AP Biology Ch.23

Assume a population in Hardy-Weinberg equilibrium for a character trait with these genotypic frequencies: AA = 0.25, Aa = 0.50, and aa = 0.25. If you remove all the homozygous dominants and allow the remaining population to reproduce (again under Hardy-Weinberg conditions), what will be the frequency of homozygous dominants in the next generation? A) 0 B) 0.11 C) 0.22 D) 0.44 E) 0.50

B) 0.11

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

B) 2-3

Which of the following scenarios would most likely result in the microevolution of a population of humans? A) Only random mating takes place among all the people that reproduce in North America. B) A colony of humans on the moon is isolated from Earth. C) The incidence of skin cancer in adults over age 40 rises significantly. D) Hundreds of thousands of people are killed in a natural disaster. E) Both random mating and an increase in middle-aged skin cancer occur.

B) A colony of humans on the moon is isolated from Earth.

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? A) Gene flow will increase. B) Alleles that promote "tallness" will decrease in frequency. C) Genetic drift will play less of a role in the evolution of humans. D) It will increase in number since shorter people use fewer resources than taller people. E) The mutation rate will increase.

B) Alleles that promote "tallness" will decrease in frequency.

_____ and _____ generate variation, while _____ results in an adaptation to the environment. A) Genetic drift; natural selection; mutation B) Mutation; sexual recombination; natural selection C) Overproduction of offspring; mutation; sexual recombination D) Natural selection; mutation; sexual recombination E) Sexual recombination; natural selection; overproduction

B) Mutation; sexual recombination; natural selection

What is the importance of neutral variation in evolution? A) DNA forensics relies on neutral variation among humans. B) Neutral variation increases genetic variation, allowing a population to carry more alleles that may help it respond to environmental change. C) Relative frequencies of neutral variations are controlled by natural selection. D) Neutral variation is usually removed from the population by natural selection because it does not confer an advantage in the current environment. E) Many mutations are silent and do not affect the amino acid that is coded for.

B) Neutral variation increases genetic variation, allowing a population to carry more alleles that may help it respond to environmental change.

Which example below would most likely be a cline? A) Individuals who are heterozygotic for the sickle-cell disease allele have a greater resistance to malaria. B) Rabbits that live in colder regions tend to have smaller ears than rabbits of the same species that live in warmer regions. C) Male bowerbirds decorate stations to attract females. D) Cows are selectively bred to gain a higher milk yield. E) Seals have flippers that make them great swimmers but make their movements on rocks and land very cumbersome.

B) Rabbits that live in colder regions tend to have smaller ears than rabbits of the same species that live in warmer regions.

An earthquake hits a small island. All but a small group of closely related lizards are eliminated, and the survivors spread out over the island. This is an instance of _____. A) founder effect B) bottleneck effect C) gene flow D) mutation E) nonrandom mating

B) bottleneck effect

Antibiotic resistance in bacteria is an example of which of the following? A) stabilizing selection B) directional selection C) disruptive selection D) Hardy-Weinberg equilibrium E) macroevolution

B) directional selection

Which type of mutation plays the most important role in increasing the number of genes in the gene pool? A) Mutations are so rare that there are no mutations that can have such an important effect. B) duplication C) point mutation D) rearrangement of gene loci E) changes in nucleotide sequence

B) duplication

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

B) gene flow

A population of 15 birds inhabits a fairly new island. Ten of the birds are dark brown and five of them are light brown. By chance, two of the dark brown birds and three of the light brown birds die before producing any offspring. All of the birds in the next generation are dark brown. This change in phenotypic frequency can be attributed to _____. A) natural selection B) genetic drift C) gene flow D) disruptive selection E) a cline

B) genetic drift

Birds with average-size wings survived a severe storm more successfully than other birds in the same population with longer or shorter wings. If severe storms occur regularly, then over time, one should expect these storms to bring about _____. A) the bottleneck effect B) stabilizing selection C) artificial selection D) gene flow E) disruptive selection

B) stabilizing selection

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

B) stabilizing selection.

No two people are genetically identical, except for identical twins. The chief cause of genetic variation among human individuals is A) new mutations that occurred in the preceding generation. B) the reshuffling of alleles in sexual reproduction. C) genetic drift due to the small size of the population. D) geographic variation within the population. E) environmental effects.

B) the reshuffling of alleles in sexual reproduction.

In a population in Hardy-Weinberg equilibrium, 1% of the individuals in a population show the recessive trait of a certain characteristic. In this situation, what is the value of p? A) 99% B) 0.81 C) 0.9 D) 0.18 E) The answer cannot be determined from the information given.

C) 0.9

The human genome consists of approximately 3 billion base pairs. If humans typically differ from one another by about 3 million base pairs, what is the nucleotide variability of Homo sapiens? A) 10% B) 1% C) 50% D) 3% E) 0.1%

E) 0.1%

In a certain group of African people, 4% are born with sickle-cell disease (homozygous recessive). If this group is in Hardy-Weinberg equilibrium, what percentage of the group has the selective advantage of being more resistant to malaria (heterozygous) than those individuals who are homozygous for normal hemoglobin or for sickle-cell disease? A) 2% B) 4% C) 8% D) 16% E) 32%

E) 32%

Which of these individuals is a homozygous genotype? A) AA B) Aa C) Gg D) AG E) aG

A) AA

In the context of populations, how do we define evolution? A) Evolution is a change in a population's allelic frequencies over generations B) Evolution is the tendency for some individuals in a population to leave more offspring than others C) Evolution is the way in which sexual reproduction can rapidly spread advantageous traits throughout a population D) Evolution is the explanation for how organic molecules formed from inorganic molecules. E) Evolution is always caused by natural selection.

A) Evolution is a change in a population's allelic frequencies over generations

Which type of selection maintains stable frequencies of two or more phenotypic forms in a population? A) balancing selection B) neutral variation C) heterozygote advantage D) stabilizing selection E) relative fitness

A) balancing selection

Stabilizing selection _____. A) favors intermediate variants in a population B) prevents mutations from occurring C) occurs when some individuals migrate to an area with different environmental conditions D) can take place only in species exhibiting sexual dimorphism E) occurs only in plants

A) favors intermediate variants in a population

All the genes in a population are that population's _____. A) gene pool B) fitness C) genotype D) Hardy-Weinberg E) phenotype

A) gene pool

There are 40 individuals in population 1, all of which have genotype A1A1, and there are 25 individuals in population 2, all of genotype A2A2. Assume that these populations are located far from one another and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation is mostly likely an example of A) genetic drift. B) gene flow. C) disruptive selection. D) discrete variation. E) directional selection.

A) genetic drift.

Homologous pairs of chromosomes are lined up independently of other such pairs during _____. A) metaphase I B) anaphase I C) prophase II D) metaphase II E) telophase II

A) metaphase I

Generation-to-generation change in the allele frequencies in a population is _____. A) microevolution B) genetic drift C) natural selection D) mutation E) macroevolution

A) microevolution

In the equation for Hardy-Weinberg equilibrium, 1 represents _____. A) the sum of the frequencies of the genotypes for a particular gene locus B) the frequency of heterozygous individuals in the populations C) the frequency of homozygous recessive individuals in the population D) all the possible phenotypes in the population E) the frequency of homozygous dominant individuals in the population

A) the sum of the frequencies of the genotypes for a particular gene locus

How does natural selection fashion organisms? A) The best traits for the current environment arise in the population and are selected for. B) Brand new body plans arise often, giving natural selection many new possibilities to work with. C) Chance and the environment interact with natural selection, so that the best available traits are selected for. D) Sexual selection acts to make organisms better adapted to their environments. E) Neutral traits are often selected for because they will eventually produce alleles that confer an advantage.

C) Chance and the environment interact with natural selection, so that the best available traits are selected for.

Tay-Sachs disease, which is lethal, results from having the homozygous recessive condition of the responsible gene. Which one of the following statements is true? A) Because homozygous recessive individuals die, the recessive allele will eventually be lost from the population. B) Only homozygous dominant individuals will be able to survive and reproduce. C) Heterozygous individuals will survive and may pass the recessive allele on to their offspring. D) In the heterozygous condition, the dominant allele will overcome the recessive allele and only the dominant allele will be passed on to offspring. E) Homozygous dominant individuals will be more likely to reproduce than heterozygous individuals.

C) Heterozygous individuals will survive and may pass the recessive allele on to their offspring

A number of mosquito populations today are resistant to insecticides that were once quite effective. Biologists think that insecticide resistance evolved in mosquitoes because _____. A) individual mosquitoes built up an immunity to an insecticide after being exposed to it B) mosquitoes needed to develop insecticide resistance to survive after the insecticide was used C) a few mosquitoes were probably resistant to the insecticide before it was ever used, and these individuals were more likely to survive and reproduce D) mosquitoes attempted to adapt to their environment E) a new allele developed in response to the insecticide that provided future generations the benefit of resistance

C) a few mosquitoes were probably resistant to the insecticide before it was ever used, and these individuals were more likely to survive and reproduce

Approximately 1 out of every 2,500 Caucasians in the United States is born with the recessive disease cystic fibrosis. According to the Hardy-Weinberg equilibrium equation, approximately how many people are carriers? A) about 1 in 50 B) about 96 in 100 C) about 1 in 25 D) about 1 in 10 E) none of the above

C) about 1 in 25

A population of squirrels is preyed upon by small hawks. The smaller squirrels can escape into burrows. The larger squirrels can fight off the hawks. After several generations, the squirrels in the area tend to be very small or very large. What process is responsible for this outcome? A) stabilizing selection B) directional selection C) disruptive selection D) balancing selection E) Hardy-Weinberg equilibrium

C) disruptive selection

Which of the following most accurately measures an organism's fitness? A) how strong the organism is when pitted against others of its species B) its mutation rate C) how many fertile offspring it produces D) its ability to withstand environmental extremes E) how much food it is able to make or obtain

C) how many fertile offspring it produces

Crossing over, resulting in an increase in genetic variation, occurs between _____. A) sex cells and somatic cells B) sister chromatids of homologous chromosomes C) nonsister chromatids of homologous chromosomes D) sister chromatids of nonhomologous chromosomes E) nonsister chromatids of nonhomologous chromosomes

C) nonsister chromatids of homologous chromosomes

For several years, scientists have warned doctors of the danger of overprescribing antibiotics such as penicillin. Scientists are concerned because _____. A) humans will become tolerant to the effects of drugs B) the organisms that produce many of the antibiotics are overexploited and could become extinct C) strains of microorganisms that are resistant to these drugs will be selected for D) the drugs will be metabolized more quickly by our bodies, decreasing their effectiveness E) none of the above

C) strains of microorganisms that are resistant to these drugs will be selected for

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? A) 0.7 B) 0.49 C) 0.21 D) 0.42 E) 0.09

D) 0.42

In a large population of bonobos, the frequency of the recessive allele is initially 0.1. There is no migration and no selection. What is the frequency of the dominant allele? Assume that there are two alleles of this gene. A) 10% B) 20% C) 50% D) 90% E) 99%

D) 90%

Which example below correctly describes average heterozygosity? A) Average heterozygosity refers to the number of individuals in a population that are heterozygous for a certain trait. B) Average heterozygosity is measured by comparing the nucleotide sequences of DNA samples, and then averaging the data from the comparison. C) Average heterozygosity is usually less than the average difference between nucleotide sequences. D) Average heterozygosity refers to the average percentage of loci that are heterozygous in a population. E) Average heterozygosity is measured by looking at changes in karyotypes.

D) Average heterozygosity refers to the average percentage of loci that are heterozygous in a population.

Which of the following is the best example of gene flow? A) A small population of humans colonizes a newly formed island. B) Genes are shuffled by the crossing over of chromosomes during meiosis. C) An earthquake results in the formation of a canyon, splitting a population of toads apart. D) Wind blows pollen from one population of plants to another and cross-fertilization occurs. E) All the mutations in a population were neutral.

D) Wind blows pollen from one population of plants to another and cross-fertilization occurs.

Which of the following mechanisms can alter allele frequencies? A) genetic drift B) natural selection C) gene flow D) all of the above E) none of the above

D) all of the above genetic drift natural selection gene flow

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

D) genetic drift

Which of the following would seem to be an example of neutral variation? A) homozygosity of the cheetah population B) polymorphism of the Gálapagos finches C) founder effect D) human fingerprints E) moth coloration

D) human fingerprints

Which of the following sets of conditions is required for Hardy-Weinberg equilibrium? A) a large population, no mutations, and natural selection B) a large population, random mutations, and no migration of alleles in or out of the population C) no mutations, sexual selection, and no natural selection D) random mating, no natural selection, and a large population E) random mating, a small population, and no mutations

D) random mating, no natural selection, and a large population

Selection that acts over evolutionary time to preserve traits that increase an individual's ability to mate is known as _____. A) directional selection B) disruptive selection C) stabilizing selection D) sexual selection E) balancing selection

D) sexual selection

Genetic drift is a process based on _____. A) differential reproductive success correlated to the relationship between a phenotype and the environment B) immigration C) mutation D) the role of chance E) emigration

D) the role of chance

A mutation occurs when _____. A) individuals leave a population B) individuals enter a population C) some individuals leave more offspring than other individuals D) there is a change in the DNA sequence of a gene E) population sizes are small

D) there is a change in the DNA sequence of a gene

Which statement below is true about sexual selection? A) Intrasexual selection leads to the death of most unfit males in combat. B) Showy secondary sexual characteristics cannot be explained because they break all of the rules of natural selection. C) In most vertebrates, females court the males. D) There is no evidence that intrasexual selection takes place between females. E) Sexual selection can result in sexual dimorphism-marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction.

E) Sexual selection can result in sexual dimorphism-marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction.

Natural selection changes allele frequencies because some ________ survive and reproduce more successfully than others. A) alleles B) loci C) gene pools D) species E) individuals

E) individuals

Sexual recombination includes the shuffling of chromosomes in _____ and fertilization. A) mitosis B) genetic drift C) natural selection D) mutation E) meiosis

E) meiosis

New alleles originate from _____. A) natural selection B) genetic drift C) sexual recombination D) the environment E) mutation

E) mutation

In the Hardy-Weinberg equation, p2 represents _____. A) the total alleles in the gene pool B) the frequency of heterozygous dominant individuals in the population C) the frequency of homozygous recessive individuals in the population D) all of the possible phenotypes in the gene pool E) the expected frequency of homozygous dominant individuals in the population

E) the expected frequency of homozygous dominant individuals in the population

In a large population of randomly breeding organisms, the frequency of a recessive allele is initially 0.3. There is no migration and no selection. Humans enter this ecosystem and selectively hunt individuals showing the dominant trait. When the gene frequency is reexamined at the end of the year, _____. A) the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will go up, and the frequency of the homozygous recessives will remain the same B) the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will remain the same, and the frequency of the homozygous recessives will go up C) the frequency of the homozygous dominants will go up, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go down D) the frequency of the homozygous dominants will go up, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go up E) the frequency of the individuals who express the dominant phenotype will go down and the frequency of homozygous recessive individuals will go up

E) the frequency of the individuals who express the dominant phenotype will go down and the frequency of homozygous recessive individuals will go up