Evolution Flashcards
Hardy-Weinberg, Evolution, Mutation
In the Hardy-Weinberg equation, what does each variable represent?
p = frequency of dominant allele q = frequency of recessive allele p^2 = frequency of homozygous dominant individuals q^2 = frequency of homozygous recessive individuals 2pq = frequency of heterozygous individuals
What is the Hardy-Weinberg equation?
Method of determining genotype frequencies from allele frequencies. A mathematical representation of a gene pool. Assumes the population is in genetic equilibrium.
p^2 + 2pq + q^2
(should add to 1)
How do you calculate allele frequencies from genotype frequencies?
p = RR + 1/2 Rr q = rr + 1/2 Rr
What are the three requirements for natural selection?
- There is heritable variation
- There is a struggle for existence
- The heritable variation influences the struggle
What does the Hardy-Weinberg equation assume?
- No Mutations
- No Gene Flow
- Random Mating
- No Genetic Drift
- No Selection
What is Microevolution?
An accumulation of small changes in a group or species. A change in the gene pool of a population over time.
What is a population?
A group of individuals of the same species living together in the same area at the same time.
-Smallest biological unit that can evolve.
When is a population said to be Polymorphic for a characteristic?
When two or more morphs or forms are present in noticeable numbers.
How do mutation and sexual recombination produce new genetic variation?
Mutation creates new variation. Ultimate source of variation.
Meiosis reshuffles the existing variation. Contributes the most to genetic variation between individuals.
What are the causes of microevolution?
- Mutations
- Gene Flow
- Non-random Mating
- Genetic Drift
- Natural selection
What is assortative mating?
Individuals tend to mate with those with the same phenotype, results in more homozygotes than expected.
What is disassortative mating?
Individuals tend to mate with those with a different phenotype, resulting in more heterozygotes than expected.
What is sexual selection?
Males fight for the right to reproduce and females choose males with a particular phenotype.
What is inbreeding?
The most common form of non-random mating.
Individuals tend to mate with genetic relatives, resulting in more homozygotes than expected.
What is genetic drift?
Changes in the allele frequency of a population due to random chance. Has a larger effect on smaller populations.
What is the bottleneck effect?
Happens when an event causes a drastic reduction in population size, preventing the majority of genotypes from entering the next generation. This results in a loss of genetic variability
What is the founder effect?
One or a few individuals disperse and form a new population. Some alleles are lost and others change in frequency.
What is disruptive selection?
Selection that favors the two extremes, and acts to eliminate intermediate types. M
What is directional selection?
An extreme phenotype is favored and the distribution curve shifts in that direction. Acts to eliminate one extreme.
What is stabilizing selection?
Occurs when an intermediate phenotype is favored. Acts to eliminate both extremes.
What is heterozygote advantage?
Heterozygotes are favored over homozygotes.
Works to maintain both alleles in the population.
What is frequency-dependent selection?
When the fitness of a phenotype depends on how frequently or infrequently a phenotype occurs in a population.
What is negative frequency-dependent selection?
When rare phenotypes are favored by selection.
- Maintains variation in the population.
What is positive frequency-dependent selection?
When common phenotypes are favored by selection.
- Eliminates variation from the population.
