题目内容
C
★★★★★
Elephants have strong defenses against cancer that can prevent it forming,say scientists. They were trying to explain why the animals have lower levels of cancer than would be expected considering their size.
People think that every cell can become cancerous,so the more of them you have,the more likely you are to get cancer. So if an elephant has 100 times as many cells as a person,then it should be 100 times more likely to have the disease. And yet the analysis showed only 5% of elephants die from cancer compared to up to 25% of people.
The scientists turned to elephants’ DNA. Cancer is caused by mutations (变异) in a ceir s DNA that produce faulty instructions leading to (遏制不住的) growth. But animals also have “smoke alarms” that detect the damage and lead to the cell being repaired or killed. One of these alarms is called TP53,and while humans have one TP53 gene,elephants have 20.As a result,elephants seem far keener to kill off cells.
But Mel Greaves,from the Institute of Cancer Research in London,said, “We should focus on why humans have such high levels of cancer. In terms of adaptive mechanisms (机制) against cancer we have the same as chimps,but a lot more humans get cancer than chimps. I think the answer is that humans are completely unique as a species in having very rapid social evolution (进化) in a short period of time." He pointed to the rise of unhealthy,cancer-causing behavior,such as obesity and sunbathing. “You’ve never seen an elephant smoke!” he added.
In an evolutionary sense, “success” is judged by the number of kids you have rather than how long you live. Elephants have the greatest reproductive success towards the end of their lives,while humans can live for decades after we are no longer able to getting pregnant. It means there is little evolutionary pressure in humans to develop ways of preventing cancer in old age.
9. What is the text mainly about? ,
A. When elephants will get ill.
B. How elephants live a long life.
C. What elephants do when having cancer.
D. Why elephants have slight chances of getting cancer.
10. Why are elephants keener to kill off cells compared with humans?
A. They are larger in size.
B. They have a unique alarm.
C. They have more TP53 genes.
D. They have healthier eating habits.
11. In the eyes of Greaves, .
A. chimps get more cancer than humans
B. humans* unhealthy behavior increases cancer risk
C. chimps have better adaptive mechanisms than humans
D. elephants have more rapid social evolution than chimps
12. When elephants become old,they will .
A. fall into bad habits
B. suffer from various diseases
C. go on producing baby elephants
D. have less evolutionary pressure
C篇
研究发现,体型庞大的大象很少受到癌症的困扰。
9. D.主旨大意题。从全文整体看,本文分析了大象 为什么很少受到癌症困扰的原因,故选D项。
10. C.推理判断题。根据第三段中的one of these alarms is called TP53 …elephants have 20. As a result,elephants seem far keener to kill off cells bI 知,与人类相比大象体内有更多的TP53.所以对杀死细胞更灵敏。
11. B.推理判断题。根据第四段中的内容可知,人类的不良生活习惯是引起癌症多发的因素之一。
12. C.细节理解题。根据最后一段中的ElePhants have the greatest reproductive success towards the end of their lives可知,大象即使年迈后仍会生育小象。