When prehistoric man arrived in new parts of the world, something strong happene

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When prehistoric man arrived in new parts of the world, something strong happened to the large animals; they suddenly became extinct. Smaller species survived; the large, slow-growing animals were easy game, and were quickly hunted to extinction. 
Now something similar could be happening in the oceans. That the seas are being over-fished has been known for years and researchers such as Ransom Myers and Boris Worm have shown how fast things are changing. They have looked at half a century of data from fisheries around the world. Their methods do not attempt to estimate the actual biomass (the amount of living biological matter) of fish species in particular parts of the ocean, but rather changes in that biomass over time. According to their latest paper published in Nature, the biomass of large predators (animals that kill and eat other animals) inanes fishery is reduced on average by 80% within 15 years of the start of exploitation. In some long-fished areas, it has halved again since then.
Dr. Worm acknowledges that these figures are conservative (保守的). One reason for this is that fishing technology has improved. Today’s vessels can find their prey using satellites and sonar, which were not available 50 years ago. That means a higher proportion of what is in the sea is being caught, so the real difference between present and past is likely to be worse than the one recorded by changes in catch sizes. In the early days, too, longlines would have been more saturated with fish. Some individuals would therefore not have been caught, since baited hooks would have been available to trap them, leading to an underestimate of fish stocks in the past. Furthermore, in the early days of longline fishing, a lot of fish were lost to sharks after they had been hooked. That is no longer a problem, because there are fewer sharks around noise.
Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account. They believe the date support an idea current among marine biologists, that of the “shifting baseline”. The notion is that people have failed to detect the massive changes which have happened in the ocean because they have been looking back only a relatively short time into the past. That matters because theory suggests that the maximum sustainable yield that can be cropped from a fishery comes when the biomass of a target species is about 50% of its original levels. Most fisheries are well below that, which is a bad way to do business.
小题1:The aim of the extinction of large prehistoric animals is to suggest that _______.

A．large animal were not easy to survive in the changing environment

B．small species survived as large animals disappeared

C．large sea animals may face the same threat today.

D．Slow-growing fish outlive fast-growing ones

小题2:We can infer from Dr Myers and Dr. Worm’s paper that _______.

A．the stock of large predators in some old fisheries has reduced by 90%

B．there are only half as many fisheries are there were 15 years ago

C．the catch sizes in new fisheries are only 20% of the original amount

D．the number of larger predators dropped faster in new fisheries than in the old

小题3:By saying these figures are conservative (line 1, paragraph 3), Dr worm means that_______.

A．fishing technology has improved rapidly

B．then catch-sizes are actually smaller then recorded

C．the marine biomass has suffered a greater loss

D．the date collected so far are out of date.

小题4:Dr Myers and other researchers hold that _______.

A．people should look for a baseline that can’t work for a longer time

B．fisheries should keep the yield below 50% of the biomass

C．the ocean biomass should restore its original level.

D．people should adjust the fishing baseline to changing situation.

小题5:The author seems to be mainly concerned with most fisheries’ _______.

A．management efficiency

B．biomass level

C．catch-size limits

D．technological application.

答案

小题1:C
小题2:A
小题3:C
小题4:D
小题5:B

解析

试题分析：文章讲述了研究人员现在指出海洋中由于过度捕捞，鱼类正在减少，说明了鱼类正在减少原因及呼吁改变捕鱼的底线来改变现在的状况。
小题1:推断题。从文章第一自然段和第二自然段的描写中，我们可知大型史前动物的灭绝的目的是为了表明如今海洋中的大型生物可能也同样遭受着威胁，故选C
小题2:推断题。从文章the biomass of large predators (animals that kill and eat other animals) inanes fishery is reduced on average by 80% within 15 years of the start of exploitation. In some long-fished areas, it has halved again since then. 可知，在一些老的渔场，大型捕食动物的储藏量已经减少了90%，文章提到的是平均80%，所以可知A正确。
小题3:细节题。从文One reason for this is that fishing technology has improved.Today’s vessels can find their prey using satellites and sonar,可知，这些数字之所以是保守估计，是因为现代科学技术的进步，给捕鱼带来带来了方便，海洋生物已经遭受了更大的破坏，故选C
小题4:推断题。从文章Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account. 及最后可知，现在绝大多数的渔场的鱼的数量只是以前的一半，甚至更少，所以人们应该调整捕鱼的基线来改变现在状态，故选D
小题5:推断题。文章整个文段都在围绕"海洋生物总量"这个话题展开的，文中多次出现了"biomass"这个词，故选B
点评：本文较难，取自于2006年考研的题目。对于此类科普类文章对于学生来说，很难把握作者写作的主要意图和言外之意。那么在解答的过程中就必须结合题目中的选项，仔细的来推敲文章所表达的意思，对于一下子无法解决的问题，可以待所有题目解答完后，再来仔细的作答。