn Small PopulationsAn Allele Can Become More Or Less Common By Chance

  • Genetic DriftSmaller Populations Can Have Shifts In The Relative Frequency Of Alleles Much Faster Than Larger PopulationsTheir Gene Pool Is SmallerGenetic Drift Is The Random ChangeIn Allele Frequency

  • Genetic DriftKey Concept:In Small Populations, Individuals That Carry A Particular Allele May Leave More Descendents Than Other Individuals, Just By Chance. Over Time, A Series Of Chance Occurrences Of This Type Can Cause An Allele To Become Common In A Population

  • Genetic DriftCircumstances That May Result In Genetic Drift:Founder EffectColonization Of A New Habitat By A Small Number of IndividualsHawaiian Fruit FliesDarwins FinchesHawaiian Honey Creepers

  • Founder Effect

  • Genetic DriftThe Bottleneck EffectOccurs When Man Made, or Natural Disasters Destroy Most Of A Population.The Remaining Members Usually Possess A Severely Diminished Gene Pool

  • Hardy-Weinberg Principle (1908)Key Concept:Five Conditions Are Required To Maintain Genetic Equilibrium From Generation To Generation:There Must Be Random MatingThe Population Must Be Very LargeThere Can Be No Movement In or Out Of The PopulationNo MutationsNo Natural Selection

  • Random MatingAll Members Of The Population Must have An Equal Opportunity To Produce Offspring

  • Large PopulationGenetic Drift Has Less Effect On Large Populations

  • No Movement Into or Out Of The PopulationNew Alleles Must Not Enter

    Rare Alleles Must Not Be Allowed To Leave

  • No MutationsMutations Introduce New Alleles Causing A Change In Allele Frequencies

  • No Natural SelectionAll Genotypes Must Have Equal Opportunity To Survive & Reproduce

    No Phenotype Can Have An Advantage Over Another