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
外语
All along me chain of biological evolution, the extinction of species appears to have been a stage in the process of adapting ge
All along me chain of biological evolution, the extinction of species appears to have been a stage in the process of adapting ge
admin
2010-02-20
38
问题
All along me chain of biological evolution, the extinction of species appears to have been a stage in the process of adapting genetic lineages to changing environmental conditions. Although some catestrophic extinction occurred naturally, producing total loss of a genetic line, such catastrophes were comparatively rate. In modern times, however, human activities have altered the fundamental nature of this process, resulting in nearly total genetic losses.
It is not difficult to gain general agreement that man -induced increases in the endangerment and extinction of wildlife whether due to habitat alteration or loss, pollution, insufficiently regulated hunting, or other factors are undesirable. It is, however, more difficult to obtain consensus when consideration is given to the economic costs of correcting such trends, including natural habitat preservation, regulation of pesticides and other toxic substances, and wildlife and park management. Endangered species often are, in effect, competitors with humans for habitat and other resources which also provide other kinds of human use and need.
Measures needed to protect endangered species vary considerably in difficulty and cost. Of the approximately 400 inverterate species which at present appear to be threatened, for example, about one third could probably be restored by such inexpensive means as modifying the boundaries of designated natural are as, acquiring and protecting caves and other small areas which contain the particular species, and additional management ’of parks and refuges.
Another one - third of the endangered lower animal species are threatened principally by water pollution and could be protected by improved control, particularly of five southern rivers.
The remaining one - third of the 400 endangered shellfish species would be considerably more difficult to protect. These are threatened by complex factors, such as overcollecting, channelization, highway and housing development, clams introduced species such as the Asian snail, dredging, quarry washing, poor erosion control, and lowering of water table.
The identification of threatened species and other significant wildlife trends must precede any corrective measures, and our knowledge base for making such identification is deficient in many respects. Our present lists of threatened species and subspecies are known to be incomplete, except in those geographical areas which contain habitats of species that have important commercial or sports harvest value.
It can be inferred from the passage that studies of endangered species ______.
选项
A、have revealed little of importance to improve wildlife preservation
B、are more likely to be carded out when a financially concerned interest group is involved
C、sometimes endanger the very species they hope to protect
D、show that endangered species can never be saved except at great cost
答案
B
解析
文章最后一句表明由于商业或捕猎的原因,这些地方的某些物种即全部灭绝,在其它地方情况则会好一些,这种对比表明这些研究要不是对一部分人有收益,就不会展开。
转载请注明原文地址:https://kaotiyun.com/show/hMvO777K
0
专业英语八级
相关试题推荐
Democracyissomuchapartofournationalidentitythatitalmostseemsabirthright.Buttheironyisthat,evenaswehopet
Whenprehistoricmanarrivedinnewpartsoftheworld,somethingstrangehappenedtothelargeanimals:theysuddenlybecameex
A、Hewasattendingaweddingceremony.B、HewasonhiswaytoEdinburgh.C、Hewasinthefootballstadium.D、Hewasinthecinem
A、Thepricefortheroomismorethanheexpected.B、Roomsareoverbookedforthatevening.C、Therearenomoreroomsavailable
TheWelshlanguagehasalwaysbeentheultimatemarkerofWelshidentity,butagenerationagoitlookedasifWelshwouldgoth
A、Ibarelyhadenoughtimetofinishmypaper.B、Ididn’thearthephonebecauseIwastyping.C、SomeonecalledjustasIstarte
A、Thediseaseisnowspreadingfrompatientstodoctors.B、10%ofAfricansareHIVpositive.C、Thediseasehasspreadveryfast
Theappealofhydrogenfuelcellshaslongbeenobvious.Becausethesedevicesuseelectrochemicalreactionstogenerateelectri
Inthesummerof2010,record-hightemperatureshitMoscow.Atfirstitwasjustanother【C1】______butthescorchingheatthats
随机试题
在对市场营销成本进行分析之后,还应该考察以下几个反映企业盈利能力的指标:
某公路工程路线长2.192km,其中软土地基路段约400m,填土高度平均4.5m,位于冲积平原,地层厚度均匀,层位稳定,地层主要由第四系新近沉积的淤质土和第四系下更新统的灰、杂色粘土和砂层构成。其层次由上至下分别为粘土(硬壳层)、淤泥质粉质粘土、粉质粘土、
当前在建设工程管理领域中信息化的重要标志是()。
因故不能按时开工的,应当向发证机关申请延期,延期以()为限。
根据物权法律制度的规定,下列各项中,不属于物权的原始取得的是()。
以下情形中,可以申请个人住房贷款的是()。
实行内部成本核算的事业单位,购入无形资产发生的支出,应在受益期内分期平均摊销。()
简述我国实行既统一又分层的立法体制的原因。
历代文人墨客对西湖吟诗赋词。因此,西湖为后人留下了底蕴丰厚的文学资源。以下哪个诗句是描写西湖的?()
ThemainpurposeofEnglishessaywritingistointroduceyoutotheconventionsofacademicwritingandcriticalthinking.
最新回复
(
0
)