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In recent years a new farming revolution has begun, one that involves the manipulation of life at a fundamental level—the gene. The study of genetics has (51) a new industry called biotcehnology. As the name suggests, it (52) biology and modern technology through such techniques as genetic engineering. Some of the new biotech companies specialize in agriculture and are working feverishly to (53) seeds that give a high yield, that (54) diseases, drought and frost, and that reduce the need for hazardous chemicals, If such goals could be achieved, it would be most (55) . But some have raised concerns about genetically engineered crops. In nature, genetic diversity is created within certain (56) . A rose can be crossed with a different kind of rose, but a rose will never cross with a potato. Genetic engineering, (57) usually involves taking genes from one species and inserting them into another in an attempt to transfer a desired characteristic. This could mean, for example, selecting a gene which leads to the production of a chemical with anti-freeze (58) from an artic fish, and inserting it into a potato or strawberry to make it frost, resistant, in essence, then, biotechnology allows humans to (59) the genetic walls that separate species. Just like the green revolution, (60) some call the gene revolution contributes to the problem of genetic uniformity-some say even more so (61) geneticists can employ techniques such as cloning and (62) culture (培养) and processes that produce perfectly (63) copies. Concerns about the erosion of biodiversity, therefore, remain. Genetically altered plants, however, raise new (64) ,such as the effects that they may have on us and the environment. "We are tlying blindly into a new era of agricultural biotechnology with high hopes, few constraints, and little idea of the potential (65) ," said science writer Jeremy Rifkin.
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Passage 1 The changing profile of a city in the United States is apparent in the shifting definitions used by the United States Bureau of the Census. In 1870 the census officially distinguished the nation’s "urban" from its "rural" population for the first time. "Urban population" was defined as persons living in towns of 8,000 inhabitants or more. But after 1900 it meant persons living in incorporated places having 2,500 or more inhabitants. Then, in 1950 the Census Bureau radically changed its definition of "urban" to take account of the new vagueness of city boundaries. In addition to persons living in incorporated units of 2,500 or more, the census now included those who lived in unincorporated units of that size, and also all persons living in the densely settled urban fringe, including both incorporated and unincorporated areas located around cities of 50,000 inhabitants or more. Each such unit, conceived as an integrated economic and social unit with a large population nucleus, was named a Standard Metropolitan Statistical Area (SMSA). Each SMSA would contain at least (a) one central city with 50,000 inhabitants or more or (b) two cities having shared boundaries and constituting, for general economic and social purposes, a single community with a combined population of at least 50,000, the smaller of which must have a population of at least 15,000. Such an area included the county in which the central city is located, and adjacent counties that are found to be metropolitan in character and economically and socially integrated with the county of the central city. By 1970, about two-third of the population of the United States was living in these urbanized areas, and of that figure more than half were living outside the central cities. With the Census Bureau and the United States government used the term SMSA (by 1969 there were 233 of them), social scientists were also using new terms to describe the elusive, vaguely defined areas reaching out from what used to be simple "towns" and "cities". A host of terms came into use: "metropolitan regions", "polynucleared population groups", "metropolitan clusters", and so on. According to the passage, why did the Census Bureau revise the definition of urban in 1950
What kind of city is Tokyo
Intelligent car door clamps up when danger’s about Accidents caused by car doors being opened into the path of oncoming vehicles or cyclists are common in cities. But these incidents could become a thing of the past, if doors that react to potential impacts catch on. The creative idea of Michael Graf at BMW and Michael Strolz’s team at the Technical University of Munich, the "haptic"-technology that gives tactile feedback-doors could cut both road injuries and repair bills, they say. The current prototype looks like a normal car door, but an extra metal bar runs through its centre and connects to the car’s frame between the hinges. In normal mode, the bar moves freely and doesn’t affect the door’s movement. However, if sensors detect a nearby obstacle at the same time as an accelerometer detects an attempt to open the door, the door’s swing is restricted by a linear motor attached to the bar. To pass on more information to the user, the amount of door resistance is in proportion to the proximity of an object-for example, you might swing a door halfway open without problems before it gets stiffer as it nears a lamp post. The current prototype uses supersonic sensors to spot dangers, but because they have a limited field of view, the next version will use cameras that can span 180°, says Strolz. "Then we will be able to sense the complete workspace of the door and detect people walking by the car or cycling towards it," he says. Reactions from 16 volunteers who tried the new door at BMW’s Munich research centre have been encouraging, the team told a recent conference on haptics in Salt Lake City, Utah. The technology is mature enough that a car factory could be pumping it out in cars within a year, says Strolz. The basic mechanism is like one already featured in some cars-for example, taxis with automatic passenger doors. However, BMW is yet to make any decision on whether to roll it out. The passage mainly talks about
Half of world’s primates face extinction Almost 50% of the world’s 634 primate (灵长类动物) species face extinction, according to a report from the International Union for the Conservation of Nature. Habitat loss is a major cause, but many monkeys and apes are being hunted to extinction for food, especially in forests of south-east Asia. "It’s cheaper to go into the forest and kill a monkey than to raise a chicken," says Jean-Christophe rie, deputy head of the IUCN’s species programmeand a co—author of the report. "We’ve raised concerns for years about primates being in danger, but now we have solid data to show the situation is far more severe than we imagined," says Russell Mittermeier, president of Conservation International, which co-funded the study. The areas most at risk are in Vietnam and Cambodia, where 90% of species are being driven to extinction by demand for monkey meat and baby monkeys as pets. Most acutely affected are medium-sized monkeys such as gibbons(长臂猿), leaf monkeys and langurs, which are easy for hunters to track down and kill because of their size and the noise they make. In South America. spider monkeys and capuchin monkeys(卷尾猴)have been hit hardest. In Africa, red colobus monkeys are now critically endangered. Eleven of the 13 species assessed were listed as critically endangered or endangered. Two may already be extinct. " Among the African species, the great apes such as gorillas (大猩猩) and bonobos have always tended to grab the limelight, and even thought they’re deeply threatened, it is smaller primates such as the red colobus that could die out first," says Richard Wrangham, president of the International Primatological Society. Huge political efforts are needed now to reverse the impending losses of threatened species, says Vid. "What’s needed is national legislation to protect biodiversity, creation of protected areas with dedicated staff, crackdowns on corruption, and captive breeding programmes," he says. But it will be difficult to halt and reverse the damage done by habitat destruction and the hunters. Once habitat is gone, animals have nowhere to go. Also, killing primates rapidly depletes populations, because they have fewer young than many other mammals and take much longer to breed and raise families. What is the maj or cause that half of the primate species face extinction
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