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Evolution of Populations

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

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Evolution of Populations

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  1. Evolution of Populations Other Mechanisms of Genetic Change

  2. Gene Flow Movement of Alleles From One Population To Another • Increases Genetic Variation Of The Receiving Population • Less Gene Flow – More Differences Between Populations • Increases Probability of Each Population Becoming Separate Species.

  3. Genetic Drift • Natural Selection Is Not The Only Source of Evolutionary Change • InSmall Populations • An Allele Can Become More Or Less Common By Chance

  4. Genetic Drift • Smaller Populations • Can Have Shifts In The Relative Frequency Of Alleles Much Faster Than Larger Populations • Their Gene Pool Is Smaller Genetic DriftIs The Random Change In Allele Frequency

  5. Genetic Drift Key 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

  6. Genetic Drift • Circumstances That May Result In Genetic Drift: • Founder Effect • Colonization Of A New Habitat By A Small Number of Individuals • Hawaiian Fruit Flies • Darwin’s Finches • Hawaiian Honey Creepers

  7. Founder Effect

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

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

  10. Random Mating All Members Of The PopulationMust have An Equal OpportunityTo Produce Offspring

  11. Large Population Genetic DriftHas Less EffectOn Large Populations

  12. No Movement Into or Out Of The Population • New Alleles Must Not Enter • Rare Alleles Must NotBe Allowed To Leave

  13. No Mutations Mutations Introduce New Alleles Causing A Change InAllele Frequencies

  14. No Natural Selection All GenotypesMust Have Equal OpportunityTo Survive & Reproduce No PhenotypeCan Have An AdvantageOver Another

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