Foothill High School Science Department Evolution of Populations Evolution As Genetic Change

Foothill High School Science Department Natural Selection NOT Does NOT Act Directly On Genes Phenotypes Does Act On Phenotypes But, In Order To Modify the Gene Pool: The Phenotype Gives The Survival Edge But, In Order To Modify the Gene Pool: Survivors Must Reproduce Alters Relative Frequency of Alleles Over Time

Foothill High School Science Department Evolution Acts On Populations NOT Evolution Does NOT Act On Individuals

Foothill High School Science Department Natural Selection on Single Gene Traits Key Concept Natural Selection On Single-Gene Traits Can Lead To Changes In Allele Frequencies And Thus To Evolution

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Foothill High School Science Department Camouflage

Foothill High School Science Department Camouflage

Foothill High School Science Department Natural Selection on Single Gene Traits BUT: What If Black Allowed The Lizard To Warm Up Faster & Move Quicker??????

Foothill High School Science Department Natural Selection on Polygenic Traits Traits Controlled By More Than One Gene – Effects On Natural Selection Are More Complex

Foothill High School Science Department Natural Selection on Polygenic Traits Key Concept Natural Selection Can Affect The Distribution Of Phenotypes In Any Of Three Ways: 1.Directional Selection 2.Stabilizing Selection 3.Disruptive Selection

Foothill High School Science Department Directional Selection Individuals At One End Of The Standard Curve Have Higher Fitness Than Individuals In The Middle, Or At The Other End – Curve Moves, Over Time, Toward The End With Increased Fitness

Foothill High School Science Department Directional Selection

Foothill High School Science Department Stabilizing Selection When Individuals Near Center Higher Fitness The Center Of The Standard Curve Have Higher Fitness Than Individuals On Either End May Narrow The Curve Example: Human Birth Weight

Foothill High School Science Department Stabilizing Selection

Foothill High School Science Department Disruptive Selection When Individuals At The Upper And The Lower End Higher Fitness Have Higher Fitness Than Individuals Near The Middle. If Severe Enough, May Cause The Development Of TWO Phenotypes

Foothill High School Science Department Disruptive Selection