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40 Cards in this Set

  • Front
  • Back
a localized group of individuals that can interbreed and produce fertile offspring
Gene Pool
all the genes in a population
Population Genetics
the study of how populations change genetically over time
alternative versions of the same gene
Allele Frequency
Each allele has a frequency in a population
Harvey-Weinberg Theorem
the genotype frequencies at a single gene locus will become fixed at a particular equilibrium value
Conditions - Harvey-Weinberg
"Not evolving"
1. extremely large population size
2. no gene flow
3. no mutations in alleles being studied
4. no random mating among the population
5. no natural selection
Harvey-Weinberg Equilibrium
p2 + 2pq + q2 = 1
Causes of Evolution
1. Mutation
2. Sexual recombination
3. Natural Selection
4. Genetic Drift
5. Gene Flow
Change in the DNA sequence of a gene
1 in 100,000
Sexual recombination
Crossing over (Chiasmata)
homologous chromosomes
Natural selection
If a gene confers a selective advantage on its bearer, than that bearer will produce more offspring
Genetic drift
unpredictable fluctations in allele frequency from one generation to the next
Bottleneck effect
dramatic reduction in the size of a population leaves only a few survivors. Decrease in variation due to significantly smaller gene pool
Founder effect
small group is isolated from a larger population and establishes a new population.
Decrease in variation due to significantly smaller gene pool
Gene flow
genetic additions or subtractions to or from a population. movement of fertile individuals or gametes. Reduces genetic difference in Populations
the contribution an individual makes to the gene pool of the next generation
Relative fitness
the contribution of a genotype to the next generation compared to the contribution of alternative genotypes for the same locus
Directional selection
favors variants at one extreme of a distribution
Disruptive selection
favors individuals on both extremes of a phenotypic range over intermediate phenotypes
Stabilizing selection
favors intermediate variants and acts against extreme phenotypes
Heterozygosity provides protection for destructive recessive alleles
Heterozygote advantage
heterozygotes for a particular trait have greater overall fitness over homozygotes.
Example: Sickle-cell anemia
Frequency-dependent selection
fitness of a phenotype declines as it becomes too common in a population
Neutral Variation
Genes that have no impact on reproductive success are not affected by natural selection.
Sexual selection
Natural selection relies on reproductive success. Sexual selection can result in “bad genes” being propagated over generations.
Why not PERFECT organisms??
1. Evolution is limited by history
2. Adaptations are often compromises
3. Chance and natural selection interact
4. Selection can only edit existing variations – new alleles cannot arise on demand
Reproductive handicap
sexual reproduction produces fewer offspring than asexual reproduction
Aide in disease resistance
sexual reproduction
Intrasexual selection
competition among individuals of one sex for mates of the opposite sex
Intersexual selection
individuals of one sex are choosy in selecting their mates
sexual dimorphism
marked differences between the sexes in secondary sexual characteristics
change in genetic makeup of a population from one generation to the next
The modern synthesis
Poulations as units of evolution

Population genetics integrates Mendelian genetics with Darwin's Theory of Evolution
Point mutation
change in one base in a gene, could be harmless or fatal
two or more distinct morphs for a characteristic are represented in a high frequency
Genetic variation _ heterozygosity
Average percentage of loci that are heterozygous
Discrete characters
either-or basis
vary along a continuum
graded change in a trait along a geographic axis