Ch. 23: Evolutionary Processes

Units of evolution are genes (mendel), mechanism of evolution is selection (darwin)

Occurs by chance through mutation and recombination

Change in allele fequencies in a population over time

Study of evolution at its smallest scale (population)

Localized group of organisms of the same species that are capable of interbreeding

A version of a gene (AA, aa, Aa), humans have 2 alleles for each gene on each

No variation at a locus, common in rare species

Composition of alleles for a population at a specific time, separates genes from individuals

1. Genetic drift (small population size)
2. Non-random mating
3. Mutation
4. Gene flow
5. Natural selection

1. Meiosis
2. Independent assortment
3. Sexual reproduction

Random and unpredictable change in allele frequencies, bottleneck effect and founder effect

Determine if allele frequencies are actually changing (Hardy-Weinberg equation), if a population is at H-W equillibrium, evolution does not happen (rarely happens)

Maintain, increase, or reduce

Reduce via loss or fixation of alleles

May increase genetic variation by introducing new alleles, may decrease by removing alleles

1. Large population
2. Random mating
3. No mutations
4. No migrations
5. No natural selection

Large populations typically have lots of genetic variability, if most of population is killed, some genetic variability is lost (sudden environmental change)

Members of a population establish a new and isolated population

When it is expressed as a phenotype

Favors one extreme phenotype, causes average phenotype to change in one direction

Favors phenotypes near the middle, maintaining average phenotype

Favors extreme phenotypes at both ends of the phenotypic variation

Diploidy, heterozygote advantage, negative frequency dependent selection, neutral variation

Diploid condition can hide genetic diversity from selection (carriers for recessive alleles), less favorable alleles can persist as heterozygous individuals

As a phenotype gets more common, it is less successful

Little to no impact on success. In time, neutral alleles change frequency by genetic drift.