新托福ets真題閱讀56篇2010年02月日

新托福ETS閱讀精選56時(shí)間：20100202日更新Exam1篇）AppliedArtsandFineArts(OG TheOriginsofCetaceans(OGPracticeSet1, DesertFormation(OGPracticeSet2, EarlyCinema(OGPracticeSet3, Aggression(OGPracticeSet ArtisansandIndustrialization(OGPracticeSet SwimmingMachines(OGPracticeSet Nineteenth-CenturyPoliticsintheUnitedStates(OG TheExpressionofEmotions(OG GeologyandLandscape(OG FeedingHabitsofEastAfricanHerbivores(OG LoieFuller(OGTest GreenIcebergs(OGTest OpportunistsandCompetitors(Online LascauxCavePaintings(Online ElectricityfromWind(Online MeteoriteImpactandDinosaurExtinction(OfficialModel TheOriginsofTheater Architecture DepletionoftheOgallalaAquifer TheLong-TermStabilityofEcosystems DeerPopulationsofthePugetSound CaveArtinEurope PetroleumResources MineralsandPlants TheOriginofthePacificIslandPeople TheCambrianExplosion WilliamSmith TheGeologicHistoryoftheMediterranean AncientRomeandGreece Agriculture,Iron,andtheBantuPeoples TheRiseofTeotihuacan ExtinctionoftheDinosaurs RunningWaterMars ColonizingtheAmericasviatheNorthwestCoast TheArrivalofPlantLifeinHawall ChinesePottery VariationsintheClimate AncientEgyptianSculpture BeggingbyNestlings WhichHandDidTheyUse? TransitiontoSoundinFilm WaterintheDesert TypesofSocialGroups BiologicalClocks MethodsofStudyingInfantPerception MayaWaterProblems PastoralisminAncientInnerEurasia 新托福TPO1-13套考期對(duì)（康老師提供考試日OG+網(wǎng)上06.12.08(閱讀+口語(yǔ)06.12.15(+寫(xiě)作06.12.08(+獨(dú)立寫(xiě)作06.12.15(閱讀+口語(yǔ)07.12.01(綜合寫(xiě)作AppliedArtsandFineArts(OGAlthoughwenowtendtorefertothevariouscraftsaccordingtothematerialsusedtoconstructthem—clay,glass,wood,fiber,andmetal—itwasoncecommontothinkofcraftsintermsoffunction,whichledtotheirbeingknownasthe"appliedarts."Approachingcraftsfromthepointofviewoffunction,wecandividethemintosimplecategories:containers,sheltersandsupports.Thereisnowayaroundthefactthatcontainers,shelters,andsupportsmustbefunctional.Theappliedartsarethusboundbythelawsofphysics,whichpertaintoboththematerialsusedintheirmakingandthesubstancesandthingstobecontained,supported,andsheltered.Theselawsareuniversalintheirapplication,regardlessofculturalbeliefs,geography,orclimate.Ifapothasnobottomorhaslargeopeningsinites,itcouldhardlybeconsideredacontainerinanytraditionalsense.Sincethelawsofphysics,notsomearbitrarydecision,havedeterminedteralformofapplied-artobjects,theyfollowbasicpatterns,somuchsothatfunctionalformscanvaryonlywithincertainlimits.Buildingswithoutroofs,forexample,areunusualbecausetheydepartfromthenorm.However,notallfunctionalobjectsareexactlyalike;thatiswhywerecognizeaShangDynastyvaseasbeingdifferentfromanIncavase.Whatvariesisnotthebasicformbuttheincidentaldetailsthatdonotobstructtheobject'sprimaryfunction.Sensitivitytophysicallawsisthusanimportantconsiderationforthemakerofapplied-artobjects.Itisoftentakenforgrantedthatthisisalsotrueforthemakeroffine-artobjects.Thisassumptionmissesasignificantdifferencebetweenthetwodisciplines.Fine-artobjectsarenotconstrainedbythelawsofphysicsinthesamewaythatapplied-artobjectsare.Becausetheirprimarypurposeisnotfunctional,theyareonlylimitedintermsofthematerialsusedtomakethem.Sculpturesmust,forexample,bestable,whichrequiresanunderstandingofthepropertiesofmass,weightdistribution,andstress.Paintingsmusthaverigidstretcherssothatthecanvaswillbetaut,andthepaintmustnotdeteriorate,crack,ordiscolor.Theseareproblemsthatmustbe ebytheartistbecausetheytendtointrudeuponhisorherconceptionofthework.Forexample,intheearlyItalianRenaissance,bronzestatuesofhorseswitharaisedforelegusuallyhadacannonballunderthathoof.Thiswasdonebecausethecannonballwasneededtosupporttheweightoftheleg.Inotherwords,thedemandsofthelawsofphysics,notthesculptor'saestheticintentions,placedtheballthere.Thatthisdevicewasanecessarystructuralcompromiseisclearfromthefactthatthecannonballquicklydisappearedwhensculptorslearnedhowtostrengthentheinternalstructureofastatuewithironbraces(ironbeingmuchstrongerthanbronze).Eventhoughthefineartsinthetwentiethcenturyoftentreatmaterialsinnewways,thebasicdifferenceinattitudeofartistsinrelationtotheirmaterialsinthefineartsandtheappliedartsremainsrelativelyconstant.Itwouldthereforenotbetoogreatanexaggerationtosaythatpractitionersofthefineartswork ethelimitationsoftheirmaterials,whereasthoseengagedintheappliedartsworkinconcertwiththeirmaterials.[PassageParagraph1:Althoughwenowtendtorefertothevariouscraftsaccordingtothematerialsusedtoconstructthem-clay,glass,wood,fiber,andmetal-itwasoncecommontothinkofcraftsintermsoffunction,whichledtotheirbeingknownasthe"appliedarts."Approachingcraftsfromthepointofviewoffunction,wecandividethemintosimplecategories:containers,sheltersandsupports.Thereisnowayaroundthefactthatcontainers,shelters,andsupportsmustbefunctional.Theappliedartsarethusboundbythelawsofphysics,whichpertaintoboththematerialsusedintheirmakingandthesubstancesandthingstobecontained,supported,andsheltered.Theselawsareuniversalintheirapplication,omearbitrarydecision,havedetermined eralomearbitrarydecision,havedetermined eralformofapplied-artfollowpatterns,somuchsothatfunctionalformscanvaryonlywithincertainlimits.Buildingswithoutroofs,forexample,areunusualbecausetheydepartfromthenorm.However,notallfunctionalobjectsareexactlyalike;thatiswhywerecognizeaShangDynastyvaseasbeingdifferentfromanIncavase.Whatvariesisnotthebasicformbuttheincidentaldetailsthatdonotobstructtheobject'sprimaryfunction.ThewordtheyinthepassagerefersThelawsofThesidesofWhichofthefollowingbestexpressestheessentialinformationinthehighlightedsentence?Incorrectanswerchoiceschangethemeaninginimportantwaysorleaveoutessentialinformation.Functionalapplied-artobjectscannotvarymuchfromthebasicpatternsdeterminedbythelawsofThefunctionofapplied-artobjectsisdeterminedbybasicpatternsinthelawsofSincefunctionalapplied-artobjectsvaryonlywithincertainlimits,arbitrarydecisionscannothavedeterminedtheirgeneralform.Teralformofapplied-artobjectsislimitedbysomearbitrarydecisionthatisnotdeterminedbythelawsofphysics.Accordingtoparagraph2,sculptorsintheItalianRenaissancestoppedusingcannonballsinbronzestatuesofhorsesbecauseTheybeganusingamaterialthatmadethestatuesweighTheyfoundawaytostrengthenthestatuesTheaesthetitesofthepublichadchangedoverThecannonballsaddedtoomuchweighttotheWhydoestheauthordiscussthebronzestatuesofhorsescreatedbyartistsintheearlyItalianToprovideanexampleofaproblemrelatedtothelawsofphysicsthatafineartist ToarguethatfineartistsareunconcernedwiththelawsofTocontrasttherelativesophisticationofmodernartistsinsolvingproblemsrelatedtothelawsofTonoteanexceptionalpieceofartconstructedwithouttheaidofAnintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Somesentencesdonotbelonginthesummarybecausetheyexpressideasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.Thispassagediscussesfundamentaldifferencesbetweenapplied-artThispassagediscussesfundamentaldifferencesbetweenapplied-artobjectsandfine-artobjects.●●●AnswerThefineartsareonlyaffectedbythelawsofphysicsbecauseofthelimitationsofthematerialsthatareApplied-artobjectsareboundbythelawsofphysicsintwoways:bythematerialsusedtomakethem,andthefunctiontheyaretoserve.Craftsareknownas"appliedarts"becauseitusedtobecommontothinkofthemintermsoftheirInthefinearts,artistsmustworkto ethelimitationsoftheirmaterials,butintheappliedarts,artistsworkinconcertwiththeirmaterials.Makingfine-artobjectsstablerequiresanunderstandingofthepropertiesofmass,weight,distribution,andstress.Inthetwentiethcentury,artistsworkinginthefineartsoftentreatmaterialsinnewwaysappliedartsspecialistscontinuetothinkofcraftsintermsofDirections:Completethetablebelowtosummarizeinformationaboutthetwotypesofartdiscussedinthepassage.Matchtheappropriatestatementstothetypesofartwithwhichtheyareassociated.Thisquestionisworth3points.TheFineArtsSelect●TheFineArtsSelect●●TheAppliedArtsSelect●●●Anobject'spurposeisprimarilyObjectsserveafunctionalTheincidentaldetailsofobjectsdonotArtistswork ethelimitationsoftheirThebasicformofobjectsvarieslittleacrossArtistsworkinconcertwiththeirAnobject'splaceoforiginisdifficulttoDragyouranswerchoicestothespaceswheretheybelong.Toreviewthepassage,clickonViewANSWERSAND. 24 2561參考譯在現(xiàn)代，人們將根據(jù)工藝品的制造材質(zhì)對(duì)他們進(jìn)行分類(lèi)，如陶土，玻璃，木頭，纖維還有金屬。但最分為：容器，遮蔽物，支撐物。它們都是具有一定功能的物品。這些實(shí)用工藝品以自然規(guī)律為基礎(chǔ)，它們的制作材料及其容納、支撐、遮蓋的內(nèi)容需要符合這些規(guī)律。這些規(guī)律在工藝品應(yīng)用過(guò)程中非常那么它在任何傳統(tǒng)意義上都很難被視為是一個(gè)容器。自然規(guī)律決定了實(shí)用工藝品的一般形式，而不是武斷的結(jié)論決定的，它們遵循基本的樣式，以至于它們的功能不會(huì)變化太大。舉個(gè)例子，沒(méi)有屋頂?shù)慕ㄖ呛苌僖?jiàn)的，因?yàn)樗俗匀灰?guī)律。但是，并不是所有的功能物品都一模一樣，比如我們知道的為什么商代且油畫(huà)不可以有毀損，裂紋，褪色。類(lèi)似都是藝術(shù)家們必須克服的，這些困擾往往影響了藝術(shù)家對(duì)于術(shù)家的美學(xué)意愿。當(dāng)?shù)袼芗覍W(xué)會(huì)如何了用鐵支架加強(qiáng)雕塑的結(jié)構(gòu)后（鐵比青銅更結(jié)實(shí)），就不再使用TheOriginsofCetaceans(OGPracticeSet1,Itshouldbeobviousthatcetaceans—whales,porpoises,anddolphins-aremammals.Theybreathethroughlungs,notthroughgills,andgivebirthtoliveyoung.Theirstreamlinedbodies,theabsenceofhindlegs,andthepresenceofafluke1andblowhole2cannotdisguisetheiraffinitieswithlanddwellingmammals.However,unlikethecasesofseaottersandpinnipeds(seals,sealions,andwalruses,whoselimbsarefunctionalbothonlandandatsea),itisnoteasytoenvisionwhatthefirstwhaleslookedlike.Extinctbutalreadyfullymarinecetaceansareknownfromthefossilrecord.■Howwasthegapbetweenawalkingmammalandaswimmingwhalebridged?■Missinguntilrecentlywerefossilsclearlyintermediate,ortransitional,betweenlandmammalsandcetaceans.Veryexcitingdiscoverieshavefinallyallowedscientiststoreconstructthemostlikelyoriginsofcetaceans.■In1979,ateamlookingforfossilsinnorthernPakistanfoundwhatprovedtobetheoldestfossilwhale.ThefossilwasofficiallynamedPakicetusinhonorofthecountrywherethediscoverywasmade.Pakicetuswasfoundembeddedinrocksformedfromriverdepositsthatwere52millionyearsold.TheriverthatformedthesedepositswasactuallynotfarfromanancientoceanknownastheTethysSea.Thefossilconsistsofacompleteskullofanarchaeocyte,anextinctgroupofancestorsofmoderncetaceans.Althoughlimitedtoaskull,thePakicetusfossilprovidespreciousdetailsontheoriginsofcetaceans.Theskulliscetacean-likebutitsjawboneslacktheenlargedspacethatisfilledwithfatoroilandusedforreceivingunderwatersoundinmodernwhales.Pakicetusprobablydetectedsoundthroughtheearopeningasinlandmammals.Theskullalsolacksablowhole,anothercetaceanadaptationfordiving.Otherfeatures,however,showexpertsthatPakicetusisatransitionalformbetweenagroupofextinctflesh-eatingmammals,themesonychids,andcetaceans.IthasbeensuggestedthatPakicetusfedonfishinshallowwaterandwasnotyetadaptedforlifeintheopenocean.Itprobablybredandgavebirthonland.AnothermajordiscoverywasmadeinEgyptin1989.Severalskeletonsofanotherearlywhale,Basilosaurus,werefoundinsedimentsleftbytheTethysSeaandnowexposedintheSaharadesert.Thiswhalelivedaround40millionyearsago,12millionyearsafterPakicetus.Manypleteskeletonswerefoundbuttheyincluded,forthefirsttimeinanarchaeocyte,acompletehindlegthatfeaturesafootwiththreetinytoes.Suchlegswouldhavebeenfartoosmalltohavesupportedthe50-foot-longBasilosaurusonland.Basilosauruswasundoubtedlyafullymarinewhalewithpossiblynonfunctional,orvestigial,hindlegs.Anevenmoreexcitingfindwasreportedin1994,alsofromPakistan.ThenowextinctwhaleAmbulocetusnatans("thewalkingwhalethatswam")livedintheTethysSea49millionyearsago.Itlivedaround3millionyearsafterPakicetusbut9millionbeforeBasilosaurus.Thefossilluckilyincludesagoodportionofthehindlegs.Thelegswerestrongandendedinlongfeetverymuchlikethoseofamodernpinniped.Thelegswerecertainlyfunctionalbothonlandandatsea.Thewhaleretainedatailandlackedafluke,themajormeansof otioninmoderncetaceans.Thestructureofthebackboneshows,however,thatAmbulocetusswamlikemodernwhalesbymovingtherearportionofitsbodyupanddown,eventhoughaflukewasmissing.Thelargehindlegswereusedforpropulsioninwater.Onland,whereitprobablybredandgavebirth,Ambulocetusmayhavemovedaroundverymuchlikeamodernsealion.Itwasundoubtedlyawhalethatlinkedlifeonlandwithlifeatsea.Fluke:thetwopartsthatconstitutethelargetriangulartailofaBlowhole:aholeinthetopoftheheadusedfor[PassageDirections:Markyouranswerbyfillingintheovalnexttoyourchoice.Inparagraph1,whatdoestheauthorsayaboutthepresenceofablowholeinItclearlyindicatesthatcetaceansareItcannotconcealthefactthatcetaceansareItisthemaindifferencebetweencetaceansandland-dwellingItcannotyieldcluesabouttheoriginsofWhichofthefollowingcanbeinferredfromparagraph1aboutearlyseaItisnotdifficulttoimaginewhattheylookedThereweregreatnumbersofTheylivedintheseaTheydidnotleavemanyfossilThewordpreciousinthepassageisclosestinmeaningPakicetusandmoderncetaceanshaveTheworditinthepassagerefersThewordexposedinthepassageisclosestinmeaningThehindlegofBasilosauruswasasignificantfindbecauseitshowedthatLivedlaterthanAmbulocetusLivedatthesametimeasWasabletoswimCouldnothavewalkedonItcanbeinferredthatBasilosaurusbredandgavebirthinwhichofthefollowingOnBothonlandandatInshallowInamarineWhydoestheauthorusethewordhindlegs?

luckilyinmentioningthattheAmbulocetusnatansfossilFossillegsofearlywhalesarearareThelegsprovidedimportantinformationabouttheevolutionofThediscoveryallowedscientiststoreconstructacompleteskeletonoftheUntilthattime,onlythefrontlegsofearlywhaleshadbeenWhichofthesentencesbelowbestexpressestheessentialinformationinthehighlightedsentenceinthepassage?IncorrectchoiceschangethemeaninginimportantwaysorleaveoutessentialEventhoughAmbulocetusswambymovingitsbodyupanddown,itdidnothaveaThebackboneofAmbulocetus,whichallowedittoswim,providesevidenceofitsmissingAlthoughAmbulocetushadnofluke,itsbackbonestructureshowsthatitswamlikemodernBymovingtherearpartsoftheirbodiesupanddown,modernwhalesswiminadifferentwayfromthewayAmbulocetusswam.ThewordpropulsioninthepassageisclosestinmeaningDecreasingLookatthefoursquares[■]thatindicatewherethefollowingsentencecanbeaddedtotheThisisaquestionthathaspuzzledscientistsforWherewouldthesentencebest1234.Directions:Anintroductorysentenceforabriefsummaryofthepassageisprovidedbelow.CompletethesummarybyselectingtheTHREEanswerchoicesthatexpressthemostimportantideasinthepassage.Someanswerchoicesdonotbelonginthesummarybecausetheyexpreeasthatarenotpresentedinthepassageorareminorideasinthepassage.Thisquestionisworth2points.ThispassagediscussesfossilsthathelpThispassagediscussesfossilsthathelptoexplainthelikelyoriginsofcetaceanswhales,porpoises,anddolphins.●●●Answer1.Recentdiscoveriesoffossilshavehelpedtoshowthelinkbetweenlandmammalsand2.ThediscoveryofAmbulocetusnatansprovidedevidenceforawhalethatlivedbothonlandandat3.TheskeletonofBasilosauruswasfoundinwhathadbeentheTethysSea,anarearichinfossil4.Pakicetusistheoldestfossilwhaleyettobe5.Fossilsthoughttobetransitionalformsbetweenwalkingmammalsandswimmingwhaleswere6.Ambulocetus'hindlegswereusedforpropulsionintheANSWERSAND1.ThisisaFactualInformationquestionaskingforspecificinformationthatcanbefoundinparagraph1.Choice2isthebestanswer.Itisessentiallyarephrasingofthestatementinparagraph1thatblowholescannotdisguisecetaceans’affinitieswithothermammals.Theotherthreechoicesarerefuted,eitherdirectlyorindirectly,bythatparagraph.2.ThisisanInferencequestionaskingforinformationthatcanbeinferredfromparagraph1.Choice1isthebestanswerbecauseparagraph1saysthatseaottersareunlikeearlymammalswhoseappearancesarenoteasytoimagine.Byinference,then,theearlyappearanceofseaottersmustbeeasy(ornotdifficult)toimagine.3.ThisisaVocabularyquestion.Thewordbeingtestedisprecious.Itishighlightedinthepassage.Thecorrectanswerischoice3,"valuable."Anythingthatispreciousisveryimportantandthereforevaluable.4.ThisisaFactualInformationquestionaskingforspecificinformationthatcanbefoundinthepassage.Choice3isthebestanswer.Paragraph3describesthedifferencesandsimilaritiesbetweenPakicetusandmoderncetaceans.Sentence3ofthatparagraphstatesthattheirskullsaresimilar.Theotherthreechoicesdescribedifferences,notsimilarities.5.ThisisaReferencequestion.ThewordbeingtestedisIt.Thatwordishighlightedinthepassage.Thisisasimplepronounreferentitem.ChoiceI,"Pakicetus"isthecorrectanswer.ThewordItherereferstoacreaturethatprobablybredandgavebirthonland.Pakicetusistheonlyoneofthechoicestowhichthiscouldapply.6.ThisisaVocabularyquestion.Thewordbeingtestedisexposed.Itishighlightedinthepassage.Thecorrectanswerischoice2,"visible."Exposedmeans"uncovered."Askeletonthatisuncoveredcanbeseen.Visiblemeans"canbeseen."7.ThisisaFactualInformationquestionaskingforspecificinformationthatcanbefoundintheChoice4isthebestanswerbecauseitistheonlydetailabouttheskeletonofBasilosaurusmentionedinparagraph4,meaningthatitissignificant.Choice1istrue,butitisnotdiscussedinthedetailthatchoice4is,anddoesnotrepresentthesignificanceofthediscovery.Choice3isnotmentioned,andchoice2isnot:me.8.ThisisanInferencequestionaskingforaconclusionthatcanbedrawnfromtheentirepassage.Choice4isthebestanswerbasedonthelastenceofparagraph4,whichdescribesBasilosaurusasafullymarinewhale.Thatimpliesthateverythingitdid,includingbreedingandgivingbirth,couldhavebeendoneonlyinamarineenvironment.9.ThisisanInferencequestionaskingforaconclusionthatcanbedrawnfromthepassage.Paragraph5explainsthatthisdiscoveryprovidedimportantinformationtoscientiststhattheymightnothavebeenabletoobtainwithoutit.Therefore,youcaninferthatthediscoverywasa"lucky"one.Thepassageoffersnosupportfortheotherchoices.Therefore,choice2isthebestanswer.10.ThisisaSentenceSimplificationquestion.Aswithalloftheseitems,asinglesentenceinthepassageisThestructureofthebackboneshows,however,thatAmbulocetusswamlikemodernwhalesbymovingtherearportionofitsbodyupanddown,eventhoughaflukewasmissing.Choice3isthebestanswerbecauseitcontainsalloftheessentialinformationinthehighlightedChoice1isnottruebecauseAmbulocetusdidhaveabackbone.Choice2isnottruebecausethesentencesaysthatthebackboneshowedhowtheAmbulocetusswam,notthatitwasmissingafluke.Choice4isuntruebecausethesentencestatesthatAmbulocetusandmodernwhalesswaminthesame11.ThisisaVocabularyquestion.Thewordbeingtestedispropulsion.Itishighlightedinthepassage.Choice4,"movingforward"isthebestanswerbecauseitmeanstheactionofpropelling.Thewhaleinthesentenceuseditshindlegstopushitselfforwardinthewater.12.ThisisanInsertTextquestion.Youcanseethefourblacksquaresinparagraphs1and2thatrepresentthepossibleanswerchoiceshere.Extinctbutalreadyfullymarinecetaceansareknownfromthefossilrecord.■Howwasthegapbetweenawalkingmammalandaswimmingwhalebridged?■Missinguntilrecentlywerefossilsclearlyintermediate,ortransitional,betweenlandmammalsandcetaceans.Veryexcitingdiscoverieshavefinallyallowedscientiststoreconstructthemostlikelyoriginsofcetaceans.■In1979.ateamlookingforfossilsinnorthernPakistanfoundwhatprovedtobetheoldestfossilwhale.Thesentenceprovidedis"Thisisaquestionthathaspuzzledscientistsforages."Thebestplacetoinsertitisatsquare2.Thesentencethatprecedessquare2isintheformofarhetoricalquestionandtheinsertedsentenceexplicitlyprovidesaresponsetoit.Noneoftheothersentencesprecedingsquaresisaquestion,sotheinsertedsentencecannotlogicallyfollowanyoneofthem.13..12

參考譯豹，海獅，海象）的原貌那么簡(jiǎn)單。一些完全水生的鯨類(lèi)動(dòng)物雖然已經(jīng)，但仍可通過(guò)化石來(lái)對(duì)它們進(jìn)行。陸棲哺乳動(dòng)物和海洋鯨類(lèi)之間有何聯(lián)系？近期發(fā)現(xiàn)的化石已經(jīng)可以很清晰地幫助人們了解這個(gè)問(wèn)科學(xué)家們通過(guò)一些令人振奮的發(fā)現(xiàn)重現(xiàn)了鯨類(lèi)動(dòng)物幾近真實(shí)的。1979年，在北部，一個(gè)尋找化石的隊(duì)發(fā)掘到了最古老的鯨魚(yú)化石。這塊化石被命名為Pakicifus，以紀(jì)念人們發(fā)現(xiàn)它的地方。這塊化石是在一條河的沉積巖中發(fā)現(xiàn)的，這條河有5200萬(wàn)年的歷史，離古地中海不遠(yuǎn)Pakicifus包括一個(gè)完整原始動(dòng)物的頭蓋骨，它的主人是現(xiàn)代鯨類(lèi)的祖先。盡管只是個(gè)頭蓋骨，但它卻提供了研究原始鯨類(lèi)動(dòng)物的珍貴信息。這個(gè)頭蓋骨和鯨類(lèi)動(dòng)物的很像，但它的下頜骨和現(xiàn)代鯨類(lèi)略有不同，現(xiàn)代鯨類(lèi)動(dòng)物的下頜骨中含有額外的空間脂肪或者油脂來(lái)吸收水下。Pakicifus的主人可能會(huì)像陸生哺乳動(dòng)物那樣通過(guò)張開(kāi)的耳朵來(lái)探測(cè)聲音。另外，這個(gè)頭蓋骨沒(méi)孔，而鯨類(lèi)動(dòng)物有，這的食肉哺乳動(dòng)物（中獸科動(dòng)物）和鯨類(lèi)動(dòng)物的過(guò)渡型。有人認(rèn)為Pakicifus靠吃淺水的魚(yú)類(lèi)為生，未能，在埃及有了另一個(gè)重大發(fā)現(xiàn)。人們?cè)诠诺刂泻埩舻某练e物中發(fā)現(xiàn)了另一類(lèi)早期鯨魚(yú)Basilosaurus的一些骨骸，這些骨骸如今在撒哈拉大沙漠上。Basilosaurus大約4000萬(wàn)年前，比Pakicifus鯨魚(yú)晚了1200萬(wàn)年。盡管發(fā)現(xiàn)的這些骨骼并不完整，但這是們第一次在原始動(dòng)物身上發(fā)在陸地行走。因此，Basilosaurus必定是完全水生的鯨魚(yú)，它們的后肢已經(jīng)不起任何作用，或者說(shuō)已經(jīng)退行的鯨類(lèi)）4900Pakicetus300Basilosaurus900萬(wàn)留了尾巴，但它們?nèi)鄙佻F(xiàn)代水生鯨類(lèi)動(dòng)物用于行動(dòng)的主要身體部位——Ambulocetus的脊椎結(jié)構(gòu)上可以看出，即使缺少尾片，它們也能像現(xiàn)代鯨魚(yú)那樣通過(guò)身體背部的上下擺動(dòng)來(lái)。大的后肢DesertFormation(OGPracticeSet2,Thedeserts,whichalreadyoccupyapproximayafourthoftheEarth'slandsurface,haveinrecentdecadesbeenincreasingatarmingpace.Theexpansionofdesertlikeconditionsintoareaswheretheydidnotpreviouslyexistiscalleddesertification.Ithasbeenestimatedthatanadditionalone-fourthoftheEarth'slandsurfaceisthreatenedbythisprocess.Desertificationis plishedprimarilythroughthelossofstabilizingnaturalvegetationandthesubsequentacceleratederosionofthesoilbywindandwater.Insomecasestheloosesoilisblowncompleyaway,leavingastonysurface.Inothercases,thefinerparticlesmayberemoved,whilethesand-sizedparticlesareaccumulatedtoformmobilehillsorridgesofsand.Evenintheareasthatretainasoilcover,thereductionofvegetationtypicallyresultsinthelossofthesoil'sabilitytoabsorbsubstantialtiesofwater.Theimpactofraindropsontheloosesoiltendstotransferfineclayparticlesintothetiniestsoilspaces,sealingthemandproducingasurfacethatallowsverylittlewaterpenetration.Waterabsorptionisgreatlyreduced;consequentlyrunoffisincreased,resultinginacceleratederosionrates.Thegradualdryingofthesoilcausedbyitsdiminishedabilitytoabsorbwaterresultsinthefurtherlossofvegetation,sothycleofprogressivesurfacedeteriorationisestablished.Insomeregions,theincreaseindesertareasisoccurringlargelyastheresultofatrendtowarddrierclimaticconditions.Continuedgradualglobalwarminghasproducedanincreaseinaridityforsomeareasoverthepastfewthousandyears.Theprocessmaybeacceleratedinsubsequentdecadesifglobalwarmingresultingfromairpollutionseriouslyincreases.Thereislittledoubt,however,thatdesertificationinmostareasresultsprimarilyfromhumanactivitiesratherthannaturalprocesses.Thesemiaridlandsborderingthedesertsexistinadelicateecologicalbalanceandarelimitedintheirpotentialtoadjusttoincreasedenvironmentalpressures.Expandingpopulationsaresubjectingthelandtoincreasingpressurestoprovidethemwithfoodandfuel.Inwetperiods,thelandmaybeabletorespondtothesestresses.Duringthedryperiodsthatarecommonphenomenaalongthedesertmargins,though,thepressureonthelandisoftenfarinexcessofitsdiminishedcapacity,anddesertificationresults.Fourspecificactivitieshavebeenidentifiedasmajorcontributorstothedesertificationprocesses:overcultivation,overgrazing,firewoodgathering,andoverirrigation.Thecultivationofcropshasexpandedintoprogressivelydrierregionsaspopulationdensitieshavegrown.Theseregionsareespeciallylikelytohaveperiodsofseveredryness,sothatcropfailuresarecommon.Sincetheraisingofmostcropsnecessitatesthepriorremovalofthenaturalvegetation,cropfailuresleaveextensivetractsoflanddevoidofaplantcoverandsusceptibletowindandwatererosion.Theraisingoflivestockisamajoreconomicactivityinsemiaridlands,wheregrassesaregenerallythedominanttypeofnaturalvegetation.Theconsequencesofanexcessivenumberoflivestockgrazinginanareaarethereductionofthevegetationcoverandthetramplingandpulverizationofthesoil.Thisisusuallyfollowedbythedryingofthesoilandacceleratederosion.Firewoodisthechieffuelusedforcookingandheatinginmanycountries.Theincreasedpressuresofexpandingpopulationshaveledtotheremovalofwoodyplantssothatmanycitiesandtownsaresurroundedbylargeareascompleylackingintreesandshrubs.Theincreasinguseofdriedanimalwasteasasubstitutefuelhasalrtthesoilbecausethisvaluablesoilconditionerandsourceofplantnutrientsisnolongerbeingreturnedtotheland.Thefinalmajorhumancauseofdesertificationissoilsalinizationresultingfromoverirrigation.Excesswaterfromirrigationsinksdownintothewatertable.Ifnodrainagesystemexists,thewatertablerises,bringingdissolvedsaltstothesurface.Thewaterevaporatesandthesaltsareleftbehind,creatingawhitecrustallayerthatpreventsairandwaterfromreachingtheunderlyingsoil.Theextremeseriousnessofdesertificationresultsfromthevastareasoflandandthetremendousnumbersofpeopleaffected,aswellasfromthegreatdifficultyofreversingorevenslowingtheprocess.Oncethesoilhasbeenremovedbyerosion,onlythepassageofcenturiesormillenniawillenablenewsoiltoform.Inareaswhereconsiderablesoilstillremains,though,arigorouslyenforcedprogramoflandprotectionandcover-cropplantingmaymakeitpossibletoreversethepresentdeteriorationofthe[PassageParagraph1:Thedeserts,whichalreadyoccupyapproximayafourthoftheEarth'slandsurface,haveinrecentdecadesbeenincreasingatarmingpace.Theexpansionofdesertlikeconditionsintoareaswheretheydidnotpreviouslyexistiscalleddesertification.Ithasbeenestimatedthatanadditionalone-fourthoftheEarth'slandsurfaceisthreatenedbythisprocess.ThewordthreatenedinthepassageisclosestinmeaningParagraph3:Evenintheareasthatretainasoilcover,thereductionofvegetationtypicallyresultsinthelossofthesoil'sabilitytoabsorbsubstantialtiesofwater.Theimpactofraindropsontheloosesoiltendstotransferfineclayparticlesintothetiniestsoilspaces,sealingthemandproducingasurfacethatallowsverylittlewaterpenetration.Waterabsorptionisgreatlyreduced;consequentlyrunoffisincreased,resultinginacceleratederosionrates.Thegradualdryingofthesoilcau