大学六级模拟544Word文件下载.docx

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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

Inthissection,youwillhearSshortconversationsand2longconversations.Attheendofeachconversation,