1. Evolution and Gene Frequencies
Chapter 5
Zoology

2. Populations and Gene Pools
Population – group of individuals of the same species occupying a given area at the same time and sharing a common set of genes
Gene Pool – The sum of all alleles for all traits in a sexually reproducing population
4 ways the gene pool changes: independent Assortment, crossing over, chance fertilization, mutations

3. Most, if not all, Populations are Evolving
Hardy-Weinberg theorem states that evolution stops only when 4 principles are met:
Large population size
No migration in or out
No mutations
Sexual reproduction must be random

4. Four Mechanisms of Evolutionary Change
Genetic Drift - chance events influencing the frequencies of genes
Gene Flow - immigration or emmigration in a population
Mutation - changes in the structure of genes and chromosomes
Natural Selection - certain phenotypes having an environmental advantage over other phenotypes (survival of the fittest)

5. Types of Selection
Disruptive Selection - produces distinct subpopulations
Sexual Selection - mating patterns that produce varying degrees of success of individuals of a population
Stabilizing Selection - narrows the phenotypic range

6. Speciation
Speciation – the formation of a new species (can only occur through reproductive isolation)
Allopatric Speciation – occurs when populations become geographically isolated
Parapatric Speciation – occur in small, local populations (ex. frogs in an isolated pond)
Sympatric Speciation – occurs within a single population (brood parasites)

7. Rates of Evolution
Phyletic Gradualism – slow, continuous change over long period of time (Darwin)
Punctuated Equilibrium – rapid change, followed by periods of stasis, or no change, over long periods of time

8. Molecular Evolution
Using molecular genetics to study base-paring in DNA is a high-tech way of tracking evolution through the genome

9. Mosaic Evolution