大学英语六级考试快速阅读模拟题训练.docx

大学英语六级考试快速阅读模拟题训练.docx

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大学英语六级考试快速阅读模拟题训练

Unit1

　　PartⅡReadingComprehension（SkimmingandScanning）

　　（15minutes）

　　Directions:

Inthispart,youwillhave15minutestogooverthepassagequicklyandanswerthequestionsonAnswerSheet1.

　　Forquestions14,mark

　　Y（forYES）ifthestatementagreeswiththeinformationgiveninthepassage;

　　N（forNO）ifthestatementcontradictstheinformationgiveninthepassage;

　　NG（forNOTGIVEN）iftheinformationisnotgiveninthepassage.

　　Forquestions5-10,completethesentenceswiththeinformationgiveninthepassage.

　　Rainforests

　　Tropicalrainforestsarethemostdiverseecosystem（生态系统）onEarth,andalsotheoldest.Today,tropicalrainforestscoveronly6percentoftheEarth'sgroundsurface,buttheyarehometooverhalfoftheplanet'splantandanimalspecies.

　　WhatIsaRainforest?

　　Generallyspeaking,arainforestisanenvironmentthatreceiveshighrainfallandisdominatedbytalltrees.Awiderangeofecosystemsfallintothiscategory,ofcourse.Butmostofthetimewhenpeopletalkaboutrainforests,theymeanthetropicalrainforestslocatedneartheequator.

　　Theseforestsreceivebetween160and400inchesofrainperyear.Thetotalannualrainfallisspreadprettyevenlythroughouttheyear,andthetemperaturerarelydipsbelow60degreesFahrenheit.

　　Thissteadyclimateisduetothepositionofrainforestsontheglobe.BecauseoftheorientationoftheEarth'saxis,theNorthernandSouthernhemisphereseachspendpartoftheyeartiltedawayfromthesun.Sincerainforestsareatthemiddleoftheglobe,locatedneartheequator,theyarenotespeciallyaffectedbythischange.Theyreceivenearlythesameamountofsunlight,andthereforeheat,allyear.Consequently,theweatherintheseregionsremainsfairlyconstant.

　　Theconsistentlywet,warmweatherandamplesunlightgiveplantlifeeverythingitneedstothrive.Treeshavetheresourcestogrowtotremendousheights.andtheyliveforhundreds,eventhousands,ofyears.Thesegiants,whichreach60to150ftintheair,formthebasicstructureoftherainforest.Theirtopbranchesspreadwideinordertocapturemaximumsunlight.Thiscreatesathickcanopy（树冠）levelatthetopoftheforest,withthinnergreenerylevelsunderneath.Somelargetreesgrowsotallthattheyeventoweroverthecanopylayer.

Asyougolower,downintotherainforest,youfindlessandlessgreenery.Theforestfloorismadeupofmoss,fungi,anddecayingplantmatterthathasfallenfromtheupperlayers.Thereasonforthisdecreaseingreeneryisverysimple：

Theoverabundanceofplantsgatheringsunlightatthetopoftheforestblocksmostsunlightfromreachingthebottomoftheforest,makingitdifficultforrobustplantstothrive.

　　TheForestfortheTrees

　　Theamplesunlightandextremelywetclimateofmanytropicalareasencouragethegrowthoftoweringtreeswithwidecanopies.Thisthicktoplayeroftherainforestdictatesthelivesofallotherplantsintheforest.Newtreeseedlingsrarelysurvivetomakeittothetopunlesssomeoldertreesdie,creatinga"hole"inthecanopy.Whenthishappens,alloftheseedlingsonthegroundlevelcompeteintenselytoreachthesunlight.

　　Manyplantspeciesreachthetopoftheforestbyclimbingthetalltrees.Itismucheasiertoascendthisway,becausetheplantdoesn'thavetoformitsownsupportingstructure.

　　Someplantspecies,calledepiphytes,growdirectlyonthesurfaceofthegianttrees.Theseplants,whichincludeavarietyoforchidsandferns,makeupmuchoftheunderstory,thelayeroftherainforestrightbelowthecanopy.Epiphytesarecloseenoughtothetoptoreceiveadequatelight,andtherunofffromthecanopylayerprovidesallthewaterandnutrients（养分）theyneed,whichisimportantsincetheydon'thaveaccesstothenutrientsintheground.

　　StranglersandButtresses

　　Someepiphyteseventuallydevelopintostranglers.Theygrowlong,thickrootsthatextenddownthetreetrunkintotheground.Astheycontinuetogrow,therootsformasortofwebstructureallaroundthetree.Atthesametime,thestranglerplant'sbranchesextendupward,spreadingoutintothecanopy.Eventually,thestranglermayblocksomuchlightfromabove,andabsorbsuchahighpercentageofnutrientsfromthegroundbelow,thatthehosttreedies.

　　Competitionovernutrientsisalmostasintenseascompetitionforlight.Theexcessiverainfallrapidlydissolvesnutrientsinthesoil,makingitrelativelyinfertileexceptatthetoplayers.Forthisreason,rainforesttreerootsgrowoutwardtocoverawiderarea,ratherthandownwardtolowerlevels.Thismakesrainforesttreessomewhatunstable,sincetheydon'thaveverystronganchorsintheground.Sometreescompensateforthisbygrowingnaturalbuttresses.Thesebuttressesarebasicallytreetrunksthatextendoutfromthesideofthetreeanddowntotheground,givingthetreeadditionalsupport.

　　Rainforesttreesaredependentonbacteriathatarecontinuallyproducingnutrientsintheground.Rainforestbacteriaandtreeshaveaveryclose,symbiotic（共生的）relationship.Thetreesprovidethebacteriawithfood,intheformoffallenleavesandothermaterial,andthebacteriabreakthismaterialdownintothenutrientsthatthetreesneedtosurvive.

Oneofthemostremarkablethingsaboutrainforestplantlifeisitsdiversity.ThetemperaterainforestsofthePacificNorthwestaremainlycomposedofadozenorsotreespecies.Atropicalrainforest,ontheotherhand,mighthave300distincttreespecies.

　　AllCreatures,GreatandSmall

　　Rainforestsarehometothemajorityofanimalspeciesintheworld.Andagreatnumberofspecieswhonowliveinotherenvironments,includinghumans,originallyinhabitedtherainforests.Researchersestimatethatinalargerainforestarea,theremaybemorethan10milliondifferentanimalspecies.

　　Mostofthesespecieshaveadaptedforlifeintheupperlevelsoftherainforest,wherefoodismostplentiful.Insects,whichcaneasilyclimborflyfromtreetotree,makeupthelargestgroup（antsarethemostabundantanimalintherainforest）.Insectspecieshaveahighlysymbioticrelationshipwiththeplantlifeinarainforest.Theinsectsmovefromplanttoplant,enjoyingthewealthoffoodprovidedthere.Astheytravel,theinsectsmaypickuptheplants'seeds,droppingthemsomedistanceaway.Thishelpstodispersethepopulationoftheplantspeciesoveralargerarea.

　　Thenumerousbirdsoftherainforestalsoplayamajorpartinseeddispersal.Whentheyeatfruitfromaplant,theseedspassthroughtheirdigestivesystem.Bythetimetheyexcrete（排泄）theseeds,thebirdsmayhaveflownmanymilesawayfromthefruit-bearingtree.

　　Therearealsoalargenumberofreptilesandmammalsintherainforest.Sincetheweatherissohotandhumidduringtheday,mostrainforestmammalsareactiveonlyatnight,duskordawn.Themanyrainforestbatspeciesareespeciallywelladaptedforthislifestyle.Usingtheirsonar,batsnavigateeasilythroughthemassoftreesintherainforest,feedingoninsectsandfruit.

　　Whilemostrainforestspeciesspendtheirlivesinthetrees,thereisalsoalotoflifeontheforestfloor.Greatapes,wildpigs,bigcatsandevenelephantscanallbefoundinrainforests.Thereareanumberofpeoplewholiveintherainforests,aswell.Thesetribes-which,upuntilrecently,numberedinthethousands-arebeingforcedoutoftherainforestsatanalarmingratebecauseofdeforestation.

　　Deforestation

　　Inthepasthundredyears,humanshavebegundestroyingrainforestsatanalarmingrate.Today,roughly1.5acresofrainforestaredestroyedeverysecond.Peoplearecuttingdowntherainforestsinpursuitofthreemajorresources：

　　•Landforcrops

　　•Lumberforpaperandotherwoodproducts

　　•Landforlivestockpastures

　　Inthecurrenteconomy,peopleobviouslyhaveaneedforalloftheseresources.Butalmostallexpertsagreethat,overtime,wewillsuffermuchmorefromthedestructionoftherainforeststhanwewillbenefit. 

Theworld'srainforestsareanextremelyvaluablenaturalresource,tobesure,butnotfortheirlumberortheirland.TheyarethemaincradleoflifeonEarth,andtheyholdmillionsofuniquelifeformsthatwehaveyettodiscover.Destroyingtherainforestsiscomparabletodestroyinganunknownplanet-wehavenoideawhatwe'relosing.Ifdeforestationcontinuesatitscurrentrate,theworld'stropicalrainforestswillbewipedoutwithin40years.

　　1.VirtuallyallplantandanimalspeciesonEarthcanbefoundintropicalrainforests.

　　2.Thereisnotmuchchangeintheweatherinthetropicalrainforestsalltheyearround.

　　3.ThelargestnumberofrainforestsintheworldarelocatedontheAfricancontinent.

　　4.Belowthecanopylevelofatropicalrainforestgrowsanoverabundanceofplants.

　　5.Newtreeseedlingswillnotsurvivetoreachthecanopylevelunless________.

　　6.Epiphytes,whichformmuchoftheunderstoryoftherainforest,getalltheirwaterandnutrientsfrom________.

　　7.Stranglersaresocalledbecausethey________byblockingthesunlightandcompetingforthenutrients.

　　8.Sincerainforestbacteriaandtreesdependoneachotherforlife,therelationshiptheyformistermed________.

　　9.Plantspeciesaredispersedoveralargeareawiththehelpof________.

　　10.Aswearestillignorantofmillionsofuniquelifeformsintherainforest,deforestationcanbecomparedtothedestructionof________.

　　Unit1

　　1.N2.Y3.NG4.N

　　5.guaranteed6.Internetaccess

　　7.twocustomersatisfactionprograms/acustomerhotlineandacustomercall-backprogram

　　8.higherpricesoftheirpizzas

　　9.recklessdrivingbythe