托福作文寫作范文詳解dvers

托福作文寫作范文詳解ReadingGeneticmodification,aprocessusedtochangeanorganism’sgenesandhenceitscharacteristics,isnowbeingusedtoimprovetreesthroughgeneticmodification.Itispossibletocreatetreesthatproducemorefruit,growfaster,orwithstandadverseconditions.Plantinggeneticallymodifiedtreesonalargescalepromisestobringanumberofbenefits.First,geneticallymodifiedtreesaredesignedtobeharderthannaturetrees;thatis,theyaremorelikelytosurvivethantheirunmodifiedcounterparts.InHawaii,forexample,anewpest‐resistantspeciesofpapayatreeshasbeendevelopedinresponsetoringspotvirusinfectionsthathaverepeatedlydamagedthenativepapayatreepopulation.Plantingthegeneticallymodifiedpapayashaslargelyputanendtotheringspotproblem.Moreover,geneticallymodifiedtreespromisetobringanumberofeconomicbenefitstothosewhogrowthem.Geneticallymodifiedtreestendtogrowfaster,givegreateryieldsoffood,fruit,orotherproductsandbehardier.Thisallowstreefarmertogetfasterandgreaterreturnsontheirfarminginvestmentandsaveonpesticidesaswell.Finally,theuseofgeneticallymodifiedtreescanpreventoverexploitationofwildtrees.Becauseofthegrowingdemandforfirewoodandbuildingtimber,manyforestsaroundtheworldarebeingcutdownfasterthantheycanbereplaced.Introducinggeneticallymodifiedtrees,designedforfastgrowthandhighyieldingivengeographicconditions,wouldsatisfythedemandforwoodinmanyofthoseareasandsavetheendangerednativetrees,whichoftenincludeuniqueorrarespecies.ListeningSure,therearesomebenefitstoplantgeneticallymodifiedtrees,but,arethesetreesasreallygreatastheyfirstsound?Whenyouexaminethesubjectfirstly,therearesomeseriousproblemsandcostsassociatedwithgeneticallymodifiedtrees.First,geneticallymodifiedtreesmayberesistanttooneparticularcondition.Butthatdoesn’tnecessarilyensuretheirsurvival.Yousee,atypicalnonmodifiedtrees’populationisgeneticallydiverse.Thatmeansthatformostthreateningconditions,orclimate,whatever,therewillbeatleastsomeindividualtressofanygivenspeciesoftreethatareresistant.Soevenifmostofonekindoftreesarekilled,thosefewresistanttresswillsurviveandensurethesurvivalofthatspeciesoftree.Butgeneticallymodifiedtreesaregeneticallymuchmoreuniform.Soifthey’reexposedtoanenvironmentalchallengetheyhavenotbeendesignedfor,theyalldie.Soiftheclimatechanges,thegeneticallymodifiedtreeswilllikelytobecompletelywipedout.Nowastothesecondpoint,they’rehiddencostsassociatedwithgeneticallymodifiedtrees.Yousee,thecompanythatgeneticallymodifythetreecanchargetreefarmersmoreforitsseedsthanun‐geneticallymodifiedtreeswouldcost.Also,asyou’vegrownthetree,youcan’tjustcollecttheseedsandplantthenewtreeforfree.Bylaw,youhavetopaythecompanyeverytimeyouplant.Andfinally,geneticallymodifiedtreesmightactuallycauseevenmoredamagetothelocalwildtrees.Yousee,geneticallymodifiedtreesoftengrowmoreaggressivelythannaturaltreesdo.And,geneticallymodifiedtreesaretypicallyplantedamongnaturaltrees.Asaresult,thegeneticallymodifiedtreesoutcompetethenativetreesforresources,sunlight,soil,nutrients,andwater,eventuallycrowdingoutthenaturaltrees.一、閱讀聽力要點概括ReadingPassageMainpoints:Geneticmodificationonlargescalewillbringbenefits.Subpoint1:Canbecompletelywipedoutbycertainenvironment.Subpoint2:Modifiedtreesareeconomicallybetter.Subpoint3:Modifiedtreesgrowfastandsavewildtrees.LectureAttitude:Against.(Seriousproblemandassociatedcost.)SubPoint1:Thereareeffectivewaystostopmusselsintoday’sknowledgeSubPoint2:Hiddencostsassociatedlikeseeds.SubPoint3:Domoredamagetowildtrees.Growsofastandoutcompetethewildtree.二、范文逐段賞析Paragraph1Thelecturerpointsoutthreedifferentshortcomingsofgeneticallymodifiedtrees.Intheaspectsofadaptation,economiclucrativeness,andenvironmentalvalue,theyneverpresentoverwhelmingadvantagescomparedwithnaturaltrees.Thismeansthepointsmadeinthereadingarepartialandbiased.此段功能：(Listeningpassage后文提到用L代替)(Readingpassage后文用R代替)文章首先總結(jié)了三個分論點，十分新穎。三個分論點從三方面出發(fā)，環(huán)境適應性，經(jīng)濟有利性，環(huán)保價值性。然后寫到L告訴大家R在三個方面的觀點都是片面的，改造樹和野生樹在這三方面的比較并沒顯出絕對優(yōu)勢。確認了相反的邏輯關(guān)系，準備開始辯論。此段結(jié)構(gòu)：此段為分總結(jié)構(gòu)，列舉三個要討論的方面，然后才說L對R的意見，為接下來的辯論做好了充足的準備。Paragraph2First,geneticmodificationdoesn’tnecessarilymakeanaturaltreemoreresistanttoenvironmentaladversities.Althoughgeneticmodificationmayallowaspeciestomanifestcertainstrengthsinspecificconditions,asthereadingindicates,thenewtypelacksthegeneticdiversityofanaturalspecies.Thankstothemarginaldifferencesbetweenindividualtrees,therecanalwaysbesomesurvivorsamongnaturalspeciesfollowingalargeinterruptionlikeclimatechangeorpestinvasion.Butsuchchangesmaycausethedistinctionofageneticallymodifiedspeciesfortheirunificationincharacteristics,decreasingtheiroverallsurvivabilityinmanycases.此段功能：討論第一個環(huán)境適應性方面的論點。L指出改造樹并不一定在任何情況下都比野生樹更強壯。因為改造樹的基因非常單一，而不像野生樹一樣隨機分布。在新惡劣天氣情況下，改造樹可能因為沒有對抗基因而全部死亡，野生樹里卻千差萬別，相對應的個體樹會存活而不會導致與滅族。所以改造樹的整體存活率是不高的。此段結(jié)構(gòu)：此段為總分結(jié)構(gòu)，陳列證據(jù)十分對稱，Althoughbut句型很好的列舉了相對立的觀點和證據(jù)。最后證明R之前的論點不可取。Paragraph3Second,treefarmersdon’tgetguaranteedeconomicbenefitsiftheyplantgeneticallynewstrains.Companiesthatdevelopnewplantsalwayschargefarmershigherpricesforartificiallyimprovedseeds,andreceivemoneyfromfarmerseachtimefarmersgrowthatsameplant.Suchlawsandcompanypoliciescandeprivefarmersofanyeconomicgainmentionedinthereadingpassage.此段功能：第二個經(jīng)濟有利性的討論中。L的觀點是農(nóng)民使用改造樹不一定能有好收益。收益包括成本和產(chǎn)出，改造樹成本很高，而且公司會對農(nóng)民重復收費。這種政策使得R提到的產(chǎn)出高也沒有用。此段結(jié)構(gòu)：此段為總分結(jié)構(gòu)，L表明了自己觀點后，用了一大段證據(jù)支撐改造樹的成本高。從而到達了駁倒R的最后收益一定高的道理。Paragraph4Third,geneticallymodifiedtreesdon’tpromisetoprotectwildtrees.Infact,sincetheycangrowfasterwithfewerresources,theyaremoreecologicallyinvasivethannormaltrees.Normally,theyareabletooutpaceandstiflethegrowthofnaturaltreesbyusingtheavailablenaturalresourceslikesunshine,waterandsoil.It’sfarfromtheidealisticsituationdescribedinthereading.此段功能：最后，L說改造樹不一定能保護野生樹。因為改造樹由于生長快，所以侵略性強