题目内容
Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
Running a lever was once thought to be the prerogative of warm-blooded creatures, whose internal temperatures are independent of the weather. But, as Matthew Kluger reported in "The Importance of Being Feverish" (January 1976), lizards can also develop fevers, even though there is no question that they are cold-blooded. They raise their temperatures by moving into the sun or, in the case of Kluger's experiments, under a sun lamp. And it seems to do them some good. Sick lizards kept in cages at feverish temperatures fare much better than their counterparts in normal mid cool environments.
Now, fever has spread to invertebrates(无脊椎动物). Recent studies have shown that crayfish and scorpions can develop fevers. Crayfish injected with bacteria and scorpions injected with prostaglandins(前列腺素) swam and scuttled to hot areas. (Prostaglandins are hormones thought to be instrumental in the development of a fever. )
Evidence is also mounting that moderate fevers have their benefits, which might explain why the fever process is so widespread. Leukocytes, white blood cells that are active in fighting bacterial infections, are more mobile at febrile temperatures. And fevers reduce the amount of iron available to bacteria. That reduction, combined with high temperatures, has been shown to inhibit bacterial growth.
Which of the following best states the main idea of the passage？
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Which of the following statements is true？
A project manager believes that modifying the scope of the project may provide added value
The subject of paragraph is ______.
Why Humans Walk on Two Legs
A team of scientists that studied chimpanzees (黑猩猩) trained to use treadmills(跑步机) has gathered new evidence suggesting that our earliest apelike ancestors started walking on two legs because it required less energy than getting around on all fours.
Michael Sockol, researcher of UC Davis, worked for two years to find an animal trainer willing to coax (劝诱) adult chimps to walk on two legs and to walk on ail fours.
The five chimps also wore face masks used to help the researchers measure oxygen consumption. While the chimps worked out, the scientists collected data that allowed them to calculate which method of locomotion (移动) used less energy and why. The team gathered the same information for four adult humans walking on a treadmill.
The researchers found that human walking used about 75 percent less energy and burned 75 percent fewer calories than quadrupedal and bipedal walking in chimpanzees. They also found that for some but not all of the chimps, walking on two legs was no more costly than on all fours.
"We were prepared to find that all of the chimps used more energy walking on two legs -but that finding wouldn't have been as interesting," Sockol said. "What we found was much more telling. For three chimps, bipedalism was more expensive, but for the other two chimps, this wasn't the case. One spent about the same energy walking on two legs as on all fours. The other used less energy walking upright." These two chimps had different gaits (步法) and anatomy (解剖) than their quadrupedal peers.
Taken together, the findings provide support for the hypothesis that anatomical (解剖学的) differences affecting gait existed among our earliest apelike ancestors, and that these differences provided the geneticvariation which natural selection could act on when changes in the environment gave bipeds an advantage over quadrupeds.
Fossil and molecular evidence suggests the earliest ancestors of the human family lived in forested areas in equatorial Africa in the late Miocene era (中世纪) some 8 to 10 million years ago, when changes in climate may have increased the distance between food patches. That would have forced our earliest ancestors to travel longer distances on the ground and favored those who could cover more ground using less energy.
"This isn't the complete answer," Sockol said. "But it's a good piece of a puzzle humans have always wondered about: How and why did we become human？ And why do we alone walk on two legs？"
Michael Sockol and his team were interested in
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