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33 Cards in this Set

  • Front
  • Back
measured in terms of reproductive success and the relative genertic contribution of an individual to the future of the population
Natural Selection
- chance variations occur thanks to mutation and recombination
- if the variation is "selected for" by the environment, that individual will be more "fit" and more likely to survive to reproductive age
- survival of the fittest leads to an increase of those favorable genes in the gene pool
homologous structure
similar in structure and share a common evolutionary origin
analogous structure
share a functional similarity but arose from different evolutionary origins
vestigial structure
remnants of organs that have lost their ancestral functions
Hardy-Weinberg equilibrium conditions
1. Large population
2. No mutations
3. Mating is random
4. No migration
5. Genes in population are equally successful ar reproducing

allele frequency
p + q = 1

genotypic frequency
p2 + 2pq + q2 = 1
5 deviations from Hardy-Weinberg
1. Natural selection
2. Mutation
3. Assortive mating
4. Genetic drift
5. Gene flow
Natural selection
genotypes with favorable variations are selected through natural selection, and the frequency of favorable genes increases within the gene pool
Gene mutations change allele frequencies in a population, shifting gene equilibria
Assortive Mating
Mates not randomly chosen, but selected according to criteria
Genetic Drift
Regers to changes in composition of gene pool due to chance
Gene Flow
Migration of individuals between populations will resultin a loss or gain of genes
Three different modes of natural selection
1. stabilizing selection
2. directional selection
3. disruptive selection
Stabilizing selection
reduces the frequency of extreme phenotypes, thereby reducing variation
directional selection
increase in proportion of individuals with an extreme phenotype
- occurs when organisms must adapt to changing environment
disruptive selection
favors both phenotypic extremes over intermediates
- leads to existence of two or more phenotypic forms within a population (polymorphism)
altruistic behavior
benerfits one individual at the expense of another
groups that can interbreed freely with each other, but not with membres of another species
- due to reproductive isolation
Prezygotic causes for reproductive isolation
- temporal isolation
- ecolgical isolation
- behavioral isolation
- reproductive isolation
- gametic isolation
Postzygotic causes for reproductive isolation
- hybrid sterility
- hybrid instability
- hybrid breakdown
temporal isolation
breed during different seasons or different times of day
ecological isolation
live in same territory but in different habitats
behavioral isolation
not sexually attracted to each other due to things like pheromones or courtship
reproductive isolation
physically incompatible
gametic isolation
intercourse can occur, but fertilization cannot
hybrid inviability
genetic incompatibilities between two species abort hybrid zygote development, even if fertilization does not occur
hybrid sterility
hybrid offspring are steril, thus incapable of producing functional gametes
hybrid breakdown
first-generation hybrids are viable and fertile, but secondary-generation are inviable and/or infertile
convergent evolution
refers to independent development of similar characteristics in two or more lineages NOT sharing a recent common ancestor
divergent evolution
regers to independent development of dissimilar characteristics in two or more lineages sharing common ancestry
parallel evolution
regers to the process whereby related species evolve in similar ways for a long period of time in response to analogous environmental selection process