TPO阅读文本无水印

1、TPO36-1TheFirstEyePuttingadateonthefirstappearanceofeyesdependsonwhatonemeansbyeye.Ifthetermreferstoamulticellularorgan,evenifithasjustafewcells,thenbydefinition,eyescouldnotformbeforethereweremulticellularanimals.Butmanyprotists(animal-like,plantlike,orfungus-likeunicellularorganismsthatrequireawat

2、er-basedenvironment)candetectlightbyusingaggregationsofpigmentmolecules,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneouslyandindependently).Oneofthefamiliarlivingexamples,probablyknowntoanyonewhohastakenabiologyclass,istheaquaticprotozoanEuglena,whichhasa

3、neyespotnearitsmotilefIagellum(hairlikestructure).Somelivingprotistsareveryliketheirancestralformsembeddedinancientsedimentaryrocks,andthissimilaritysuggeststhattheabilitytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforaverylongtime.Animalsarosefromoneofsuchunicellularcreatures,perhap

4、sfromonealreadyspecializedforaprimitivekindofvision.Aneyeisacollectionofcellsthatarespecializedforlightdetectionthroughthepresenceofphotosensitivepigmentaswellasameansofrestrictingthedirectionofincominglightthatwillstrikethephotosensitivecells.Thisdefinitionsaysnothingaboutimageformation,lenses,eyem

5、ovements,oranyoftheotherfeaturesweassociatewithourowneyes,butitdoesrecognizethesimplestformoffunctionalandanatomicalspecialisationnamely,detectionoflight.Everythingelsecanbebuiltupfromthissimplebeginning,andsomeanimalsappeartohavehadeyesalmostfromthebeginningoftheanimalkingdom.Animalswerescarce600mi

6、llionyearsagointhegeologicaleracalledthePrecambrian.Thereareveryfewfossilremainsfromthattime(thoughmorekeepturningup),andmostevidenceofthepresenceofanimalsisindirect,suchassmalltunnelsinrockthatcouldbeancientwormburrowings.Butjust50millionyearsorsolater,fossilizedbitsandpiecesofanimalsabound,suggest

7、ingthatagreatburstofevolutionarycreativityoccurredinthe50-million-yearinterval.Thissurgeofnewlife,markedbyanabundanceofanimals,iscalledtheCambrianexplosion.Thefirstdirectevidencefortheearlyoriginofeyescomesfromfossilsthatareabout530millionyearsold,atimeshortlyaftertheCambrianexplosion;theywerefoundo

8、namountainsideinBritishColumbiainadepositknownastheBurgessShale.TheBurgessShalefossilsareextraordinarilyimportantbecauseamongthemareremainsofsoft-bodiedcreatures,manyofthemlackingshellsandotherhardpartsthatfossilizeeasily.Consequently,theirpreservationislittleshortofmiraculous(asarethedelicatemethod

9、susedtoreconstructthree-dimensionalstructurefromtheseflattenedfossils),andtheyareoneofthefewknownrepositoriesofearlysoft-bodiedanimals.NotalloftheBurgessanimalshadeyes.However,somedid.(Grossfeatureslocation,size,andhemisphericshapeareresponsibleforthedesignationofsomestructuresaseyes).Thereconstruct

10、edeyesoftheseBurgessanimalslooksuperficiallylikeeyesofsomelivingcrustaceans,particularlythoseofshrimpandcrabswhoseeyesaremountedonstalksthatimprovetherangeofvisionbyraisingtheeyesabovethesurfaceofthehead.TheeyesofsomeBurgessorganismssatonstalks;thoseofotherswereonorapartofthebodysurface.Oneanimal,Op

11、abinia,hadfiveeyes:twolateralpairsandasinglemedialeye;atleastoneofthelateralpairshadstalksthatcouldhavebeenmovable.Andsometrilobite-likeanimalsintheBurgessShalehadfacetedeyesmuchlikethoseoflaterfossiltrilobites.AlthoughthepresenceofeyesonsomeoftheBurgessanimalsindicatesthateyeshavebeenaroundforavery

12、longtime,itisunlikelythatthesewerethefirsteyes;theyseemmuchtoolargeand(potentially)welldevelopedtobebrandnewinventions.ThebestwecandoisputtheoriginofeyessomewherebetweenthebeginningoftheCambrianexplosion,about600millionyearsago,andthedeathoftheBurgessanimals,some530millionyearsago.Paragraph1:Putting

13、adateonthefirstappearanceofeyesdependsonwhatonemeansbyeye.Ifthetermreferstoamulticellularorgan,evenifithasjustafewcells,thenbydefinition,eyescouldnotformbeforethereweremulticellularanimals.Butmanyprotists(animal-like,plantlike,orfungus-likeunicellularorganismsthatrequireawater-basedenvironment)cande

14、tectlightbyusingaggregationsofpigmentmolecules,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneouslyandindependently).Oneofthefamiliarlivingexamples,probablyknowntoanyonewhohastakenabiologyclass,istheaquaticprotozoanEuglena,whichhasaneyespotnearitsmotilefIag

15、ellum(hairlikestructure).Somelivingprotistsareveryliketheirancestralformsembeddedinancientsedimentaryrocks,andthissimilaritysuggeststhattheabilitytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforaverylongtime.Animalsarosefromoneofsuchunicellularcreatures,perhapsfromonealreadyspecialize

16、dforaprimitivekindofvision.Thewordaggregationsinthepassageisclosestinmeaningto口Parts.口Reactions.口Groups.口Types.Paragraph1supportsallofthefollowingstatementsaboutprotistsEXCEPT:口Somearemulticellular.口Someareabletomove.口Somehavepigmentmolecules.口Theyliveinenvironmentsthatcontainmoisture.Accordingtopar

17、agraph1,whathavescientistsconcludedfromthefactthatsomelivingprotistsareveryliketheirancestralforms口Theeyedidnotevolveuntilmulticellularorganismsarose.口Theabilitytodetectlightandchangebehaviorinresponsetolighthasexistedforalongtime.口Theancestralformsoftheselivingprotistslikelyhadaneyespotnearthemotil

18、eflagellum.口Theancestralformsoftheselivingprotistsdependedprimarilyonlightasthemechanismformodifyingtheirmetabolicactivityormotility.Paragraph2:Aneyeisacollectionofcellsthatarespecializedforlightdetectionthroughthepresenceofphotosensitivepigmentaswellasameansofrestrictingthedirectionofincominglightt

19、hatwillstrikethephotosensitivecells.Thisdefinitionsaysnothingaboutimageformation,lenses,eyemovements,oranyoftheotherfeaturesweassociatewithourowneyes,butitdoesrecognizethesimplestformoffunctionalandanatomicalspecialisationnamely,detectionoflight.Everythingelsecanbebuiltupfromthissimplebeginning,ands

20、omeanimalsappeartohavehadeyesalmostfromthebeginningoftheanimalkingdom.Paragraph2implieswhichofthefollowingabouttheearlyeyes口Theywereabletodetectsimplemovementsalmostfromthebeginningoftheirevolution.口Theywerenotassensitivetolightasoncethought.口Theycouldnotformimages.口Theircellshadmorephotosensitivepi

21、gmentthandohumaneyesParagraph3:Animalswerescarce600millionyearsagointhegeologicaleracalledthePrecambrian.Thereareveryfewfossilremainsfromthattime(thoughmorekeepturningup),andmostevidenceofthepresenceofanimalsisindirect,suchassmalltunnelsinrockthatcouldbeancientwormburrowings.Butjust50millionyearsors

22、olater,fossilizedbitsandpiecesofanimalsabound,suggestingthatagreatburstofevolutionarycreativityoccurredinthe50-million-yearinterval.Thissurgeofnewlife,markedbyanabundanceofanimals,iscalledtheCambrianexplosion.Whichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepa

23、ssage.Incorrectchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.口TherearefewfossilsfromthePrecambrian,thoughmorekeepturningup.口MostevidenceofanimalsinthefossilrecordisindirectandlittleofitisfromthePrecambrian.口TunnelsinPrecambrianrocksthatmayhavebeenmadebywormsprovideindirectevid

24、enceoftheseanimalsexistingatthattime.口ThereareveryfewfossilsofanimalsfromthePrecambrianandmostevidenceofanimallifefromthatperiodisindirect.Accordingtoparagraph3,theCambrianperiodwascharacterizedby口Agreatabundanceofanimals口Aslowrateofanimalextinction口Therapidfossilizationofanimals口Anincreaseinthelife

25、spanofsomeanimalsParagraph4:Thefirstdirectevidencefortheearlyoriginofeyescomesfromfossilsthatareabout530millionyearsold,atimeshortlyaftertheCambrianexplosion;theywerefoundonamountainsideinBritishColumbiainadepositknownastheBurgessShale.TheBurgessShalefossilsareextraordinarilyimportantbecauseamongthe

26、mareremainsofsoft-bodiedcreatures,manyofthemlackingshellsandotherhardpartsthatfossilizeeasily.Consequently,theirpreservationislittleshortofmiraculous(asarethedelicatemethodsusedtoreconstructthree-dimensionalstructurefromtheseflattenedfossils),andtheyareoneofthefewknownrepositoriesofearlysoft-bodieda

27、nimals.Thephraselittleshortofmiraculousisclosestinmeaning口Toveryhighlyvalued口Amazingbecausealmostimpossible口Causingcontroversy口AlmostbutnotquitecompleteAccordingtoparagraph4,allofthefollowingaretrueoftheBurgessShaleEXCEPT:口Itsfossilswereinaflattenedconditionwhendiscovered.口Itsfossilsprovidedirectevi

28、denceabouttheoriginofeyes.口ItcontainsfossilsofbothPrecambrianandCambriananimals.口Itcontainsfossilizedremainsofsoft-bodiedorganisms.Paragraph5:NotalloftheBurgessanimalshadeyes.However,somedid.(Grossfeatureslocation,size,andhemisphericshapeareresponsibleforthedesignationofsomestructuresaseyes).Thereco

29、nstructedeyesoftheseBurgessanimalslooksuperficiallylikeeyesofsomelivingcrustaceans,particularlythoseofshrimpandcrabswhoseeyesaremountedonstalksthatimprovetherangeofvisionbyraisingtheeyesabovethesurfaceofthehead.TheeyesofsomeBurgessorganismssatonstalks;thoseofotherswereonorapartofthebodysurface.Onean

30、imal,Opabinia,hadfiveeyes:twolateralpairsandasinglemedialeye;atleastoneofthelateralpairshadstalksthatcouldhavebeenmovable.Andsometrilobite-likeanimalsintheBurgessShalehadfacetedeyesmuchlikethoseoflaterfossiltrilobites.Theworddesignationinthepassageisclosestinmeaningto口Evolution口Identification口Recons

31、truction口ConfusionThewordlateralinthepassageindicatesalocationatthe口Front口Back口Top口SideWhydoestheauthorpointoutthatTheeyesofsomeBurgessorganismssatonstalks?口TosuggestthatsomeBurgessorganismshadagreaterrangeofvisionthandolivingshrimpandcrabs口ToexplainwhyitisthoughtthatoneofthelateralpairsofeyesinOpab

32、iniamayhavebeenmovable口ToexplainwhytheeyesofsomeBurgessanimalswerenotrecognizableassuchbeforetheywerereconstructed口TosupportthestatementthatthereconstructedeyesofBurgessanimalslooksuperficiallyliketheeyesofsomelivingcrustaceansParagraph6:AlthoughthepresenceofeyesonsomeoftheBurgessanimalsindicatestha

33、teyeshavebeenaroundforaverylongtime,itisunlikelythatthesewerethefirsteyes;theyseemmuchtoolargeand(potentially)welldevelopedtobebrandnewinventions.ThebestwecandoisputtheoriginofeyessomewherebetweenthebeginningoftheCambrianexplosion,about600millionyearsago,andthedeathoftheBurgessanimals,some530million

34、yearsago.Paragraph6suggeststhatthefirsteyesprobably口Cameintoexistencelongbefore600millionyearsago口CameintoexistenceatalatepointintheCambrianperiod口ExistedbeforetheanimalsoftheBurgessShaleexisted口WerelargerthanthoseofanimalsfoundintheBurgessShaleParagraph1:Puttingadateonthefirstappearanceofeyesdepend

35、sonwhatonemeansbyeye.Ifthetermreferstoamulticellularorgan,evenifithasjustafewcells,thenbydefinition,eyescouldnotformbeforethereweremulticellularanimals.Butmanyprotists(animal-like,plantlike,orfungus-likeunicellularorganismsthatrequireawater-basedenvironment)candetectlightbyusingaggregationsofpigment

36、molecules,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneouslyandindependently).Oneofthefamiliarlivingexamples,probablyknowntoanyonewhohastakenabiologyclass,istheaquaticprotozoanEuglena,whichhasaneyespotnearitsmotilefIagellum(hairlikestructure).Somelivingpr

37、otistsareveryliketheirancestralformsembeddedinancientsedimentaryrocks,andthissimilaritysuggeststhattheabilitytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforaverylongtime.Animalsarosefromoneofsuchunicellularcreatures,perhapsfromonealreadyspecializedforaprimitivekindofvision.Lookatthef

38、oursquaresthatindicatewherethefollowingsentencecouldbeaddedtothepassage.MolariaspiniferaandH.Optata,bothofwhichlivedinwaterlevelsbeyondthereachoflight,fitintothiscategory.Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesth

39、atexpressthemostimportantideasinthepassage.Somesentencesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.Dragyourchoicestothespaceswheretheybelong.Toreviewthepassage.clickonViewText.AnswerChoices口Theabilityofsomeunice

40、llularorganismstodetectlightandchangetheirbehavioraccordinglysuggeststhateyesdidnotoriginatewithmulticellularanimals.口Theearliesteyesapparentlycontainedmoleculesthatwerecapableofformingandfocusingimages.口ToofewfossilsfromthePrecambrianhavebeenfoundtodeterminewhichifanyPrecambrianorganismshadeyes.口Ev

41、idencefromtheBurgessShalesuggeststhateyesofsomeearlyanimalsweresimilartotheeyesoflivingcrustaceans.口FossilevidencesuggeststhatorganismsintheBurgessShalewithfacetedeyesdevelopedlaterthanorganismsintheBurgessShalewithnonfacetedeyes.口ThelargesizeandpossiblecomplexityoftheeyesofsomeorganismsintheBurgess

42、Shalesuggestthattheireyeswerenotthefirsteyes.TPO36-2TheoriginofEarthsatmosphereInordertounderstandtheoriginofEarthsatmosphere,wemustgobacktotheearliestdaysofthesolarsystem,beforetheplanetsthemselveswereformedfromadiskofrockymaterialspinningaroundtheyoungSun.Thismaterialgraduallycoalescedintolumpscal

43、ledplanetesimalsasgravityandchancesmashedsmallerpiecestogether,achaoticandviolentprocessthatbecamemoresoasplanetesimalsgrewinsizeandgravitationalpull.Withineachorbit,collisionsbetweenplanetesimalsgeneratedimmenseheatandenergy.Howviolenttheseprocesseswereissuggestedbytheoddtiltandspinofmanyoftheplane

44、ts,whichindicatethateachoftheplanetswas,likeabilliardball,struckatsomestagebyanotherlargebodyofsomekind.VisualevidenceoftheseprocessescanbeseenbylookingattheMoon.BecausetheMoonhasnoatmosphere,itssurfaceisnotsubjecttoerosion,soitretainsthemarksofitsearlyhistory.Itsfaceisdeeplyscarredbymillionsofmeteo

45、ricimpacts,asyoucanseeonaclearnightwithapairofbinoculars.TheearlyEarthdidnothavemuchofanatmosphere.Beforeitgrewtofullsize,itsgravitationalpullwasinsufficienttopreventgasesfromdriftingoffintospace,whilethesolarwind(thegreatstreamofatomicparticlesemittedfromtheSun)hadalreadydrivenawaymuchofthegaseousm

46、aterialfromtheinnerorbitsofthesolarsystem.SowemustimaginetheearlyEarthasamixtureofrockymaterials,metals,andtrappedgases,subjecttoconstantbombardmentbysmallerplanetesimalsandwithoutmuchofanatmosphere.Asitbegantoreachfullsize,Earthheatedup,partlybecauseofcollisionswithotherplanetesimalsandpartlybecaus

47、eofincreasinginternalpressuresasitgrewinsize.Inaddition,theearlyEarthcontainedabundantradioactivematerials,alsoasourceofheat.AsEarthheatedup,itsinteriormelted.Withinthemolteninterior,undertheinfluenceofgravity,differentelementsweresortedoutbydensity.Byabout40millionyearsaftertheformationofthesolarsy

48、stem,mostoftheheaviermetallicelementsintheearlyEarth,suchasironandnickel,hadsunkthroughthehotsludgetothecentergivingEarthacoredominatedbyiron.ThismetalliccoregivesEarthitscharacteristicmagneticfield,whichhasplayedanextremelyimportantroleinthehistoryofourplanet.AsheavymaterialsheadedforthecenterofEar

49、th,lightersilicates(suchasthemineralquartz)driftedupward.ThedensersilicatesformedEarthsmantle,aregionalmost3,000kilometersthickbetweenthecoreandthecrust.Withthehelpofbombardmentbycomets,whosemanyimpactsscarredandheatedEarthssurface,thelightestsilicatesrosetoEarthssurface,wheretheycooledmorerapidlyth

50、anthebetter-insulatedmaterialsinEarthsinterior.Theselightermaterials,suchastherockswecallgranites,formedalayerofcontinentalcrustabout35kilometersthick.RelativetoEarthasawhole,thisisasthinasaneggshell.Seafloorcrustiseventhinner,atabout7kilometers;thus,evencontinentalcrustreachesonlyabout1/200thofthew

51、aytoEarthscore.MuchoftheearlycontinentalcrusthasremainedonEarthssurfacetothepresentday.Thelightestmaterialsofall,includinggasessuchashydrogenandhelium,bubbledthroughEarthsinteriortothesurface.SowecanimaginethesurfaceoftheearlyEarthasamassivevolcanicfield.Andwecanjudgeprettywellwhatgasesbubbleduptoth

52、atsurfacebyanalyzingthemixtureofgasesemittedbyvolcanoes.Theseincludehydrogen,helium,methane,watervapor,nitrogen,ammonia,andhydrogensulfide.Othermaterials,includinglargeamountsofwatervapor,werebroughtinbycometarybombardments.Muchofthehydrogenandheliumescaped;butonceEarthwasfullyformed,itwaslargeenoug

53、hforitsgravitationalfieldtoholdmostoftheremaininggases,andtheseformedEarthsfirststableatmosphere.Paragraph1:InordertounderstandtheoriginofEarthsatmosphere,wemustgobacktotheearliestdaysofthesolarsystem,beforetheplanetsthemselveswereformedfromadiskofrockymaterialspinningaroundtheyoungSun.Thismaterialg

54、raduallycoalescedintolumpscalledplanetesimalsasgravityandchancesmashedsmallerpiecestogether,achaoticandviolentprocessthatbecamemoresoasplanetesimalsgrewinsizeandgravitationalpull.Withineachorbit,collisionsbetweenplanetesimalsgeneratedimmenseheatandenergy.Howviolenttheseprocesseswereissuggestedbytheo

55、ddtiltandspinofmanyoftheplanets,whichindicatethateachoftheplanetswas,likeabilliardball,struckatsomestagebyanotherlargebodyofsomekind.VisualevidenceoftheseprocessescanbeseenbylookingattheMoon.BecausetheMoonhasnoatmosphere,itssurfaceisnotsubjecttoerosion,soitretainsthemarksofitsearlyhistory.Itsfaceisd

56、eeplyscarredbymillionsofmeteoricimpacts,asyoucanseeonaclearnightwithapairofbinoculars.TheearlyEarthdidnothavemuchofanatmosphere.Beforeitgrewtofullsize,itsgravitationalpullwasinsufficienttopreventgasesfromdriftingoffintospace,whilethesolarwind(thegreatstreamofatomicparticlesemittedfromtheSun)hadalrea

57、dydrivenawaymuchofthegaseousmaterialfromtheinnerorbitsofthesolarsystem.SowemustimaginetheearlyEarthasamixtureofrockymaterials,metals,andtrappedgases,subjecttoconstantbombardmentbysmallerplanetesimalsandwithoutmuchofanatmosphere.Thewordcoalescedinthepassageisclosestinmeaningto口Collided口Joined口Changed

58、口ShrankThewordchaoticinthepassageisclosestinmeaningto口Rapid口Disorganized口Intense口Long-lastingAllofthefollowingaretrueoftheplanetesimalsmentionedinparagraph1EXCEPT:口TheywereformedofrockymaterialspinningaroundtheearlySun.口Theycollidedviolentlywitheachother.口Theygraduallygrewinsize.口Theylosttheiratmosp

59、heresastheywerehitbylargerbodies.Thewordretainsinthepassageisclosestinmeaningto口Reveals口Acquires口Hides口PreservesTheauthordiscussestheMooninparagraph1inorderto口HelpexplainwhyEarthhadfewermeteoricimpactsthanotherplanetsinthesolarsystem口Showwhyitisdifficulttounderstandhowthefirstplanetaryatmospheresdev

60、eloped口Helpexplaintheprocessesthattookplaceintheformationoflargeplanetarybodiesinthesolarsystem口IllustratewhytheMoonsspinandtiltareuniqueamongotherplanetarybodiesinthesolarsystemThewordconstantinthepassageisclosestinmeaningto口Considerable口Unpredictable口Continual口ViolentParagraph2:Asitbegantoreachful