资源描述
TPO361TheFirstEyePuttingadateonthefirstappearanceofeyesdependsonwhatonemeansbyeye.Ifthetermreferstoamulticellularorgan,evenifithasjustafewcells,thenbydefinition,eyescouldnotformbeforethereweremulticellu1aranimals.Butmanyprotists(anima1-like,plantlike,orfungus-1ikeunicel1ularorganismsthatrequireawater-basedenvironment)candetectlightbyusingaggregationsofpigmentmolecu1es,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneouslyandindependently).Oneofthefami1iarlivingexamples,probablyknowntoanyonewhohastakenabiologyclass,istheaquaticprotozoanEug1ena,whichhasaneyespotnearitsmotilefIagellum(hair1ikestructure).Some1ivingprotistsareveryliketheirancestralformsembeddedinancientsedimentaryrocks,andthissimilaritysuggeststhattheabi1itytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforaverylongtime.Animalsarosefromoneofsuchunicel1u1arcreatures,perhapsfromonea1readyspecia1izedforaprimitivekindofvision.AneyeisacollectionofcellsthatarespecializedforlightdetectionthroughthepresenceofphotosensitivepigmentaswellasameansofrestrictingthedirectionofincominglightthatwillstrikethephotosensitiveceIls.Thisdefinitionsaysnothingaboutimageformation,lenses,eyemovements,oranyoftheotherfeaturesweassociatewithourowneyes,butitdoesrecognizethesimplestformoffunctionalandanatomica1specialisationname1y,detectionoflight.Everythingelsecanbebuiltupfromthissimplebeginning,andsomeanimalsappeartohavehadeyesalmostfromthebeginningoftheanimalkingdom.Animalswerescarce600mi1lionyearsagointhegeologica1eracalledthePrecambrian.Thereareveryfewfossilremainsfromthattime(thoughmorekeepturningup),andmostevidenceofthepresenceofanimalsisindirect,suchassmalltunnelsinrockthatcouldbeancientwormburrowings.Butjust50mi1lionyearsorso1ater,fossi1izedbitsandpiecesofanimalsabound,suggestingthatagreatburstofevolutionarycreativityoccurredinthe50-million-yearinterval.Thissurgeofnew1ife,markedbyanabundanceofanimals,iscalledtheCambrianexp1osion.Thefirstdirectevidencefortheearlyoriginofeyescomesfromfossilsthatareabout530millionyearsold,atimeshortlyaftertheCambrianexp1osion;theywerefoundonamountainsideinBritishColumbiainadepositknownastheBurgessSha1e.TheBurgessSha1efossilsareextraordinarilyimportantbecauseamongthemareremainsofsoft一bodiedcreatures,manyofthemlackingshellsandotherhardpartsthatfossilizeeasily.Consequently,theirpreservationislittleshortofmiraculous(asarethedelicatemethodsusedtoreconstructthree-dimensionalstructurefromthesef1attenedfossils),andtheyareoneofthefewknownrepositoriesofear1ysoft-bodiedanimals.NotalloftheBurgessanimalshadeyes.However,somedid.(Grossfeatureslocation,size,andhemisphericshapeareresponsibleforthedesignationofsomestructuresaseyes).ThereconstructedeyesoftheseBurgessanimalslooksuperficiallylikeeyesofsome1ivingcrustaceans,particu1arlythoseofshrimpandcrabswhoseeyesaremountedonstalksthatimprovetherangeofvisionbyraisingtheeyesabovethesurfaceofthehead.TheeyesofsomeBurgessorganismssatonstalks;thoseof0therswereonorapartofthebodysurface.Oneanima1,Opabinia,hadfiveeyes:two1ateralpairsandasing1emedia1eye；atleastoneofthelateralpairshadstalksthatcouldhavebeenmovable.AndsometrilobitelikeanimalsintheBurgessShalehadfacetedeyesmuchlikethoseoflaterfossiltrilobites.AlthoughthepresenceofeyesonsomeoftheBurgessanimalsindicatesthateyeshavebeenaroundforavery1ongtime,itisunlikelythatthesewerethefirsteyes;theyseemmuchtoolargeand(potential1y)we1ldevelopedtobebrandnewinventions.ThebestwecandoisputtheoriginofeyessomewherebetweenthebeginningoftheCambrianexplosion,about600millionyearsago,andthedeathoftheBurgessanimals,some530mi1lionyearsago.Paragraph1：Puttingadateonthefirstappearanceofeyesdependsonwhatonemeansbyeye.Ifthetermreferstoamu1ticellularorgan,evenifithasjustafewcells,thenbydefinition,eyescouIdnotformbeforethereweremultice1lularanima1s.Butmanyprotists(animal-like,plantlike,orfungus-likeunicel1ularorganismsthatrequireawater-basedenvironment)candetectlightbyusingaggregationsofpigmentmolecu1es,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneouslyandindependently).Oneofthefamiliarlivingexamples,probab1yknowntoanyonewhohastakenabiologyc1ass,istheaquaticprotozoanEuglena,whichhasaneyespotnearitsmotilefIagellum(hairlikestructure).Somelivingprotistsareveryliketheirancestralformsembeddedinancientsedimentaryrocks,andthissimi1aritysuggeststhattheabilitytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforavery1ongtime.Animalsarosefromoneofsuehunicellularcreatures,perhapsfromonealreadyspecializedforaprimitivekindofvision.1 .Thewordaggregations“inthepassageisclosestinmeaningtoParts.Reactions.Groups.Types.2 .Paragraph1supportsallofthefol1owingstatementsaboutprotistsEXCEPT:Somearemulticellular.Someareabletomove.Somehavepigmentmolecu1es.Theyliveinenvironmentsthatcontainmoisture.3. .Accordingtoparagraph1,whathavescientistsconc1udedfromthefactthatsome1ivingprotistsareveryliketheirancestralformsTheeyedidnotevo1veuntilmulticel1ularorganismsarose.Theabilitytodetect1ightandchangebehaviorinresponsetolighthasexistedforalongtime.Theancestralformsoftheselivingprotistslike1yhadaneyespotnearthemotileflagellum.Theancestralformsoftheselivingprotistsdependedprimarilyon1ightasthemechanismformodifyingtheirmetabolicactivityormotility.Paragraph2:Aneyeisacollectionofcellsthatarespecializedforlightdetectionthroughthepresenceofphotosensitivepigmentaswellasameansofrestrictingthedirectionofincominglightthatwillstrikethephotosensitivecel1s.Thisdefinitionsaysnothingaboutimageformation,lenses,eyemovements,oranyoftheotherfeaturesweassociatewithourowneyes,butitdoesrecognizethesimplestformoffunctionalandanatomicalspecia1isationnamely,detectionoflight.Everythinge1secanbebuiltupfromthissimp1ebeginning,andsomeanimalsappeartohavehadeyesa1mostfromthebeginningoftheanimalkingdom.4. Paragraph2imp1ieswhichofthefollowingabouttheear1yeyesTheywereab1etodetectsimplemovementsa1mostfromthebeginningoftheirevolution.Theywerenotassensitivetolightasoncethought.Theycou1dnotformimages.TheircellshadmorephotosensitivepigmentthandohumaneyesParagraph3:Animalswerescarce600mil1ionyearsagointhegeo1ogicaleracalledthePrecambrian.Thereareveryfewfossilremainsfromthattime(thoughmorekeepturningup),andmostevidenceofthepresenceofanimalsisindirect,suchassmalltunnelsinrockthatcouldbeancientwormburrowings.Butjust50millionyearsorsolater,fossi1izedbitsandpiccesofanimalsabound,suggestingthatagreatburstofevolutionarycreativityoccurredinthe50-millionyearinterval.Thissurgeofnew1ife,markedbyanabundanceofanimals,isca1ledtheCambrianexp1osion.5. .Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage.Incorrectchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.TherearefewfossilsfromthePrecambrian,thoughmorekeepturningup.Mostevidenceofanimalsinthefossilrecordisindirectand1ittleofitisfromthePrecambrian.TunnelsinPrecambrianrocksthatmayhavebeenmadebywormsprovideindirectevidenceoftheseanimalsexistingatthattime.ThereareveryfewfossilsofanimalsfromthePrecambrianandmostevidenceofanimal1ifefromthatperiodisindirect.6. Accordingtoparagraph3,theCambrianperiodwascharacterizedbyAgreatabundanceofanimalsAslowrateofanimalextinctionTherapidfossi1izationofanimalsAnincreaseinthelifespanofsomeanimalsParagraph4：Thefirstdirectevidencefortheearlyoriginofeyescomesfromfossilsthatareabout530millionyearsold,atimeshort1yaftertheCambrianexp1osion;theywerefoundonamountainsideinBritishColumbiainadepositknownastheBurgessSha1e.TheBurgessShalefossilsareextraordinarilyimportantbecauseamongthemareremainsofsoftbodiedcreatures,manyofthemlackingshellsandotherhardpartsthatfossilizeeasily.Consequently,theirpreservationis1ittleshortofmiraculous(asarethede1icatemethodsusedtoreconstructthree-dimensionalstructurefromtheseflattenedfossi1s),andtheyareoneofthefewknownrepositoriesofearlysoft-bodiedanimals.7. Thephraselittleshortofmiracu1ousisclosestinmeaningToveryhighlyvaluedAmazingbecausealmostimpossibleCausingcontroversyA1mostbutnotquitecomplete8. Accordingtoparagraph4,allofthefollowingaretrueoftheBurgessShaleEXCEPT:Itsfossi1swereinaf1attenedconditionwhendiscovered.Itsfossilsprovidedirectevideneeabouttheoriginofeyes.ItcontainsfossilsofbothPrecambrianandCambriananima1s.Itcontainsfossilizedremainsofsoft-bodiedorganisms.Paragraph5:NotalloftheBurgessanimalshadeyes.However,somedid.(Grossfeatureslocation,size,andhemisphericshapeareresponsibleforthedesignationofsomestructuresaseyes).ThereconstructedeyesoftheseBurgessanima1slooksuperficia1lylikeeyesofsomelivingcrustaceans,particularlythoseofshrimpandcrabswhoseeyesaremountedonstalksthatimprovetherangeofvisionbyraisingtheeyesabovethesurfaceofthehead.TheeyesofsomeBurgessorganismssatonstalks;thoseofotherswereonorapartofthebodysurface.Oneanimal,Opabinia,hadfiveeyes:twolateralpairsandasinglemedialeye;atleastoneofthe1ateralpairshadstalksthatcou1dhavebeenmovab1e.Andsometrilobitelikeanima1sintheBurgessShalehadfacetedeyesmuchlikethoseoflaterfossiltrilobites.9. Theworddesignationinthepassageisc1osestinmeaningtoEvolutionIdentificationReconstructionConfusion10. Thewordlateralinthepassageindicatesa1ocationattheFrontBackTopSide11. WhydoestheauthorpointoutthatTheeyesofsomeBurgessorganismssatonstalks?TosuggestthatsomeBurgessorganismshadagreaterrangeofvisionthandolivingshrimpandcrabsToexplainwhyitisthoughtthatoneofthelateralpairsofeyesinOpabiniamayhavebeenmovableToexplainwhytheeyesofsomeBurgessanimalswerenotrecognizableassuchbeforetheywerereconstructedTosupportthestatementthatthereconstructedeyesofBurgessanimals100ksuperficiallyliketheeyesofsomelivingcrustaceansParagraph6:AlthoughthepresenceofeyesonsomeoftheBurgessanimalsindicatesthateyeshavebeenaroundforaverylongtime,itisunlikelythatthesewerethefirsteyes;theysecmmuchtoolargeand(potentially)welldevelopedtobebrandnewinventions.ThebestwecandoisputtheoriginofeyessomewherebetweenthebeginningoftheCambrianexplosion,about600mi1lionyearsago,andthedeathoftheBurgessanimals,some530mi1lionyearsago.1 2.Paragraph6suggeststhatthefirsteyesprobablyCameintoexistencelongbefore600millionyearsagoCameintoexistenceatalatepointintheCambrianperiodExistedbeforetheanima1softheBurgessShaleexistedWerelargerthanthoseofanima1sfoundintheBurgessShaleParagraph1:Puttingadateonthefirstappearanceofeyesdependsonwhatonemeansbyeye.Ifthetermreferstoamultice1lularorgan,evenifithasjustafewce1ls,thenbydefinition,eyescouldnotformbeforethereweremulticel1ularanimals.Butmanyprotists(animal-like,plantlike,orfungus-likeunice1lularorganismsthatrequireawater1. asedenvironment)candetectlightbyusingaggregationsofpigmentmolecules,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneous1yandindependently).HOneofthefamiliarlivingexamples,probablyknowntoanyonewhohastakenabiologyclass,istheaquaticprotozoanEug1ena,whichhasaneyespotnearitsmoti1efIagellum(hairlikestructure).BSomelivingprotistsareveryliketheirancestra1formsembeddedinancientsedimentaryrocks,andthissimilaritysuggeststhattheabilitytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforaverylongtime.0nimalsarosefromoneofsuchunicellularcreatures,perhapsfromonealreadyspecializedforaprimitivekindofvision.13. Lookatthefoursquaresthatindicatewherethefo1lowingsentencecou1dbeaddedtothepassage.Mo1ariaspiniferaandH.Optata,bothofwhichlivedinwaterlevelsbeyondthereachof1ight,fitintothiscategory.14. Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Somesentencesdonotbelonginthesummarybecausctheyexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.Dragyourchoicestothespaceswheretheybelong.Toreviewthepassage,clickonViewText.AnswerChoicesTheabilityofsomeunicellularorganismstodetectlightandchangetheirbehavioraccordinglysuggeststhateyesdidnotoriginatewithmulticellularanimals.Theearliesteyesapparentlycontainedmoleculesthatwerecapab1eofformingandfocusingimages.ToofewfossilsfromthePrecambrianhavebeenfoundtodeterminewhichifanyPrecambrianorganismshadeyes.EvidencefromtheBurgessSha1esuggeststhateyesofsomeearlyanimalsweresimi1artotheeyesoflivingcrustaceans.FossilevidencesuggeststhatorganismsintheBurgessSha1ewithfacetedeyesdevelopedlaterthanorganismsintheBurgessShalewithnonfacetedeyes.ThelargesizeandpossiblecomplexityoftheeyesofsomeorganismsintheBurgessShalesuggestthattheireyeswerenotthefirsteyes.TPO36-2TheoriginofEarthsmtosphereInordertounderstandtheoriginofEarthsatmosphere,wemustgobacktotheearliestdaysoftheso1arsystem,beforetheplanetsthemselveswereformedfromadiskofrockymaterialspinningaroundtheyoungSun.Thismaterialgradual1ycoalescedintolumpscalledplanetesimalsasgravityandchancesmashedsmallerpiecestogether,achaoticandviolentprocessthatbecamemoresoasplanetesimalsgrewinsizeandgravitationa1pull.Withineach0rbit,col1isionsbetweenplanetesimalsgeneratedimmenseheatandenergy.Howviolenttheseprocesseswereissuggestedbytheoddti1tandspinofmanyoftheplanets,whichindicatethateachoftheplanetswas,1ikeabil1iardba1l,struckatsomestagebyanotherlargebodyofsomekind.VisualevidenceoftheseprocessescanbeseenbylookingattheMoon.BecausetheMoonhasnoatmosphere,itssurfaceisnotsubjecttoerosion,soitretainsthemarksofitsear1yhistory.Itsfaceisdeeplyscarredbymillionsofmeteoricimpacts,asyoucanseeonac1earnightwithapairofbinoculars.Theear1yEarthdidnothavemuchofanatmosphere.Beforeitgrewtoful1size,itsgravitationalpullwasinsufficienttopreventgasesfromdriftingoffintospace,whilethesolarwind(thegreatstreamofatomicparticlesemittedfromtheSun)hadalreadydrivenawaymuchofthegaseousmateria1fromtheinnerorbitsofthesolarsystem.Sowemustimaginetheear1yEarthasamixtureofrockymateria1s,metals,andtrappedgases,subjecttoconstantbombardmentbysmallerplanetesimalsandwithoutmuchofanatmosphere.Asitbegantoreachfullsize,Earthheatedup,partlybecauseofcollisionswithotherplanetesimalsandpartlybecauseofincreasinginternalpressuresasitgrewinsize.Inaddition,theearlyEarthcontainedabundantradioactivematerials,alsoasourceofheat.AsEarthheatedup,itsinteriorme1ted.Withinthemo1teninterior,undertheinfluenceofgravity,differentelementsweresortedoutbydensity.Byabout40millionyearsaftertheformationofthesolarsystem,mostoftheheaviermeta11icelementsintheear1yEarth,suchasironandnickel,hadsunkthroughthehotsludgetothecentergivingEarthacoredominatedbyiron.ThismetalliccoregivesEarthitscharacteristicmagneticfield,whichhasplayedanextremelyimportantroleinthehistoryofourplanet.AsheavymaterialsheadedforthecenterofEarth,lightersilicates(suchasthemineralquartz)driftedupward.ThedensersilicatesformedEarthsmantle,aregionalmost3,000kilometersthickbetweenthecoreandthecrust.Withthehelpofbombardmentbycomets,whosemanyimpactsscarredandheatedEarthssurface,thelightestsilicatesrosetoEarthssurface,wheretheycooledmorerapidlythanthebetterinsulatedmaterialsinEarthsinterior.Theselightermaterials,suehastherockswecallgranites,formedalayerofcontinentalcrustabout35kilometersthick.RelativetoEarthasawhole,thisisasthinasaneggshe1l.Seafloorcrustiseventhinner,atabout7kilometers;thus,evencontinentalcrustreachsonlyabout1/200thofthewaytoEarthscore.MuchoftheearlycontinentalcrusthasremainedonEarthssurfacetothepresentday.Thelightestmateria1sofa1l,includinggasessuchashydrogenandhe1ium,bubbledthroughEarthsinteriortothesurface.SowecanimaginethesurfaceoftheearlyEarthasamassivevolcanicfield.Andwecanjudgeprettywellwhatgasesbubbleduptothatsurfacebyanalyzingthemixtureofgasesemittedbyvolcanoes.Theseincludehydrogen,helium,methane,watervapor,nitrogen,ammonia,andhydrogensulfide.Othermaterials,inc1udinglargeamountsofwatervapor,werebroughtinbycometarybombardments.Muchofthehydrogenandheliumescaped;butonceEarthwasfullyformed,itwaslargeenoughforitsgravitationa1fieldtoholdmostoftheremaininggases,andtheseformedEarthsfirststableatmosphere.Paragraph1:InordertounderstandtheoriginofEarthsatmosphere,wemustgobacktotheearliestdaysoftheso1arsystem,beforetheplanetsthemselveswereformedfromadiskofrockymaterialspinningaroundtheyoungSun.Thismaterialgradua11ycoalescedinto1umpscalledp1anetesima1sasgravityandchancesmashedsmallerpiecestogether,achaoticandviolentprocessthatbecamemoresoasplanetesimalsgrewinsizeandgravitationalpull.Withineach0rbit,collisionsbetweenplanetesima1sgeneratedimmenseheatandenergy.Howviolenttheseprocesseswereissuggestedbytheoddtiltandspinofmanyofthep1anets,whichindicatethateachoftheplanetswas,likeabi11iardbal1,struckatsomestagebyanotherlargebodyofsomekind.Visua1evidenceoftheseprocessescanbeseenbylookingattheMoon.BecausetheMoonhasnoatmosphere,itssurfaceisnotsubjecttoerosion,soitretainsthemarksofitsearlyhistory.Itsfaceisdeeplyscarredbymi1lions0fmeteoricimpacts,asyoucanseeonaclearnightwithapairofbinocu1ars.Theear1yEarthdidnothavemuchofanatmosphere.Beforeitgrewtofu11size,itsgravitationa1pullwasinsufficienttopreventgasesfromdriftingoffintospace,whiletheso1arwind(thegreatstreamofatomicparticlesemittedfromtheSun)hadalreadydrivenawaymuchofthegaseousmaterialfromtheinnerorbitsofthesolarsystem.SowemustimaginetheearlyEarthasamixtureofrockymateria1s,metals,andtrappedgases,subjecttoconstantbombardmentbysmallerplanetesimalsandwithoutmuchofanatmosphere.1. ThewordcoalescedinthepassageisclosestinmeaningtoCo1lidedJoinedChangedShrank2. ThewordchaoticinthepassageisclosestinmeaningtoRapidDisorganizedIntenseLonglasting3. Allofthefo1lowingaretrueoftheplanetesimalsmentionedinparagraph1EXCEPT:TheywereformedofrockymaterialspinningaroundtheearlySun.Theycollidedviolentlywitheachother.Theygraduallygrewinsize.Theylosttheiratmospheresastheywerehitbylargerbodies.4. ThewordretainsinthepassageisclosestinmeaningtoRevealsAcquiresHidesPreserves5. TheauthordiscussestheMooninparagraph1inordertoHelpexp1ainwhyEarthhadfewermeteoricimpactsthanotherplanetsintheso1 arsystemShowwhyitisdifficu1ttounderstandhowthefirstplanetaryatmospheresdevelopedHelpexp1aintheprocessesthattookplaceintheformationoflargeplanetarybodiesinthesolarsystemIllustratewhytheMoonsspinandtiltareuniqueamongotherplanetarybodiesinthesolarsystem6. ThewordconstantinthepassageisclosestinmeaningtoConsiderableUnpredictableContinualViolentParagaaph2:Asitbegantoreachfullsize,Earthheatedup,part1ybecauseofco1lisionswithotherplanetesimalsandpartlybeeauseofincreasinginternalpressuresasitgrewinsize.Inaddition,theearlyEarthcontainedabundantradioactivematerials,alsoasourceofheat.AsEarthheatedup,itsinteriormelted.Withinthemolteninterior,undertheinf1uenceofgravity,differentelementsweresortedoutbydensity.Byabout40mi1lionyearsaftertheformationofthesolarsystem,mostoftheheaviermeta1licelementsintheearlyEarth,suchasironandnickel,hadsunkthroughthehotsludgetothecentergivingEarthacoredominatedbyiron.Thismeta1liccoregivesEarthitscharacteristicmagneticfield,whichhasplayedanextremelyimportantroleinthehistoryofourplanet.7 .Paragraph2answerswhichofthefollowingquestionsaboutearlyEarthWhatcausedmateriaIsonEarthtobecomeradioactiveWhatpercentageofEarthscorewasnickelWhatinternalpressurescausedEarthtoheatupasitgrewinsizeWhatcausedEarthsmagneticfie1d8 .Accordingtoparagraph2,Earthscoreismostlyironbecause,comparedtomostothere1ementsonearlyEarth,ironwasdensermeltedmoreeasilywasmoreradioactivewasmoreplentifu1Paragraph3:AsheavymaterialsheadedforthecenterofEarth,1ightersilicates(suchasthemineralquartz)driftedupward.ThedensersilicatesformedEarthsmantle,aregionalmost3,000ki1ometersthickbetweenthecoreandthecrust.Withthehelpofbombardmentbycomets,whosemanyimpactsscarredandheatedEarthssurface,thelightestsilicatesrosetoEarthssurface,wheretheycoo1edmorerapidlythanthebetter-insu1atedmaterialsinEarthsinterior.Theselightermateria1s,suchastherockswecal1granites,formedalayerofc
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