gre考试阅读真题解析(A)

　　Investigators of monkeys social behavior have always been struck by monkeys aggressive potential and the consequent need for social control of their aggressive behavior. Studies directed at describing aggressive behavior and the situations that elicit it, as well as the social mechanisms that control it, were therefore among the first investigations of monkeys social behavior.

　　Investigators initially believed that monkeys would compete for any resource in the environment: hungry monkeys would fight over food, thirsty monkeys would fight over water, and, in general, any time more than one monkey in a group sought the same incentive simultaneously, a dispute would result and would be resolved through some form of aggression. However, the motivating force of competition for incentives began to be doubted when experiments like Southwicks on the reduction of space or the withholding of food failed to produce more than temporary increases in intragroup aggression. Indeed, food deprivation not only failed to increase aggression but in some cases actually resulted in decreased frequencies of aggression.

　　Studies of animals in the wild under conditions of extreme food deprivation likewise revealed that starving monkeys devoted almost all available energy to foraging, with little energy remaining for aggressive interaction. Furthermore, accumulating evidence from later studies of a variety of primate groups, for example, the study conducted by Bernstein, indicates that one of the most potent stimuli for eliciting aggression is the introduction of an intruder into an organized group. Such introductions result in far more serious aggression than that produced in any other types of experiments contrived to produce competition.

　　These studies of intruders suggest that adult members of the same species introduced to one another for the first time show considerable hostility because, in the absence of a social order, one must be established to control interanimal relationships. When a single new animal is introduced into an existing social organization, the newcomer meets even more serious aggression. Whereas in the first case aggression establishes a social order, in the second case resident animals mob the intruder, thereby initially excluding the new animal from the existing social unit. The simultaneous introduction of several animals lessens the effect, if only because the group divides its attention among the multiple targets. If, however, the several animals introduced to a group constitute their own social unit, each group may fight the opposing group as a unit; but, again, no individual is subjected to mass attack, and the very cohesion of the groups precludes prolonged individual combat. The submission of the defeated group, rather than unleashing unchecked aggression on the part of the victorious group, reduces both the intensity and frequency of further attack. Monkey groups therefore see to be organized primarily to maintain their established social order rather than to engage in hostilities per se.

　　17. The author of the passage is primarily concerned with

　　 advancing a new methodology for changing a monkeys social behavior

　　 comparing the methods of several research studies on aggression among monkeys

　　 explaining the reasons for researchers interest in monkeys social behavior

　　 discussing the development of investigators theories about aggression among monkeys

　　 examining the effects of competition on monkeys social behavior

　　18. Which of the following best summarizes the findings reported in the passage about the effects of food deprivation on monkeys behavior?

　　 Food deprivation has no effect on aggression among monkeys.

　　 Food deprivation increases aggression among monkeys because one of the most potent stimuli for eliciting aggression is the competition for incentives.

　　 Food deprivation may increase long-term aggression among monkeys in a laboratory setting, but it produces only temporary increases among monkeys in the wild.

　　 Food deprivation may temporarily increase aggression among monkeys, but it also leads to a decrease in conflict.

　　 Food deprivation decreases the intensity but not the frequency of aggressive incidents among monkey.

　　19. According to the author, studies such as Southwicks had which of the following effects on investigators theories about monkeys social behavior?

　　 They suggested that existing theories about the role of aggression among monkeys did not fully account for the monkeys ability to maintain an established social order.

　　 They confirmed investigators theories about monkeys aggressive response to competition for food and water.

　　 They confirmed investigators beliefs about the motivation for continued aggression among monkeys in the same social group.

　　 They disproved investigators theory that the introduction of intruders in an organized monkey group elicits intragroup aggressive behavior.

　　 They cast doubt on investigators theories that could account for observed patterns of aggression among monkeys.

　　20. The passage suggests that investigators of monkeys social behavior have been especially interested in aggressive behavior among monkeys because

　　 aggression is the most common social behavior among monkeys

　　 successful competition for incentives determines the social order in a monkey group

　　 situations that elicit aggressive behavior can be studied in a laboratory

　　 most monkeys are potentially aggressive, yet they live in social units that could not function without control of their aggressive impulses

　　 most monkeys are social, yet they frequently respond to newcomers entering existing social units by attacking them

　　21. It can be inferred from the passage that the establishment and preservation of social order among a group of monkeys is essential in order to

　　 keep the monkeys from straying and joining other groups

　　 control aggressive behavior among group members

　　 prevent the domination of that group by another

　　 protect individuals seeking to become members of that group from mass attack

　　 prevent aggressive competition for incentives between that group and another

　　22. The passage supplies information to answer which of the following questions?

　　 How does the reduction of space affect intragroup aggression among monkeys in an experimental setting?

　　 Do family units within a monkey social group compete with other family units for food?

　　 What are the mechanisms by which the social order of an established group of monkeys controls aggression within that group?

　　 How do monkeys engaged in aggression with other monkeys signal submission?

　　 Do monkeys of different species engage in aggression with each other over food?

　　23. Which of the following best describes the organization of the second paragraph?

　　 A hypothesis is explained and counter evidence is described.

　　 A theory is advanced and specific evidence supporting it is cited.

　　 Field observations are described and a conclusion about their significance is drawn.

　　 Two theories are explained and evidence supporting each of them is detailed.

　　 An explanation of a general principle is stated and specific examples of its operation are given.

　　Analysis of prehistoric air trapped in tiny bubbles beneath the polar ice sheets and of the composition of ice surrounding those bubbles suggests a correlation between carbon dioxide levels in the Earths atmosphere and global temperature over the last 160,000 years. Estimates of global temperature at the time air in the bubbles was trapped rely on measuring the relative abundances of hydrogen and its heavier isotope, deuterium, in the ice surrounding the bubbles. When global temperatures are relatively low, water containing deuterium tends to condense and precipitate before reaching the poles; thus, ice deposited at the poles when the global temperature was cooler contained relatively less deuterium than ice deposited at warmer global temperatures. Estimates of global temperature based on this information, combined with analysis of the carbon dioxide content of air trapped in ice deep beneath the polar surface, suggest that during periods of postglacial warming carbon dioxide in the Earths atmosphere increased by approximately 40 percent.

　　24. In the passage, the author is primarily concerned with doing which of the following?

　　 Describing a new method of estimating decreases in global temperature that have occurred over the last 160,000 years

　　 Describing a method of analysis that provides information regarding the relation between the carbon dioxide content of the Earths atmosphere and global temperature

　　 Presenting information that suggests that global temperature has increased over the last 160,000 years

　　 Describing the kinds of information that can be gleaned from a careful analysis of the contents of sheets

　　 Demonstrating the difficulty of arriving at a firm conclusion regarding how increases in the amount of carbon dioxide in the Earths atmosphere affect global temperature

　　25. It can be inferred from the passage that during periods of postglacial warming, which of the following occurred?

　　 The total volume of air trapped in bubbles beneath the polar ice sheets increased.

　　 The amount of deuterium in ice deposited at the poles increased.

　　 Carbon dioxide levels in the Earth atmosphere decreased.

　　 The amount of hydrogen in the Earths atmosphere decreased relatively the amount of deuterium.

　　 The rate at which ice was deposited at the poles increased.

　　26. The author states that there is evidence to support which of the following assertions?

　　 Estimates of global temperature that rely on measurements of deuterium in ice deposited at the poles are more reliable than those based on the amount of carbon dioxide contained in air bubbles beneath the polar surface.

　　 The amount of deuterium in the Earths atmosphere tends to increase as global temperature decreases.

　　 Periods of postglacial warming are characterized by the presence of increased levels of carbon dioxide in the Earths atmosphere.

　　 Increases in global temperature over the last 160,000 years are largely the result of increases in the ratio of deuterium to hydrogen in the Earths atmosphere.

　　 Increases in global temperature over the last 160,000 years have been accompanied by decreases in the amount of deuterium in the ice deposited at the poles.

　　27. It can be inferred from the passage that the conclusion stated in the last sentence would need to be reevaluated if scientists discovered that which of the following were true?

　　 The amount of deuterium in ice deposited on the polar surface is significantly greater than the amount of deuterium in ice located deep beneath the polar surface.

　　 Both the air bubbles trapped deep beneath the polar surface and the ice surrounding them contain relatively low levels of deuterium.

　　 Air bubbles trapped deep beneath the polar surface and containing relatively high levels of carbon dioxide are surrounded by ice that contained relatively low levels of deuterium.

　　 The current level of carbon dioxide in the Earths atmosphere exceeds the level of carbon dioxide in the prehistoric air trapped beneath the polar surface.

　　 Increases in the level of carbon dioxide in the Earths atmosphere are accompanied by increases in the amount of deuterium in the ice deposited at the poles.

答案：DDEDDAABBCC