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