Date post: | 18-Dec-2015 |
Category: |
Documents |
Upload: | percival-rice |
View: | 215 times |
Download: | 2 times |
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
Genetic Equilibrium
• Allele frequency in a gene pool is not changing– Hardy Weinberg
• Disruption of Equilibrium = Change
Types of Natural Selection
Directional Selection - extreme phenotype has higher fitness
• Peppered Moth
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
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