Chapter 16: How Populations Evolve

British land snails are an example of disruptive selection. In the grassy fields, the light-banded snails escape bird predators. In the darker forest, the dark snails survive and the light-banded snails are eaten. As long as the snails continue to cruise across the British landscape mating at the same season, why doesn't this "disruptive selection" eventually lead to two separate species? A. There is no reproductive isolation to prevent gene flow. B. They are already two separate species, and the intermediate forms are hybrids. C. The color forms are probably not genetically determined. D. There must be some unknown factor producing an equal stabilizing selection "to hold the species together." E. This will result in the formation of two species if given long enough time.

A. There is no reproductive isolation to prevent gene flow.

Occasionally, "living fossils" such as the coelacanth are found. These organisms appear to be little changed from their ancestors preserved in rock strata many millions of years ago. Such organisms often occur in ocean depths and in soil and desert environments that change less often over time. This is an indication that A. although gene mutations may be common, there may be little selection among individuals already well adapted to a uniform, stable environment. B. these organisms do not have the same high mutation rate of most organisms. C. by chance, these organism's mutations are all in alleles that do not affect morphology. D. the Hardy-Weinberg equilibrium prevents these organisms from evolving very fast. E. there is extensive inbreeding in such organisms.

A. although gene mutations may be common, there may be little selection among individuals already well adapted to a uniform, stable environment.

If two adjacent populations of the same species show gene flow, then the two populations will A. become more similar in their gene pools. B. become isolated from each other. C. develop into different species. D. adapt to different conditions and become separate.

A. become more similar in their gene pools.

A random alteration in the sequence of DNA nucleotides that provides a new variant allele is A. gene mutation. B. polymorphism. C. gene frequency. D. disruption.

A. gene mutation.

The recessive allele for sickle cell anemia is more prevalent in regions of Africa where malaria is prevalent, than it is in regions where there is no malaria. This is due to a: A. heterozygous advantage B. Founder Effect C. frequency dependent selection D. bottleneck effect

A. heterozygous advantage

Which of these conditions is NOT among the requirements of the Hardy-Weinberg equilibrium of allele frequencies in a population? A. small population with genetic drift B. no net migration of alleles into or out of the population C. no net mutations D. no selection of one genotype over another E. random mating population

A. small population with genetic drift

Which of the following is true about genetic drift? A. It is more likely to occur in a large population than in a small population. B. It may lead to an allele's becoming fixed in a population when its alternative allele is lost from the population. C. It increases the number of heterozygotes in a population. D. It increases the frequency of rare alleles in a population.

B. It may lead to an allele's becoming fixed in a population when its alternative allele is lost from the population.

Which of the following would change the allele frequencies of a population? A. DNA is stable from generation to generation and does not change, so allele frequencies do not change. B. Tall people in a population preferentially marry other tall people and do not marry people who are short or average height. C. A population on an island remains isolated and no one leaves or moves onto the island. D. All of the above would change allele frequencies of a population.

B. Tall people in a population preferentially marry other tall people and do not marry people who are short or average height.

Another student proposes that handedness could just as easily be passed to children by how the parents carry the child and interact with it, a learning process that may perpetuate the parents' handedness. Assuming all parents and children are expressing their "true handedness," the occurrence of which case below would cast the most serious doubt on a simple genetic basis for handedness, with left-handedness recessive? A. Two right-handed parents have a left-handed child. B. Two left-handed parents have a right-handed child. C. Left-handed parents only have left-handed children. D. Right-handed parents only have right-handed children. E. None of the choices is correct.

B. Two left-handed parents have a right-handed child.

Perissodus are small, scale-eating fish that live in Lake Tanganyika in Africa. They attack larger fish from behind. The right-mouthed Perissodus attack on the left side of the larger fish and the left-mouthed Perissodus attack on the right side of the larger fish. The existence of the right-mouthed variety ensures the equally successful existence of the left-mouthed variety. This is an example of: A. a heterozygous advantage B. frequency dependent selection C. genetic drift D. sexual selection

B. frequency dependent selection

In a population, the allele frequency for red flower color remained at 0.7 and the allele frequency for white flower remained at 0.3 for six generations. This ____ an example of a Hardy Weinberg equilibrium in that __________. A. is not, evolution occurred B. is, evolution did not occur C. is, evolution occurred D. is not, evolution did not occur

B. is, evolution did not occur

The most common source of genetic variation in sexually reproducing organisms is A. mutation. B. recombination of alleles through meiosis and fertilization. C. duplication of chromosomes. D. duplication of genes.

B. recombination of alleles through meiosis and fertilization.

A student proposes that left-handedness is a recessive trait that is therefore hidden in much of the human population. A survey of a class of 36 students finds that 27 (0.75) are right-handed and 9 (0.25) are left-handed. Using the Hardy-Weinberg formula, what would the expected genotypes and allele frequencies be in this theoretical population? A. 0.75 homozygous dominant and 0.25 homozygous recessive, and a 3-to-1, right-to-left handed allele ratio in the population. B. 0.25 homozygous dominant, 0.50 heterozygous, and 0.25 homozygous recessive, and a 0.75 dominant allele frequency and a 0.25 recessive allele frequency. C. 0.25 homozygous dominant, 0.50 heterozygous, and 0.25 homozygous recessive, and a 0.5 allele frequency for each allele D. 0.50 homozygous dominant, 0.25 heterozygous, and 0.25 homozygous recessive, and a 0.5 allele frequency for each allele E. They cannot be estimated using these limited data.

C. 0.25 homozygous dominant, 0.50 heterozygous, and 0.25 homozygous recessive, and a 0.5 allele frequency for each allele

Mutations that result in resistance to specific antibiotics in bacterial organisms occur: A. only when the bacteria are exposed to the drug to which they become resistant. B. more often when the bacteria are exposed to the drug. C. at any time, even when the bacteria are not exposed to the drug. D. only when the bacteria are exposed to radiation or other mutagens.

C. at any time, even when the bacteria are not exposed to the drug.

A certain species of butterfly varies in color from white to dark blue. The birds found in the same area feed on the white or lightly colored butterflies, leaving butterflies that are darkly colored. This may result in what type of selection? A. stabilizing selection B. disruptive selection C. directional selection

C. directional selection

Social research indicates that a person is most likely to marry someone from the same village or city, or a high school or college classmate. Therefore, the Hardy-Weinberg equilibrium does not apply well to human populations because A. allelic changes in one direction are balanced by changes in the opposite direction. B. there is no directional trend in selection of mates since most individuals marry someone. C. individuals are not pairing up by chance across the whole population D. this increases gene flow. E. we accumulate adaptive traits that improve the population.

C. individuals are not pairing up by chance across the whole population

What is the term used to describe the changes in allele frequencies of a population over generations? A. genetic drift B. founder effect C. microevolution D. directional selection

C. microevolution

All the members of a single species that occupy a particular area at the same time are known as a: A. subspecies. B. gene pool. C. population. D. group. E. sub-population.

C. population.

If the mutation rate of individual genes is taken to be about one in 100,000 genes per cell cycle across many organisms, we might expect evolution to proceed at a consistent rate for various forms of life. Which factor could make the accumulation of gene mutations faster or slower among different organisms? A. Organisms with more genes will likely have more mutations per generation. B. More selection of mutations can occur in a shorter period of time for bacteria that replicate each twenty minutes than for humans with a (roughly) 20-year generation span. C. Organisms vary in the proportion of DNA that is active and in the percent of loci that have multiple alleles. D. All of the choices are correct.

D. All of the choices are correct.

Variations within a population are maintained by A. mutation. B. genetic recombination due to fertilization. C. gene flow. D. All of the choices are correct.

D. All of the choices are correct.

While we have seen how natural selection and the use of pesticides can lead to the development of resistant varieties of insects, two economically important flies, the Mediterranean fruit fly (Medfly) and the screwworm fly, can be driven to local extinction by the continuous release of sterile flies of those species. The critical factor is that the female of these species only mates once. But which of the following is/are also necessary for sterile release to work? A. The target species is truly just one species. B. The insect can be raised artificially in large numbers. C. The insects to be released can be sterilized with radiation without affecting their ability to attract a mate in the wild. D. All of the choices are correct.

D. All of the choices are correct.

What do the Founder Effect and the Bottleneck Effect have in common? A. Both the Founder Effect and the bottleneck effect result from mutation B. Both the Founder Effect and the bottleneck effect result from increase gene flow C. Both the Founder Effect and the bottleneck effect are examples of disruptive selection D. Both the Founder Effect and the bottleneck effect occur by chance.

D. Both the Founder Effect and the bottleneck effect occur by chance.

The northern elephant seal was hunted almost to extinction during the 18th and 19th centuries. Less than 100 seals were left to contribute to the gene pool of their future generations. Since the early 20th century, the elephant seals have been protected by law in both the U.S. and Mexico. Over 100,000 seals now inhabit the western shores of North America, all related to the small population that survived the slaughter of hunters. Scientists fear the elephant seals may be more susceptible to disease and pollution due to a _____. A. a heterozygous advantage B. disruptive selection C. Founder Effect D. Bottleneck Effect

D. Bottleneck Effect

Which statement is NOT true about natural selection? A. Directional selection occurs when one extreme phenotype is favored over another different extreme phenotype. B. Stabilizing selection favors an intermediate phenotype over either of the extreme phenotypes. C. Disruptive selection favors both of the extreme phenotypes over the intermediate phenotype. D. Directional selection leads to improved selection in a stable environment. E. Disruptive selection leads to polymorphism, favoring different forms of the same species.

D. Directional selection leads to improved selection in a stable environment.

Our domesticated honey bee—originally from Europe—is slow to sting, requires abundant flower nectar, gets up late in the morning, and stores much honey but only produces enough new brood to swarm once a year. Because the European honey bee was performing poorly as a honey producer in South America, the African subspecies was imported in a breeding experiment. The African honey bee formed small nests, foraged earlier and on smaller nectar sources, produced less honey stores and more brood, swarmed four or five times a year, and was fast to sting. However, when the African queens escaped, the two populations interbred and the African genotype spread several hundred miles north each year. Surprisingly, a hundred miles behind the expanding range of the African honey bees, the European and hybrid strains died out and the bees were essentially 100 percent African. How would this be explained in evolutionary genetics terms? A. Gene flow is not occurring and therefore these are two separate species. B. This is a natural consequence of the Hardy-Weinberg equilibrium. C. Obviously the African bee genes are dominant over the European honey bee alleles. D. Gene flow is occurring between these subspecies but the African bee is 'ecologically better suited" E. This can be understood as a classic case of genetic drift.

D. Gene flow is occurring between these subspecies but the African bee is 'ecologically better suited"

In the case of the peppered moths in England, when Kettlewell set up cameras to document that more white or black moths were eaten by birds on clean or sooty trees, he was verifying which factor involved in evolution by natural selection? A. The organisms vary in traits and that these traits may be acquired during a lifetime. B. The variation is inherited. C. More young are born than can survive, so there will always be competition. D. Some individuals are better adapted to a particular environment than other individuals.

D. Some individuals are better adapted to a particular environment than other individuals.

Which statement is NOT true about the Founder Effect? A. It is a form of genetic drift. B. It produces a high frequency of some rare alleles in a small isolated population. C. Founding members contain a tiny fraction of the alleles found in the original population. D. The Founder Effect occurs when a population is subjected to near extinction and then recovers so that only a few alleles are left in survivors.

D. The Founder Effect occurs when a population is subjected to near extinction and then recovers so that only a few alleles are left in survivors.

If the Hardy-Weinberg equilibrium is met, what is the net effect? A. evolution leading to a population better adapted to an unchanging environment B. evolution leading to a population better adapted to a changing environment C. very slow and continuous evolution with no increased adaptation D. no evolution because the alleles in the population remain the same

D. no evolution because the alleles in the population remain the same

Which of the following is/are a biological "population?" A. all of the corn plants in a cornfield B. all of the variable-colored ladybird beetles of the species Harmonia axyridis in a forest C. all male and female English sparrows that reside in your community D. all of the human population of a rural western town E. All of the choices are correct.

E. All of the choices are correct.

Which of the following reflect(s) the likely presence of (a) gene mutation(s)? A. Fruit flies subjected to intense radiation produce a wider array of variable offspring. B. A chemical leaking from the surface of an old abandoned coal mine alters a regulatory gene so that a cricket nymph develops an extra set of eyes. C. The bacteria that cause gonorrhea, a common sexually transmitted disease, have previously been killed by penicillin; however, after continuous usage of the antibiotic, penicillin-resistant strains are now becoming prevalent. D. Radiation causes an alteration in a DNA nucleotide sequence, which is discovered when mapped, but which appears to be neither increasing nor decreasing in successive generations. E. All of the choices are correct.

E. All of the choices are correct.

Which of the following is required for natural selection to occur in a population? A. variation in the population B. inheritance of variation through genetic differences C. differential reproduction so that the more fit individuals have more offspring that survive to reproduce D. accumulation of adaptive traits so that they increase in the population E. All of the choices are required.

E. All of the choices are required.

If early Viking explorers in Greenland and North America had survived and become the main ancestors of early North American settlers, rather than the mixture of immigrants from across Europe and other continents, today there would be a much higher incidence of Nordic traits in the U.S. population. Such a scenario would demonstrate A. gene flow from continent to continent. B. the bottleneck effect. C. genetic drift among the original Viking explorers. D. directional selection. E. the Founder Effect.

E. the Founder Effect.