1、雅思（阅读）历年真题试卷汇编 8及答案与解析 0 You should spend about 20 minutes on Questions 1-13 which are based on Reading Passage 1 below. Going Bananas The worlds favourite fruit could disappear forever in 10 yearstime. The banana is among the worlds oldest crops. Agricultural scientists believe that the first edibl
2、e banana was discovered around ten thousand years ago. It has been at an evolutionary standstill ever since it was first propagated in the jungles of South-East Asia at the end of the last ice age. Normally the wild banana, a giant jungle herb called Musa acuminata, contains a mass of hard seeds tha
3、t make the fruit virtually inedible. But now and then, hunter-gatherers must have discovered rare mutant plants that produced seedless, edible fruits. Geneticists now know that the vast majority of these soft-fruited plants resulted from genetic accidents that gave their cells three copies of each c
4、hromosome instead of the usual two. This imbalance prevents seeds and pollen from developing normally, rendering the mutant plants sterile. And that is why some scientists believe the worlds most popular fruit could be doomed. It lacks the genetic diversity to fight off pests and diseases that are i
5、nvading the banana plantations of Central America and the smallholdings of Africa and Asia alike. In some ways, the banana today resembles the potato before blight brought famine to Ireland a century and a half ago. But it holds a lesson for other crops, too, says Emile Frison, top banana at the Int
6、ernational Network for the Improvement of Banana and Plantain in Montpellier, France. The state of the banana, Frison warns, can teach a broader lesson: the increasing standardisation of food crops round the world is threatening their ability to adapt and survive. The first Stone Age plant breeders
7、cultivated these sterile freaks by replanting cuttings from their stems. And the descendants of those original cuttings are the bananas we still eat today. Each is a virtual clone, almost devoid of genetic diversity. And that uniformity makes it ripe for disease like no other crop on Earth. Traditio
8、nal varieties of sexually reproducing crops have always had a much broader genetic base, and the genes will recombine in new arrangements in each generation. This gives them much greater flexibility in evolving responses to disease and far more genetic resources to draw on in the face of an attack.
9、But that advantage is fading fast, as growers increasingly plant the same few, high-yielding varieties. Plant breeders work feverishly to maintain resistance in these standardised crops. Should these efforts falter, yields of even the most productive crop could swiftly crash. “When some pest or dise
10、ase comes along, severe epidemics can occur， “ says Geoff Hawtin, director of the Rome-based International Plant Genetic Resources Institute. The banana is an excellent case in point. Until the 1950s, one variety, the Gros Michel, dominated the worlds commercial banana business. Found by French bota
11、nists in Asia in the 1820s, the Gros Michel was by all accounts a fine banana, richer and sweeter than todays standard banana and without the latters bitter aftertaste when green. But it was vulnerable to a soil fungus that produced a wilt known as Panama disease. “Once the fungus gets into the soil
12、 it remains there for many years. There is nothing farmers can do. Even chemical spraying wont get rid of it,“ says Rodomiro Ortiz, director of the International Institute for Tropical Agriculture in Ibadan, Nigeria. So plantation owners played a running game, abandoning infested fields and moving t
13、o “clean“ land until they ran out of clean land in the 1950s and had to abandon the Gros Michel. Its successor, and still the reigning commercial king, is the Cavendish banana, a 19th-century British discovery from southern China. The Cavendish is resistant to Panama disease and, as a result, it lit
14、erally saved the international banana industry. During the 1960s, it replaced the Gros Michel on supermarket shelves. If you buy a banana today, it is almost certainly a Cavendish. But even so, it is a minority in the worlds banana crop. Half a billion people in Asia and Africa depend on bananas. Ba
15、nanas provide the largest source of calories and are eaten daily. Its name is synonymous with food. But the day of reckoning may be coming for the Cavendish and its indigenous kin. Another fungal disease, black Sigatoka, has become a global epidemic since its first appearance in Fiji in 1963. Left t
16、o itself, black Sigatoka which causes brown wounds on leaves and premature fruit ripening cuts fruit yields by 50 to 70 per cent and reduces the productive lifetime of banana plants from 30 years to as little as 2 or 3. Commercial growers keep Sigatoka at bay by a massive chemical assault. Forty spr
17、ayings of fungicide a year is typical. But even so, diseases such as black Sigatoka are getting more and more difficult to control. “As soon as you bring in a new fungicide, they develop resistance,“ says Frison. “One thing we can be sure of is that the Sigatoka wont lose in this battle.“ Poor farme
18、rs, who cannot afford chemicals, have it even worse. They can do little more than watch their plants die. “Most of the banana fields in Amazonia have already been destroyed by the disease,“ says Luadir Gasparotto, Brazils leading banana pathologist with the government research agency EMBRAPA. Produc
19、tion is likely to fall by 70 per cent as the disease spreads, he predicts. The only option will be to find a new variety. But how? Almost all edible varieties are susceptible to the diseases, so growers cannot simply change to a different banana. With most crops, such a threat would unleash an army
20、of breeders, scouring the world for resistant relatives whose traits they can breed into commercial varieties. Not so with the banana. Because all edible varieties are sterile, bringing in new genetic traits to help cope with pests and diseases is nearly impossible. Nearly, but not totally. Very rar
21、ely, a sterile banana will experience a genetic accident that allows an almost normal seed to develop, giving breeders a tiny window for improvement. Breeders at the Honduran Foundation of Agricultural Research have tried to exploit this to create disease-resistant varieties. Further backcrossing wi
22、th wild bananas yielded a new seedless banana resistant to both black Sigatoka and Panama disease. Neither Western supermarket consumers nor peasant growers like the new hybrid. Some accuse it of tasting more like an apple than a banana. Not surprisingly, the majority of plant breeders have until no
23、w turned their backs on the banana and got to work on easier plants. And commercial banana companies are now washing their hands of the whole breeding effort, preferring to fund a search for new fungicides instead. “We supported a breeding programme for 40 years, but it wasnt able to develop an alte
24、rnative to Cavendish. It was very expensive and we got nothing back,“ says Ronald Romero, head of research at Chiquita, one of the Big Three companies that dominate the international banana trade. Last year, a global consortium of scientists led by Frison announced plans to sequence the banana genom
25、e within five years. It would be the first edible fruit to be sequenced. Well, almost edible. The group will actually be sequencing inedible wild bananas from East Asia because many of these are resistant to black Sigatoka. If they can pinpoint the genes that help these wild varieties to resist blac
26、k Sigatoka, the protective genes could be introduced into laboratory tissue cultures of cells from edible varieties. These could then be propagated into new, resistant plants and passed on to farmers. It sounds promising, but the big banana companies have, until now, refused to get involved in GM re
27、search for fear of alienating their customers. “Biotechnology is extremely expensive and there are serious questions about consumer acceptance,“ says David McLaughlin, Chiquitas senior director for environmental affairs. With scant funding from the companies, the banana genome researchers are focusi
28、ng on the other end of the spectrum. Even if they can identify the crucial genes, they will be a long way from developing new varieties that smallholders will find suitable and affordable. But whatever biotechnologys academic interest, it is the only hope for the banana. Without it, banana productio
29、n worldwide will head into a tailspin. We may even see the extinction of the banana as both a lifesaver for hungry and impoverished Africans and as the most popular product on the worlds supermarket shelves. Questions 1-3 Complete the sentences below with NO MORE THAN THREE WORDS from the passage. W
30、rite your answers in boxes 1-3 on your answer sheet. 1 The banana was first eaten as a fruit by humans almost_years ago. 2 Bananas were first planted in_. 3 The taste of wild bananas is adversely affected by its_. 3 Look at the following statements(Questions 4-10)and the list of people below. Match
31、each statement with the correct person, A-F. Write the correct letter, A-F, in boxes 4-10 on your answer sheet. NB You may use any letter more than once. List of people A Rodomiro Oritz B David McLaughlin C EmileFrison D Ronald Romero E Luadir Gasparotto F Geoff Hawtin 4 A pest invasion may seriousl
32、y damage the banana industry. 5 The effect of fungal infection in soil is often long-lasting. 6 A commercial manufacturer gave up on breeding bananas for disease resistant species. 7 Banana disease may develop resistance to chemical sprays. 8 A banana disease has destroyed a large number of banana p
33、lantations. 9 Consumers would not accept genetically altered crop. 10 Lessons can be learned from bananas for other crops. 10 Do the following statements agree with the information given in Reading Passage 1? In boxes 11-13 on your answer sheet, write TRUE if the statement agrees with the informatio
34、n FALSE if the statement contradicts the information NOT GIVEN if there is no information on this 11 The banana is the oldest known fruit. （ A）真 （ B）假 （ C） Not Given 12 The Gros Michel is still being used as a commercial product. （ A）真 （ B）假 （ C） Not Given 13 Banana is the main food in some countrie
35、s. （ A）真 （ B）假 （ C） Not Given 13 You should spend about 20 minutes on Questions 14-26 which are based on Reading Passage 2 below. Coastal Archaeology of Britain The recognition of the wealth and diversity of Englands coastal archaeology has been one of the most important developments of recent years
36、. Some elements of this enormous resource have long been known. The so-called submerged forests off the coasts of England, sometimes with clear evidence of human activity, had attracted the interest of antiquarians since at least the eighteenth century, but serious and systematic attention has been
37、given to the archaeological potential of the coast only since the early 1980s. It is possible to trace a variety of causes for this concentration of effort and interest. In the 1980s and 1990s, scientific researches into climate change and its environmental impact spilled over into a much broader pu
38、blic debate as awareness of these issues grew; the prospect of rising sea levels over the next century, and their impact on current coastal environments, have been a particular focus for concern. At the same time archaeologists were beginning to recognise that the destruction caused by natural proce
39、sses of coastal erosion and by human activity was having an increasing impact on the archaeological resource of the coast. The dominant process affecting the physical form of England in the post-glacial period has been the rise in the altitude of sea level relative to the land, as the glaciers melte
40、d and the landmass readjusted. The encroachment of the sea, the loss of huge areas of land now under the North Sea and the English Channel, and especially the loss of the land bridge between England and France which finally made Britain an island, must have been immensely significant factors in the
41、lives of our prehistoric ancestors. Yet the way in which prehistoric communities adjusted to these environmental changes has seldom been a major theme in discussions of the period. One factor contributing to this has been that, although the rise in relative sea level is comparatively well documented
42、, we know little about the constant reconfiguration of the coastline. This was affected by many processes, mostly quite localised, which have not yet been adequately researched. The detailed reconstruction of coasdine histories and the changing environments available for human use will be an importa
43、nt theme for future research. So great has been the rise in sea level and the consequent regression of the coast that much of the archaeological evidence now exposed in the coastal zone, whether being eroded or exposed as a buried land surface, is derived from what was originally terrestrial occupat
44、ion. Its current location in the coastal zone is the product of later unrelated processes, and it can tell us little about past adaptation to the sea. Estimates of its significance will need to be made in the context of other related evidence from dry land sites. Nevertheless, its physical environme
45、nt means that preservation is often excellent, for example in the case of the Neolithic structure excavated at the Stumble in Essex. In some cases these buried land surfaces do contain evidence for human exploitation of what was a coastal environment, and elsewhere along the modern coast there is si
46、milar evidence. Where the evidence does relate to past human exploitation of the resources and the opportunities offered by the sea and the coast, it is both diverse and as yet little understood. We are not yet in a position to make even preliminary estimates of answers to such fundamental questions
47、 as the extent to which the sea and the coast affected human life in the past, what percentage of the population at any time lived within reach of the sea, or whether human settlements in coastal environments showed a distinct character from those inland. The most striking evidence for use of the se
48、a is in the form of boats, yet we still have much to learn about their production and use. Most of the known wrecks around our coast are not unexpectedly of post-medieval date, and offer an unparalleled opportunity for research which has as yet been little used. The prehistoric sewn-plank boats such
49、 as those from the Humber estuary and Dover all seem to belong to the second millennium BC; after this there is a gap in the record of a millennium, which cannot yet be explained, before boats reappeared, but built using a very different technology. Boatbuilding must have been an extremely important activity around much of our coast, yet we know almost nothing about it. Boats were some of the most complex artefacts produced by pre-modern societies, and further researches on their production and use make an important contribution to our understanding of pa
