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Explain why variations in a population
are seen as a bell shaped curve.
Agenda Tuesday May 31st
1. Patterns and Mechanism notes
2. Peppered moth thing
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Genetic Equilibrium
• Allele frequency in a gene pool is not
changing
– Hardy Weinberg
• Disruption of Equilibrium = Change
1. Natural Selection
Types of Natural Selection
Directional Selection - extreme phenotype has
higher fitness
• Peppered Moth
• Stabilizing Selection - intermediate
phenotype has a higher fitness
• Disruptive Selection - intermediate
phenotypes are of lower fitness than
extreme phenotypes
2. Mutation
• Neutral mutation – no impact on survival or
reproduction
• Beneficial mutation – increase in survival
or reproduction
3. Gene Flow/Migration
• Individuals enter or leave a population
– emigrate = lose alleles
– immigrate = gain alleles
4. Genetic Drift
• Unpredictable changes in allele frequency
due to small population size
– Population bottleneck –reduction of a
population
– Founder Effect – individuals leave a population
and establish a new one
5. Nonrandom Mating
• Choosing a mate
• Sexual Selection – ability to attract a mate
Coevolution
• Change of two or more species in close
association with each other
• Predators and prey
• Parasites and hosts
• Plant eating animals and plants
Convergent Evolution
• Environment selects similar phenotypes
although ancestral types were different
• Sharks and dolphins
Divergent Evolution
• Two or more related populations or
species become more and more different
• Response in differing habitats
• Result in new species
Adaptive Radiation
• Many related species evolve from a single
ancestral species
Artificial Selection
• Intentional breeding for specific traits
Rates of Evolutionary Change
• Rapid rates of evolution occur when
conditions favor new traits
– Otherwise evolution is slow
• Based on many factors
– Mutation rate, lifespan of organism
Rate of Speciation
Patterns of Evolutionary
Change
• Novel features evolved infrequently
– Most changes are modifications
• Organisms have increased in size and
complexity
• Predations rates increased = evolution of
better defenses
Why don’t horses have wheels?
http://app.discoveryeducation.com/player/view/assetG
uid/699BD8D0-46A9-4C1A-9A7F-ADE52747FE5E
Describe convergent evolution.
Agenda for Wednesday Feb 25th
1. Quiz
2. Evolution Rat island
3. Evidence of Evol.