Explain why variations in a population are seen as a bell shaped curve.

Agenda for Friday Feb 20th

1. Patterns and Mechanism notes

2. Go over variation lab

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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

Patterns of Evolution

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

Describe convergent evolution.

Agenda for Thursday May 29th

1. Bunny Lab