1. Population Genetics and Natural Selection
Chapter 8
Microsatellite alleles for three loci depict genetic variation within a Great Tit population.

2. Definitions
Evolution – a change in gene frequencies in a population; may lead to speciation.
Natural Selection – differential reproduction and survival of individuals in a pop. due the environmental influences on the pop.; the environment affects fitness.
Offspring like parents
Variation among individuals is heritable.
More offspring than environment can support
Some individuals have higher fitness under particular environmental conditions.

3. Alleles – alternative forms of a gene
Gene – a discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA
Alleles – alternative forms of a gene
Genotype – the genetic makeup of an individual
Phenotype – the physical and physiological traits of an organism
Campbell and Reese 2002

4. Variation Within Populations
Phenotype is environmental and genetic
Variation in Plant Populations
Many plant species differ dramatically in form from one elevation to another (e.g. ) Potentilla glandulosa.
Distinctive ecotypes
locally adapted and genetically distinctive populations within a species.
Cross breeds produce viable seeds that are reproductive – not separate species.

5. Hypothesis: Morphology differences partly due to genetics.
Null Hypothesis: No genetic difference; all environmental.

6. Hardy Weinberg
Hardy Weinberg principle states that in a population mating at random in the absence of evolutionary forces (natural selection), allele frequencies will remain constant.
The H-W Model allows for predicting genetic change due to environmental forces.
Hypothesis: environmental factor influences change in allele frequency change.
Null Hypothesis: allele frequency remains unchanged.
1 = (p+q)2 = p2+2pq+q2

7. Conditions Necessary for Hardy Weinberg
Random Mating
No Mutations
Large Population Size
No Immigration
Equitable Fitness Between All Genotypes
Likely, at least one of these will not be met and allele frequencies will change.
Potential for evolutionary change in natural populations is very great.

8. Natural Selection
Some individuals in a population, because of their phenotypic characteristics, produce more offspring that themselves live to reproduce.
Natural selection can favor, disfavor, or conserve the genetic make-up of a population.

9. Stabilizing Selection
Stabilizing selection acts to impede changes in a population by acting against extreme phenotypes and favoring average phenotypes.

10. Directional Selection
Directional selection leads to changes in phenotypes by favoring an extreme phenotype over other phenotypes in the population.

11. Disruptive Selection
Disruptive selection creates bimodal distributions by favoring two or more extreme phenotypes over the average phenotype in a population.

12. Change Due To Chance
Random processes can change gene frequencies in populations, especially in small populations. Called genetic drift.
Major concern of habitat fragmentation is reducing habitat availability to the point where genetic drift will reduce genetic diversity within natural populations.

13. Genetic Variation In Island Populations
In general, genetic variation is lower in isolated and generally smaller, island populations.
Reduced genetic variation indicates a lower potential for a population to evolve.

14. Microsatellite Analysis

15. Whose your Daddy?

16. Linkage to social function (Young and Hammock, 2005)