Chapter 16 - Population Genetics Flashcards
Population:
All individuals of same species living in a given geographical area
Gene:
Discreet segment of DNA that codes for a particular trait
Ex: Hair Color; Skin Color
Gene Pool:
All the genes of a population
Allele Frequency
Relative proportion of each allele in a population
Population of pea plants were purple alleles, W, the allele frequency would be 100%
25 individuals, 50 alleles, 20/50 result in black fur, allele freq. = 0.40
Key
Evolution is change of allele frequencies within a population over time/generations
Hardy-Weinberg Principle
Allele frequencies and genotypes frequencies remain unchanged - no evolution!
Examples of Non-Evolution
Changes in diet/exercise + weight
Conditions for Hardy-Weinberg Principle
No mutation, no gene flow, no immigration, no emigration.
Very large population, completely random mating, no natural selection = no differential fitness.
Gene Flow
Movement of alleles to/from another population. Rampant in modern humans. Plant population example: Pollen, Spores, Seeds, Wind, etc.
Genetic Drift
Some random event that removes some alleles from a small population. Ex: Black and white rabbits, white rabbits are dominant. Genetic drift can allow all black rabbits to survive while all white are eliminated.
Bottleneck
One cause of genetic drift. Population decreases due to an event resulting in allele decrease. Ex: northern elephant seals have reduced variation due to humans hunting them
Founder Effect
Small portion of population “founds” new area. Examples: the Amish
All genotypes are equally unsuccessful
Any trait that gives any advantage will have increased success.
Survival of the Fittest
Herbert Spencer
Success depends on
Survival and Reproduction
Natural Selection favors…
allele with increased success. acts on phenotypes, but phenotypes and genotypes are closely linked
Successful phenotypes…
Help an organism survive and reproduce in a specific environment
Competition:
Struggle for scarce resources. Most severe between members of the same species and populations.
Predator/Prey Interactions
Interactions so strong that they exert selection pressures on each other = co-evolution
Sexual Selection
Selection that acts on traits that are used to acquire a mate.
Ex: Peacocks, the bigger the tail, the more frequently they mate.
3 Effects of Natural Selection on Populations
Directional
Stabilizing
Disruptive
Directional:
Favors individuals with one extreme of the bell curve
Stabilizing
Favors individuals with the average trait, variation is reduced.
