AP Bio: Chapter 21

What is the frequency of the A1A2 genotype in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals? 0.1 0.4 0.5 80

0.4

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2? 0.21 0.7 0.09 0.49 0.42

0.42

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population? 0.36 0.75 0.64 0.80

0.80

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the frequency of individuals with AA genotype? 0.32 0.81 0.20 0.42 Genotype frequency cannot be determined from the information provided.

0.81

All the genes in a population are that population's _____. 1. genotype 2. Hardy-Weinberg 3. phenotype 4. gene pool 5. fitness

gene pool

Allele frequencies in a gene pool may shift randomly and by chance. What is this random shift called? gene flow directional selection genetic drift

genetic drift

Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations, which one most consistently requires a small population as a precondition for its occurrence? nonrandom mating natural selection genetic drift gene flow mutation

genetic drift

Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans. disease genetic drift mutation natural selection gene flow

genetic drift

When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of stabilizing selection. frequency-dependent selection. sexual selection. disruptive selection. balancing selection.

frequency-dependent selection.

The ease with which humans travel across the globe is likely to increase _____. mutation gene flow natural selection genetic drift all of these

gene flow

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus? gene variability = 0%; number of alleles = 0 gene variability = 0%; number of alleles = 1 gene variability = 0%; number of alleles = 2 gene variability > 0%; number of alleles = 2 Without more information, gene variability and number of alleles cannot be determined.

gene variability = 0%; number of alleles = 1

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from disruptive selection directional selection nonrandom mating gene flow genetic drift

genetic drift

If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of genetic drift and the founder effect. genetic drift. the bottleneck effect. the founder effect. all three of these.

genetic drift and the founder effect.

In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes. If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite different in the subsequent generations. This would be an example of disruptive selection. diploidy. gene flow. stabilizing selection. genetic drift.

genetic drift.

The original source of all genetic variation is _____. 1. natural selection 2. sexual reproduction 3. recombination 4. independent assortment 5. mutation

mutation

What is the only evolutionary mechanism that consistently leads to adaptive evolution? natural selection the bottleneck effect gene flow neutral variation genetic drift

natural selection

Which type of selection tends to increase genetic variation? Directional selection Stabilizing selection Disruptive selection

Disruptive selection

Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then 1. selection was acting more directly upon genotype than upon phenotype. 2. stabilizing selection was occurring in these species concerning larynx size. 3. sexual dimorphism was developing over time in these species. 4. intrasexual selection seems to have occurred.

sexual dimorphism was developing over time in these species.

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool. 1. sexual reproduction 2. genetic drift 3. mutation 4. sexual selection 5. immigration

sexual reproduction

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating neutral variation. the bottleneck effect. stabilizing selection. frequency-dependent selection disruptive selection.

stabilizing selection.

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus 1. the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change. 2. this means that, at this locus, two alleles are present in equal proportions. 3. natural selection, gene flow, and genetic drift are acting equally to change an allele's frequency. 4. the population itself is not evolving, but individuals within the population may be evolving.

the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change.

The evolutionary effects of genetic drift are greatest when _____. 1. sexual selection occurs 2. intraspecific competition is weak 3. the population size is large 4. the population size is small 5. intraspecific competition is intense

the population size is small

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is 1. natural selection. 2. the reshuffling of alleles in sexual reproduction. 3. environmental effects. 4. new mutations that occurred in the preceding generation. 5. genetic drift due to the small size of the population.

the reshuffling of alleles in sexual reproduction.

Genetic drift is a process based on _____. 1. differential reproductive success correlated to the relationship between a phenotype and the environment 2. immigration 3. the role of chance 4. mutation 5. emigration

the role of chance

A mutation occurs when _____. 1. population sizes are small 2. some individuals leave more offspring than other individuals 3. there is a change in the DNA sequence of a gene 4. individuals leave a population 5. individuals enter a population

there is a change in the DNA sequence of a gene

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true? 1. Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted. 2. Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation. 3. The frequency of the strong-beak alleles increased in each bird as the drought persisted. 4. Each bird evolved a deeper, stronger beak as the drought persisted.

Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted.

True or false? Heterozygote advantage refers to the tendency for heterozygous individuals to have better fitness than homozygous individuals. This higher fitness results in less genetic variation in the population. True False

False

Which of the following evolutionary forces consistently results in adaptive changes in allele frequencies? 1. Inbreeding 2. Selection 3. Mutation 4. There is no evolutionary force that results in adaptive changes in allele frequencies.

Selection

Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards? Directional selection Disruptive selection Stabilizing selection

Stabilizing selection

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies? Stabilizing selection Disruptive selection Directional selection

Stabilizing selection

In a bell-shaped curve, the x-axis (horizontal direction) of the graph represents which of the following? 1. The number of individuals 2. The value of a particular characteristic; characteristics of an organism can include such traits as size and color. 3. Time

The value of a particular characteristic; characteristics of an organism can include such traits as size and color.

During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following terms are appropriately applied to this situation? intersexual selection mate choice sexual selection Three of the responses are correct. Two of the responses are correct.

Three of the responses are correct.

In the wild, male house finches (Carpodus mexicanus) vary considerably in the amount of red pigmentation in their head and throat feathers, with colors ranging from pale yellow to bright red. These colors come from carotenoid pigments that are found in the birds' diets; no vertebrates are known to synthesize carotenoid pigments. Thus, the brighter red the male's feathers are, the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal). During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following is true of this situation? 1. There should be directional selection for bright red feathers in males. 2. Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations. 3. Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations. 4. Three of the statements are correct. 5. Two of the statements are correct.

Three of the statements are correct

True or false? The Hardy-Weinberg model makes the following assumptions: no selection at the gene in question; no genetic drift; no gene flow; no mutation; random mating.

True

In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool. The sickle-cell allele is pleiotropic (i.e., it affects more than one phenotypic trait). Specifically, this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria. Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria. Thus, pleiotropic genes/alleles such as this can help explain why 1. evolution is limited by historical constraints. 2. adaptations are often compromises. 3. chance events can affect the evolutionary history of populations. 4. new advantageous alleles do not arise on demand.

adaptations are often compromises.

Evolution 1. requires the operation of natural selection. 2. can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met. 3. requires that populations become better suited to their environments. 4. must happen whenever a population is not well adapted to its environment. 5. must happen, due to organisms' innate desire to survive.

can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met

In evolutionary terms, an organism's fitness is measured by its _____. 1. mutation rate 2. health 3. contribution to the gene pool of the next generation 4. genetic variability 5. stability in the face of environmental change

contribution to the gene pool of the next generation

You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to 1. shock the flies with a brief treatment of heat or cold to make them more hardy. 2. cross your flies with flies from another lab. 3. reduce the number of flies that you transfer at each generation. 4. change the temperature at which you rear the flies. 5. transfer only the largest flies.

cross your flies with flies from another lab.

The recessive allele that causes phenylketonuria (PKU) is harmful, except when an infant's diet has appropriate levels of the amino acid phenylalanine. What maintains the presence of this harmful allele in a population's gene pool? balancing selection stabilizing selection diploidy heterozygote advantage

diploidy

Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____. directional selection neutral variation genetic drift disruptive selection stabilizing selection

directional selection

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population? gene flow bottleneck effect founder effect mutation nucleotide variability

founder effect

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be 46%. 23%. 54%. There is not enough information to say.

54%

You sample a population of butterflies and find that 56% are heterozygous at a particular locus. What should be the frequency of the recessive allele in this population? 0.07 0.70 0.09 0.08 Allele frequency cannot be determined from this information.

Allele frequency cannot be determined from this information.

Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population? 1. Alleles that promote "tallness" will decrease in frequency. 2. Gene flow will increase. 3. It will increase in number since shorter people use fewer resources than taller people. 4. The mutation rate will increase. 5. Genetic drift will play less of a role in the evolution of humans.

Alleles that promote "tallness" will decrease in frequency.

The same gene that causes various coat patterns in wild and domesticated cats also causes a cross-eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations? 1. Evolution is progressive and tends toward a more perfect population. 2. In all environments, coat pattern is a more important survival factor than is eye-muscle tone. 3. Polygenic inheritance is generally maladaptive, and should become less common in future generations. 4. Natural selection reduces the frequency of maladaptive genes in populations over the course of time. 5. Phenotype is often the result of compromise.

Phenotype is often the result of compromise.

Which variable is likely to undergo the largest change in value resulting from a mutation that introduces a new allele into a population at a locus for which all individuals formerly had been fully homozygous? 1. average number of loci 2. average heterozygosity 3. geographic variability 4. nucleotide variability

average heterozygosity

In human gamete production there is an average of _____ crossover events per chromosome pair. 0-1 2-3 9-10 10+ 5-6

2-3

Arrange the following from most general (i.e., most inclusive) to most specific (i.e., least inclusive): 1. natural selection 2. microevolution 3. intrasexual selection 4. evolution 5. sexual selection 4, 2, 1, 3, 5 1, 4, 2, 5, 3 4, 1, 2, 3, 5 1, 2, 4, 5, 3 4, 2, 1, 5, 3

4, 2, 1, 5, 3

You read about soapberry bugs and select the correct statement describing relative fitness in these individuals. 1. A soapberry bug with high relative fitness feeds more successfully on fruits than do other bugs. 2. A soapberry bug with high relative fitness has a relatively high number of offspring that survive to reproductive age. 3. A soapberry bug with high relative fitness has more mates than other bugs.

A soapberry bug with high relative fitness has a relatively high number of offspring that survive to reproductive age.

Which of these individuals is a homozygous genotype? aG Aa Gg AA AG

AA

Which of the following are causes of evolutionary change? mutation genetic drift natural selection gene flow All of the above

All of the above

Based on the information presented in the accompanying figure, when both finches are found on the same island, what is the most likely factor to determine the difference in beak size? Predation Genetic drift Nonrandom mating Competition

Competition

Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today? Directional selection Disruptive selection Stabilizing selection

Directional selection

Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers? Directional selection Stabilizing selection Disruptive selection

Disruptive selection

Which of the following are basic components of the Hardy-Weinberg model? 1. Allele frequencies, phenotype frequencies 2. Allele frequencies in a subset of the population 3. Allele frequencies, number of individuals in the population 4. Frequencies of two alleles in a gene pool before and after many random matings

Frequencies of two alleles in a gene pool before and after many random matings

Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. When this occurs, it is possible for genes from bird flu virus and human flu virus to be combined. If the human flu virus contributes a gene for Tamiflu resistance (Tamiflu is an antiviral drug) to the new virus, and if the new virus is introduced to an environment lacking Tamiflu, then what is most likely to occur? 1. If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency. 2. If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will become dormant until Tamiflu is present. 3. The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment. 4. The new virus will maintain its Tamiflu-resistance gene, just in case of future exposure to Tamiflu.

If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency.

How does diploidy help to preserve genetic variation? 1. It allows the frequency of a recessive allele in a population to be predicted under certain conditions. 2. It fosters the exchange of genes between different populations. 3. It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes. 4. It helps individual organisms make a greater contribution to the gene pool of the next generation. 5. It restricts the gene pool by chance events such as floods or other catastrophic events.

It allows recessive alleles that may not be favored in the current environment to be preserved in the gene pool by propagation in heterozygotes.

Which of the following statements best summarizes evolution as it is viewed today? 1. It is synonymous with the process of gene flow. 2. It is a change in allele frequencies in a population over generations. 3. It is the descent of humans from the present-day great apes. 4. It represents the result of selection for acquired characteristics.

It is a change in allele frequencies in a population over generations.

What is true of microevolution? 1. It is evolution that influences only a small subset of the populations that comprise a species. 2. It is evolution that involves only tiny changes to DNA, such as point mutations, producing only small (if any) changes to phenotype. 3. It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations. 4. It is evolution that is restricted to individual organisms. 5. It is evolution that results in the origin of small numbers of new species.

It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations.

Which of the following is a true statement concerning genetic variation? 1. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity. 2. It arises in response to changes in the environment. 3. It is created by the direct action of natural selection. 4. It tends to be reduced by the processes involved when diploid organisms produce gametes. 5. It must be present in a population before natural selection can act upon the population.

It must be present in a population before natural selection can act upon the population.

Which of the following evolutionary forces could create new genetic information in a population? 1. Genetic drift 2. Selection 3. Nonrandom mating 4. Mutation

Mutation

The fruit fly Drosophila melanogaster has an allele that confers resistance to DDT and similar insecticides. Laboratory strains of D. melanogaster have been established from flies collected in the wild in the 1930s (before the widespread use of insecticides) and the 1960s (after 20 years of DDT use). Lab strains established in the 1930s have no alleles for DDT resistance. In lab strains established in the 1960s, the frequency of the DDT-resistance allele is 37%. Which statement is correct? 1. Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance. 2. The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread. 3. Resistance to DDT evolved in some fruit flies in order to allow them to survive.

The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread.

What genotype frequencies are expected under Hardy-Weinberg equilibrium for a population with allele frequencies of p = 0.8 and q = 0.2 for a particular gene? 1. The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2 , and A2A2 , respectively. 2. The expected genotype frequencies are 0.25, 0.5, and 0.25 for A1A1, A1A2 , and A2A2 , respectively. 3. The expected genotype frequencies are 0.33, 0.33, and 0.33 for A1A1, A1A2 , and A2A2 , respectively. 4. The expected genotype frequencies are 0.32, 0.64, and 0.04 for A1A1, A1A2 , and A2A2 , respectively.

The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2 , and A2A2 , respectively.

What is the frequency of the A1 allele in a population composed of 20 A1A1 individuals, 80 A1A2 individuals, and 100 A2A2 individuals? 1. The frequency of the A1 allele is 0.7. 2. The frequency of the A1 allele is 0.5. 3. The frequency of the A1 allele is 0.3. 4. The frequency of the A1 allele is 0.1.

The frequency of the A1 allele is 0.3.

Which of the following statements is not a part of the Hardy-Weinberg principle? 1. When alleles are transmitted according to the rules of Mendelian inheritance, their frequencies do not change over time. 2. Even if allele A1 is dominant to allele A2 , it does not increase in frequency. 3. The genotype frequencies in the offspring generation must add up to two. 4. If allele frequencies in a population are given by p and q, then genotype frequencies will be given by p 2, 2pq, and q 2 for generation after generation.

The genotype frequencies in the offspring generation must add up to two.

A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants. What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time? 1. The two phenotypes are about equally adaptive under laboratory conditions. 2. The genotype AA is lethal. 3. The population is undergoing genetic drift. 4. There has been sexual selection favoring allele a. 5. There has been a high rate of mutation of allele A to allele a.

The two phenotypes are about equally adaptive under laboratory conditions.

Which statement correctly describes the role of chance in evolution? 1. Evolution by natural selection proceeds by an accumulation of changes that occur by chance. 2. The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA. 3. An allele that increases evolutionary fitness cannot be lost from a population by chance events.

The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA

Natural selection changes allele frequencies because some ________ survive and reproduce more successfully than others. gene pools alleles individuals loci species

individuals

Homologous pairs of chromosomes are lined up independently of other such pairs during _____. anaphase I telophase II metaphase I prophase II metaphase II

metaphase I

Generation-to-generation change in the allele frequencies in a population is _____. 1. macroevolution 2. genetic drift 3. mutation 4. microevolution 5. natural selection

microevolution

Crossing over, resulting in an increase in genetic variation, occurs between _____. 1. sex cells and somatic cells 2. nonsister chromatids of nonhomologous chromosomes 3. sister chromatids of nonhomologous chromosomes 4. sister chromatids of homologous chromosomes 5. nonsister chromatids of homologous chromosomes

nonsister chromatids of homologous chromosomes

The higher the proportion of loci that are "fixed" in a population, the lower is that population's 1. nucleotide variability only. 2. nucleotide variability and average heterozygosity. 3. nucleotide variability, average heterozygosity, and chromosome number. 4. average heterozygosity only. 5. chromosome number only.

nucleotide variability and average heterozygosity.

You are studying three populations of birds. Population A has 10 birds, of which 1 is brown (a recessive trait) and 9 are red. Population B has 100 birds, of which 10 are brown. Population C has 30 birds, and 3 of them are brown. Which population is most likely to be subject to the bottleneck effect? They are all equally likely. population C population B population A It is impossible to tell from the information given.

population A