D

    Scientists are trying to make the deserts into good land again. They want to bring water to the deserts，so people can live and grow food. They are learning a lot about the deserts. But more and more of the earth is becoming deserts all the time. Scientists may not be able to change the deserts. Scientists think that people make deserts. People are doing bad things to the earth.

    Some places on the earth don't get much rain. But they still don't become desert. This is because some green plants are growing there. Small green plants and grass are very helpful to dry places. Plants don't let the hot sun make the earth even drier. Plants don't let the wind blow the earth away. When a little bit of rain falls，the plants hold the water. Without the plants，the land can become a desert much more easily.

For the first time, researchers have discovered that some plants can kill insects in order to get additional nutrients. New research shows that they catch and kill small insects with their own sticky hairs near the roots and then absorb nutrients through their roots when the insects are killed and fall to the ground.

Professor Mark Chase, of Kew and Queen Mary, University of London, said: “The cultivated (改良的) tomatoes and potatoes still have the hairs. Tomatoes in particular are covered with these sticky hairs. They do trap small insects on a regular basis. They do kill insects.”

The number of these carnivorous plants is thought to have came up to 50 percent and many of them have until now been wrongly regarded as among the most harmless plants. Among them are species of petunia(矮牵牛), some special tobacco plants and cabbages, some varieties of potatoes and tomatoes, etc. Researchers at Royal Botanical Gardens Kew, which carried out the study, now believe there are hundreds more killer plants than previously realized.

It is thought that the technique was developed in the wild to get necessary nutrients in poor quality soil ­ and even various plants grown in your vegetable garden still have the ability.

The researchers, publishing their finding in the Botanical Journal of the Linnean Society, said: “We may be surrounded by many more murderous plants than we think.” “We are accustomed to thinking of plants as being immobile and harmless, and there is something deeply frightening about the thought of meat­eating plants，” they added.

Many studies have shown that the company of pets can help lower blood pressure and raise chances of recovering from a heart attack, reduce loneliness and help control body weight.

Any pet owner will tell you how much joy a pet brings. For some, an animal provides more comfort than a husband/wife. A 2002 study by Karen Allen of the State University of New York measured stress levels and blood pressure in people (half of them were pet owners) while they performed 5 minutes of mental arithmetic (算术) or held a hand in ice water. People completed the tasks alone, with a husband/wife, a close friend or with a pet. People with pets did it best. Those tested with their animal friends had smaller change in blood pressure and returned most quickly to baseline heart rates. With pets in the room, people also made fewer math mistakes than when doing in front of other companions. It seems that people feel more relaxed around pets, says Allen, who thinks it may be because pets don’t judge.

   A study reported last fall suggests that having a pet dog may also have an effect on your body weight. Researchers at Northwestern Memorial Hospital spent a year studying two groups of fat people who were put on a diet-and-exercise program: one group with pet dogs, and the other without. On average, dog owners lost about 11 pounds, or 5% of their body weight; While those without dogs lost about 8 pounds. The pet owners, said researchers, got more exercise overall (mostly with their dogs) and found it worth doing.

Are you unhappy about your nose? Or you feel that your ears are too big or your eyes too small? They can all be put right by a surgeon. Surgeons are doctors who make sick people well by operating on them. But some surgeons today are really beauty specialists. Their job, which is called plastic surgery, is to make ugly or plain people beautiful.

    Plastic surgeons are very popular in some countries. They make lots of money by selling beauty to persons, especially women. Plastic surgery is very expensive. Suppose I can afford to pay so much money and want to change my ugly nose for a more handsome one, I must consult a plastic surgeon.

    First of all, he will ask me to enter a nursing home（护理院）. I shall have to spend about three weeks there. The surgeon will give me an anesthetic（麻醉药）. Then he will operate on my nose. He will put a plaster case to keep its new shape. I shall have to spend the next week or two anxiously wondering whether the operation has been successful or not. “Will my nose really look better or leave scars? What shall I do if my nose is not the shape I wanted?” And so on. Then the surgeon will take off the bandages and the plaster, I shall see my expensive new nose! Will it be worth all the trouble and expense? Sometimes these operations go wrong, and then patient comes away looking worse than before.

           A

       The idea of fighting a noise by making more noise sounds strange, but What's exactly that motor engineers are doing in Germany and some other countries．

　　Carmakers' research and development laboratories have already proved that mixing in more noise with the help of loudspeakers can reduce the unwanted noise．

　　 Physicists have known about the technique for a long time．Sound is make up of pressure waves in the air．If two sound waves of the same frequency(频率)mix so that the highest point of one wave happens at the same time with the lowest point of the other wave, the result is no sound．Therefore, by producing a perfect copy of the noise and delaying it by half a wave cycle(周期), we can kill the unwanted noise．Using this technique many carmakers are racing to develop noise-killing systems both inside and outside the cars．Another good thing about the use of noise-killing systems is that it saves the need for a silencer, which not only reduces the weight of a car, but also makes the motor bum less oil and work better．

　　 Some engineers believe that the noise-killing system will be used in most cars in 1996．But the carmakers haven't decided if they will put it into production because it would add several hundred dollars to the cost of their ears．

    For visitors, Teller Lake looks like a delightful fishbowl filled with thousands of beautiful goldfish floating around. However, to the Colorado Parks and Wildlife Department they are a group of invasive (入侵的) species that could finally destroy the lake's entire ecosystem if not removed soon.

    The problem lies in the fact that these fish have no enemies. This allows them to reproduce in large numbers. In fact, park officials believe that the 3,000~4,000 samples floating around are all the result of a few unwanted pet goldfish that were dumped into the lake. They estimate the incident occurred about three years ago.

    As this non-native species grow in numbers, they compete with the existing fish for food sources. Given that there is only a limited supply of resoureas, this could result in the goldfish overpowering the native fish species. In the ease of Teller Lake, the officials are particularly worried that the goldfish will move downstream and affect the population of some of the endangered native species that live there. Another major cause for concern is the diseases the goldfish may be bringing. This could be fatal (致命的) to the native species since they can't fight new illnesses.

    Fish are not the only unwanted pets that are thrown away. Florida has been fighting an invasion of Burmese pythons (巨蟒). But one of the worst cases recorded is that of the Red Lionfish. They are currently swimming their way to the Atlantic Ocean's ecosystem all the way.

    According to experts, the best way to get rid of unwanted fish or any other animal is to get advice from the people that originally sold them the pet. However, saving one pet often results in destroying the area's ecosystem and hurting other innocent animals.

C

      Delicate step gives mosquitoes strength to walk on water.

   It's not a magical power. Mosquitoes can walk on water because of the angle at which their legs touch its surface.

   A mosquito's leg is strong enough to bear up to 23 times its total body weight, which is one reason why it can walk on water so effortlessly. This is far greater than the leg strength of other water-walking insects like water striders(水黾), whose legs have been more carefully studied.

   Jian-Lin Liu of the China University of Petroleum in Qingdao and his colleagues thought a mosquito's advantage might also come from the protective wax and microscopic scales(鳞片) coating its legs. They removed these layers(层) and measured the change in the leg's load-bearing capacity(承重能力), but found that the layers were responsible for less than 12.5 percent of the overall supporting force.

   The main player turned out to be the angle between the leg and the water surface. The supporting force was strongest when the leg was nearly parallel to the surface. Any angle greater than 62 degrees would make the mosquito fall through the surface.

The researchers believe that mosquitoes can adjust this angle during landing and take-off to ensure they remain on the water's surface. This ability is very important because many species land on fresh or still water to lay their eggs in it.

    The work could inspire insect-like robots and waterproof materials, the team says.

       What will man be like in the future——in 5000 or even 50,000 years from now? We can only make guesses, of course, but we can be sure that he will be different from what he is today, for man is slowly changing all the time.

　  　Let us take an obvious example. Man, even five hundred years ago, was shorter than he is today. Now, on average, men are about three inches(英寸) taller. Five hundred years is relatively short period of time, so we may assume（设想）that man will continue to grow taller. Again, in the modern world we use our brains a great deal. Even so, we still make use of only about 20% of the brain’s capacity(容量）. As time goes on, however, we shall have to use our brains more and more, and eventually we shall need larger ones! This is likely to bring about a physical change to the head, in particular the forehead, will grow larger.

　   　Nowadays our eyes are in constant use. In fact, we use them so much that very often they become weaker and we have to wear glasses. But over very long period of time it is likely that man’s eyes will grow stronger.

　 　On the other hand, we tend to make less use of our arms and legs. These, as a result, are likely to grow weaker. At the same time, however, our fingers will grow more sensitive because they are used a great deal in modern life.

　　But what about hair? This will probably disappear from the body altogether in course of time because it does not serve a useful purpose any longer. In the future, then, both sexes are likely to be bald（秃头的）.

　　Perhaps all this gives the impression that future man will not be a very attractive creature to look at! This may well be true. All the same, in spite of all these changes, future man will still have a lot in common with us. He will still be a human being, with thoughts and emotions similar to our own.

C

  A new study showed that one of the best ways to control greenhouse gas emissions(温室气体排放) is to eat less meat. In fact, the study showed that meat consumption(食用量) in developed countries should be cut by 50% per person before 2050.

  Meat production and consumption are expected to rise very quickly to a high level by 2050. That’s because the global population is expected to grow from the present 7 billion to 9 billion. But also, the diets of people in many developing countries are changing. Countries that are developing rapidly are seeing a fast rise in protein consumption, especially red meat.

Dr. Eric Davidson, the president and senior scientist at the Woods Hole Research Center in Massachusetts, said changing the way people eat can have a great effect on greenhouse gas emissions. People in developed countries, he said, already eat much more protein than the daily requirement.

“In the developed world, there is large room for us to manage the frequency with which we eat meat. If there is a growing need for meat, that is going to end up requiring use of more nitrogen fertilizer(肥料) and production of more livestock manure(家畜粪肥), both of which end up resulting in release of various forms of greenhouse gases to the atmosphere,” he said.

Davidson said farmers should be encouraged to use fertilizers and manure in a more careful way. “ If we want to meet the greatest goal of making harmful climate change under control, we need to improve the efficiency(效能) with which we use fertilizers in agriculture. We need to improve the efficiency of the management of manure. And we also need to consider changes in dietary patterns(饮食方式). And that means hopefully better diets in the developing world and better balanced diets in the developed world,” he said.

Even if it were possible to turn off all harmful greenhouse gas emissions today, he said climate change would continue. “ But that does not mean that we can do nothing for it now, because the sooner we start to take action, the more choices our children and grandchildren will have in terms of being able to feed themselves and have comfortable lifestyles without environmental degradation(退化),” he said.

Using too much water or throwing rubbish into our rivers are clear ways that humans can put our water supply in danger, but we also affect our water supply in less obvious ways. You may wonder how paving(铺砌) a road can lead to less useable fresh water. A major part of the  water we use every day is groundwater. Groundwater does not come from lakes or rivers.It comes from underground. The more roads and parking lots we pave, the less water can flow into the ground to become groundwater.

    Human activity is not responsible for all water shortages. Drier climates are of course more likely to have droughts than areas with more rainfall，but in any case, good management can help to make sure there is enough water to meet our basic needs.

    Thinking about the way we use water every day can make a big difference, too. In the United States, a family of four can use 1.5 tons of water a day! This shows how much we depend on water to live，but there's a lot we can do to lower the number.

You can take steps to save water in your home.To start with, use the same glass for your drinking water all day. Wash it only once a day. Run your dishwasher only when it is full. Help your parents fix any leaks in your home. You can even help to keep our water supply clean by recycling batteries instead of throwing them away.