Chapter 23- The Evolution of Populations

Arrange the following in order from most general to most specific. 1 natural selection 2. microevolution 3. intrasexual selection 4. evolution 5. sexual selection

4, 2, 1, 5, 3

Suppose 64% of a remote mountain village can taste phenylthiocarbamide (PTC) and must, therefore, have at least one copy of the dominant PTC taster allele. If this population conforms to Hardy-Weinberg equilibrium for this gene, what percentage of the population must be heterozygous for this trait? A. 48% B. 40% C. 32% D. 16%

48%

Comparisons of Neanderthal DNA revealed that there are more similarities to non-African DNA than reference sequences from West Africans. Additionally, scientists found that Neanderthal DNA is as closely related to East Asians as to Europeans. This indicates that interbreeding occurred before human migration further east. What process of population genetics generated these results? A. Gene flow B. Nonrandom mating C. Adaptive evolution D. Gene drift

A. Gene flow

There are 40 individuals in population 1, all with genotype A1A1, and there are 25 individuals in population 2, all with genotype A2A2. 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 is most likely an example of... A. Genetic drift B. Discrete variation C. Directional selection D. Disruptive selection E. Gene flow

A. Genetic drift

Natural selection changes allele frequencies because some ____ survive and reproduce more successfully than others. A. Individuals B. Alleles C. Loci D. Gene pools E. Species

A. Individuals

The higher the proportion of loci that are "fixed" in a population, the lower are that population's.... A. Nucleotide variability and average heterozygosity B. Chromosome number C. Nucleotide variability D. Average heterozygosity

A. Nucleotide variability and average heterozygosity

Which one of these processes describes bottleneck effect? A. Sudden change in environments that alters gene frequency of a population B. Transfer of alleles in and out of a population due to movement of fertile individuals C. Alleles transferred to the next generation in portions that differ from previous generation D. Chance events that change allele frequency

A. Sudden change in environments that alters gene frequency of a population

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus,... A. The allele's frequency should not change from one generation to the next B. Two alleles are present in equal proportions C. Individuals within the population are evolving D. Natural selection, gene flow, and genetic drift are acting equally to change an allele's frequency

A. The allele's frequency should not change from one generation to the next

The inability of organisms to evolve anything that could be an advantage reflects... A. The limits of choices of genes within a species B. The consequences of inbreeding C. The consequences of random mutations D. The inability to compromise

A. The limits of choices of genes within a species

One out of 10,000 babies born in North America is affected by cystic fibrosis, a recessive condition. Assuming that the North American human population is in Hardy-Weinberg equilibrium for this trait, what percentage of the population is heterozygous for this trait? (Remember the equation for a population in Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1.) A. 0.01% B. 2% C. 1%

B. 2% If the trait is in Hardy-Weinberg equilibrium, then its frequency is not changing in the population from one generation to the next

Genetic drift produces variation for evolution when... A. A gene pool decreases because a smaller group establishes a new population B. Chance events cause allele frequencies to fluctuate unpredictably C. Sudden change in environment drastically reduces the gene pool D. A population has heritable traits better suited to the environment

B. Chance events cause allele frequencies to fluctuate unpredictably

Genetic variation... A. Arises in response to changes in the environment B. Must be present in a population before natural selection can act upon the population C. Tends to be reduced when diploid organisms produce gametes D. Is created by the direct action of natural selection

B. Must be present in a population before natural selection can act upon the population

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 proportion of the population is probably heterozygous (Aa) for this trait? A. 0.05 B. 0.25 C. 0.5 D. 0.75

C. 0.5

Consider the following mutations to the nucleotide sequence of a gene. Which of these mutations would not alter the reading frame of the gene's genetic message? A. A single nucleotide-pair deletion B. A deletion that removes 4 nucleotides C. A single nucleotide-pair substitution D. A single nucleotide-pair insertion

C. A single nucleotide-pair substitution

Why does the fitness of a phenotype depend on frequency-dependent selection? A. Because sexual produces dimorphism B. Because selection favors the least common phenotype C. Because frequency-dependent selection acts against extreme phenotypes D. Because the least number of alleles are at that locus

C. Because frequency-dependent selection acts against extreme phenotypes

In evolutionary terms, an organism's fitness is measured by its.... A. Stability in the face of environmental change B. Mutation rate C. Contribution to the gene pool of the next generation D. Health E. Genetic variability

C. 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 _____. A. Transfer only the largest flies B. Change the temperature at which you rear the flies C. Cross your flies with flies from another lab D. Reduce the number of flies that you transfer at each generation

C. Cross your flies with flies from another lab

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s. They do not marry with members outside their own immediate community. Today, the Dunkers are genetically unique and differ in gene frequencies, at many loci, from all other populations including those in their original homeland. Which of the following likely explains the genetic uniqueness of this population? A. Population bottleneck and Hardy-Weinberg equilibrium B. Mutation and natural selection C. Founder effect and genetic drift D. Heterozygote advantage and stabilizing selection

C. Founder effect and genetic drift

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? A. If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will increase in frequency B. The new virus will maintain its Tamiflu-resistance gene, in case of future exposure to Tamiflu C. If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency D. The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment

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

What is true of microevolution? A. It is evolution that is restricted to individual organisms B. It is evolution that influences only a small subset of the populations that comprise a species C. 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 D. It is evolution that involved only tiny changes to DNA, such as point mutations, producing only small (if any) changes to phenotype. E. It is evolution that results in the origin of small numbers of new species

C. 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 Microevolution is a generation-to-generation change in allele frequency

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? A. Alleles for DDT resistance arose by mutation during the period of DDT use because of selection for pesticide resistance B. Resistance to DDT evolved in some fruit flies in order to allow them to survive C. The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread

C. The evolutionary fitness associated with the heritable trait of DDT resistance changed once DDT use became widespread As the environment changed with the increased use of DDT, the advantages of the heritable trait of DDT resistance increased. Natural selection has different effects in different environments

The evolutionary effects of genetic drift are greatest when.... A. Intraspecific competition is intense B. Sexual selection occurs C. The population size is small D. Intraspecific competition is weak E. The population size is large

C. The population size is small Changes in the gene pool of a small population are frequently due to genetic drift

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? A. There has been a high rate of mutation of allele A to allele a B. There has been sexual selection favoring allele a C. The two phenotypes are about equally adaptive under laboratory conditions D. The genotype AA is lethal

C. The two phenotypes are about equally adaptive under laboratory conditions

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele? A. 9.0 B. 0.49 C. 0.9 D. 0.09

D. 0.09

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 estimated frequency of allele A in the gene pool? A. 0.5 B. 0.25 C. 0.125 D. 0.75

D. 0.5

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? A. 0.36 B. 0.75 C. 0.64 D. 0.8

D. 0.8

Which of the following is the best modern definition of evolution? A. Change in the number of genes in a population over time B. Inheritance of acquired characters C. Survival of the fittest D. Descent with modification

D. Descent with modification

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

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

Which Hardy-Weinberg condition is affected by population size? A. gene flow B. selection C. no mutation D. genetic drift

D. Genetic drift

In the formula for determining a population's genotype frequencies, the "pq" in the term 2pq is necessary because... A. Heterozygotes can come about in two ways B. The population is diploid C. The population is doubling in number D. Heterozygotes have two alleles

D. Heterozygotes have two alleles

In 1986, a nuclear power accident in Chernobyl, USSR (now Ukraine), led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Based on your understanding of evolutionary mechanisms, which of the following most likely occurred in the rodent populations following the accident? A. Mutation caused genetic drift and decreased fitness B. Mutations caused major changes in rodent physiology over time C. Mutation caused the fixation of new alleles D. Mutation led to increased genetic variation

D. Mutation led to increased genetic variation

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... A. Intrasexual selection seems to have occurred in both species B. Selection was acting more directly upon genotype than upon phenotype C. Stabilizing selection was occurring in these species concerning larynx size D. Sexual dimorphism was evolving over time in these species

D. Sexual dimorphism was evolvingover time in these species

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is.... A. New mutations that occurred in the preceding generation B. Geographic variation within the population C. Genetic drift due to the small size of the population D. The reshuffling of alleles in sexual reproduction E. Environmental effects

D. The reshuffling of alleles in sexual reproduction

Which one of the following conditions would allow gene frequencies to change by chance? A. Large population B. Mutation C. Gene flow D. Small populations

D. small populations

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus? A. Gene variability = 0%, number of alleles = 2 B. Gene variability = 0%, number of allies = 0 C. Without more information, gene variability and number of alleles cannot be determined D. Gene variability >0%, number of alleles = 2 E. Gene variability = 0%, number of alleles = 1

E. Gene variability = 0%, number of alleles = 1

The original source of all genetic variation is... A. Natural selection B. Sexual reproduction C. Independent assortment D. Recombination E. Mutation

E. Mutation Mutation is, in itself, very important to evolution because it is the original source of the genetic variation that serves as the raw material for evolution