TPO36阅读文本和题目正式版

TPO36-1TheFirstEyePuttingadateonthefirstappearanceofeyesdependsonwhatonemeansbyeye.Ifthetermreferstoamulticellularorgan,evenifithasjustafewcells,thenbydefinition,eyescouldnotformbeforethereweremulticellularanimals.Butmanyprotists(animal-like,plantlike,orfungus-likeunicellularorganismsthatrequireawater-basedenvironment)candetectlightbyusingaggregationsofpigmentmolecules,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneouslyandindependently).Oneofthefamiliarlivingexamples,probablyknowntoanyonewhohastakenabiologyclass,istheaquaticprotozoanEuglena,whichhasaneyespotnearitsmotilefIagellum(hairlikestructure).Somelivingprotistsareveryliketheirancestralformsembeddedinancientsedimentaryrocks,andthissimilaritysuggeststhattheabilitytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforaverylongtime.Animalsarosefromoneofsuchunicellularcreatures,perhapsfromonealreadyspecializedforaprimitivekindofvision.Aneyeisacollectionofcellsthatarespecializedforlightdetectionthroughthepresenceofphotosensitivepigmentaswellasameansofrestrictingthedirectionofincominglightthatwillstrikethephotosensitivecells.Thisdefinitionsaysnothingaboutimageformation,lenses,eyemovements,oranyoftheotherfeaturesweassociatewithourowneyes,butitdoesrecognizethesimplestformoffunctionalandanatomicalspecialisationnamely,detectionoflight.Everythingelsecanbebuiltupfromthissimplebeginning,andsomeanimalsappeartohavehadeyesalmostfromthebeginningoftheanimalkingdom.Animalswerescarce600millionyearsagointhegeologicaleracalledthePrecambrian.Thereareveryfewfossilremainsfromthattime(thoughmorekeepturningup),andmostevidenceofthepresenceofanimalsisindirect,suchassmalltunnelsinrockthatcouldbeancientwormburrowings.Butjust50millionyearsorsolater,fossilizedbitsandpiecesofanimalsabound,suggestingthatagreatburstofevolutionarycreativityoccurredinthe50-million-yearinterval.Thissurgeofnewlife,markedbyanabundanceofanimals,iscalledtheCambrianexplosion.Thefirstdirectevidencefortheearlyoriginofeyescomesfromfossilsthatareabout530millionyearsold,atimeshortlyaftertheCambrianexplosion;theywerefoundonamountainsideinBritishColumbiainadepositknownastheBurgessShale.TheBurgessShalefossilsareextraordinarilyimportantbecauseamongthemareremainsofsoft-bodiedcreatures,manyofthemlackingshellsandotherhardpartsthatfossilizeeasily.Consequently,theirpreservationislittleshortofmiraculous(asarethedelicatemethodsusedtoreconstructthree-dimensionalstructurefromtheseflattenedfossils),andtheyareoneofthefewknownrepositoriesofearlysoft-bodiedanimals.NotalloftheBurgessanimalshadeyes.However,somedid.(Grossfeatureslocation,size,andhemisphericshapeareresponsibleforthedesignationofsomestructuresaseyes).ThereconstructedeyesoftheseBurgessanimalslooksuperficiallylikeeyesofsomelivingcrustaceans,particularlythoseofshrimpandcrabswhoseeyesaremountedonstalksthatimprovetherangeofvisionbyraisingtheeyesabovethesurfaceofthehead.TheeyesofsomeBurgessorganismssatonstalks;thoseofotherswereonorapartofthebodysurface.Oneanimal,Opabinia,hadfiveeyes:twolateralpairsandasinglemedialeye;atleastoneofthelateralpairshadstalksthatcouldhavebeenmovable.Andsometrilobite-likeanimalsintheBurgessShalehadfacetedeyesmuchlikethoseoflaterfossiltrilobites.AlthoughthepresenceofeyesonsomeoftheBurgessanimalsindicatesthateyeshavebeenaroundforaverylongtime,itisunlikelythatthesewerethefirsteyes;theyseemmuchtoolargeand(potentially)welldevelopedtobebrandnewinventions.ThebestwecandoisputtheoriginofeyessomewherebetweenthebeginningoftheCambrianexplosion,about600millionyearsago,andthedeathoftheBurgessanimals,some530millionyearsago.Paragraph1:Puttingadateonthefirstappearanceofeyesdependsonwhatonemeansbyeye.Ifthetermreferstoamulticellularorgan,evenifithasjustafewcells,thenbydefinition,eyescouldnotformbeforethereweremulticellularanimals.Butmanyprotists(animal-like,plantlike,orfungus-likeunicellularorganismsthatrequireawater-basedenvironment)candetectlightbyusingaggregationsofpigmentmolecules,andtheyusethisinformationtomodifytheirmetabolicactivityormotility(theabilitytomovespontaneouslyandindependently).Oneofthefamiliarlivingexamples,probablyknowntoanyonewhohastakenabiologyclass,istheaquaticprotozoanEuglena,whichhasaneyespotnearitsmotilefIagellum(hairlikestructure).Somelivingprotistsareveryliketheirancestralformsembeddedinancientsedimentaryrocks,andthissimilaritysuggeststhattheabilitytodetectlightandmodifybehaviorinresponsetolighthasbeenaroundforaverylongtime.Animalsarosefromoneofsuchunicellularcreatures,perhapsfromonealreadyspecializedforaprimitivekindofvision.1.Theword“aggregations”inthepassageisclosestinmeaningtoParts.Reactions.Groups.Types.2.Paragraph1supportsallofthefollowingstatementsaboutprotistsEXCEPT:Somearemulticellular.Someareabletomove.Somehavepigmentmolecules.Theyliveinenvironmentsthatcontainmoisture.3.Accordingtoparagraph1,whathavescientistsconcludedfromthefactthatsomelivingprotistsareveryliketheirancestralformsTheeyedidnotevolveuntilmulticellularorganismsarose.Theabilitytodetectlightandchangebehaviori