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Chimpanzees 1 Chimpanzees (黑猩猩) will soon be extinct (灭绝). If the present rate of hunting and habitat (栖息地) destruction continues, then within 20 years, there will be no chimpanzees living in the wild. But this is more than an environmental or moral tragedy (悲剧). Chimpanzee extinction may also have profound implications (含意) for the survival of their distant relatives - human beings. 2 In 1975 the biologist Marie-Claire King and Allan Wilson discovered that the human and chimpanzee genomes (基因组) match by over 98%. Compare this to the mouse, used as model for human disease in lab tests, which shares only 60% of its DNA with us. In fact, chimpanzees are far more similar to humans than they are to any other species of monkey. As well as resembling us genetically, chimps are highly intelligent and able to use tools. These facts alone should be enough to make protection of chimps an urgent priority (优先). But there is another, more selfish reason to preserve the chimp. 3 The chimpanzees’ trump card (王牌) comes in the field of medical research. Chimpanzees are so similar to humans that veterinarians (兽医) often refer to human medical textbooks when treating them. Yet chimpanzees do show differences in several key areas. In particular, chimps are much more resistant to a number of major diseases. It is this ability that is so interesting. 4 For example, chimps seem to show a much higher resistance than humans to HIV, the virus that causes AIDS. Indeed, their use as experimental animals in AIDS research has declined because they are so resistant. 5 By sequencing the chimp genome and pinpointing (找到) the place where the chimpanzee DNA sequence differs from that of humans, scientists hope to be able to discover which part of the genetic code gives chimps their increased resistance to some diseases. This, they hope, will allow them to develop new and more effective treatments for the human forms of these diseases. Such treatments could include the production of new drugs or even the alteration (改变) of the human genetic sequence. The recently completed human genome sequencing project has shown that such an effort is now well within our reach.23 Paragraph _____1.24 Paragraph _____2.25 Paragraph _____3.26 Paragraph _____4.A Reasons for HIV resistanceB Implications of chimpanzee extinction for humansC Effective AIDS treatmentD Genetic similarities between chimps and humansE Chimps’ resistance to HIVF Genetic differences between chimps and humans27 Chimpanzee extinction may affect28 There is a difference of less than 2% between the chimp and29 Scientists suspect that genes.PlaY a significant role in protecting chimps from getting30 The discovery of the genetic code of chimps will be helpful toA some human disease treatmentsB some diseasesC human survivalD human genomesE key areasF healthier lifestyle
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One Good Reason to Let Smallpox Live It’s now a fair bet that we will never see the total extinction (灭绝) of the smallpox (天花) virus. When smallpox was completely got rid of in the world, scientists wanted to (51) the killer virus in the last two labs - one in the US and one in Russia. They asked: If smallpox has truly gone from the planet, (52) point was therein keeping these reserves in reality, of course, it was naive to (53) that everyone would let go of such a powerful potential weapon. Undoubtedly several nations still have (54) vials (小药瓶). And the last "official" stocks of live virus bred mistrust of the US and Russia, (55) no obvious gain. Now American researchers have (56) an animal model of the human disease, opening the (57) for tests on new treatments and vaccines (疫苗). So once again there’s a good reason to (58) the virus -just in (59) the disease puts in a reappearance. How do we (60) with the mistrust of the US and Russia (61) . Keep the virus (62) international support in a well-guarded UN laboratory that’s open to all countries. The US will object, of course, just as it (63) a multilateral (多边的) approach to just about everything. But it doesn’t mean the idea is (64) . If the virus is useful, then let’s (65) it the servant of all humanity not just a part of it.
第三篇 Water The second most important constituent (构成成份) of the biosphere (生物圈) is liquid water. This can only exist in a very narrow range of temperatures, since water freezes at 0℃ and boils at 100℃. Life as we know it would only be possible on the surface of a planet which had temperatures somewhere within this narrow range. The earth’s supply of water probably remains fairly constant in quantity. The total quantity of water is not known very accurately, but it is about enough to cover the surface of the globe to a depth of about two and three-quarter kilometers. Most of it is in the form of the salt water of the oceans about 97 percent. The rest is fresh, but three quarters of this is in the form of ice at the Poles and on mountains, and cannot be used by living systems until melted. Of the remaining fractional which is somewhat less than one per cent of the whole, there is 10—20 times as much stored underground water as there is actually on the surface. There is also a tiny, but extremely important fraction of the water supply which is present as water vapor in the atmosphere. Water vapor in the atmosphere is the channel through which the whole water circulation (循环) of the biosphere has to pass. Water evaporated (蒸发) from the surface of the oceans, from lakes and rivers and from moist (潮湿的) earth is added to it. From it the water comes out again as rain or snow, falling on either the sea or the land. There is, as might be expected, a more intensive evaporation per unit area over the sea and oceans than over the land, but there is more rainfall over the land than over the oceans, and the balance is restored by the runoff from the land in the form of rivers. There is more rainfall
The policemen acted quickly because lives were at stake.
第二篇 Mind-reading Machine A team of researchers in California has developed a way to predict what kinds of objects people are looking at by scanning (扫描) what’s happening in their brains. When you look at something, your eyes send a signal about that object to your brain. Different regions of the brain process the information your eyes send. Cells in your brain called neurons (神经元) are responsible for this processing. The fMRI (functional Magnetic Resonance Imaging) (功能性磁振造影) brain scans could generally match electrical activity in the brain to the basic shape of a picture that someone was looking at. Like cells anywhere else in your body, active neurons use oxygen. Blood brings oxygen to the neurons, and the more active a neuron is, the more oxygen it will consume. The more active a region of the brain, the more active its neurons, and in turn, the more blood will travel to that region. And by using fMRI, scientists can visualize (使…显现) which parts of the brain receive more oxygen-rich blood - and therefore, which parts are working to process information. An fMRI machine is a device that scans the brain and measures changes in blood flow to the brain. The technology shows researchers how brain activity changes when a person thinks, looks at something, or carries out an activity like speaking or reading. By highlighting the areas of the brain at work when a person looks at different images, fMRI may help scientists determine specific patterns of brain activity associated with different kinds of images. The California researchers tested brain activity by having two volunteers view hundreds of pictures of everyday objects, like people, animals, and fruits. The scientists used an fMRI machine to record the volunteers’ brain activity with each photograph they looked at. Different objects caused different regions of the volunteers’ brains to light up on the scan, indicating activity. The scientists used this information to build a model to predict how the brain might respond to any image the eyes see. In a second test, the scientists asked the volunteers to look at 120 new pictures. Like before, their brains were scanned every time they looked at a new image. This time, the scientists used their model to match the fMRI scans to the image. For example, if a scan in the second test showed the same pattern of brain activity that was strongly related to pictures of apples in the first test, their model would have predicted the volunteers were looking at apples. Which of the following can best replace the title of the passage
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