Bio 1 - Chapter 20: Genes Within Populations

Which of the following accurately describes sperm competition?

A female mates with multiple males and not every male's sperm has equal chances of fertilizing an egg.

Why does selection occur?

Because some individuals in a population possess more favorable phenotypes than others.

Changes in allele frequencies within a population may result from ___, which are changes in the nucleotide sequences of an organism's DNA.

Mutation

What is gene flow?

The movement of alleles into or out of a population.

When a female mates with multiple males, not every male's sperm has an equal chance to fertilize an egg; in these cases, we observe sperm ___ between males

competition

When a population is in Hardy-Weinberg equilibrium

no natural selection is occurring.

In a population of seahorses, red seahorses on average produce 125 offspring and brown seahorses produce 75 offspring. What is the fitness of the brown phenotype?

0.6

Consider a population with 100 cats. If 72 cats are black and 28 are white, what is the phenotypic frequency of black cats?

0.72

The most fit phenotype is assigned a fitness value of ______.

1

Which evolutionary mechanism changes genotype frequencies but does not change allele frequencies?

Assortative mating

Selection against intermediate-sized beaks in African black-bellied seedcracker finches is an example of which of the following?

Disruptive selection

What term quantifies reproductive success of a phenotype?

Fitness

Which of the following statements about the reproductive strategies of males and females is true?

Males and females often have different reproductive strategies.

Choose all the components of fitness from the list below:

Mating success Individual survival Production of viable, numerous offspring

___ selection is a type of natural selection in which competition for mates drives the evolution of certain traits.

Sexual

In many species of animals, males and females look very different as a result of sexual selection. These animal species exhibit which of the following?

Sexual dimorphism

Select the conditions that must be met for a population to be in Hardy-Weinberg equilibrium.

The population is very large. Mating is random. No new mutations occur.

What is fitness?

The relative likelihood that a genotype will contribute to the gene pool of the next generation

The phenotype frequency is calculated by dividing the total number of individuals with a particular phenotype by which of the following?

The total number of individuals in that population

Select all of the following criteria that must be present for natural selection to occur and cause evolutionary change in a population.

Variation must have a genetic basis. Variation must exist among individuals. Variation must result in differences in the number of offspring surviving in the next generation.

Fitness is a measure of

mating success. survival. number of offspring produced per mating.

Features that increase the chance that a male will be chosen by a female (for example, bright plumage in many male birds) are known as ___ ___ characteristics.

secondary sexual

Genetic drift has a greater impact on which of the following?

small populations

What conclusion can be drawn from the observation that a population is not in Hardy-Weinberg equilibrium?

Evolutionary forces are affecting the population.

Which of the following is true of evolutionary forces in natural populations?

Evolutionary forces can alter allele frequencies in natural populations

___ is the ultimate source of genetic variation.

Mutation

What can likely happen to uncommon alleles in small, isolated populations as a result of genetic drift?

They are likely to be lost.

Assortative mating changes ______ frequencies but does not change ______ frequencies.

genotype; allele

Ground finches with large bills are favored during times of drought, while ground finches with small bills are favored during times when water is abundant. This is an example of

oscillating selection

The energy and time each sex invests in producing and rearing offspring is known as

parental investment

Select all of the following that could cause evolutionary change by natural selection.

A moth that has a gene for cryptic coloration A plant with an enzyme that makes it disease-resistant

Sexual selection is a type of natural selection in which the evolution of certain traits is driven by which of the following types of competition?

Competition for mates

Natural selection can lead to ___ if variation is genetically based.

Evolution

True or false: Within the same species, females and males usually employ the same reproductive strategy.

False

Which of the following agents of evolutionary change occurs when alleles move from one population to another?

Gene flow

What evolutionary mechanism results in random changes in allele frequencies from one generation to the next?

Genetic Drift

Evolutionary change is not caused by phenotypic variation if the phenotypic variation lacks which of the following?

Genetic basis

Many 19th century scientists believed that natural selection always favored an optimal form, and therefore would tend to reduce or eliminate which of the following?

Genetic variation

Consider a gene with two alleles, A1 and A2. If the fitness of A1A2 individuals is higher than the fitness of both A1A1 and A2A2, we are observing

Heterozygote Advantage

According to the theory of blending Inheritance, offspring were expected to be phenotypically ___ relative to their parents, which would dilute any new genetic variants.

Intermediate

How does natural selection affect allele frequencies?

It causes beneficial alleles to become more common. It causes detrimental alleles to become less common.

By favoring different phenotypes at different times, oscillating selection acts in which way?

It maintains genetic variation in a population

Select all of the following processes that can cause changes in allele or genotype frequencies in populations.

Mutations Natural selection Genetic drift Gene flow Nonrandom Mating

Which evolutionary mechanism causes beneficial traits that are heritable to become more common in a population?

Natural Selection

Evolutionary change within a population can result from which of the following?

Natural Selection Migration Mutations

___ selection is a process that can lead to change, and ___ is the outcome or record of change over time.

Natural; evolution

If we find evidence that a population is experiencing changes in allele frequencies from one generation to the next, we say that this population is which of the following?

Not in Hardy-Weidberg equilibrium

The sex that is most choosy in selecting a mate is generally the sex that invests the most energy and time in producing and rearing offspring. Which of the following refers to the investment of time and energy?

Parental Investment

What is genetic drift?

Random changes in the allele frequencies of a population over time

A deer's antlers, a ram's horns and the bright plumage of a male paradise bird are all examples of which of the following?

Secondary sexual characteristics

The amount of genetic variation present in naturally occurring populations is

Significant

True or false: Genetic drift, mutations, and nonrandom mating are three agents that can act to produce evolutionary changes in a population.

True

In many animals, selection has favored traits that confer greater ability in mate competition; as a result of such selection, one of the sexes —usually males—can look very different. This is known as sexual ___.

dimorphism

In natural populations, most genes

exhibit variation

In ___ - ___ selection, the fitness of a phenotype depends on the proportion of individuals in the population that have that phenotype.

frequency - dependent

The processes that lead to evolutionary change are mutations, natural selection, ___drift, gene flow and ___ mating.

genetic, nonrandom

A type of sexual selection in which members of one sex, usually females, choose mates based on particular characteristics such as courtship songs is called

intersexual selection

___ selection is a form of sexual selection based on same-sex competition usually involving males, in which the winner "gains" a mating partner.

intrasexual

Changes in allele frequencies within a population may result from ______, which are changes in the nucleotide sequences of an organism's DNA.

mutations

In frequency-dependent selection

the fitness of a phenotype depends on its frequency in the population

New mutations are not a major factor affecting the allele frequencies in a population because

the rate at which new mutations occur is low