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