Which assumption must be met for a population to be in Hardy-Weinberg equilibrium for a specific gene?
-No genetic drift can affect allele frequencies for the gene.
-Mating must be nonrandom with respect to the gene.
-Natural selection must favor one phenotype.
-The number of immigrants must equal the number of organisms emigrating.
answer
No genetic drift can affect allele frequencies for the gene.
Any condition that changes allele frequencies in the population represents a violation of the Hardy-Weinberg principle and means that the population will not be in Hardy-Weinberg equilibrium.
question
Which statement about inbreeding is correct?
-Offspring produced by inbreeding have high fitness.
-Inbreeding increases random mating.
-Inbreeding increases the rate of purifying selection.
-Inbreeding changes allele frequencies in a population.
answer
Inbreeding increases the rate of purifying selection.
Because inbreeding tends to increase the production of homozygotes, it exposes lethal or deleterious recessive alleles that would be masked in a heterozygote.
question
Which evolutionary mechanism results in adaptation?
-Gene flow
-Mutation
-Genetic drift
-Natural selection
answer
Natural selection
An adaptation is a heritable trait that increases the fitness of an individual, relative to individuals without the trait, in a particular environment. Natural selection is the evolutionary mechanism that produces adaptation.
question
Give an example of intersexual selection.
answer
Male zebra finches with more brightly colored beaks have greater reproductive success.
In intersexual selection, members of one sex (usually females) choose mates with traits that signal health and high genetic quality.
question
Which statement about balancing selection is correct?
-When balancing selection occurs, all phenotypes have equal fitness.
-When balancing selection occurs, certain phenotypes are favored when they are common but not when they are rare.
-When balancing selection occurs, phenotype does not matter.
-When balancing selection occurs, no single phenotype has a distinct advantage over others in terms of fitness.
answer
When balancing selection occurs, no single phenotype has a distinct advantage over others in terms of fitness.
Balancing selection describes a situation in which there is balance among several phenotypes in terms of their fitness, and thus balancing selection acts to maintain genetic variation in the population.
question
How do stabilizing and disruptive selection differ?
answer
Stabilizing selection reduces the amount of variation in a trait. Disruptive selection increases the amount of variation in a trait.
question
Which mode of natural selection is most likely to contribute to speciation?
-Natural selection does not lead to speciation.
-Directional selection
-Disruptive selection
-Stabilizing selection
answer
Disruptive selection
By selecting against the average or intermediate individuals, the population is being divided into two different groups, which may evolve independently.
question
Which statement about genetic drift is correct?
-Genetic drift increases adaptation of individuals to their environment.
-The direction of evolutionary change due to genetic drift is random.
-Genetic drift becomes increasingly important with increasing population size.
-Genetic drift results from migration of new individuals into a population.
answer
The direction of evolutionary change due to genetic drift is random.
Genetic drift is not driven by a directional effect but is due to chance effects in small populations.
question
Select the correct statement about gene flow.
-Gene flow decreases genetic diversity within a population.
-Gene flow leads to random changes in allele frequencies in a population.
-Gene flow makes allele frequencies more similar between populations.
-Gene flow increases genetic diversity within a population.
answer
Gene flow makes allele frequencies more similar between populations.
Gene flow brings alleles from one population into another, homogenizing allele frequencies among populations.
question
Which evolutionary mechanism increases genetic variation in a population?
-Genetic bottleneck
-Mutation
-Genetic drift
-Founder effect
answer
Mutation
Mutations may or may not be of adaptive value, but they increase genetic variation in the population.
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