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Population GENETICS
Population GeneticsVocab list
gene pool
allele frequency
genetic equilibrium
genetic drift
gene flow
stabilizing selection
directional selection
disruptive selection
speciation
geographic isolation
reproductive isolation
gradualism
punctuated equilibrium
adaptive radiation
divergent evolution
convergent evolution
coevolution
Population GeneticsPopulation Genetics
Changes in evolution occur in populations, not individuals
Population GeneticsPopulation Genetics
•gene pool
–entire collection of genes in a population
•allele frequency
–number of times an allele appears in a gene pool
•genetic equilibrium
–gene pool which is not changing in allele frequencies
–a population at genetic equilibrium is not evolving
Population GeneticsMechanisms for Change
Change in small populations
•mutations
–introduces of new alleles into gene pool
Population GeneticsMechanisms for Change
•genetic drift
–random change in allele frequency over time
Population GeneticsMechanisms for Change
•gene flow
–increase of possible alleles between populations
–this can change the allele frequency of both populations
Population GeneticsMechanisms for Change
For larger populations natural selection is the significant factor which causes changes in allele frequency
Mechanisms for Change
Steps of Natural Selection
• In nature organisms produce more offspring than can survive.
Population Genetics
Population GeneticsMechanisms for Change
Steps of Natural Selection
2. In any population, individuals have variations.
Population GeneticsMechanisms for Change
Steps of Natural Selection
3. Individuals with certain useful variations survive in their environment, passing those variations to the next generation.
Population GeneticsMechanisms for Change
Steps of Natural Selection
4. Over time, offspring with certain variations make up most of the population and may look entirely different from their ancestors.
Population GeneticsNatural Selection
on one variation
•stabilizing selection
–selection against extremes, favors the average
Population GeneticsNatural Selection
on one variation
•directional selection
–selection against one extreme, favors other extreme
Population GeneticsNatural Selection
on one variation
•disruptive selection
–selection against average, favors both extremes
Population GeneticsEvolution of a Species
•speciation
–the production of two or more species
what leads to a new species?
•geographic isolation
–physical barrier which separates populations
Population GeneticsEvolution of a Species
what leads to a new species?
•reproductive isolation
–groups can no longer sexually reproduce
–ex: behavior, mating patterns, physical differences
Population GeneticsEvolution of a Species
Speed of speciation
•gradualism
–species evolve at a slow constant rate
Population GeneticsEvolution of a Species
Speed of speciation
•punctuated equilibrium
–rapid significant changes over a short time
Population GeneticsPatterns in Evolution
•adaptive radiation
–new species develop from a single common ancestor
Population GeneticsPatterns in Evolution
•divergent evolution
–new species develop from a single common ancestor
Population GeneticsPatterns in Evolution
•convergent evolution
–different species develop similar traits
Population GeneticsPatterns in Evolution
•co-evolution
–different species develop traits as a result of a close relationship with the other species
