Mel Bio 23

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. sexual dimorphism was developing over time in these species. B. intrasexual selection seems to have occurred. C. selection was acting more directly upon genotype than upon phenotype. D. stabilizing selection was occurring in these species concerning larynx size.

A

In a very large population, a quantitative trait has the following distribution pattern: If the curve in the figure shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations. Which of the following is (are) probably occurring? 1. immigration or emigration 2. directional selection 3. adaptation 4. genetic drift 5. disruptive selection A. 2 and 3 B. 4 and 5 C. 4 only D. 1 only E. 1, 2, and 3

A

In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population? A. directional selection B. stabilizing selection C. No selection would operate because the population is in Hardy-Weinberg equilibrium. D. disruptive selection

A

In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All ten of the original colonists had free earlobes, and two were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes. If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite different in the subsequent generations. This would be an example of A. genetic drift. B. gene flow. C/ stabilizing selection. D. diploidy. E. disruptive selection.

A

Sexual dimorphism is most often a result of A. intersexual selection. B. intrasexual selection. C/. stabilizing selection. D. pansexual selection. E. artificial selection.

A

The higher the proportion of loci that are "fixed" in a population, the lower is that population's A. nucleotide variability and average heterozygosity. B. average heterozygosity only. C. chromosome number only. D. nucleotide variability, average heterozygosity, and chromosome number. E. nucleotide variability only.

A

Use this information to answer the following question. You are studying three populations of birds. Population A has ten birds, of which one is brown (a recessive trait) and nine are red. Population B has 100 birds, of which ten are brown. Population C has 30 birds, and three of them are brown. Which population is most likely to be subject to the bottleneck effect? A. population A B. population B C. population C D. They are all equally likely. E. It is impossible to tell from the information given.

A

Which of the following statements best summarizes evolution as it is viewed today? A. It is the differential survival and reproduction of the most-fit phenotypes. B. It is the descent of humans from the present-day great apes. C. It is synonymous with the process of gene flow. D. It represents the result of selection for acquired characteristics.

A

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. cross your flies with flies from another lab. B. shock the flies with a brief treatment of heat or cold to make them more hardy. C. reduce the number of flies that you transfer at each generation. D.transfer only the largest flies. E. change the temperature at which you rear the flies.

A

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

B

When imbalances occur in the sex ratio of sexual species that have two sexes (i.e., other than a 50:50 ratio), the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex. This is most clearly an example of A. balancing selection. B. frequency-dependent selection. C. sexual selection. D. stabilizing selection. E. disruptive selection.

B

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. The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment. B. The new virus will maintain its Tamiflu-resistance gene, just 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. If the Tamiflu-resistance gene confers no benefit in the current environment, and has no cost, the virus will become dormant until Tamiflu is present.

C

What is true of microevolution? A. It is evolution that results in the origin of small numbers of new species. 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 involves only tiny changes to DNA, such as point mutations, producing only small (if any) changes to phenotype. E. It is evolution that is restricted to individual organisms.

C

A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses, whales, and bats. The actual forelimbs of these mammals do not seem to be optimally arranged because A. in many cases, phenotype is not merely determined by genotype, but by the environment as well. B. though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design. C. natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time. D. natural selection is generally limited to modifying structures that were present in previous generations and in previous species.

D

During breeding season, one should expect female house finches to prefer to mate with males with the brightest red feathers. Which of the following terms are appropriately applied to this situation? A.sexual selection B. intersexual selection C. mate choice D. Three of the responses are correct. \E Two of the responses are correct.

D

The original source of all genetic variation is _____. A. sexual reproduction B. recombination C. independent assortment D. mutation E. natural selection

D

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus A. the population itself is not evolving, but individuals within the population may be evolving. B. this means that, at this locus, two alleles are present in equal proportions. C. natural selection, gene flow, and genetic drift are acting equally to change an allele's frequency. D. the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change.

D

Which of the following is a true statement concerning genetic variation? A. It is created by the direct action of natural selection. B. It arises in response to changes in the environment. C. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity. D. It must be present in a population before natural selection can act upon the population. E. It tends to be reduced by the processes involved when diploid organisms produce gametes.

D

Which of the following is most likely to produce an African butterfly species in the wild whose members have one of two strikingly different color patterns? A. artificial selection B. stabilizing selection C. directional selection D. disruptive selection E. sexual selection

D

Which variable is likely to undergo the largest change in value resulting from a mutation that introduces a new allele into a population at a locus for which all individuals formerly had been fully homozygous? A. nucleotide variability B. average number of loci C. geographic variability D. average heterozygosity

D

If the original finches that had been blown over to the Galápagos from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of A. genetic drift. B. bottleneck effect. C. founder effect. D. all three of these. E. both the first and third of these.

E

According to the Hardy-Weinberg theorem, the frequencies of alleles in a population will remain constant if _____ is the only process that affects the gene pool. A. genetic drift B. sexual selection C. immigration D. mutation E. sexual reproduction

E

Blue poppies native to China were grown at a plant-breeding center in California. The plants with the thickest leaves were most likely to survive and reproduce in the drier climate. After several generations, the percentage of thick-leaved plants had increased by 42%. This adaptation of the poppies to their new environment is due to _____. A. genetic drift B. neutral variation C. stabilizing selection D. disruptive selection E. directional selection

E

Which statement about variation is true? A. All geographic variation results from the existence of clines. B. All phenotypic variation is the result of genotypic variation. C. All nucleotide variability results in neutral variation. D. All genetic variation produces phenotypic variation. E. None of the above

E