Chapter 20 Practice Questions
they are not camouflaged as well as the green one
A caterpillar can be a pale green color or a bright yellow color. The yellow caterpillars are usually found in very low frequency because
0.75
A gene has two alleles, T and t. If the frequency of the dominant allele (T) is 0.25, then the frequency of the recessive allele (t) is ______.
a natural disaster
A population bottleneck could be caused by
directional
A sudden and permanent change in the environment can lead to a type of natural selection called _____________ selection
intermediate
According to the theory of blending inheritance, offspring were expected to be phenotypically ______________ relative to their parents, which would dilute any new genetic variants
would vary from one genotype to another
As a result of epistasis, the selective advantage of an allele
genotype; alelle
Assortative mating changes _________ frequencies but does not change ___________ frequencies
disruptive
Beaks in African black-bellied seedcracker finches are small or large, but not intermediate in size. This is an example of _________ selection.
Stabilizing
Birds that lay intermediate numbers of eggs have greater fitness than birds that lay too few or too many eggs. This is an example of which type of selection?
It maintains genetic variation in a population
By favoring different phenotypes at different times, oscillating selection acts in what way?
modification
Charles Darwin referred to evolution as "descent with _____________"
They are different, because in oscillating selection and frequency-dependent selection
Compare oscillating selection and frequency-dependent selection
1
Consider a gene that has 4 alleles in a particular population: F, M, S and VS. What is the sum of all of the frequencies of all the alleles for this gene in that population?
genetic variation
Different alleles of genes are found within different individuals of a population. This is known as
acts to eliminate one extreme from a range of phenotypes
Directional selection
genetic
Evolutionary change cannot occur in populations with no __________ variation
Genetic basis
Evolutionary change is not caused by phenotypic variation if the phenotypic variation lacks what?
Mutations, natural selection & migration
Evolutionary change within a population can result from
selection must occur & resistance must be genetic
For insect populations to become increasingly resistant to pesticides
Promote or reduce evolutionary change, and remove or introduce new alleles to a population
Gene flow may
Small populations
Genetic drift has a greater impact on which population?
small
Genetic drift is more likely to overwhelm natural selection when populations are ____________
allele frequencies
Genetic variation in a population results from evolutionary forces that cause changes in
large; random
Hardy-Weinberg equilibrium requires that the population size is __________ and that mating is _________.
The allele frequencies in the founding members of the population differ from the allele frequencies in the original large population
How can the founder effect cause a previously rare genetic disorder to become common in the new population?
It changes allele frequencies without regard for their fitness
How does genetic drift affect allele frequencies in a population?
The larger the population, the lower the chance of genetic drift is
How is the size of a population related to the likelihood that the population will experience genetic drift?
Those with the rare form of the trait
If a trait is subject to negative frequency-dependent selection, individuals with which form of the trait will have the highest fitness?
0.16
If the frequency of allele A is 0.6 and the frequency of allele a is 0.4, what is the probability that an individual will receive two a alleles
0.7
If the frequency of allele b i a population is equal to 0.7 then the frequency with which a gamete will carry allele b, is equal to _______ if the population is in Hardy-Weinberg equilibrium
the gene for the alternative enzyme is nonfunctional
In E.coli the alleles for the gene for the enzyme 6-PGD only have a selective advantage if
negative; positive
In __________ frequency-dependent selection, as rare genotypes become increasingly common, their selective advantage decreases. In ___________ frequency-dependent selection, as common genotypes become increasingly rare, their selective advantage decreases
negative
In __________ frequency-dependent selection, individuals whose resource requirements are rarer have fewer competitors for resources than individuals whose resource requirements are more common
frequency-dependent
In _______________-________________ selection, the fitness of a phenotype depends on the proportion of individuals in the population that have that phenotype
drab coloration and small size
In areas of predation, natural selection seems to favor South American guppies that display
high; low
In field experiments, South American guppies transplanted from ________ predation environments to _______ predation environments experienced rapid evolutionary change, becoming brightly colored and greater in size.
exhibit variation
In natural populations, most genes
not high enough
In nature, mutation rates are usually ______________________ to maintain alleles that are not favored in a population by natural selection
only individuals who are well adapted to the environment contribute their alleles to the next generation
Natural selection results in a population better adapted to its environment because
Alternative alleles of genes encoding enzymes
Protein electrophoresis gels can be used to distinguish what?
variation
Selection for speed in thoroughbred horses has removed genetic ____________ from the population at a faster rate than mutation can replace it
Single-nucleotide polymorphisms (SNPs)
Single-base differences between individuals in a population are known as
homozygous; heterozygous
Survival is significantly lower in individuals who are __________ for the sickle cell allele because of the lethal effect of the alleles, but individuals that are _____________ for the sickle cell allele are more resistant to malaria because only the blood cells containing the malaria parasite sickle and are filtered out by the spleen
Central Africa
The allele for sickle cell mutation is most common in
they are not camouflaged as well as the green ones
The caterpillar can be a pale green color or a bright yellow color. The yellow caterpillars are usually found in very low frequency because
population genetics
The field of biology that studies the properties of genes in populations is __________ ____________
flow; natural
The frequency of the heavy-metal resistance allele in populations of bent grass growing on soils contaminated with heavy metals reflects a balance between the rate at which gene ________ brings a less favored allele in to the population and the rate at which _________ selection favors the resistance allele.
The bottleneck effect
The low level of genetic diversity among northern elephant seals is best explained by which phenomenon?
allele frequency
The number of copies of an allele in a population divided by the total number of all alleles for that gene in a population is the
The total number of individuals in that population
The phenotype frequency is calculated by dividing the total number of individuals with a particular phenotype by what?
advantage
The term heterozygote _______________ refers to situations in which heterozygotes are more fit than either homozygotes
selection
The theory of natural __________ as a mechanism of evolution was proposed by Charles Darwin
assortative
The type of nonrandom mating in which phenotypically similar individuals mate is called _____________ mating
enzyme allele frequencies can vary with geographic latitude
We know that selection can occur based on climatic conditions, because biologists have found that
Selection of mates with similar or dissimilar phenotypes
What are some examples of nonrandom mating?
Evolutionary forces are affecting the population
What conclusion can be drawn from the observation that a population is NOT in Hardy-Weinberg equilibrium?
Certain parts of the human genome contain more variation than others
What describes the rates of variation in different parts of the human genome, as determined by the 1000 genomes project?
Genetic drift
What evolutionary mechanism results in random changes in allele frequencies from one generation to the next?
The movement of alleles into or out of a population
What is gene flow?
p^2 + 2pq + q^2 = 1
What is the correct version of the Hardy-Weinberg equation for genotype frequencies in a population in equilibrium?
Changes in allele frequencies that result from the colonization of a new location by a small group of individuals from a larger population
What is the founder effect?
Mutation
What is the ultimate source of all new alleles?
Mutation, gene flow, nonrandom mating, genetic drift in small populations and the pressures of the natural selection
What processes lead to evolutionary change in populations?
Fitness
What term quantifies reproductive success of a phenotype?
Natural selection
Which evolutionary mechanism causes beneficial traits that are heritable to become more common in a population?
Because some individuals in a population possess more favorable phenotypes than others
Why does selection occur?
Stabilizing
_________ selection favors individuals with intermediate phenotypes and selects against individuals with extreme phenotypes
Directional
__________ selection favors individuals at one extreme of a phenotypic range. Those individuals usually greater reproductive success in a particular environment.
Disassortative
___________ mating is a type of nonrandom mating in which phenotypically different individuals tend to mate more often. This produces an excess of heterozygotes