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70天攻克考研英语阅读 DAY23

2006-7-28 01:04  

  Increasing reading speed

  Directions: Do the phrase recognition drill below. Quickly underline or mark the key phrase every time it appears in the columns. Try to finish in 10 seconds or less by reading down the column, not left to right.

  Starting Time:

  Key phrase: blood pressureblood pressureblood vessels

  blood stream          blood pressure

  economic pressure      military pressure

  blood pressure        pressure bottle

  blood typing          blood pressure

  blood brother        elder brother

  blood pressure        social pressure

  blood group          pressure gauge

  blood plasma        blood pressure

  fresh blood          word processor

  blood pressure        good professor

  blood relation       blood pressure

  blood volume        blood hungry

  blood pressure        mental pressure

  heavy pressure        blood pressure

  Finishing Time:  Total Reading Time:

  The key phrase appears 10 times.

  How many did you mark?GiraffesImagine there is no such thing as giraffes and your job is to design one. As it happens, you would have to solve several tricky problems that dont apply to any other known animal.

  For one thing, an adult giraffes head is about six feet above its heart. This means that to pump enough blood up to the brain, you would have to make the circulatory system strong enough to keep the blood at very high pressure. If the blood pressure were the same as that in most other animals, the blood would rise only part way up the neck and never reach the brain.

  Biologists have known for some time that giraffes solve this problem by having unusually high blood pressure, about double that of human beings. So far, so good.

  But an international team of biologists who started thinking like giraffe designers began to wonder about this. If giraffes have such high blood pressure, they should have a terrible problem with swelling in their legs and feet. The pressure that pushes blood up also pushes it down. Gravity adds its force pulling the blood down and trying to keep  it down. Even people who dont have high blood pressure but who stay on their feet all day can suffer from swollen feet from the effects of gravity alone. Why, the scientists wondered, dont giraffes have swollen feet?

  Giraffes should have another problem, too. Every time they bend their heads down to drink ,the blood should rush to their heads and have a hard time flowing back up (when the head is down) to the heart. How come giraffes dont black out when they drink?

  The scientists realized that nature must have designed giraffes to prevent these problems. But what was the design?What was the gimmick that solved the potentially bad side effects of high blood pressure?

  The answer to the swollen feet problem, the researchers found, is that giraffes have what the researchers call a "natural antigravity suit." It turns out that the skin and other tissues in their legs and feet are much stiffer and tougher than those of other animals. As a result, the scientists found, the blood vessels in the leg cannot swell. Therefore, the blood has nowhere to go but back up to the heart.

  What about blood rushing to the head whenever the giraffe bends down to drink? As expected, giraffes were designed with another gimmick to prevent the problem.

  The researchers found that the giraffes jugular vein, which carries blood from the head back to the heart, has lots of oneway yams in it. Human leg veins have similar oneway "flapper" valves but human jugulars do not.

  In giraffes and people, the valves consists of flaps inside the vein that open if blood tries to move in the right direction but that close if blood tries to flow the wrong way. The flaps dont move the blood; but they do turn the vein into a pumping chamber if the vein happens to be squeezed by surrounding muscles that are flexing for other purposes.

  Human leg veins, for example, are repeatedly squeezed by the leg muscles as people walk or run. The squeezing pushes the blood in all directions but the valves allow it to move only one way back to the heart. This is the human design to minimize swollen feet.

  In the giraffes neck, there are lots of muscles that flex and relax repeatedly as the animal moves its head and sucks up drinking water. By squeezing the valved jugular vein, they keep blood moving back to the heart even while the animal is drinking.

  ——from Science World, Dec. 4,1987

  Time:  609 words=wpm

  Minutes

  EXERCISESⅠ。 READING COMPREHENSION

  Select the answer which is most accurate according to tile information given in the passage.

  1. To make the blood rise up to the brain, giraffes blood pressure should be  that of human beings.

  A. three times higher thanB. about twice as high as

  C. just as high as       D. a bit lower than

  2. Giraffes legs and feet are free from swelling even though the blood pressure is relatively high. The reason for that lies in .

  A. their circulatory system   B. the oneway valves

  C. the skin that covers their legs and feet  D. the effects of gravity

  3. Which of the following statements is true according to what you have read in the passage?

  A. Man has much fewer oneway valves in his jugular vein than the giraffe because his neck is much shorter.

  B. The giraffe has no oneway valves in its leg vein.

  C. Man has no oneway valves in his leg veins.

  D. Mans leg veins have many oneway valves similar to those in the giraffes jugular vein.

  4. As a person walks or runs, the "flapper" valves protect his legs from swelling by .

  A. accelerating the blood flow

  B. blocking the bloodflow to all passages but heart

  C. squeezing the leg veins

  D. creating a pumping chamber in the vein

  5. The purpose of the passage is to introduce  to its readers.

  A. some peculiar physiological features of the giraffe

  B. the giraffes high blood pressure

  C. the giraffes circulatory system

  D. the flapper valves in the giraffes jugular vein

  6. As a giraffe bends its head down to drink, enables the blood to flow back up to the heart.

  A. the jugular vein     B. the "natural antigravity suit"

  C. the squeezing of jugular muscles upon the jugular vein

  D. its leg veins

  7. Which of the following statements is meant by the author?

  A. The flapper valves in the human jugular vein perform the same functions as those in a giraffes jugular vein.

  B. Every time when giraffes lower their heads down to drink, the blood rushes to their heads and has a hard time flowing back up to the heart.

  C. There are no oneway "flapper" valves in the human jugular vein.

  D. An international team of biologists started working as giraffe designers.

  Ⅱ。 CONTEXTUAL REFERENCE

  Read the following article and figure out the words in italics using the context given and wordbuilding skills.

  A wellknown adaptation for the protection of the young is found among the kangaroos (大袋鼠) and wallabies (小袋鼠) of Australia and the opossums (负鼠) of North and South America. This is the marsupial (有袋动物的) pouch, a pocket on the surface of the females abdomen. The marsupial pouch serves as a place of refuge for the young. These vary in number from one or two, in the case of kangaroos, to the fourteen or more of a Virginia opossum. The young are small, immature and quite helpless at birth. But they are housed safely in the pouch, where they can get at the milk glands without leaving their shelter.

  A kangaroo carries her young around in her pouch until it has grown to considerable size. When pursued by an enemy, a kangaroo will sometimes pull a young one from the pouch and throw it to the ground. It is not known whether she does so in order to lighten her own load, or to provide for the escape of the young kangaroo in case the mother is overtaken by her pursuer.

  Some animals safeguard their young by remarkable adaptations of behavior. The female Siamese hornbill (犀鸟) makes her nest in a cavity in a tree. After she has begun to sit on her eggs, the male hornbill seals up the entrance to the hole almost entirely with mud. This dries and hardens, leaving a slit-like opening, through which the male feeds his mate while she is nesting. The opening is not large enough to permit the entrance of animal foes that climb about among the trees in warm countries.

  ——from Selected Reading for Biology Students, pp. 307 - 308

  Ⅲ。 CLOZE

  Complete the following passage by filling in the blanks with appropriate words.

  Eager Beaver

  Every people has its own special words and expressions that become part of the language. One 1     American expression is "eagerbeaver." An "eagerbeaver" is a  2     who is always willing and excited to do     3     is expected of him. The expression comes     4     the name of the hardworking     5, the beaver. Beavers are strangelooking     6. They are rodents (齿动物), 7 mice and rats, but much larger. Some weigh     8     than 25 kilograms. Beavers have a large black, flat     9     to help them swim. They also have     10     brown hair and fur to     11     them warm in cold water, and they have front teeth sharp     12     to cut down large trees. Beavers spend a lot of     13     in the water     14     dams to create little lakes or ponds. They work hard to cut 15   trees, remove branches and      16     them together with mud to make     17. Few other animals are     18     hardworking. Historians say the beaver had an important     19     in the settlement of North America. There were hundreds of

  20     of beavers when European     21     first arrived. The settlers put great value     22     the fur of the beaver. In fact, for 200 years or more,     23     was the most valuable      24     in North America. Most of the beavers were trapped or     25. For a time, they were in     26     of disappearing completely. But laws were passed to     27     the beaver. And today the population is rising. In fact, wild beavers are building     28   in a national park only 50 kilometers from Washington. And like the animal, the expression "eagerbeaver" is in no danger of dying out.

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