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
It is estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction?
It is estimated that over 99 percent of all species that ever existed have become extinct. What causes extinction?
admin
2004-12-30
40
问题
It is estimated that over 99 percent of all species that ever existed have become
extinct. What causes extinction? When a species is no longer adapted to a changed
environment, it may perish. The exact causes of a species’ death vary from situation .
to situation. Rapid ecological change may render an environment hostile to a species.
(5) For example, temperatures may change and a species may not be able to adapt. Food
Resources may be affected by environmental changes, which will then cause problems
For a species requiring these resources. Other species may become better adapted to an
Environment, resulting in competition and, ultimately, in the death of a species.
The fossil record reveals that extinction has occurred throughout the history of Earth.
(10) Recent analyses have also revealed that on some occasions many species became extinct
at the same time―a mass extinction. One of the best-known examples of mass extinction
occurred 65 million years ago with the demise of dinosaurs and many other forms of life.
Perhaps the largest mass extinction was the one that occurred 225 million years ago,
When approximately 95 percent of all species died, Mass extinctions can be caused by
(15) a relatively rapid change in the environment and can be worsened by the close
interrelationship of many species. If, for example, something were to happen to destroy
much of the plankton in the oceans, then the oxygen content of Earth would drop,
affection even organisms not living in the oceans. Such a change would probably lead to a
mass extinction.
(20) One interesting, and controversial, finding is that extinctions during the past 250
Million years have tended to be more intense every 26 million years. This periodic .
extinction might be due to intersection of the Earth’s orbit with a cloud of comets, but
this theory is purely speculative. Some researchers have also speculated tat extinction
may often be random. That is, certain species may be eliminated and others may survive
(25) for no particular reason. A species’ survival may have nothing to do with its ability or
inability to adapt. If so, some of evolutionary history may reflect a sequence of essentially
random events.
选项
A、environment
B、species
C、extinction
D、99 percent
答案
B
解析
转载请注明原文地址:https://jikaoti.com/ti/VYAYFFFM
0
托福(TOEFL)
相关试题推荐
Completethenotesbelow.ChooseONEWORDfromthepassageforeachanswer.Writeyouranswersinboxes7-13onyouranswershee
Whichtypeofwildlifebenefitsmostfromurbangardens?
InsidethemindoftheconsumerCouldbrain-scanningtechnologyprovideanaccuratewaytoassesstheappealof
Completethesummaryusingthelistofwords/phrases,A-l,below.ProblemsforpreschoolusersofvideogamesPr
TacklingHungerinMsekeniATherearenotenoughclassroomsattheMsekeniprimaryschool,sohalfthelessonstakeplaceinth
WealthinAColdClimateLatitudeiscrucialtoanation’seconomicstrength.ADrWilliamMasterswasreadingabookaboutmosq
Whatpercentageofthestudentsaremature?New-townisEngland’s______city.
【21】Mikathinksthatnon-nativespeakerscanimprove______.
WritetheappropriatelettersA-CagainstQuestions17-20.WhatarethelocationsofthefollowingplacesinRadford?(A)par
Choosethecorrectletter,A,BorC.ThetutorrecommendsagainsttakingHumanPhysiologybecauseitwouldnotbethebest
随机试题
可以妊娠的心脏病患者是
初产妇,足月妊娠,胎膜破裂24小时,胎儿手脱出于阴道口,胎心140次/分,宫口开全,下腹部脐耻之间出现一凹陷。最好的处理方法
行阴道冲洗时,患者的常见体位是
医学人道主义的核心内容不包括()
张某为甲合伙制房地产经纪机构(以下称甲机构)的注册房地产经纪人。王某因举家南迁将自己的住房委托甲机构销售。在甲机构授权下,张某与王某签订了房地产经纪服务合同,合同约定甲机构为王某提供订立房地产交易合同的机会和交易媒介服务,王某向甲机构支付佣金。张某接受业务
某旅游公司组织100人到北京旅游,每人收取旅游费5000元,由公司支付每人长城景点费100元、租车赍100元、故宫门票费60元、其他住宿、餐饮费用1000元,则旅游公司应纳营业税为()元。
“驴打滚”是名点()的又一称谓。
实现由理性认识向实践飞跃的条件有
标准ASCII码字符集共有多个编码?()
HowtoKeepFitTenyearsagoIusedtobeveryfit.IcycledtoworkandIdidalotofexerciseattheweekends.Iusedtopla
最新回复
(
0
)