Genetics Chap 25 population genetics

• microevolution: changes in allele frequencies over time within a species
• macroevolution: evolutionary changes that lead to emergence of new forms and species

one unitary species evolves into another unitary species

ancestral specie gives rise to two or more species

species unchanging over evoluntionary time

populations of actually or potentially interbreeding organisms that are reproductively isolated from all other such groups

organisms that are monophyletic (same taxonomic group) and share one or more uniquely derived characteristics

genetically related interbreeding individuals that live in the same environment

evolution of new species via divergence and reproductive isolation often predicted via geographic or ecological isolation

reproductive success, contribution of individual organisms to future generations, high fitness=high reproductive success

artificial breeding

favors intermediate phenotype, may optimize adaptation of a population to a stable environment

favors extremes, changes the mean value of the trait and allele frequencies over time

against intermediate, favors both extremes, increasing bimodal character of population, may optimize adaptation to a heterogenous environment

for most mutations, they have no immediate adaptive significance and can be maintained without cost

most variation is neutral; allelic variation arises through mutation and is maintained due to  (random) drift (coincidence)

reduced gene flow between populations, selection, and genetic drift

prezygotic and postzygotic barriers that prevent interbreeding

all of the alleles shared within the population

the study of allele frequency distribution and change under influence of evolutionary processes including natural selection, genetic drift and mutation

investigate pattern of genetic variation within and among interbreeding popuations

describes relationship between allele frequencies and genotypes in an ideal population

• infinitely large, not subject to mutations, migration or selection, mating at random.
• in such a population, the frequency of alleles in the gene pool do not change over time.

enables calculation of frequencies of alternative genotypes for that gene.

• mutation
• selection
• migration
• drift
• non-random mating

nonrandom difference in survival or reproduction among individuals with different phenotypes

differences among genotypes in fitness must be large

10^-5/gene/generation

mutation creates new alleles to replace those lost by selection

random fluctuations in small populations of allele frequencies due to chance

population originates from a small population of individuals, altering allele frequencies (generally increasing a subset of)

population undergoes substantial but temporary reduction in number altering (generally reducing) allele frequencies

does not change allele frequencies, but it does alter frequencies but it does alter frequencies of different diploid genotypes

similar genotypes more likely to mate, dissimilar genotypes more likely to mate

mating between two individuals more closely related than two individuals randomly from the population; increases number of homozygotes

is a measure of reduction of fitness due to inbreeding increases homozygosity for deleterious recessive alleles

quantifies the probability that two alleles of a gene in an individual are identical because they descend from the same copy of the allele of a shared ancestor

homologous genes in different species that originated via vertical descent from a single ancestral gene in the last common ancestor

homologous genes within a species that originated via gene duplication event preceding, during or subsequent to the origin of that species