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1、托福作文写作范文详解ReadingThecanetoadisalarge(1.8kg)amphibianspeciesnativetoCentralandSouthAmerica.ItwasdeliberatelyintroducedtoAustraliain1935withtheexpectationthatitwouldprotectfarmerscropsbyeatingharmfulinsects.Unfortunately,thetoadmultipliedrapidlyzandalargecanetoadpopulationnowthreatenssmallnativeanimal
2、sthatarenotpests.SeveralmeasureshavebeenproposedtostopthespreadofthecanetoadinAustralia.Onewaytopreventthespreadofthetoadwouldbetobuildanationalfence.AfencethatblockstheadvanceofthetoadswillpreventthemfrommovingintothosepartsofAustraliathattheyhavenotyetcolonized.Thisapproachhasbeenusedbefore:anatio
3、nalfencewaserectedintheearlypartofthetwentiethcenturytopreventthespreadofrabbits,anotheranimalspeciesthatwasintroducedinAustraliafromabroadandhadaharmfulimpactonitsnativeecosystems.Second,thetoadscouldbecapturedanddestroyedbyvolunteers.Canetoadscaneasilybecaughtinsimpletrapsandcanevenbecapturedbyhan
4、d.Youngtoadsandcanetoadeggsareeveneasiertogatheranddestroy,sincetheyarerestrictedtothewater.IftheAustraliangovernmentweretoorganizeacampaignamongAustraliancitizenstojoinforcestodestroythetoadszthecollectiveeffortmightstopthetoadfromspreading.Third,researchersaredevelopingadisease-causingvirustocontr
5、olthecanetoadpopulations.Thisviruswillbespeciallydesigned:althoughitwillbeabletoinfectanumberofreptileandamphibianspecies,itwillnotharmmostoftheinfectedspecies;itwillspecificallyharmonlythecanetoads.Theviruswillcontrolthepopulationofcanetoadsbypreventingthemfrommaturingandreproducing.ListeningThecan
6、etoadwontbeaseasytogetridofasthereadingsuggests.Themeasuresproposedbythereadingarelikelyeithertobeunsuccessfulortocauseunwantedenvironmentaldamage.Firstofall,anationalfenceprobablywontstopthespreadofthetoad.Thatsbecauseyoungtoadsandtoadeggsarefoundinriversandstreams.Nomatterwherethefenceislocated,at
7、somepointtherewillberiversorstreamsflowingfromonesidetotheother.Thesewaterwayswillbeabletocarrytheyoungtoadsandtheireggstotheotherside.Sinceitsonlynecessaryforafewyoungtoadsoreggstogetthroughthefenceinordertoestablishpopulationontheotherside,thefenceisunlikelytobeeffective.Secondly,amassivegroupofvo
8、lunteerscouldhavesuccesstrappinganddestroyingtoads.ButitslikelythattheseuntrainedvolunteerswouldinadvertentlydestroymanyofAustraliasnativefrogs.Someofwhichareendangered.Itsnotalwayseasytotellthecanetoadapartfromnativefrogsespeciallywhenitsyoung.Third,usingthevirusisabadideabecauseitcouldhaveterrible
9、consequencesforcanetoadsintheiroriginalhabitatinCentralandSouthAmerica.YoumightbewonderinghowcanavirusreleasedinAustraliacauseharmintheAmerica.WellzAustralianreptilesandamphibiansareoftentransportedtoothercontinentsbyresearchersorpetcollectorsforexample.OncetheanimalsinfectedbythevirusreachCentralan
10、dSouthAmerica,theviruswillattackthenativecanetoadsanddevastatetheirpopulations.ThatwouldbeandecologicaldisasterbecauseintheAmericacanetoadsareanativespeciesandavitalpartoftheecosystem.Soiftheyareeliminated,thewholeecosystemwillsuffer.一、阅读听力要点概括ReadingPassageMainpoints:Severalmeasuresareproposedtosto
11、pCaneToadspreading.Subpoint1:Buildanationalfence.Subpoint2:Volunteerscandestroytoads.Subpoint3:Viruscancontrolthecanetoadpopulations.LectureAttitude:Unsuccessfulorunwanteddamage.SubPoint1:Fencewontstopthespread.(Eggsinriversandstreams,afewcanpassthefence.)SubPoint2:Volunteercandestroynativefrogs.(Un
12、trained,frogsendangered.)SubPoint3:ViruscanbetransferredtoAmerica.(Byreptilesandamphibians,Disasterforecosystem.)二、范文逐段赏析Paragraph1Thelecturerarguesagainstthethreemeasuresmentionedinthereadingpassagethoughttoreducethepopulationofthecanetoad,aspeciesintroducedtotheAustraliancontinent.此段功能：（Listeningp
13、assage后文提到用L代替）（Readingpassage后文用R代替）以L的观点为主要观点，作者说L反对R中提到的三点，并总结了要解决的问题：如何解决澳洲大陆上的蟾蛛数量。此段结构：作者用一句话总结了全文讨论的问题，并告诉大家全文逻辑为相反。极其简练直接，随即展开全文辩论。Paragraph2Thelecturerarguesthatthefirstmeasure,anationalfence,wouldnotpreventtheflowofstreamsorriversandztherefore,wouldallowyoungtoadsortoadeggstotravelthrought
14、hefence.Thereadingpassage,however,arguesthatsuchafencewouldeffectivelycutofftheroutethatanimalsusetoestablishcoloniesandexpandinpopulation.此段功能：以L的观点起头，谈第一种方法，全国栅栏并不能阻止小溪河流，这样小蟾蛛或者蟾嫁卵可以通过栅栏继续传播。所以R中提到的栅栏方法没有用。此段结构：此段为分分结构，从L的辩论开始，列举了栅栏会失效的证据，最后达到说明R中的栅栏是无用的目的。Paragraph3Regardingthesecondmeasure,recr
15、uitingalargegroupofvolunteers,thelecturerexplainsthatvolunteersoftenhavedifficultydistinguishingbetweencanetoadsandnativefrogs,whichareanendangeredspecies.Therefore,volunteersmightunintentionallykillmembersofbothspecies.Thereadingpassagegivestheoppositeview:organizingalargegroupofvolunteerstojoinane
16、xterminationcampaigncouldspeedthedestructionofcanetoads.此段功能:继续转入下一方法，志愿者杀蟾蛛方案。L解释到这些志愿者很难分辨蟾蛛和当地的珍贵青蛙，这样会造成无辜的伤害。所以R中提到的这个方法，也是行不通的。此段结构：此段为分分结构，先列出L中举的证据，最后达到说明R的想法不周全的结果。Paragraph4Finallythelecturerobjectstothethirdmeasure:usinganinfectiousvirustokillthepopulationoftoads.ShepointsoutthatavirusintendedtoeliminateAustraliascanetoadpopulationcouldbetransmittedtoothercontinentswherecanetoadsareanesse
