懂你英语笔记L4U2
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L4——U2——1/4listening
Earthformsandextinction
A
1.Theearthwasformedaboutfourpointsixbillion(46亿)yearsago.
2.Thefirstlifeappearedaboutabillion(10亿)yearslater.
3.Thefirstplant-like didn’tappearuntilaround twobillion(20亿)yearsago.
4.Untilaboutfivehundredeightymillion(五亿八千
万)yearsagolifeformsweresmallandmicroscopic(极小的，微小的).
5.Sincethattime,lifehasevolved(进化)intomanydifferenttypesorspecies.
6.Howeverscientistsestimate(估计)thatmorethanninetyninepercent（99%）
ofthemarenowextinct(灭绝的).
B
1.Therehavebeenseveralextinction(绝种)eventsinthehistoryoftheearth.
2.Inanextinctioneventsmanylifeformsorspeciesoflifedieout.
3.Thecausesofmassextinctioneventsareunsolvedmysteries(未解之谜).
4.Theseeventsarenotpredictable(预告)andcanhappenatanytime.
5.Scientiststhinkthatsomeofthemwerestartedbyasteroidimpacts(影响，碰击或者装
机)orvolcaniceruptions(火山爆发).
6.Eventslikethis,canchangetheglobalconditionsthatlifedependson.
C
1.Onemajorextinctioneventhappenedaboutsixty-sixmillion(6600万)yearsago.
2.Thateventmayhavebeenstartedbyalargeasteroidthathittheearth.
3.Asaresult,thedinosaursandabouthalfofallspecies(物种，种类，类型)ontheplanetdieout.
4.Whentheasteroidshittheearth,itstartedachainofevents.
5.Achainofeventsisaseriesofeventslinkedtogetherlikeachain.
D
1.Thisparticularchainofeventshappenedoveraperiodofmonthsandyears.
2.Whentheasteroidhittheearth,itcausedahugecloudofdusttoentertheatmosphere.
3.ThiscloudofdustblockedtheSunanddarkenedtheEarthformanymonths.
4.Withoutenoughsunlight,plantsandplant-eatinganimalsquicklydied.
5.Withthedeathsofsomanyplantsandanimals,thefoodchaincollapsed.
6.Thisledtothedeathsofmanymorespecies.
E
1.Massextinctioneventshaveplayedanimportantpartintheevolution(演变，发生，进化
论)oflife.
2.Infact,someextinctioneventshavehelpedtoaccelerate(加快，加速)evolution.
3.Forexample,somemammals(哺乳动
物
4.
5.
6.
1.灭
绝
2.
3.
4.
的
5.
1.
2.
3.Asaresult,sealevelsarerisingandweatherpatterns(气候模式)arechanging.
4.Inaddition(另外),wehumansaredestroyingthehabitats(动物的栖息
地)ofmanyplantsandanimals.
5.Cuttingdownforestsandpollutingriversdestroythehabitatsofmanyformsoflife.
H
1.Thereisnolongeranydoubtthatthisishappening.
2.Species(物种，类型)oflifearedisappearingatanincreasingrate.
3.Globaltemperaturesarerisingandweatherpatternsarechanging.
4.Scientistsarewarningusthatfastactionisnecessarytosaveourfuture.