高一英语必修三 UNIT 4课文详解(课堂PPT)

1,HOWLIFEBEGANONTHEEARTH,地球上生命的起源,UNIT4,课文讲解,2,1.Nooneknowsexactlyhowtheearthbegan,asithappenedsolongago.没有人确切知道地球是怎样开始形成的，因为在很早很早以前地球就形成了。2.However,accordingtoawidelyacceptedtheory,theuniversebeganwithaBigBangthatthrewmatterinalldirections.然而，一种普遍为人们所接受的理论是：宇宙起源于一次大爆炸，这次大爆炸将物质投射到四面八方。3.Afterthat,atomsbegantoformandcombinetocreatestarsandotherbodies.然后，原子开始形成并结合成恒星和其他天体。,Par1,3,4,5,6,1.ForseveralbillionyearsaftertheBigBang,theearthwasstilljustacloudofdust.大爆炸后好几十亿年过去了，但地球还只是一团尘埃。2.Whatitwastobecomewasuncertainuntilbetween4.5and3.8billionyearsagowhenthedustsettledintoasolidglobe.随后它会变成什么没人能知道，直到3845亿年前，这团尘埃才慢慢地形成一个固体的球状物。3.Theearthbecamesoviolentthatitwasnotclearwhethertheshapewouldlastornot.地球（开始）变得激烈动荡，不知道这个固体形状是否会继续存在下去。,Par2,7,8,9,4.Itexplodedloudlywithfireandrock.Theywereintimetoproducecarbon,nitrogen,watervapourandothergases,whichweretomaketheearthsatmosphere.它（地球）猛烈地爆炸喷出了烈火与岩石，最终产生了碳，氮气，水蒸气和其他多种气体，从而形成了地球的大气层。5.Whatisevenmoreimportantisthatastheearthcooleddown,waterbegantoappearonitssurface.更为重要的是，地球冷却了下来，地球的表面就开始出现了水。,10,11,12,1.WaterhadalsoappearedonotherplanetslikeMarsbut,unliketheearth,ithaddisappearedlater.在火星这些其他行星上都出现了水，但和地球不同的是，这些水后来都消失了。2.Itwasnotimmediatelyobviousthatwaterwastobefundamentaltothedevelopmentoflife.水对于生命的发展会起关键作用，这一点在当时并不明显。3.Whatmanyscientistsbelieveisthatthecontinuedpresenceofwaterallowedtheearthtodissolveharmfulgasesandacidsintotheoceansandseas.很多科学家相信，由于地球上长期有水存在，使得地球得以把有害气体和酸性物质溶解在海洋里。4.Thisproducedachainreaction,whichmadeitpossibleforlifetodevelop.这就产生了一系列的反应，使得生命就有可能开始发展了。,Par3,13,1.Manymillionsofyearslater,thefirstextremelysmallplantsbegantoappearonthesurfaceofthewater.好几百万年后，水的表面开始出现了极小的植物。2.Theymultipliedandfilledtheoceansandseaswithoxygen,whichencouragedthelaterdevelopmentofearlyshellfishandallsortsoffish.他们繁殖起来就使得海洋充满了氧气，这为早期的贝类及其他各种鱼类后来的进化创造了条件。3.Next,greenplantsbegantogrowonland.Theywerefollowedintimebylandanimals.接着，绿色植物开始出现在陆地上。4.Somewereinsects.Others,calledamphibians,wereabletoliveonlandaswellasinthewater.随后，陆地上出现了动物，其中有一些是昆虫，另外一些叫两栖动物，他们既能在陆上生活，也能在水里生存。,Par4,14,15,16,5.Laterwhentheplantsgrewintoforests,reptilesappearedforthefirsttime.后来，当植物长成了森林的时候，爬行动物首次出现了。6.Theyproducedyoungentirelybylayingeggs.他们一般是通过孵蛋而繁衍后代的。7.Afterthat,somehugeanimals,calleddinosaurs,developed.再后来一些叫做恐龙的巨型动物出现了。8.Theylaideggstooandexistedontheearthformorethan140millionyears.他们也生蛋，在地球上生存了一亿四千多万年。9.However,65millionyearsagotheageofthedinosaursended.然而，六千五百万年前，恐龙时代结束了。,17,18,10.Whytheysuddenlydisappearedstillremainsamystery.他们为什么会突然灭绝至今仍是个谜。11.Thisdisappearancemadepossibletheriseofmammalsontheearth.恐龙的灭绝使地球上哺乳动物的增多有了可能。12.Theseanimalsweredifferentfromalllifeformsinthepast,becausetheygavebirthtoyoungbabyanimalsandproducedmilktofeedthem.这些动物不同于以往所有的生物形态，因为他们能从体内生产出幼仔并给幼仔哺乳。,19,1.Finallyabout2.6millionyearsagosomesmallcleveranimals,nowwithhandsandfeet,appearedandspreadallovertheearth.最后，大约260万年前，一些小巧聪明，长着手脚的动物出现了，他们散布在地球的各个地方。2.Thustheyhave,intheirturn,becomethemostimportantanimalsontheplanet.于是，他们接着成为这个行星上最重要的动物。3.Buttheyarenotlookingaftertheearthverywell.然而，他们对地球却不怎么在意，,Par5,20,4.Theyareputtingtoomuchcarbondioxideintotheatmosphere,whichpreventsheatfromescapingfromtheearthintospace.他们把过多的二氧化碳释放到大气层中，这使得地球上的热不能释放到太空中去。5.Asaresultofthis,manyscientistsbelievetheearthmaybecometoohottoliveon.因此，许多科学家相信地球可能会变得太热而不适合生物生存。6.Sowhetherlifewillcontinueontheearthformillionsofyearstocomewilldependonwhetherthisproblemcanbesolved.所以，在未来的数百万年中，生命能否在地球上延续，取决于这个问题能否得到解决。,21,22,主语从句一个句子在复合句中充当主语叫主语从句。常用引导词：连接词：that(无词义)whetherThathewillcomeandhelpusiscertain.Whetherwestayornotmakesnodifference.连接代词:who(ever)whomwhat(ever)which(ever)whoseWhowillgototheenergyconferenceisnotimportant.连接副词：whenwherehowwhyWhenandwherethetestwillbegivenisnotdecided.,23,1.引导主语从句的连词是不能省略的。Thattheearthisroundistrue2.That-从句作主语通常用it作先行词，而将that-从句置于句末，例如：Itistruethattheearthisround.结构：,Attention,24,a.It+be+形容词+that-从句Itisnecessarythat有必要Itisimportantthat重要的是Itisobviousthat很明显b.It+be+p.p.+that-从句Itisbelievedthat人们相信Itisknowntoallthat从所周知Ithasbeendecidedthat已决定,25,c.It+be+名词+that-从句Itiscommonknowledgethat是常识Itisasurprisethat令人惊奇的是Itisafactthat事实是d.It+不及物动词+that-分句Itappearsthat似乎Ithappensthat碰巧Itoccurredtomethat我突然想起,26,2.表示“是否”意义时，一般用whether而不用if引导主语从句，Whethershewillcomeornotisstillaquestion3.有时可用形式主语it代替主语从句：e.g.Itisstillaquestionwhethershewillcomeornot.Ithasnotbeendecidedyetwhentheywillstart.,27,4.无论主语从句有多长，一般做单数处理。e.g.Whenwewillstarthasnotbeendecidedyet.注意：以what开始的主语从句如果后面的表语是复数名词，系动词用复数形式。Whathewantstobuyarethreebooksandtwopens.,28,1.Itisobvioustothestudents_theyshouldgetwellpreparedfortheirfuture.A.asB.whichC.whetherD.that,2._wantstostayinahotelhastopaytheirownway.A.AnyoneB.TheoneC.WhoeverD.Who,练一练！,29,3.Itisnotimmediatelyclear_thefinancialcrisiswillsoonbeover.A.sinceB.whatC.whenD.whether,练一练！,30,_leavestheroomlastoughttoturnoffthelights.A.AnyoneB.ThepersonC.WhoeverD.Who_thesportsmeetwillbehelddependsontheweather.A.WheneverB.IfC.WhetherD.That,_isafactthatEnglishisbeingacceptedasaninternationallanguage.A.ThereB.ThisC.ThatD.It,31,宾语从句一个句子在复合句中充当宾语就叫宾语从句连接词：that(无词义)whetherife.g.Idontknowwhether(if)youarewillingtohelpme.连接代词：what(ever)who(ever)whosewhich(ever)等连接副词：whenwherehowwhy等,32,特别提示1.由连接词that引导宾语从句时，that在句中不担任任何成分。Imgladthatyouhavepassedtheexam.2.有些词或词组如hate,love,enjoy,dislike,feellike,appreciate,take(认为),relyon,dontmind等，习惯上后面跟it做形式宾语，再接宾语从句。Itakeitthatyouwillagreewithus.,33,3.在接复合宾语的句子中，为了保持句子平衡，用it作形式宾语，而将从句放在句尾。常带复合宾语的动词有：make/find/see/hear/feel/think等。IthinkitnecessarythatItakeplentyofwatereveryday.4.某些动词后的宾语从句常用虚拟语气，如insist，order，request，suggest等。Isuggestedthatwe(should)startbefore5oclock.,34,5.必须用whether引导，不可用if:1).从句后有ornot时，不可用if:Idontknowwhetherhewillcomeornot.2).介词宾语通常用whether引导:Itdependsonwhetherheiscomingornot.3).后接动词不定式时。Canyoutellmewhethertogoortostay?4).discuss后面的宾语从句解释为是否用whetherImagineyouareinthissituation,anddiscusswhetheryoushoulddosomethingatonce.,35,5)主语从句放在句首Whetherwestayornotmakesnodifference.6）表语从句和同位语从句Thequestioniswhetherwecangetthereontime.7)当it做形式主语whether/if都可引导主语从句Ithasntbeendecidedwhether/ifweshallattendthemeeting.,36,6.用who，whom,which(ever),whose,when,what(ever),where,why,how,whoever等关联词引导的宾语从句相当于特殊疑问句，应注意句子语序要用陈述语序。Doyouknowhowoldheis?Iwanttoknowwhathehastoldyou.Shealwaysthinksofhowshecanworkwell.Shewillgivewhoeverneedshelpawarmsupport.凡需要帮助的人，她都会给予热情的支持。,37,7.think,believe,imagine,suppose等动词引起的否定性宾语从句中，要把上述主句中的动词变为否定式。即将从句中的否定形式移到主句中。例如：Wedontthinkyouarehere.我们认为你不在这。Idontbelievehewilldoso.我相信他不会这样做。,38,如果主句主语为第一人称反意疑问句常与从句的主语和谓语保持一致；其他情况看主句。例如：IdontbelieveshehasbeentoAustralia,hasshe?我认为她没去澳大利亚，是吗？Idontbelievethathecantranslatethisbook,?Shethinksthatherhusbandisthebestoneintheteam,？,canhe,doesntshe,39,Idoubtif/whetherhewillpasstheexam.Idontdoubtthatwewillwinthematch.Doyoudoubtthathediditonhisown?,doubt问题,肯定句中用if/whether,否定句中用that,疑定句中用that,Idoubt_heistellingthetruth.Weneverdoubt_theplanwillbecarriedout.Doeshedoubt_youarefromAustria?Imdoubtful_hewillagreetothis.,if/whether,that,that,if/whether,40,宾语从句中的连接词that在以下三种情况下不能省略：（1）当that从句与另一名词性从句并列作宾语时，第二个that不能省；（2）当that作介词宾语时，that不可省掉。（3）用it做形式宾语的宾语从句Everyoneknewwhat