Chapter 23

Which mechanism? Drag the appropriate label under each image to identify the evolutionary mechanism at work. Labels may be used more than once. A. New individuals move into a population. B. Camouflage enables this insect to evade predators. C. A prominent tail helps the peacock attract a mate. D. By chance, some flowers in this population reproduce, while others do not. E. The bird's beak is well-suited for cracking seeds.

A. Gene flow B. Natural selection C. Natural selection D. Genetic drift E. Natural selection

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

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

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

Which of the following specimens discovered in 1972 ignited the debate about multiple lineages within the genus Homo? 62000 1470 1972 60000

1470

Which of the following statements is not a part of the Hardy-Weinberg principle? When alleles are transmitted according to the rules of Mendelian inheritance, their frequencies do not change over time. The genotype frequencies in the offspring generation must add up to two. Even if allele A1 is dominant to allele A2, it does not increase in frequency. If allele frequencies in a population are given by p and q, then genotype frequencies will be given by p2, 2pq, and q2 for generation after generation.

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

Which of the following prompted the passing of the new legislation regarding antibiotic use in livestock? The discovery of three new antibiotics. The decreasing effectiveness of antibiotics in humans. The increasing cost of antibiotics. A worldwide shortage of antibiotics.

The decreasing effectiveness of antibiotics in humans.

In the beetles described in the animation, there were two alleles for color, brown and green. Suppose that you discover a very small population of these beetles, consisting of the individuals shown below. How can you calculate the frequency of each allele in this population? Drag the terms or numbers on the left to the appropriate blanks on the right to complete the sentences. Not all terms will be used. 1. To calculate the frequency of the brown allele, count the number of ________________ and divide by the total number of alleles in this population. 2. In this beetle population, the number of brown alleles is ___. 3. In this beetle population, the total number of alleles is ___. 4. The frequency of the brown allele in this beetle population is _____. 5. The frequency of the green allele in this beetle population is _____.

1. brown alleles 2. 8 3. 20 4. 0.4 5. 0.6

How did the drought lead to an increase in beak size in the medium ground finch population? The Grants reasoned that prior to the drought, the finch population fed primarily on small seeds that they could open easily. Although larger, tougher seeds were available, they were not typically eaten, not even by finches with larger beaks. during the drought, only a limited number of small seeds were produced, leaving mostly larger, tougher seeds available for food. Finches that were unable to eat the larger seeds died of starvation. Based on their observations and the data they collected, the Grants concluded that evolution by natural selection had occurred in the medium ground finch population. The increase in the average beak size of the offspring was a direct result of the change in the food supply during the drought. In order to have reached this conclusion, the Grants must have either assumed or proven that several other facts about the finch population were true. Which statements represent information that must be true in order for the Grants conclusion to be correct? Select the three statements that must be true. Beak size is an inherited trait in the finch population under study. An individual finch's beak size can change depending on the size of the seeds it eats. Beak size varies among the birds in the finch population under study. Birds that could eat larger, tougher seeds survived and reproduced during the drought. The drought caused a mutation that led to larger beak sizes in the finch population.

Beak size is an inherited trait in the finch population under study. Beak size varies among the birds in the finch population under study. Birds that could eat larger, tougher seeds survived and reproduced during the drought.

Which of the following is true? Current research indicates that medians are similar to islands when comparing the diversity of animals, but not of plants. Current research indicates that medians are similar to islands when comparing the diversity of plants, but not of animals. Current research indicates that medians are similar to islands when comparing the diversity of animals and plants. Current research indicates that medians are not similar to islands when comparing the diversity of animals or plants.

Current research indicates that medians are not similar to islands when comparing the diversity of animals or plants.

You discover that a company illegaly dumped old vats of PCBs into a nearby river. What do you expect to see? All of the fish will leave the area. No change in the fish. All of the fish will die. Fish with deformities.

Fish with deformities.

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

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

You discover the skull of a species very similar to 1470. Which of the following two species is it most like? Homo habilis and Homo sapiens Homo rudolfensis and Homo sapiens Homo habilis and Homo rudolfensis Homo erectus and Home sapiens

Homo habilis and Homo rudolfensis

Which of the following do most biologists currently think is true? Human evolution followed a path with a few short branches that quickly went extinct. Human evolution followed a straight path. Human evolution followed a path with many branches. Human evolution followed a circular path.

Human evolution followed a path with many branches.

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

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 evolutionary forces could create new genetic information in a population? Nonrandom mating Genetic drift Selection Mutation

Mutation

The three major mechanisms of evolution differ in how they work, and as a result often have different effects on a population. Review your understanding of natural selection, genetic drift, and gene flow by sorting the statements below into the correct bins. Drag each statement into the appropriate bin depending on whether it applies to natural selection, genetic drift, or gene flow.

Natural Selection Consistently causes a population to become better adapted to its environment A result of differential success in reproduction Cannot cause a harmful allele to become more common Genetic Drift Responsible for the founder effect Responsible for the bottleneck effect Causes allele frequencies to fluctuate randomly Gene flow Can introduce new alleles into a population's gene pool A result of the movement of fertile individuals or their gametes

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? The expected genotype frequencies are 0.32, 0.64, and 0.04 for A1A1, A1A2, and A2A2, respectively. The expected genotype frequencies are 0.25, 0.5, and 0.25 for A1A1, A1A2, and A2A2, respectively. The expected genotype frequencies are 0.64, 0.32, and 0.04 for A1A1, A1A2, and A2A2, respectively. The expected genotype frequencies are 0.33, 0.33, and 0.33 for A1A1, A1A2, and A2A2, respectively.

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

An AABbccDdEeFF individual is crossed with an individual with the genotype AaBBCCDdEeff. What is the probability that their offspring will have the genotype AaBBCcddEEFf? 1/2 1/4 1/16 1/32 1/64

1/64 To obtain the overall probability, multiply the individual probabilities for each locus: (1/2)(1/2)(1)(1/4)(1/4)(1) = 1/64.

Populations evolve for many reasons. Suppose there is a population of plants that have either purple flowers or white flowers, and the allele for purple flowers is dominant. This means that plants with two purple alleles have purple flowers. Plants with one purple allele and one white allele also have purple flowers. Only plants with two white alleles have white flowers. For each event or condition described below, answer the following questions. Which mechanism of evolution is at work? How does this event affect the population's gene pool? Do the frequencies of the two alleles change, and if so, how? Drag the labels to their appropriate locations in the table below. Drag the pink labels onto the pink targets in the table to indicate which mechanism of evolution is at work. Then drag the blue labels onto the blue targets to indicate the effect on allele frequencies. Labels can be used once, more than once, or not at all.

Event or Condition 1. During an extreme heat wave, plants with white flowers survive better. 2. A person uproots the five closest plants, which all happen to have white flowers 3. A storm kills many plants at random 4. Plants with purple flowers attract more insects, which pollinate plants. 5. Workers from a nearby greenhouse accidentally introduce white flower seeds into this population's habitat. Mechanism 1a. Natural Selection 2c. Genetic Drift 3e. Genetic Drift 4g. Natural Selection 5i. Gene flow Effect on Allele frequencies 1b. Frequency of white allele increases 2d. Frequency of purple allele increases 3f. Allele frequencies change but not predictably 4h. Frequency of purple allele increases 5j. Frequency of white allele increases

Which of the following is true? Once it is established in a population, a new mutation will always decrease in frequency over time. Once it is established in a population, a new mutation will always disappear rapidly. Once it is established in a population, a new mutation may increase or decrease in frequency depending on the environment. Once it is established in a population, a new mutation will always increase in frequency over time.

Once it is established in a population, a new mutation may increase or decrease in frequency depending on the environment.

Which of the following evolutionary forces results in adaptive changes in allele frequencies? Nonrandom mating Mutation There is no evolutionary force that results in adaptive changes in allele frequencies. Selection

Selection

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

The frequency of the A1 allele is 0.3.

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 False

True

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

duplication

You are infected with an antibiotic-resistant strain of Klebsiella pneumoniae. Where did you most likely contract it? restaurant school hospital grocery store

hospital

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

microevolution

Genetic variation _____. tends to be reduced by when diploid organisms produce gametes is created by the direct action of natural selection must be present in a population before natural selection can act upon the population arises in response to changes in the environment

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

The original source of all genetic variation is _____. mutation recombination natural selection sexual reproduction independent assortment

mutation

Which of the following mechanisms can form entirely new alleles? the environment genetic drift mutation sexual recombination natural selection

mutation

Natural selection ultimately depends on favorable what? mutations climate food availability environmental conditions

mutations

You are a researcher working closely with the Leakey family, studying the newly discovered fossils to determine their place in the human lineage. Which of the following are you? paleohistologist paleoagronomist paleoncologist paleoanthropologist

paleoanthropologist

Which of the following is the closest relative to Homo sapiens? the lemur, a strepsirrhine primate the orangutan, a great ape a howler monkey, a New World monkey a lion-tailed macaque, an Old World monkey

the orangutan, a great ape