Chapter 18 Microevolution: changes within populations
22. 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
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
Disruptive selection is described in the text with the case of British land snails. 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
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 deeps 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 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
Reproductive isolation mechanisms for a species include all of the following EXCEPT A. habitat isolation B. temporal isolation of reproduction C. mechanical isolation of copulation D. hybrid sterility E. All of the choices are mechanisms.
A
Types of natural selection for a particular trait include all of the following EXCEPT A. founder effect. B. directional selection. C. stabilizing selection. D. disruptive selection.
A
Which statement is NOT true about the maintenance of variation in a population? A. Selection for adaptation to a particular environment ensures that the population will become stronger and more viable under any conditions. B. Only phenotypes are acted on by selection, so heterozygotes serve as a reservoir of recessive alleles that may be adaptive in a different environment. C. Heterozygote superiority may lead to selection for the heterozygote above either homozygote. D. Variation is maintained through mutation, recombination, gene flow, and changed conditions.
A
Define microevolution and give an example of it.
Answers will vary.
Describe and differentiate among the effects of stabilizing selection, directional selection, and disruptive selection.
Answers will vary.
Describe the conditions that must be met to produce the Hardy-Weinberg equilibrium.
Answers will vary.
Describe the conditions under which genetic drift occurs, and give one example.
Answers will vary.
Describe the effects of chromosome mutations and gene mutations on population genetics.
Answers will vary.
Describe the effects of recombination on population genetics.
Answers will vary.
Distinguish between inbreeding and assortative mating.
Answers will vary.
Explain the development of drug resistance in bacteria.
Answers will vary.
In 1989, geneticists at the University of Texas-Houston brought many fruit fly cultures down to a few bottleneck events and allowed these populations to build back up again. When they measured the morphological diversity of the flies, they found them to be more diverse in structure rather than more uniform. Consider the explanation of the cheetah bottleneck and note that while the bottleneck may have resulted in the loss of alleles from the population, no statement is made concerning any loss of morphological diversity. A) Would a relatively uncommon recessive morphological trait in a large population be expressed very often? If it survived a bottleneck event, would it be expressed more often? B) What would be its chance of being expressed if it survived a bottleneck event and was now in a small inbred population? C) Consider that in North America, English sparrows, guinea pigs, and the African honey bee have all survived recent bottleneck events. Why might a decrease in genetic diversity not depress these highly successful populations?
Answers will vary.
Often textbooks state that "maintenance of variation is beneficial because populations that lack variation may not be able to adapt to new conditions and may become extinct." However, environments such as deserts and ocean deeps provide little variation and have changed little over thousands of years. And other organisms are mobile and can easily move to an appropriate environment in front of slow-moving glaciers, etc. Instead, focus on the internal environment each organism must sustain. A) Do all people have equal resistance to microorganisms and viruses? Examples? B) Would the rapid evolution of new strains of bacterial and viral disease agents promote or depress polymorphism in human host populations? Why?
Answers will vary.
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
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 founder effect. C. genetic drift among the original Viking explorers. D. directional selection. E. fitness for the North American environment.
B
In speciation which of the following is mismatched? A. allopatric speciation-geographic isolation B. sympatric speciation-geographic isolation C. adaptive radiation-chance for new species to adapt to new habitats D. post-zygotic isolation-hybrid offspring sterility
B
In the case of Darwin's finches, an ancestral finch species from the mainland arrived on the Galápagos Islands and soon developed into many new species via adaptive radiation. The finches did NOT undergo adaptive radiation back on the mainland. What is the most plausible biological explanation? A. Directional selection works better on islands. B. Competition from many other birds species on the mainland provided stabilizing selection that was absent on the islands. C. The environment on the mainland was completely uniform. D. The founder effect greatly expanded the variation in alleles in the Galápagos finch gene pool. E. The ancestral mainland finch was reproductively isolated.
B
The most common source of genetic variation in sexually reproducing organisms is A. mutation. B. recombination of alleles. C. duplication of chromosomes. D. duplication of genes.
B
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 level of rare alleles in a population.
B
Which of the following would change the gene frequencies of a population? A. DNA is stable from generation to generation and does not change. B. Tall people in a population 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. None of the choices would change the gene frequencies of a population.
B
Which statement is NOT true about nonrandom mating? A. Inbreeding is mating between relatives more often than by chance. B. Inbreeding is a change in allele frequencies that increases the proportion of heterozygotes in the population. C. An example of assortative mating is when a tall man marries a tall woman. D. Assortative mating tends to cause subdivision into two phenotypic classes with reduced gene flow between them.
B
A certain species of butterfly in colors ranging from white to dark blue is found. The birds found in the same area feed on the white or lightly colored butterflies, leaving butterflies that are darkly colored. This is an example of: A. stabilizing selection B. disruptive selection C. directional selection
C
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 genotype and allele frequencies be in this theoretical population? A. 0.75 right-handed homozygous dominant and 0.25 recessive homozygous for 3-to-1 right-to-left handed alleles in the population B. 0.25 right-handed homozygous, 0.50 heterozygous, and 0.25 recessive homozygous for a 3-to-1 right-to-left handed alleles in the population C. 0.25 right-handed homozygous, 0.50 heterozygous, and 0.25 recessive homozygous for a 0.5 allele frequency for each allele D. 0.50 right-handed homozygous, 0.25 heterozygous, and 0.25 recessive homozygous for a 0.5 allele frequency for each allele E. They cannot be estimated using these limited data.
C
All of the following are true statements regarding mating EXCEPT A. random mating is due to chance pairing not according to genotype or phenotype. B. sexual selection occurs when males compete for reproduction rights and females select mates based on a particular phenotype. C. short people tending to mate with tall people is an example of assortative mating. D. All of the statements are true.
C
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
Descriptions of new species of insects are more likely to contain diagrams of the shape of the male genitalia than head, wing, or leg parts. Why? A. This is where mutations usually express themselves in animals. B. Radiation damage to genes usually occurs in genitalia. C. Small changes in the genitalia cause reproductive isolation while a single species can tolerate wider variation in head, wing, and leg morphology. D. Arthropods have hard exoskeletons so head, wing, and leg structures can't vary as much. E. This is the convention or custom of entomology.
C
Drug-resistance mutations occur in bacteria A. only when they are exposed to the drug to which they become resistant. B. more often when they are exposed to the drug. C. at any time, even when they are not exposed to the drug. D. only when they are exposed to radiation or other mutagens.
C
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, and genetic drift is more likely to change gene frequencies. D. this increases gene flow. E. we accumulate adaptive traits that improve the population.
C
The Latin term for "kind" is the root word for A. mutation. B. gene. C. species. D. child or kinder. E. zygote.
C
What is the term used to describe the accumulation of small changes in the gene pool of a species over time? A. genetic drift B. founder effect C. microevolution D. directional selection
C
Which of these conditions is NOT among the requirements of the Hardy-Weinberg equilibrium? A. no net mutations B. no net migration of alleles into or out of the population C. small population with genetic drift D. no selection of one genotype over another E. sexually reproducing and random mating population
C
An insect population lives along the edge of a north-south mountain range. The populations from the east and west slope eventually join in a low northern pass and interbreed, producing fertile offspring, but they do not circle around the southern edge because of a desert barrier. When glaciers move southward, the populations are pushed south of the northern pass and are isolated. While isolated, the two populations develop enough differences over time that when the glaciers retreat north and the insects again share the same pass, they no longer mate at the same time, nor can they produce fertile offspring. Insect populations on the mountain slopes were A. always allopatric. B. always sympatric. C. first allopatric, then sympatric, then allopatric. D. first sympatric, then allopatric, then sympatric. E. There is not enough information to determine sympatry or allopatry.
D
An insect population lives along the edge of a north-south mountain range. The populations from the east and west slope eventually join in a low northern pass and interbreed, producing fertile offspring, but they do not circle around the southern edge because of a desert barrier. When glaciers move southward, the populations are pushed south of the northern pass and are isolated. While isolated, the two populations develop enough differences over time that when the glaciers retreat north and the insects again share the same pass, they no longer mate at the same time, nor can they produce fertile offspring. These insects A. began as one species and therefore remain one species. B. were originally two species and remain two species. C. were originally two species but are now one species. D. were originally one species but are now two species. E. The number of species cannot be determined from the information given.
D
Based on the text's coverage of the rate of mutation, adaptive radiation, etc., you can conclude that the rate of evolution progresses at A. a fairly constant rate and would produce the same outcome if "re-run." B. an uneven rate but would produce the same outcome if "re-run." C. a fairly constant rate but would produce different outcomes if "re-run." D. an uneven rate and would produce different outcomes if "re-run."
D
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
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 an even 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 ten 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
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. B. The variation is inherited. C. More young are born than can survive. D. Some individuals are better adapted to the environment.
D
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." E. This can be understood as a classic case of genetic drift.
D
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
Which of the following would be a cause of microevolution? A. A flood kills almost all the wild strawberry plants in a particular area. B. The largest and strongest male lion chases away other males and is the only male to mate with females and produce offspring. C. Wolves are moved from Canada and introduced into the wild in Wyoming. D. All of the choices can lead to microevolution
D
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 when the environment remains the same. E. Disruptive selection leads to polymorphism, favoring different forms of the same species.
D
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
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
A mutation to a _______ form is more likely to be recognized than any other because ______. A. beneficial, individuals with a beneficial mutation are much better adapted and survive longer in their environment B. beneficial, individuals with a beneficial mutation will always be healthier and have more offspring than others C. neutral, these mutations make up the majority of changes in the species D. harmful, these allow the individual to survive better in a different environment E. harmful, species are already well adapted and few beneficial changes are possible—but many damaging changes are possible and cause death or poor adaptation by the individual
E
Microevolution is due to A. genetic Flow. B. gene mutations. C. genetic drift. D. non-random mating. E. All of the choices apply.
E
The Greek root words meaning "together" and "fatherland" are the basis for the term A. prezygotic. B. adaptive radiation. C. speciation. D. allopatric. E. sympatric.
E
Throughout the chapter, a wide range of evidence has been brought together to describe what constitutes a species. From all of this you can conclude that A. some day we could theoretically finalize a list of all species on earth and, if correct, it could remain unchanged. B. once mating experiments have been conducted and fertile offspring detected, a species can be defined with absolute certainty. C. a species can be definitively described by DNA hybridization, DNA sequencing, or enzymes. D. just as organisms recognize their own species, all levels of taxa [class, order, family, genus] are naturally occurring entities. E. None of the choices is correct.
E
Which of the following conditions contributes to evolution? A. mutations B. gene flow C. genetic drift D. natural selection E. All of the choices are correct.
E
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 more fit individuals have more offspring D. accumulation of adaptive traits so that they increase in the population E. All of the choices are required.
E
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
Which of the following reflect(s) the likely presence of (a) gene mutation(s)? A. Fruit flies subjected to intense radiation breed 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
Which of the following would result in reproductive isolation? A. Two populations of crickets are indistinguishable in physical features, but the females in each group only come to the different songs of their males. B. Fruit flies on one Hawaiian island live for hundreds of generations and do not come in contact with fruit flies on another island except when blown there by rare tropical storms. C. One brood of the seventeen-year cicada emerged in 1987 (and will do so every 17 years) and lives a few months as adults; another brood emerged in 1992 (and will do so every 17 years); the larvae of both feed side-by-side on tree roots. D. A lion and a tiger mate in the artificial confines of a zoo but the offspring is infertile. E. All of the choices are correct.
E
A population of organisms that reproduce asexually without gametes from other individuals will display more variation than a population that reproduces sexually using gametes from other individuals.
FALSE
An allele becomes the most common allele in a population by becoming the dominant allele.
FALSE
Industrial melanism in peppered moths in England is an example of stabilizing selection.
FALSE
The Hardy-Weinberg equilibrium is usually met in most populations in changing environments.
FALSE
A reproductive isolation mechanism includes any structural, functional, or behavioral characteristic that blocks reproductive ability.
TRUE
An example of the founder effect is seen in populations such as the Amish in Pennsylvania, in which unusual genes are found in large numbers in the isolated population.
TRUE
Gene mutation occurs at any time, without respect to the mutation's adaptive value or benefit to the organism.
TRUE
Genetic drift produces changes in allele frequencies within a gene pool due to chance.
TRUE
Male birds often perform a special dance or set of physical displays to attract females. This would be an example of a behavioral isolation mechanism.
TRUE
Microevolution is evolution that occurs within a population.
TRUE
Sexual selection is a form of natural selection that does not cause adaptation to the environment.
TRUE
The bottleneck effect is thought to be responsible for the loss of variability and loss of fertility in the cheetah species.
TRUE
The gene pool is described in terms of gene frequencies in the population.
TRUE
Three types of natural selection include directional, stabilizing and disruptive.
TRUE