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43 Cards in this Set

  • Front
  • Back
population genetics
the extensize genetic variation within populations and recognizes thae importance of quantitative characters
modern synthesis
population as unit of evolution, natural selection most important mechanisms
large changes can evolve as an accumulation of small changes occuring over long periods of time
localized group of individuals belonging to the same species
group of populations whose inidividuals have the potential to interbreed and produce fertile offsrping in nature
gene pool
total aggregate of genes in a population at any one time. all alleles at all gene loci in all individuals of the population
all members of a population are homozygous for the same allele
genetic structure
populations frequencies of allels and genotypes
Hardy Weinberg theorem
frequencies of allels and genotypes in a populations gene pool remain constant over the generations unless acted pon by agents other than sexual recombination
HW in a nutshell
the sexual shufflinf of alleles due to meiosis and random fertilization has no effect on the overall genetic structure of a population
Hardy Weinberg Equilibrium
meiosis and random fertilization have maintained the same allel and genotype frewuencies that existed in the previous generation
Hardy Weinberg equation
p^2 + 2pq + q^2
enables us to calculate the frequencies of alleles in a gene pool if we know frewuencies of genotypes and vice versa/
evolution is a generation to generation change in a population's frequencies of alleles or genotypes--a change in a populations genetic structure
5 Requirement for hardy weinberg
1. large population
2. isolation from other pops.
3. no net mutations
4. random mating
5. no natural selection
Genetic Drift
changes in the gene pool of a small population due to chance. caused by pop. bottlenecks and founding of new colonies
the bottleneck effect
by chance, certain allels will be overrepresented among survivors, other alleles will be underrepresented, and some allels may be eliminated completely
the founder effect
genetic drift in a new colony
gene flow
genetic exchange due to the migration of fertile individuals or gametes between populations.
change in an organism's DNA
nonrandom mating
individuals usually mate with close neighbors. leads to interbreeding-mating between closely related partners
assortive mating
individuals select partners that are like themselves in certain phenotypic characters
natural selection
differential success in reproduction. only one that adapts a population its environment. accumulates and maintains favorable genotypes in a population
when two or more forms of a discrete character are represented ina population
two or more distinct morphs are each represented in high enough frequencies to be readily noticeable
measuring genetic variation
percentage of gene loci represented by 2+ allels in a population/ average percentage of loci that are heteroz. in individuals of pop
geographical variation
differences in genetic structure between populations
graded change in some trait along a geographic axis
new alleles originate only by this method, a change in the nucleotide sequence of DNA
sexual recombination
sex shuffles allels and deals them at random to determine individual genotypes
hides a considerable amount of genetic variation from selection inthe form of recessive allels in heterozygotes. maintain genetic possibilities
balanced polymorphism
selection itself may preserve variation at some gene loci. ability of natural selection to maintain diversity in a population
heterozygous advantage
if individuals who are hetoz at a particular locus have greated reproductive success, than any type of homoz, then 2+ allels will be maintained at that locus by natural selection
hybrid vigor
crossbreeding between 2 diff. inbred varieties often produces hybrids that are much more vigorous than either parent stock
frequency dependent selection
the reproductive success of any one morph declines if that phenotypic form becomes too common in the population
neutral variation
seems to confer no selective advantage for some individuals over others. not affected by natural selection
darwinian fitness
the measure that is critical to selection, is the relative contribution an individual makes to the gene pool of the next generation
relative fitness
contribution of a genotype to the next generation compared to the contributions of alternative genotypes for the same locus
stabilizing selection
acts against extreme phenotypes and favors the more common intermediate variants.
directional selection
shifts the frequency curve for variations in some phenotypic character in one direction of the other by favoring initially rare individuals that deviate from the average for that character
diversifying selection
environmental conditions are varied in a way that favors individuals on both extremes of a phenotypic range or intermediate phenotypes.
sexual dimorphism
distinction between the secondary sex characteristics of males and females
sexual selection
a separate selection process leading to sexual dimorphism
natural selection cannot produce perfection because:
1. orgs are locked into historical constraints
2. adaptations are often compromises
3. Not all evolution is adaptive
4. selection can only edit variations that exist