大学六级模拟544.docx

大学六级模拟544.docx

《大学六级模拟544.docx》由会员分享，可在线阅读，更多相关《大学六级模拟544.docx（31页珍藏版）》请在冰豆网上搜索。

大学六级模拟544

ModelTestOne

PartIWriting（30minutes）

Directions:

Forthispart,youareallowed30minutestowriteashortessayentitledDoCollegeStudentsNeedCareerOrientation?

Youshouldwriteatleast150wordsfollowingtheoutlinegivenbelow:

1．许多大学生缺乏明确的职业规划

2．职业规划的重要性

3．我的看法

DoCollegeStudentsNeedCareerOrientation?

PartⅡReadingComprehension（SkimmingandScanning）（15minutes）

Directions:

Inthispart,youwillhave15minutestogooverthepassagequicklyandanswerthequestionsonAnswerSheet1.Forquestions1-7,choosethebestanswerfromthefourchoicesmarkedA）,B）,C）andD）.Forquestions8-10,completethesentenceswiththeinformationgiveninthepassage.

EarthWillSurviveGlobalWarming,ButWillWe?

Thenotionthathumanactivity,ortheactivityofanyorganism,canaffectEarthonaplanetaryscaleisstillahardoneformanypeopletoswallow.Anditisthiskindofdisbeliefthatfuelsmuchofthepublicskepticismsurroundingglobalwarming.

ApollconductedlastsummerbythePewResearchCenterfoundthatonly41percentofAmericansbelievetheburningoffossilfuelscausesglobalwarming.ButinameetingthisweekinParis,officialsfrom113nationshaveagreedthatahighlyanticipatedinternationalreportwillstatethatglobalwarmingwas"verylikely"causedbyhumanactivity.Theideathatbiologycanaltertheplanetinbroadanddramaticwaysiswidelyacceptedamongscientists,andtheypointtoseveralprecedentsthroughoutthehistoryoflife.

Themightymicrobes

Human-causedglobalwarming--alsocalled"anthropogenic"globalwarming--isthelatestexampleoflifealteringEarth,butitisnotthemostdramatic.

ThattitleprobablygoestotheoxygenationofEarth'searlyatmospherebyancientmicrobesastheybegantoharnessthepowerofsunlightthroughphotosynthesis（光合作用）.

Humans"arehavingastrongeffectonglobalgeochemicalcycles,butitdoesnotcompareatalltotheadventofoxygenicphotosynthesis,"saidKatrinaEdwards,ageo-microbiologistattheUniversityofSouthernCalifornia（USC）."Thatwasacatastrophicenvironmentalchangethatoccurredbefore2.2billionyearsagowhichwreakeditsfullwrathontheEarthsystem."

Edwardsstudiesanotherwaylifeimpactstheplanetinlargelyunseenways.Shefocusesonhowmicrobeslivingonthedarkoceanfloortransformmineralsthroughakindofunderwaterpower.

"Thesemicrobesarecompletelyoffradarintermsofglobalbiogeochemicalcycles,"EdwardstoldLive-Science."Wedon'tconsiderthemaspartoftheEarthsystemrightnowinourcalculationaboutwhat'sgoingon,andwedon'tconsiderthemintermsofhowtheEarthsystemwillmoveforwardintothefuture."

Thesereactionsarestronglyinfluencedbylifeandhavebeenoccurringforbillionsofyears,foraslongastheoceanshavebeenoxygenatedandtherehavebeenmicrobesinhabitingtheseafloor,Edwardssaid.

CreatingEarth

Onland,microbes,andinparticularaformofbacteriacalledcyanobacteria（固氮蓝藻）,helpkeepsoilinplaceandsuppressdust.

"We'dcertainlyhavemoreduststormsanditwouldnotbeanywhereasniceonEarthiftheyweren'taround,"saidJayneBelnap,aresearcherwiththeUnitedStatesGeologicalSurvey.

Scientistsbelievethetinylife-formsperformedthesamerolesonearlyEarth."Oneofthebigproblemsforgeologistsisthat,OK,youhavethisbigballofrock,thesoilisweatheringoutandyouhavetheseferociouswinds.Whatintheworldisholdingthesoilinplaceasitweathersoutoftherocks?

"Belnapsaidinatelephoneinterview."Cyanobacteriaarealsocreditedwiththatfunction."

Themicrobesanchoredsoiltotheground;thiscreatedhabitatsforlandplantstoevolveandeventuallyforustoevolve."TheyliterallycreatedEarthinasense,"Belnapsaid.

"Cyanobacteriaarejustlike'it',"shecontinued."I'vebeentellingeverybodytomakeasmallaltarandoffersacrificeseverynight.Weowethemeverything."

Asnowballplanet

Themightymicrobesalsotriggeredsuddenclimaticshiftssimilartowhathumansaredoingnow.Recentstudiessuggestthattheproliferationofcyanobacteria2.3billionyearsagoledtoasuddeniceageandthecreationofa"SnowballEarth."

Astheycarryoutphotosynthesis,cyanobacteriabreakapartwaterandreleaseoxygenasawasteproduct.Oxygenisoneofthemostreactiveelementsaround,anditsreleaseintotheatmosphereinlargeamountsdestroyedmethane（沼气）,agreenhousegasthatabsorbedthesun'senergyandhelpedkeepourplanetwarm.

SomescientiststhinkthedisappearanceofthismethaneblanketplungedtheplanetintoacoldspellsoseverethatEarth'sequatorwascoveredbyamile-thicklayerofice.

Earthmightstillbefrozentodayifnotfortheappearanceofnewlifeforms.Asorganismsevolved,manydevelopedtheabilitytobreatheoxygen.Intheprocess,theyexhaledanothergreenhousegas,Carbondioxide,whicheventuallyice-outtheworld.Thatwasthefirstbiologicallytriggerediceage,butothersfollowed,saidRichardKopp,aCaltechresearcherwhohelpedpiecetogethertheSnowballEarthscenario.

Anewleaf

Whentreesfirstappearedabout380millionyearsago,theyalsodisturbedEarth'satmosphericbalance.

Unlikeanimals,plantsbreatheincarbondioxideandexpeloxygen.Treestransformsomeofthatatmosphericcarbonintolignin（木质素）--themajorconstituentofwoodandoneofthemostabundantproteinsontheplanet.Ligninisresistanttodecay,sowhenatreedies,muchofitscarbonbecomesburiedinsteadofreleasedbackintotheatmosphereascarbondioxide.LesscarbondioxideintheatmospherethinstheblanketofgasesthatkeepsEarthwarm,andthatcoolingeffectcantriggerglobalcooling,possiblyevenaniceage.

"Therewassomeglaciationthatstartedaroundthatperiodthatwasdrivenatleastinpartbytheevolutionoflandplants,"Koppsaidinatelephoneinterview.

Treesalsoaffectedtheglobalcarboncycleinanotherindirectway.Astheytunnelthroughtheground,treerootsbreakdownsilicaterocksintosedimentandsoil.Silicaterockcontainslargeamountsofcalciumandmagnesium（镁）.Whentheseelementsareexposedtoair,theyreactwithatmosphericcarbondioxidetoformcalciumcarbonate（碳酸盐）andmagnesiumcarbonate,compoundsthatarewidespreadonEarth.

Thehumandifference

ThoughitmightseemasifhumansaremerefleasalongforarideonthebackofanimmenseanimalcalledEarth,ourintelligence,technologyandsheernumbersmeanourspeciespacksapunchthatcanshaketheworldinwildways.

Whilewearenotthefirstspeciestodrasticallyalterourplanet,ourinfluenceisuniqueinanumberofways,scientistssay.

Foronething,humanshavedevelopedlarge-scaleindustry,saidSpencerWeart,asciencehistorianattheAmericanInstituteofPhysics."Wearecapableofmobilizingthingsbeyondourownbiology,"Weartsaid."Iemitacertainamountofcarbondioxide,butmyautomobileemitsfarmore."

AnotheristherateatwhichhumansarewarmingEarth.

"Humansarethemostcommonlargeanimaltoeverwalktheplanet,"saidKirkJohnson,achiefcuratorattheDenverMuseumofNature&Science:

"Population,plusbrainpowerandtechnology,isapotentcombinationandtheresultisthathumansareeffectingchangeatveryhighrates."

Belnapagrees."Idon'tthinkwe'vefundamentallychangedanyprocess.We'vejustcrankedupthespeed,"shesaid."Wehaven'tintroducedanythingnew.We'vejustchangedhowfastorslowithappens,andmostlyfast."

Butnomatterhowhighhumanscausethetemperaturetoriseandhowmuchdamagewedototheplanet,Earthandlifewillsurvive,scientistssay.Itjustmightnolongerbeintheformwepreferortheformthatallowsustothrive.

"WhatweneedtobethinkingofashumanscausingchangestotheEarthsystemiswhattheconsequenceswillbetoushumanbeings,"saidEdwards,theUSCgeo-microbiologist."TheEarthcouldcareless.WewillberecordedasaminorchaosintheEarthsystem.TheEarthwillgoon.Thequestionis:

Willwe?

"

1.Accordingtotheworldwidereport,whatisthemainreasonforglobalwarming?

A）Americanpeople.B）People'sactivity.

C）Industryactivity.D）Developedcountries.

2.Thephotosynthesisbyancientmicrobesisanexampleof______.

A）thechangeofEarthB）thelonghistoryofEarth

C）thelife'sinfluencesonEarthD）thepowerofsunlight

3.AccordingtoEdwards,themicrobesarenow______.

A）recognizedbymostpeopleB）neglectedbymostpeople

C）diedoutfromtheEarthD）outofactionoftheEarthsystem

4.Whatisthemainfunctionofcyanobacteria?

A）Tomakemoreduststorms.B）Tokeepthesoilflying.

C）Tokeepthesoiltotheground.D）Tocreatemorerocks.

5.TokeeptheEarthoutofwarm,wecandestroytheMethanewith______.

A）greenhousegasB）sunlight

C）waterD）oxygen

6.Theearthisunfrozentodaywiththeappearanceof______.

A）themethaneblanketB）amile-thicklayerofice

C）newlifeformsD）thecarbondioxide

7.Differentfromanimals,thetreesinfluencetheearth'satmosphereby______.

A）expellingcarbondioxidefromtheirleaves

B）expellingoxygenfromtheirleaves

C）directlyreducetheblanketofgases

D）turningsomecarbondioxideintolignin

8.Treescanindirectlyhelptheexpositionofcalciumandmagnesiumwiththeirroots______.

9.Eventhoughnotthefirsttoinfluencetheearth,thehumanisstillalteringtheplanetin______.

10.Undertheinfluenceofhightemperatureandmuchdamagecausedbythehuman,Earthandlifewill______.

PartⅢListeningComprehension（35minutes）

SectionA

Directions:

Inthissection,youwillhearSshortconversationsand2longconversations.Attheendofeachconversation,