1. Foothill High School Science Department Evolution of Populations Other Mechanisms of Genetic Change

2. Foothill High School Science Department Gene Flow Movement of Alleles From One Population To Another Increases Genetic Variation Of The Receiving PopulationIncreases Genetic Variation Of The Receiving Population Less Gene Flow – More Differences Between PopulationsLess Gene Flow – More Differences Between Populations –Increases Probability of Each Population Becoming Separate Species.

3. Foothill High School Science Department Genetic Drift Natural Selection Is Not The Only Source of Evolutionary ChangeNatural Selection Is Not The Only Source of Evolutionary Change InSmall PopulationsIn Small Populations –An Allele Can Become More Or Less Common By Chance

4. Foothill High School Science Department Genetic Drift Smaller PopulationsSmaller Populations –Can Have Shifts In The Relative Frequency Of Alleles Much Faster Than Larger Populations –Their Gene Pool Is Smaller Genetic Drift Is The Random Change In Allele Frequency

5. Foothill High School Science Department Genetic Drift Key Concept 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. Foothill High School Science Department Genetic Drift Circumstances That May Result In Genetic Drift:Circumstances That May Result In Genetic Drift: –Founder Effect Colonization Of A New Habitat By A Small Number of IndividualsColonization Of A New Habitat By A Small Number of Individuals –Hawaiian Fruit Flies –Darwin’s Finches –Hawaiian Honey Creepers

7. Foothill High School Science Department Founder Effect

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

9. Foothill High School Science Department

10. Hardy-Weinberg Principle (1908) Key Concept Key Concept: Five Conditions Are Required To Maintain Genetic Equilibrium From Generation To Generation: 1.There Must Be Random Mating 2.The Population Must Be Very Large 3.There Can Be No Movement In or Out Of The Population 4.No Mutations 5.No Natural Selection

11. Foothill High School Science Department Random Mating All Members Of The Population Must have An Equal Opportunity To Produce Offspring

12. Foothill High School Science Department Large Population Genetic Drift Has Less Effect On Large Populations

13. Foothill High School Science Department No Movement Into or Out Of The Population New Alleles Must Not EnterNew Alleles Must Not Enter Rare Alleles Must Not Be Allowed To LeaveRare Alleles Must Not Be Allowed To Leave

14. Foothill High School Science Department No Mutations Mutations Introduce New Alleles Causing A Change In Allele Frequencies

15. Foothill High School Science Department No Natural Selection All Genotypes Must Have Equal Opportunity To Survive & Reproduce No Phenotype Can Have An Advantage Over Another