Genetics Chap 25 population genetics
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what is the difference between microevolution and macroevolution?
- 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
what is the biologically species concept?
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
ecological species concept
genetically related interbreeding individuals that live in the same environment
what is speciation?
evolution of new species via divergence and reproductive isolation often predicted via geographic or ecological isolation
what is fitness?
reproductive success, contribution of individual organisms to future generations, high fitness=high reproductive success
what can reveal a genetic variation under a phenotype?
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
what is the neutral theory?
for most mutations, they have no immediate adaptive significance and can be maintained without cost
what is the predominant dogma?
most variation is neutral; allelic variation arises through mutation and is maintained due to (random) drift (coincidence)
what is needed in speciation?
reduced gene flow between populations, selection, and genetic drift
reproductive isolating mechanisms
prezygotic and postzygotic barriers that prevent interbreeding
what is a gene pool?
all of the alleles shared within the population
what is the study of population genetics?
the study of allele frequency distribution and change under influence of evolutionary processes including natural selection, genetic drift and mutation
what is population genetics?
investigate pattern of genetic variation within and among interbreeding popuations
what is the role of Hardy Weinberg Law
describes relationship between allele frequencies and genotypes in an ideal population
what is a hardy weinberg 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.
what does the knowing of the frequency of one genotype of a given allele help with?
enables calculation of frequencies of alternative genotypes for that gene.
what can change allele frequency?
- non-random mating
what is natural selection?
nonrandom difference in survival or reproduction among individuals with different phenotypes
what causes rapid changes in allele frequencies?
differences among genotypes in fitness must be large
what is the rate of slow mutation?
what is mutation selection balance?
mutation creates new alleles to replace those lost by selection
what is genetic drift?r
random fluctuations in small populations of allele frequencies due to chance
what is the founder effect
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
what does non-random mating change?
does not change allele frequencies, but it does alter frequencies but it does alter frequencies of different diploid genotypes
positive and negative assortative mating
similar genotypes more likely to mate, dissimilar genotypes more likely to mate
what is inbreeding
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
coefficient of inbreeding (f)
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
what are orthologous genes
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
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