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 what researchers such as Ransom Myers and Boris Worm have shown is just how fast things are changing. They have looked at half a century of data from fisheries around the world. Their methods de 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, 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 to 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 form 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 de business.

1、The extinction of large prehistoric animals is noted to suggest that
A、 large animal were vulnerable to 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

2、who can infer form 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 fisherish than in the old

3、By saying these figures are conservative (line in ,paragragf-3), Dr worm means that
A、 fishing technology has improved rapidly
B、 then catch-sizes are actually smaller then recorded
C、 the marine bio mass has suffered a greater loss
D、 the date collected so far are pit pf date.

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 restored its original level.
D、people should adjust the fishing baseline to changing situation.

5、The author seems to be mainly concerned with most fisheries'
A、 management efficiency
B、 biomass level
C、 catch-size limits
D、 technological application

Passage 3

〔背景介绍〕

文章类型：自然科学，生态学

从文章分类上来说是一个自然科学关于生态方面的文章，这是今年四篇文章中唯一的一篇自然科学的问题。讲述了一个很简单的现象--渔业过渡捕捞会导致鱼群大量衰减。

〔结构分析〕

第一段还是用常见的类比方法，作为一个引子为了引出第二段的文章主题。

第二、三段用具体的数据说明当前的问题--鱼群数量在锐减。

第四段给我们提出建议，应该转换基线，关注biomass level。

〔题目解析〕

1. [C] 细节事实题

这种题型近两年每年必考，就是问引子的作用。第一段讲到了历史上的一个情况，就是说当史前人类到达一个新世界的地方，对于大型动物有一个很奇怪的事情就发生了，就是这些大型动物很快就灭绝，小动物会生存下来。按理说应该是小动物首先灭绝，因为它抵御风险的能力高一些。为什么大动物首先灭绝呢？后面又讲到了，大动物是很容易被人捕捉到的。其实是用这样的情况类比在海洋渔业中发生的情况。海洋渔业中我们人类首先捕的是大鱼，所以大鱼灭绝速度也要快一些。因此A和B选项属于以事论事肯定错误；D选项属于一种无中生有的比较；C选项大型海洋类动物今天也面临相同的威胁是同义替换。考生们一定要记住，引子不是为了说明引子，是为了引出文章主题的，也就是为了说明主题的。

2. [A] 推理题

首先从题干定位到原文的第二段。在论文中里，这两个博士提到了新的渔场在开始开发15年之内鱼的数量平均下降了80%。在某些长期捕捞的渔场里，鱼的数量自从那个时候，又下降了一半。意思就是说原来只剩20%了，现在再下降一半，那就是说有些长期捕捞的渔场的数量下降了90%。A选项大型的食肉鱼类的数量在某些渔场减少了90%是同义替换。B选项今天渔场的数量是15年的一半这是文中未提及的信息；C选项在新的渔场捕鱼的数量只是原先的20%，文中没有讨论过捕鱼数量，而是讨论的海洋中鱼的数量，这还是偷换概念；D选项属于一种无中生有的比较，文中没有就新旧渔场进行过比较。

3. [C] 细节事实题

根据题干定位到原文第三段，前文中讲现在大型食肉鱼类数量在锐减，紧接着在说这个数据还是有保留性的，后文继续论述因为今天的科技远比50年前的先进（即说明今天探明的数量是更精确的，而50年的探明的数量只是真正数量其中一部分，换而言之，实际减少的数量要比我们统计的数据还要多）。因此C选项为同义替换。选项A"捕鱼技术飞速发展"和选项B"实际捕鱼数量比统计的要少"都是文中未提及的信息；选项D"收集的数据只是部分数据"与原文相反，今天的数据应该是相当精确的。

4. [D] 细节事实题

选项A"should look for a baseline"与末段首句矛盾，文中说他们已经给出了一个正确的基线，因此不需要再去寻找了；选项B"低于50%"与原文倒数两句话明显相反；选项C"海洋生物数量应该恢复到原始阶段"是文中未提及的信息，而且与文中的50%也不匹配。选项D"人们应该根据不断变化的情况来调整捕渔业的基线"是原文末段第二句"shifting baseline"的同义替换。

5. [B] 主旨题

这还是一道篇章性的问题，这篇文章从第二段开始都是围绕(单位面积或体积内)生物的数量来展开讨论的，当然是选择B。选项A"高效的管理"；选项C"捕鱼数量的限制"和选项D"运用科技"都是文中未提及的信息。