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
69
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://kaotiyun.com/show/rO8O777K
0
托福(TOEFL)
相关试题推荐
TheDevelopmentofMuseumsATheconvictionthathistoricalrelicsprovideinfallibletestimony
ReadthetextbelowandanswerQuestions1-7.ClearLightingUseenergymoreefficientlyan
Completethesummaryusingthelistofwords/phrases,A-l,below.ProblemsforpreschoolusersofvideogamesPr
Whatpercentageofthestudentsaremature?Theuniversityaccommodationservicesofficeisinthe______.
Onewalkincludesabreakattheoldestpubsothatthewalkerscangetsome______.
easternAtlantic
ProductionofRiceRicegivesmore(35)perhectarethanothercerealcropsandproductionhasincreasedover100%inrec
A、Incaves.B、Ontheoceanfloor.C、FarbelowtheEarth’scrustD、Insidearchaean.BAccording?to?the?woman,?where?are?the?hydrot
A、Theyareoftenhandledimproperlybyreaders.B、Thepaperisdestroyedbychemicals.C、Theinkusedinprintingdamagesthepa
AMessengerfromthePastHispeoplesaidgood-byeandwatchedhimwalkofftowardthemountains.Theyhadlittlereasonto
随机试题
A.红霉素B.罗红霉素C.克拉霉素D.克林霉素E.四环素不耐酸,口服剂型多制成酯化物的是
下列表现属于瘀血发热的有
A、胶体溶液B、微乳C、真溶液D、混悬液E、乳浊液粒径为0.1~100μm()
下列关于噻嗪类利尿药的降压机制,说法不正确的是
下列对建设工程归档文件的要求中,属于质量要求的有()。
资料一:甲有限责任公司是一家成立时间较长,大型的建筑工程公司,有在海外承揽大型工程的丰富经验。目前,该公司打算开拓南美市场,但经过分析后,拟进入的A国政局不稳,并且国内经济恶化,通货膨胀率十分严重,而且政变后新上台的军政府不承认前任政府签署的所有相关协议,
计算机软件一般包括系统软件和()。
前些年翻看先生的这本书时,尽管自己对民国话题有着欲说还休的浓厚兴趣,对这本话语剪辑独出心裁的编排方式下潜藏的_________常常默契会心,但读完仍是感到_________。依次填入画横线部分最恰当的一项是()。
设η1,η2,η3,η4是齐次线性方程组Ax=0的基础解系,则Ax=0的基础解系还可以是[].
《保险法》规定,保险业和银行业、证券业实行混业经营。()
最新回复
(
0
)