1、大学英语六级模拟试卷 89及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed 30 minutes to write a short essay entitled Studying Abroad. You should write at least 150 words following the outline given below: 1. 当前出国留学的人数日益增多 2. 留学的优势和劣势 3. 你的看法 二、 Part II Reading Comprehension (Skimming and S
2、canning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-4, mark： Y (for YES) if the statement agrees with the information given in the passage; N (for NO) if the statement contradicts th
3、e information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 2 Population Growth Rates Populations have a birth rate (the number of young produced per unit of population per unit of time), a death rate(the number of deaths per unit of time), and a growth rat
4、e. The major agent of population growth is births, and the major agent of population loss is deaths. When births exceed deaths, a population increases; and when deaths exceed additions to a population, it decreases. When births equal deaths in a given population, its size remains the same, and it is
5、 said to have zero population growth. When introduced into a favorable environment with an abundance of resources, a small population may undergo geometric, or exponential(指数的 ) growth, in the manner of compound interest. Many populations experience exponential growth in the early stages of colonizi
6、ng a habitat because they take over an underexploited niche or drive other populations out of a profitable one. Those populations that continue to grow exponentially, however, eventually reach the upper limits of the resources; they then decline sharply because of some catastrophic(灾难的 ) events such
7、 as starvation, disease, or competition from other species. In a general way, populations of plants and animals that characteristically experience cycles of exponential growth are species that produce numerous young, provide little in the way of parental care, or produce an abundance of seeds having
8、 little food reserves. These species, usually short-lived, disperse rapidly and are able to colonize harsh or disturbed environments. Such organisms are often called opportunistic species. Other populations tend to grow exponentially at first, and then logistically that is, their growth slows as the
9、 population increases, then levels off as the limits of their environment or carrying capacity are reached. Through various regulatory mechanisms, such populations maintain something of an equilibrium(平衡 ) between their numbers and available resources. Animals exhibiting such population growth tend
10、to produce fewer young but do provide them with parental care; the plants produce large seeds with considerable food reserves. These organisms are long-lived, have low dispersal rates, and are poor colonizers of disturbed habitats. They tend to respond to changes in population density (the number of
11、 organisms per unit area) through changes in birth and death rates rather than through dispersal. As the population approaches the limit of resources, birth rates decline, and mortality of young and adults increases. Community Interactions Major influences on population growth involve various popula
12、tion interactions that tie the community together. These include competition, both within a species and among species; predation(掠夺行为 ), including parasitism(寄生状态 ); and co-evolution, or adaptation. 1. Competition When a shared resource is in short supply, organisms compete, and those that are more
13、successful survive. Within some plant and animal populations, all individuals may share the resources in such a way that none obtains sufficient quantities to survive as adults or to reproduce. Among other plant and animal populations, dominant individuals claim access to the scarce resources and ot
14、hers are excluded. Individual plants tend to claim and hold onto a site until they lose vigor or die. These prevent other individuals from surviving by controlling light, moisture, and nutrients in their immediate areas. Many animals have a highly developed social organization through which resource
15、s such as space, food, and mates are apportioned among dominant members of the population. Such competitive interactions may involve social dominance, in which the dominant individuals exclude subdominant individuals from the resource; or they may involve territoriality, in which the dominant indivi
16、duals divide space into exclusive areas, which they defend. Subdominant or excluded individuals are forced to live in poorer habitats, do without the resource, or leave the area. Many of these animals succumb to starvation, exposure, and predation. Competition among members of different species resu
17、lts in the division of resources in a community. Certain plants, for example, have roots that grow to different depths in the soil. Some have shallow roots that permit them to use moisture and nutrients near the surface. Others growing in the same place have deep roots that are able to exploit moist
18、ure and nutrients not available to surface-rooted plants. 2. Predation One of the fundamental interactions is predation, or the consumption of one living organism, plant or animal, by another. While it serves to move energy and nutrients through the ecosystem, predation may also regulate population
19、and promote natural selection by weeding the unfit from a population. Thus, a rabbit is a predator on grass, just as the fox is a predator on the rabbit. Predation on plants involves defoliation(落叶 ) by grazers and the consumption of seeds and fruits. The abundance of plant predators, or herbivores,
20、 directly influences the growth and survival of the carnivores(食肉类 ). Thus, predator-prey interactions at one feeding level influence the predatorprey relations at the next feeding level. In some communities, predators may so reduce populations of prey species that a number of competing species can
21、coexist in the same area because none is abundant enough to control the resource. When predators are reduced or removed, however, the dominant species tend to crowd out other competitors, thereby reducing species diversity. 3. Parasitism Closely related to predation is parasitism, wherein two organi
22、sms live together, one drawing its nourishment at the expense of the other Parasites(寄生虫 ), which are smaller than their hosts, include many viruses and bacteria. Because of this dependency relationship, parasites normally do not kill their hosts the way predators do. As a result, hosts and parasite
23、s generally coevolve(共同进行 ) a mutual tolerance, although parasites may regulate some host populations, lower their reproductive success, and modify behavior. 4. Coevolution Coevolution is the joint evolution of two unrelated species that have a close ecological relationship that is, the evolution of
24、 one species depends in part on the evolution of the other. Coevolution is also involved in predator-prey relations. Over time, as predators evolve more efficient ways of capturing or consuming prey, the prey evolves ways to escape predation. Plants have acquired such defensive mechanisms as thorns,
25、 spines, hard seed-coats, and poisonous or ill-tasting sap that deter would be consumers. Some herbivores(草食动物 ) are able to breach these defenses and attack the plant. Certain insects, such as the monarch butterfly, can incorporate poisonous substances found in food plants into their own tissues an
26、d use them as a defense against predators. Other animals avoid predators by assuming an appearance that blends them into the background or makes them appear part of the surroundings. The chameleon is a well-known example of this interaction. Some animals possessing obnoxious odors or poisons as a de
27、fense also have warning colorations, usually bright colors or patterns, that act as further warning signals to potential predators. Another coevolutionary relationship is mutualism, in which two or more species depend on one another and cannot live outside such an association. An example of mutualis
28、m(互利共生 ) is mycorrhizae, an obligatory relationship between fungi and certain plant roots. In one group, called ectomycorrhizae, the fungi form a cap or mantle about the rootlets. The fungal hyphae(threads) invade the rootlet and grow between the cell walls as well as extending outward into the soil
29、 from the rootlet. The fungi, which include several common woodland mushrooms, depend on the tree for their energy source. In return the fungi aid the tree in obtaining nutrients from the soil and protect the rootlets of the tree from certain diseases. Without the mycorrhizae some groups of trees, s
30、uch as conifers and oaks, cannot survive and grow. Conversely, the fungi cannot exist without the trees. 2 Populations have 3 agents, namely, a birth rate, a death rate, and a growth rate. （ A） Y （ B） N （ C） NG 3 The major agents of population growth are births and deaths. （ A） Y （ B） N （ C） NG 4 A
31、small population may undergo geometric, or exponential growth when introduced into a favorable environment. （ A） Y （ B） N （ C） NG 5 Animals can not survive some catastrophic events such as starvation, disease, or competition from other species. （ A） Y （ B） N （ C） NG 6 The short-lived, rapidly disper
32、sed species are often called _. 7 Birth rates decline, and mortality of young and adults increases when the population approaches_. 8 When a shared resource is in short supply, organisms compete, and those that _survive. 9 The abundance of plant predators, or herbivores, directly influences _. 10 Pa
33、rasites, which are smaller than their hosts, include _. 11 Certain insects, such as the monarch butterfly, can incorporate poisonous substances found in food plants into their own tissues and use them as _. Section A Directions: In this section, you will hear 8 short conversations and 2 long convers
34、ations. At the end of each conversation, one or more questions will be asked about what was said. Both the conversation and the questions will be spoken only once. After each question there will be a pause. During the pause, you must read the four choices marked A, B, C and D, and decide which is th
35、e best answer. （ A） She hasnt prepared the course outline yet. （ B） The man can get the course outline after class. （ C） There arent any copies of the course outline left. （ D） Shell distribute the course outline during the next class. （ A） Tony always speaks too fast. （ B） Tonys speech is always no
36、t clear. （ C） Tony always doesnt come to the point. （ D） Tony always speaks with strong accent. （ A） The woman never travels by plane. （ B） Both speakers feel nervous when flying. （ C） The man thinks traveling by air is quite safe. （ D） The speakers feel sad about the serious loss of life. （ A） John
37、 was disappointed at his math score. （ B） John did better than he thought he was able to. （ C） John didnt pass, although he had tried his best. （ D） John got an excellent score, which was unexpected. （ A） The man should do without buying a new bicycle. （ B） Shell glad to help the man decide which bi
38、cycle to buy. （ C） The man should not be so particular about choosing a bicycle. （ D） Shes quite concerned about the mans means of transportation. （ A） Only hold one party. （ B） Keep the party small. （ C） Keep the party a secret. （ D） Arrange the party only by they two. （ A） The boss is often late f
39、or work. （ B） The boss will probably discipline the woman. （ C） The boss may disregard the womans lateness. （ D） The boss didnt know the woman was late again. （ A） She was given a raise. （ B） She was given a new job. （ C） She was criticized for being late. （ D） She was praised for her hard work. （ A
40、） Where they should move. （ B） How to negotiate with the landlord. （ C） How to fight the increase. （ D） Whether to accept an increase in rent or move. （ A） Stay and negotiate or move. （ B） Move closer to the University or near the subway. （ C） Fight for a small increases or accepts an increase offer
41、. （ D） There is no choice. （ A） It is close to the school. （ B） It is cheap. （ C） It has convenient facilities. （ D） The tenant agreement is good. （ A） New foods to try when traveling. （ B） Making reservations for the best travel. （ C） Avoiding gaining weight while traveling. （ D） Adjusting to time
42、changes when traveling. （ A） It changes the bodys metabolism through rapid weight gain. （ B） It tricks the body into responding as if it were in a different time zone. （ C） It promotes increased alertness by adding snacks to the diet. （ D） It builds resistance to illness by increasing intake of vita
43、mins. （ A） He feels rushed. （ B） He hates to pack. （ C） He doesnt like to restrict his diet. （ D） Hes worried about his lecture. （ A） He has a big appetite. （ B） He eats only at regulate mealtimes. （ C） He avoids new foods. （ D） He eats only healthful foods. Section B Directions: In this section, yo
44、u will hear 3 short passages. At the end of each passage, you will hear some questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D. （ A） Make everyone work for you. （ B） Get everyo
45、ne willing to help you. （ C） Let people know you have the final say. （ D） Keep giving orders to everyone. （ A） Gleason thought his wonderful idea was accepted by the director. （ B） Gleason succeeded in hitting upon a wonderful idea. （ C） Gleason was confident about his work the next day. （ D） Gleaso
46、n appreciated the directors way of directing films. （ A） Directing a Film. （ B） The Key to Success. （ C） A Wonderful Experience. （ D） Working with Film Stars. （ A） Most parts of it have already disappeared. （ B） It will be replaced by a new one. （ C） Some parts of it are being destroyed. （ D） The ge
47、neral length of it has shortened. （ A） The Great Wall was completed in the Ming Dynasty. （ B） Not all the foreign tourists like the Great Wall. （ C） The first part of the Great Wall was built in 221 BC. （ D） The Qin Great Wall was protected well. （ A） The local people sell the bricks for a living. （
48、 B） The local people are short of culture knowledge. （ C） The local people need bricks and stones to build houses. （ D） The local people does not realize the seriousness of the problem. （ A） They make good decisions. （ B） They lack care from others. （ C） They have little sense of fear. （ D） They sho
49、w self-centeredness. （ A） They should be strict with their children （ B） They should not set limits for their children （ C） They should give more power to their children （ D） They should not be so anxious about their children （ A） They may probably become lonely. （ B） They may probably become skillful. （ C） They may probably become relaxed. （ D） They may probably become hesitant. （ A） How bossy behavior can be controlled. （ B） What leads to childrens bossy behavior. （ C） What effect bossy behavior brings
