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
The concept of biodiversity encompasses several different levels of biological organization, from the very specific to the most
The concept of biodiversity encompasses several different levels of biological organization, from the very specific to the most
admin
2013-01-12
77
问题
The concept of biodiversity encompasses several different levels of biological organization, from the very specific to the most general. It has been clear for some time that at all of these levels of organization the rich biodiversity that has always characterized the natural world is today declining. The extinctions or threatened extinctions of many species are but the most visible and well- known manifestation of a deeper and more far-reaching trend.
Changes in how the land is used are probably the principal contributor to the current decline in biodiversity. The pressures on terrestrial resources and land depend very much on population growth and the demands of early stages of economic development. Moreover, land acquisition, especially. for agriculture and forestry, focuses initially on those areas with the most fertile soils and equable climates, which are often the areas of greatest biological diversity. Deforestation in the humid tropics is probably the best-known current example of rapid land-use change.
During the decade of the 1970s, vast areas of tropical forest in South America, Africa, and South-east Asia were cleared and converted to agriculture and other uses. In the middle-to-late 1980s, the rates of deforestation in South America slowed dramatically, largely due to economic and tax policy changes in Brazil, but the pace of cutting in Africa and Southeast Asia, though poorly quantified, remains high.
Globally, the rate of loss of tropical forests for the 1980s has been estimated at about I percent per year, but there is still considerable uncertainty. The rates of extinction of local species that accompany these rapid changes in land cover may soon be far in excess of what is found today, reaching as high as 10, 000 times the natural background rate. Analyses of potential impacts on biodiversity that are based on simple measures of deforested area can provide little more than very general conclusions. Heavy applications of fertilizers and pesticides have the potential of creating additional environmental problems as well as affecting the abundance and viability of the other plants and animals and micro-organisms in the same or adjoining areas.
In addition, because of the understandable tendency to put the best land into production first, the expansion of agriculture into less fertile areas typically requires heavier applications of chemicals, more extensive site preparation, and other forms of more intensive management. The typical result is increased chemical runoff to the landscape, and with ensuing degradation, additional pressure for expansion, and the like. It is such a cycle that has led to widespread desertification in some parts of the world, primarily through overgrazing that can be compounded by naturally occurring droughts.
In discussing the diminishing biodiversity, the author’s argument is based mainly on ______
选项
A、the correlations between biodiversity and land features.
B、the distinction between specific instances and generalizations.
C、the correspondence of deforestation to land exploitation.
D、the separation of endangered species into many sub-groups.
答案
A
解析
题干问:“在讨论不断减少的物种多样性时,作者的论点主要根据的是……”。此题可以定位在第2自然段,作者在第2自然段作出一个假设,就是第2段第2句所提出的物种多样性和它密切相关的应该是土壤,土地表面所有的特征,因此选项A“多样性和土地特征之间的相互关系”为正确选项。而选项B、C、D都不是作者所主要使用的一种写作策略或论点的根据。
转载请注明原文地址:https://www.kaotiyun.com/show/0w9O777K
0
考博英语
相关试题推荐
Inthelongrunagovernmentwillalwaysencroachuponfreedomtotheextenttowhichithasthepowertodoso.Thisisalmost
71.TheinternationalsoftwaremarketrepresentsasignificantbusinessopportunityforU.S.microcomputersoftwarecompanies,b
Weregardhimas______toourcausebecauseheacceptedalloursuggestionswithouthesitation.
Thereisnodenyingthatstudentsshouldlearnsomethingabouthowcomputerswork,justasweexpectthematleasttounderstand
Theargumentbetweenthetwoboysbecamesofiercethatfatherhadto______andtellthemtobehave.
Ourresearchhasnotshownusanythingsofar,sothereislittle______tocontinuewithit.
Inproposing(suchphilanthropicdonations),thedirectorofthecompanycertainlyspoke(from)agenuineconcern(fortheneedy
Thechairmanoftheboard______onmetheunpleasantjobofdismissinggoodworkersthefirmcannolongeraffordtoemploy.
TheSecondHagueDisarmamentConferenceof1907wasmarkedmorebydiscordthandiscourse,asignofthedeterioratingworldsit
Accordingtotheweatherforecast,whichisusually______,itwillsnowthisafternoon.
随机试题
药用部位为干燥块根的药材有
根据《素问·生气通天论》饮食偏嗜伤及五脏的论述,味过于苦则
可导致肾病综合征的疾病不包括
A.思维贫乏B.思维散漫C.思维迟缓D.思维被夺取E.思维被插入病人对医师的问题只能在表面上产生反应,缺乏进一步的联想,该症状为
中央银行的再贴现率的变动成了货币当局给银行界和公众的重要信号,()。
如果要在美国市场上筹集资本,则必须采用一级ADR。( )
甲股份有限公司委托乙证券公司发行普通股,股票面值总额4000万元,发行总额16000万元,发行费按发行总额的2%计算(不考虑其他因素),股票发行净收入全部收到。甲股份有限公司该笔业务记入“资本公积”科目的金额为()万元。
病理性遗忘的种类包括()遗忘。
“零容忍、零界限、零死角”的反腐风暴,导演了一场场“官场现形记”,让贪官闻风丧胆、如坐针毡,甚至“以死谢罪”,反腐倡廉取得了前所未有的成果。然而,在光鲜的“成绩单"背后,公款吃喝从地上转入地下、从餐厅转入食堂,止不住的“食欲”背后是无法满足的“贪欲”。干部
Amtrak—thelargestrailwaycompanyintheU.S.—wasexperiencingadownswinginridership.【B1】______majorconcernstoAmtrakand
最新回复
(
0
)