Biology Chapter 20

What conclusion can be drawn from the observation that a population is not in Hardy-Weinberg equilibrium? Evolutionary forces are affecting the population. Allele frequencies are stable from one generation to the next. The population is isolated from other populations of the same species. Genotype frequencies but not phenotype frequencies are the same from one generation to the next.

Evolutionary forces are affecting the population.

Which of the following statements about the reproductive strategies of males and females is true? Males and females of the same species always have the same reproductive strategy. Males and females often have different reproductive strategies. Males and females always have different reproductive strategies, regardless of the species in question.

Males and females often have different reproductive strategies.

select the conditions that must be met for a population to be in Hardy- Weinberg equilibrium The population is very large. Migration occurs frequently. Mating is random. Natural selection occurs.. No new mutations occur.

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

What appears to determine variations in the coloration, size and maturation of guppies in northeastern South American streams? The amount of dissolved salts in the stream The relative proportion of sunlight and shade The location of streams relative to waterfalls The temperature of the stream

The location of streams relative to waterfalls

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? 0.4 0.6 1 1.4

0.6

Evolutionary change within a population can result from which of the following? Migration Experience Natural selection Mutations

Natural selection Mutations Migration

Evolution can result from any process that changes the ______ composition of a population. age male/female habitat genetic

genetic

For a population to be in Hardy-Weinberg equilibrium, there must be no migration into or out of the population. the rate of migration into the population must be greater than the rate of migration out of the population. the rate of migration into the population must be less than the rate of migration out of the population. the rate of migration into the population must equal the rate of migration out of the population.

there must be no migration into or out of the population.

Which describes male guppies located below South American waterfalls where predation is high? They exhibit bright coloration. They grow to larger sizes. They exhibit drab coloration. They mature later.

They exhibit drab coloration.

In a laboratory experiment, researchers placed guppies in three different types of pools: no predation, low predation, and high predation. Researchers hypothesized that predation is a selective force and that large, brightly colored guppies are more conspicuous to predators. Based on that, what would you predict the guppies will look like in the pool with high predation after 10 generations? They should be very small and very brightly colored They should be very large, but not very brightly colored They should be large and brightly colored They should be smaller and not very brightly colored

They should be smaller and not very brightly colored

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

Hardy-Weinberg equilibrium requires that the population size is_____ and that mating is _______ .

large random

The most fit phenotype is assigned a fitness value of ______. 100 2 10 1

1

Which type of selection favors individuals at one extreme of a phenotypic range who have greater reproductive success in a particular environment? Balancing selection Stabilizing selection Disruptive selection Directional selection

Directional Selection

Which of the following is true of evolutionary forces in natural populations? Evolutionary forces can alter allele frequencies in natural populations Evolutionary forces have no affect on allele frequencies in natural populations

Evolutionary forces can alter allele frequencies in natural populations

The processes that lead to evolutionary change are mutations, natural selection, ________drift, gene flow and ________mating.

genetic nonrandom

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? Heterozygosity Genetic variation Equilibrium Population genetics

genetic variation

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 stabilizing selection diversifying selection balancing selection

oscillating selection

Select the observations that would indicate that a population is deviating from Hardy-Weinberg equilibrium. Allele frequencies are changing between generations. Genotype frequencies do not match those predicated by the Hardy-Weinberg equation based on existing allele frequencies. Phenotypic frequencies are different than those predicted by the Hardy-Weinberg equation because one of the alleles is dominant over another. The frequency of the genotype HH is equal to p2, where p = the frequency of H.

Allele frequencies are changing between generations. Genotype frequencies do not match those predicated by the Hardy-Weinberg equation based on existing allele frequencies.

Why does selection occur? Because some individuals in a population possess more favorable phenotypes than others. Because evolution strives to develop better traits. Because individuals move between populations and mix their genes. Because individuals must adapt to be able to survive in challenging environments.

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

Which type of selection acts to eliminate individuals which are intermediate on a phenotypic range? Stabilizing selection Directional selection Disruptive selection

Disruptive selection

How does genetic drift affect allele frequencies? It eliminates all new mutations. It changes allele frequencies randomly. It increases the frequencies of beneficial alleles that are not heritable. It increases the frequencies of beneficial alleles that are heritable.

It changes allele frequencies randomly.

By favoring different phenotypes at different times, oscillating selection acts in which way? It completely eliminates genetic variation in a population. It decreases genetic variation in a population to some extent without eliminating it completely. It maintains genetic variation in a population.

It maintains genetic variation in a population.

Which of the following is true about the reproductive strategies of males and females? Males are selective in choosing a mate about as frequently as females. Males are selective in choosing a mate much less frequently than females. Males are selective in choosing a mate much more frequently than females.

Males are selective in choosing a mate much less frequently than females.

Genetic drift has a greater impact on which of the following? Small populations Large populations Medium sized populations

Small populations

Which type of selection favors individuals with intermediate phenotypes and selects against individuals with extreme phenotypes? Sexual selection Directional selection Stabilizing selection Diversifying selection

Stabilizing selection

What is gene flow? The accumulation of mutations in a gene over time. The change from one allele to another. The movement of alleles into or out of a population. The increased survival of individuals with beneficial alleles.

The movement of alleles into or out of a population.

What is fitness? The ability to maintain an internal environment that is suitable for cellular functions The relative likelihood that a genotype will survive The ability to exercise for a prolonged period of time The relative likelihood that a genotype will contribute to the gene pool of the next generation

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

Select all of the following criteria that must be present for natural selection to occur and cause evolutionary change in a population. Variation must be the result of environmental differences. Variation must result in differences in the number of offspring surviving in the next generation. 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 Variation must have a genetic basis. Variation must exist among individuals.

The term heterozygote _______refers to situations in which heterozygotes are more fit then either homozygotes.

advantage

Genetic variation in a population results from evolutionary forces that cause changes in allele frequencies migration rates predatory habits population size

allele frequencies

Genetic variation in a population results from evolutionary forces that cause changes in migration rates predatory habits population size allele frequencies

allele frequencies

Consider two populations (population A and population B) of the same plant species and the gene Xx. Researchers discover that there is constant flow of the x allele from population B into population A. This allele happens to be detrimental to individuals in population A because of the local soil conditions. In this case gene flow appears to be constraining evolutionary change. has a random effect on evolutionary change. is strongly promoting evolutionary change.

appears to be constraining evolutionary change.

Which evolutionary mechanism changes genotype frequencies but does not change allele frequencies? Migration Natural selection Assortative mating Genetic drift

assortative mating

When researchers raised guppies in laboratory pools with high levels of predation, the guppies in those aquariums became larger and brighter in coloration as a result of natural selection after about 10 generations. became smaller and drab in coloration as a result of natural selection after just 1 generation. became larger and brighter in coloration as a result of natural selection after just 1 generation. became smaller and drab in coloration as a result of natural selection after about 10 generations.

became smaller and drab in coloration as a result of natural selection after about 10 generations.

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 between males and females Competition between unrelated individuals Competition with predators Competition for mates

competition for mates

Suppose that a population of finches migrates to a small island where most of the seeds are large. On the island, birds with large beaks are more likely to survive, and over time, the mean beak size of the population increases. This is an example of a type of natural selection known as ______selection.

directional

Selection against intermediate-sized beaks in African black-bellied seedcracker finches is an example of which of the following? Disruptive selection Oscillating selection Stabilizing selection Frequency-dependent selection

disruptive selection

election against intermediate-sized beaks in African black-bellied seedcracker finches is an example of which of the following? Stabilizing selection Frequency-dependent selection Disruptive selection Oscillating selection

disruptive selection

In theory, if mutation rates were high enough, alleles could be maintained in a population only if the alleles are favored by natural selection. if the population size is small. even if the alleles are not favored by natural selection.

even if the alleles are not favored by natural selection.

In natural populations, most genes are not variable. possess only one allele. exhibit variation. are monomorphic.

exhibit variation

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

false

In general, ______are more likely to exhibit mate choice than_______ .

females' males

What term quantifies reproductive success of a phenotype? Hardy-Weinberg equilibrium Competition Fitness Evolution

fitness

Sexual selection influences fitness. mating success. mate choice. individual genotypes.

fitness. mating success. mate choice.

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

frequency dependant

Which of the following agents of evolutionary change occurs when alleles move from one population to another? Natural selection Gene flow Assortative mating Mutations

gene flow

Assortative mating changes ______ frequencies but does not change ______ frequencies. allele; heterozygote genotype; heterozygote allele; homozygote genotype; allele

genotype; allele

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 inbreeding. heterozygote advantage. non-random mating. outbreeding.

heterozygote advantage

----- is the ultimate source of genetic variation

mutation

What is the ultimate source of all new alleles? Natural selection Genetic drift Nonrandom mating Mutation

mutation

Select all of the following processes that can cause changes in allele or genotype frequencies in populations. Genetic drift Nonrandom Mating Random Mating Gene flow Mutations Natural selection

mutations nonrandom mating natural selection gene flow genetic drift

When a population is in Hardy-Weinberg equilibrium natural selection quickly eliminates new mutations that arise. natural selection is balanced by genetic drift. no natural selection is occurring. genetic drift quickly eliminates new mutations that arise.

no natural selection is occurring

In nature, mutation rates are usually ______ to maintain alleles that are not favored in a population by natural selection. too high not high enough often able

not high enough

In Northeastern South America, which of the following is the main predator in streams found just below waterfalls? Killifish Guppies Pike cichlids

pike cichlids

Gene flow may (choose all that apply) remove alleles from a population. promote evolutionary change. reduce evolutionary change. maintain Hardy-Weinberg conditions. introduce new alleles to a population.

remove alleles from a population. promote evolutionary change. reduce evolutionary change. introduce new alleles to a population.

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

sexual

What type of selection affects traits that influence an individual's chances to find a mating partner or be chosen as a mating partner? Stabilizing selection Directional selection Diversifying selection Sexual selection Balancing selection

sexual selection

The amount of genetic variation present in naturally occurring populations is practically nonexistent. significant. very little. insignificant.

significant

_____selection favors individuals with intermediate phenotypes and selects against individuals with extreme phenotypes.

stabilizing

In frequency-dependent selection the fitness of a phenotype depends on the frequency of matings between individuals with that phenotype. In frequency-dependent selection the fitness of a phenotype depends on the frequency of matings between individuals with that phenotype. the fitness of a phenotype depends on its frequency in the population. the fitness of a phenotype depends on the frequency of mutations leading to that phenotype. the fitness of a phenotype depends on the frequency of mutations leading to that phenotype.

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 the number of alleles in a population is very high individuals who harbor new mutations are rapidly eliminated from the population by selection

the rate at which new mutations occur is low