gre考试阅读真题解析(B)

　　From the 1900s through the 1950s waitresses in the United States developed a form of unionism based on the unions defining the skills that their occupation included and enforcing standards for the performance of those skills. This occupational unionism differed substantially from the worksite unionism prevalent among factory workers. Rather than unionizing the workforces of particular employers, waitress locals 工会地方分会) sought to control their occupation throughout a city. Occupational unionism operated through union hiring halls, which provided free placement services to employers who agreed to hire their personnel only through the union. Hiring halls offered union waitresses collective employment security, not individual job securitya basic protection offered by worksite unions. That is, when a waitress lost her job, the local did not intervene with her employer but placed her elsewhere; and when jobs were scarce, the work hours available were distributed fairly among all members rather than being assigned according to seniority.

　　17. The primary purpose of the passage is to

　　 analyze a current trend in relation to the past

　　 discuss a particular solution to a longstanding problem

　　 analyze changes in the way that certain standards have been enforced

　　 apply a generalization to an unusual situation

　　 describe an approach by contrasting it with another approach

　　18. Which of the following statements best summarizes a distinction mentioned in the passage between waitress unions and factory workers unions?

　　 Waitress unions were more successful than factory workers unions in that they were able to unionize whole cities.

　　 Waitress unions had an impact on only certain local areas, whereas the impact of factory workers unions was national.

　　 Waitress union members held primarily part-time positions, whereas factory workers unions placed their members in full-time jobs.

　　 Waitress unions emphasized the occupation of workers, whereas factory workers unions emphasized the worksite at which workers were employed.

　　 Waitress unions defined the skills of their trade, whereas the skills of factory trades were determined by employers groups.

　　19. According to the passage, which of the following was characteristic of the form of union that United States waitresses developed in the first half of the twentieth century?

　　 The union represented a wide variety of restaurant and hotel service occupations.

　　 The union defined the skills required of waitresses and disciplined its members to meet certain standards.

　　 The union billed employers for its members work and distributed the earnings among all members.

　　 The union negotiated the enforcement of occupational standards with each employer whose workforce joined the union.

　　 The union ensured that a worker could not be laid off arbitrarily by an employer.

　　20. The author of the passage mentions particular employers primarily in order to

　　 suggest that occupational unions found some employers difficult to satisfy

　　 indicate that the occupational unions served some employers but not others

　　 emphasize the unique focus of occupational unionism

　　 accentuate the hostility of some employers toward occupational unionism

　　 point out a weakness of worksite unionism

　　In prehistoric times brachiopods of marine invertebrates with bivalve shells within which is a pair of arms bearing tentacles by which a current of water is made to bring microscopic food to the mouth) were one of the most abundant and diverse forms of life on Earth: more than 30,000 species of this clamlike creature have been cataloged from fossil records. Today brachiopods are not as numerous, and existing species are not well studied, partly because neither the animals fleshy inner tissue nor its shell has any commercial value. Moreover, in contrast to the greater diversity of the extinct species, the approximately 300 known surviving species are relatively uniform in appearance. Many zoologists have interpreted this as a sign that the animal has been unable to compete successfully with other marine organisms in the evolutionary struggle.

　　Several things, however, suggest that the conventional view needs revising. For example, the genus Lingula has an unbroken fossil record extending over more than half a billion years to the present. Thus, if longevity is any measure, brachiopods are the most successful organisms extant. Further, recent studies suggest that diversity among species is a less important measure of evolutionary success than is the ability to withstand environmental change, such as when a layer of clay replaces sand on the ocean bottom. The relatively greater uniformity among the existing brachiopod species may offer greater protection from environmental change and hence may reflect highly successful adaptive behavior.

　　The adaptive advantages of uniformity for brachiopods can be seen by considering specialization, a process that occurs as a result of prolonged colonization of a uniform substrate. Those that can survive on many surfaces are called generalists, while those that can survive on a limited range of substrates are called specialists. One specialist species, for example, has valves weighted at the base, a characteristic that assures that the organism is properly positioned for feeding in mud and similar substrates; other species secrete glue allowing them to survive on the face of underwater cliffs. The fossil record demonstrates that most brachiopod lineages have followed a trend toward increased specialization. However, during periods of environmental instability, when a particular substrate to which a specialist species has adapted is no longer available, the species quickly dies out. Generalists, on the other hand, are not dependent on a particular substrate, and are thus less vulnerable to environmental change. One study of the fossil record revealed a mass extinction of brachiopods following a change in sedimentation from chalk to clay. Of the 35 brachiopod species found in the chalk, only 6 survived in the clay, all of them generalists.

　　As long as enough generalist species are maintained, and studies of arctic and subarctic seas suggest that generalists are often dominant members of the marine communities there, it seems unlikely that the phylum is close to extinction.

　　21. In the passage, the author is primarily concerned with

　　 rejecting an earlier explanation for the longevity of certain brachiopod species

　　 reevaluating the implications of uniformity among existing brachiopod species

　　 describing the varieties of environmental change to which brachiopods are vulnerable

　　 reconciling opposing explanations for brachiopods lack of evolutionary success

　　 elaborating the mechanisms responsible for the tendency among brachiopod species toward specialization

　　22. It can be inferred from the passage that many zoologists assume that a large diversity among species of a given class of organisms typically leads to which of the following?

　　 Difficulty in classification

　　 A discontinuous fossil record

　　 A greater chance of survival over time

　　 Numerical abundance

　　 A longer life span

　　23. The second paragraph makes use of which of the following?

　　 Specific examples

　　 Analogy

　　 Metaphor

　　 Quotation

　　 Exaggeration

　　24. The author suggests that the scientists holding the conventional view mentioned in lines 15-16 make which of the following errors?

　　 They mistakenly emphasize survival rather than diversity.

　　 They misunderstand the causes of specialization.

　　 They misuse zoological terminology.

　　 They catalog fossilized remains improperly.

　　 They overlook an alternative criterion of evolutionary success.

　　25. It can be inferred from the passage that the decision to study an organism may sometimes be influenced by

　　 its practical or commercial benefits to society

　　 the nature and prevalence of its fossilized remains

　　 the relative convenience of its geographical distribution

　　 its similarity to one or more better-known species

　　 the degree of its physiological complexity

　　26. Which of the following, if true, would most strengthen the authors claim that it seems unlikely that the phylum is close to extinction?

　　 Generalist species now living in arctic water give few if any indications of a tendency towards significant future specialization.

　　 Zoologists have recently discovered that a common marine organism is a natural predator of brachiopods.

　　 It was recently discovered that certain brachiopod species are almost always concentrated near areas rich in offshore oil deposits.

　　 The ratio of specialist to Generalist species is slowly but steadily increasing.

　　 It is easier for a brachiopod to survive a change in sedimentation than a change in water temperature.

　　27. Information in the passage supports which of the following statements about brachiopods?

　　I. Few brachiopods living in prehistoric times were specialists.

　　II. A tendency toward specialization, though typical, is not inevitable.

　　III. Specialist species dominate in all but arctic and subarctic waters.

　　 I only

　　 II only

　　 II and III only

　　 I and III only

　　 I, II and III

答案：17-27：EDBCBCAEAAB