首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
When prehistoric man arrived in new parts of the world, something strange happened to the large animals. They suddenly became ex
When prehistoric man arrived in new parts of the world, something strange happened to the large animals. They suddenly became ex
admin
2019-05-26
47
问题
When prehistoric man arrived in new parts of the world, something strange 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 overfished 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 do nut 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) in a new 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 the 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 no 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 now.
Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account. They believe the data 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.
选项
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
答案
C
解析
这是一道理解题。文章第一段就给出了题面,只要理解后面的文章,回答这道问题应该是比较容易的。后面的文章正是说明了大型动物的很快灭绝,正和以上说明的原因一样。
转载请注明原文地址:https://kaotiyun.com/show/qQnZ777K
0
考研英语一
相关试题推荐
AlthoughtherearemanyskillfulBraillereaders,thousandsofotherblindpeoplefinditdifficulttolearnthatsystem.Theya
Sevenyearsago,agroupoffemalescientistsattheMassachusettsInstituteofTechnologyproducedapieceofresearchwhichsh
Weoftentendtoassociatesmilingastheresultofapositiveeventormood.Butresearchdemonstratesthattheactofsmiling,
Havetherealwaysbeencities?Thetrendiscitiesareincreasinglybecomingthedominantmodeofman’ssocialexistence.【F1】It
Conversationsaboutelderlyparentsandtechnologyusuallycenteronsafety,inparticularondevicesdesignedtoalertacallc
Conversationsaboutelderlyparentsandtechnologyusuallycenteronsafety,inparticularondevicesdesignedtoalertacallc
Doyourememberallthoseyearswhenscientistsarguedthatsmokingwouldkillusbutthedoubtersinsistedthatwedidn’tknow
ThemostthoroughlystudiedintellectualsinthehistoryoftheNewWorldaretheministersandpoliticalleadersofseventeenth
ReadthefollowingtextandanswerthequestionsbychoosingthemostsuitablesubtitlefromthelistA-Gforeachnumberedpara
Intheold,daysparentsfollowedasimplerule:sparetherodandspoilthechild.Thesedayslessviolentformsofdiscipline
随机试题
女性,35岁,急性阑尾炎穿孔、阑尾切除术后第5天,发热、腹痛,腹泻每天3次,稀水便,腹壁切口未见明显红肿。最可能的并发症是
A.胸骨中段B.胸骨上1/3段C.胸骨下1/3段D.胸骨上1/2段E.胸骨下1/2段胸外按压的部位
治疗霍乱首选抗菌药物为( )。
下列哪味药长于清肺火及上焦实热
有关对城市道路工程冬期施工的说法中,正确的是()。
下列经济指标中,构成财务现金流量的基本要素的有()。
甲公司系增值税一般纳税人,采用公允价值模式计量投资性房地产。有关资料如下:资料一:2×18年12月1日甲公司与A公司签订协议,将自用的办公楼出租给A公司,租期为3年,每年不含税租金为1000万元,于每年年末收取,2×19年1月1日为租赁期开始日,2×2
从所给四个选项中,选择最合适的一个填入问号处,使之呈现一定的规律性:
监狱工作人员甲多次指使被关押的罪犯殴打其他被监管人,造成被殴打的人伤残。甲的行为构成()
Personalityistoalargeextentinherent——A-typeparentsusuallybringaboutA-typeoff-spring.Buttheenvironmentmustalsoh
最新回复
(
0
)