机经-雅思5-6阅读必考

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（4个AAmbergrisisasolid,waxy,flammablesubstanceofadullgreyorblackishcolorproducedinthedigestivesystemofspermwhales.AmbergriswasusedtoperfumecosmeticsinthedaysofancientMesopotamiaandalmosteverycivilizationontheearthhasabrushwithAmbergris.Before1,000AD,theChinesenamesambergrisaslungsienhiang,"dragon'sspittleperfume",astheythinkthatitwasproducedfromthedroolingofdragonsslee onrocksattheedgeofasea.TheArabsknewambergrisasanbarwhobelievedthatitisproducedfromspringsnearseas.Italsogetsitsnamefromhere.Forcenturies,thissubstancehasalsobeenusedasaflavouringforfood.

BDuringtheMiddleAges,Europeansusedambergrisasaremedyforheadaches,colds,epilepsy,andotherailments.Inthe1851whalingnovelMoby-Dick,HermanMelvilleclaimedthatambergriswas"largelyusedinperfumery."Melvilledevotesacompletechaptertoadiscussionofambergris,withspecialattentiontotheironythat"fineladiesandgentlemenshouldregalethemselveswithanessencefoundintheingloriousbowelsofasickwhale:'Butnobodyeverknewwhereitreallycamefrom.Expertswerestillguessingitsoriginthousandsofyearslater,untilthelongagesofguessworkendedinthe1720's,whenNantucketwhalersfoundgobsofthecostlymaterialinsidethestomachsofspermwhales.Industrialwhalingquicklyburgeoned.By20thcenturyambergrisismainlyrecoveredfrominsidethecarcassesofsperm

C1Throughcountlessages,peoplehavefoundpiecesofambergrisonsandybeaches.Itwasnamedgreyambertodistinguishitfromgoldenamber,anotherraretreasure.Bothofthemwereamongthemostsought-aftersubstancesintheworld,almostasvaluableasgold.(Ambergrissellsforroughly$20agram,slightlylessthangoldat$30agram.)Amberfloatsinsaltwater,andinoldtimestheoriginofboththesesubstanceswasmysterious.Butitturnedoutthatamberandambergrishavelittleincommon.

C2AmberisafossilizedresinfromtreesthatwasquitefamiliartoEuropeanslongbeforethediscoveryoftheNewWorld,andprizedforjewelry.Althoughconsideredagem,amberisahard,transparent,wholly-organicmaterialderivedfromtheresinofextinctspeciesoftrees,mainlypines.Piecesofambertornfromtheseafloorarecastupbythewaves,andcollectedbyhand,dredging,ordiving.Elsewhere,amberismined,bothinopenworksandundergroundgalleries.

DTotheearliestWesternchroniclersambergriswasvariouslythoughttocomefromthesamebituminousseafountsasamber,fromthespermoffishesorwhales,fromthedrop sofstrangeseabirds(probablybecauseofconfusionovertheincludedbeaksofsquid)orfromthelargehivesofbeeslivingnearthesea.MarcoPolowasthefirstWesternchroniclerwhocorrectlyattributedambergristospermwhalesanditsvomit.E1Asspermwhalesnavigateintheoceans,theyoftendivedownto2kmormorebelowthesealeveltopreyonsquid,mostfamouslytheGiantSquid.It'scommonlyacceptedthatambergrisformsinthewhale'sgutorintestinesasthecreatureattemptsto"deal"withsquidbeaks.Spermwhalesareratherpartialtosquid,butseeminglystruggletodigestthehard,sharp,parrot-likebeaks.Itisthoughttheirstomachjuices ehyper-activetryingtoprocesstheirritants,andeventuallyhard,resinouslumpsareformedaroundthebeaks,andthenexpelledfromtheirinnardsbyvomiting.

E2Whenawhaleinitiallyvomitsupambergris,itissoftandhasaterriblesmell.Somemarinebiologistscompareittotheunpleasantsmellofcowdung.Butafterfloatingonthesaltyoceanforaboutadecade,thesubstancehardenswithairandsunintoasmooth,waxy,usuallyroundedpieceofnostrilheaven.Thedungsmellisgone,replacedbyasweet,smooth,muskyandpleasantearthyaroma.

FSinceambergrisisderivedfromanimals,naturallyaquestionofethicsarises,andinthecaseofambergris,itisveryimportanttoconsider.Spermwhalesareanendangeredspecies,whosepopulationsstartedtodeclineasfarbackasthe19thcenturyduetothehighdemandfortheirhighlyemollientoil,andtodaytheirstocksstillhavenotrecovered.Duringthe1970's,theSavetheWhalesmovementbroughttheplightofwhalestointernationalrecognition.Manypeoplenowbelievethatwhalesare"saved".Thiscouldn'tbefurtherfromthetruth.Allaroundtheworld,whalingstillexists.Manycountriescontinuetohuntwhales,inspiteofinternationaltreatiestoprotectthem.Manymarineresearchersareconcernedthateventhetradeinnaturallyfoundambergriscanbeharmfulbycreatingfurtherincentivestohuntwhalesforthisvaluable

GOneoftheformsambergrisisusedasavaluablefixativeinperfumesenhanceandprolongthescent.Butnowadays,sinceambergrisisrareandexpensive,bigfragrance rsthatmakemostofthefragrancesonthemarkettodaydonotdealinitforreasonsofcost,availabilityandmur啼legalissuesandmostperfumeriesprefertoaddachemicalderivativewhichmimicsthepropertiesofambergrisAsafragranceconsumer,youcanassumethatthereisnonaturalambergrisinyourperfumebottle,unlessthecompanyadvertisesthisfactandunlessyouownvintagefragrancescreatedbeforethe1980s.IfyouarewonderingifyouhavebeenwearingaperfumewiththislegendaryingredientyoumaywanttoreviewyourscentcollectionHereareafewofsomeofthetopambergriscontainingperfumes:GivenchyAmarige,ChanelNo.5,andGucciGuilty.

AAambergrisB.amberC.bothambergrisandD.neitherambergrisnorMentionedbyHermanMelvilleinhisUsedasBeingAddsflavortoCouldbeseenEmitspleasantOneWORDONLYforeach

Theformationofambergrisiscommonlyacceptedthatitisdiscoveredfromintestinesofaspecificspeciesofwhales.Spermwhaleshaveapreferenceforsquidbutcannotabsorbitstoughandparrot-shaped Thedigestivejuicelumpsaroundthesquidparts.Thentheselumps,the，releasedbytheirstomachsgraduallyformssemi-finishedambergris,areexpelledfromtheirinnardsthrough8 sunlight,thepiece9 .Atfirst,itwillemitadisgustingsmell.However,withcontactofairintoasoftandwaxysubstancewithapleasantaroma.10Mostambergriscomesfromthedeadwhales11Duetoemergenceofrelatedinternationaltreaties,whalesarefrom12Ambergrisismorecostlythan13Nowadays,Ambergrisisstillappliedextensivelyinperfume

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ForthepastdecadeDr.Engel,alecturerinenvironmentalsciencesatBritain'sOpenUniversity,hasbeencollectingexamplesofself-medicatingbehaviorinwildanimals.Sherecentlypublishedabookonthesubject.InatalkattheEdinburghScienceFestivalearlierthismonth,sheexplainedthattheideathatanimalscantreatthemselveshasbeenregardedwithsomeskepticismbyhercolleaguesinthepast.Butagrowingnumberofanimalbehaviouristsnowthinkthatwildanimalscananddodealwiththeirownmedicalneeds.

Oneexampleofself-medicationwasdiscoveredin1987.MichaelHuffmanmediSeifu,workingintheMahaleMountainsNationalParkinTanzania,noticedthatlocalchimpanzeessufferingfromintestinalwormswoulddosethemselveswiththepithofaplantcalledVeronia.Thisplantproducespoisonouschemicalscalledterpenes.Itspithcontainsastrongenoughconcentrationtokillgutparasites,butnotsostrongastokillchimps(norpeople,forthatmatter;localsusethepithforthesamepurpose).SincetheVeronia-eatingchimpswerediscovered,moreevidenceshaveemergedsuggestingthatanimalsofteneatthingsformedicalratherthannutritionalreasons.Manyspecies,forexample,consumedirt-abehaviourknownasgeophagy.Historically,thepreferredexplanationwasthatsoil smineralssuchassalt.Butgeophagyoccursinareaswheretheearthisnotausefulsourceofminerals,andalsoinplaceswheremineralscanbemoreeasilyobtainedfromcertainplantsthatareknowntoberichinthem.Clearly,theanimalsmustbegettingsomethingelseoutofeatingearth.

Thecurrentbeliefisthatsoil,andparticularlytheclayinit,helpstodetoxifythedefensivepoisonsthatsomeplantsproduceinanattempttopreventthemselvesfrombeingeaten.Evidenceforthedetoxifyingnatureofclaycamein1999,fromanexperimentcarriedoutonmacawsbyJamesGilardiandhiscolleaguesattheUniversityofCalifornia,Davis.Macawseatseedscontainingalkaloids,agroupofchemicalsthathassomenotoriouslytoxicmembers,suchasstrychnine.Inthewild,thebirdsarefrequentlyseenperchedonerodingriverbankseatingclay.Dr.Gilardifedonegroupofmacawsamixtureofaharmlessalkaloidandclay,andasecondgroupjustthealkaloid.Severalhourslater,themacawsthathadeatentheclayhad60lessalkaloidintheirbloodstreamsthanthosethathadnot,suggestingthatthehypothesisiscorrect.

Otherobservationsalsosupporttheideathatclayisdetoxifying.Towardsthetropicstheamountoftoxiccompoundsinplantsincreasesandsodoestheamountofeartheatenbyherbivores.Elephantslickclayfrommudholesallyearround,exceptinSeptemberwhentheyarebingeingonfruitwhich,becauseithasevolvedtobeeaten,isnottoxic.Andtheadditionofclaytothedietsofdomesticcattleincreasestheamountofnutrientsthattheycanabsorbfromtheirfoodby10%-20.

Athirdinstanceofanimalself-medicationistheuseofmechanicalscourstogetridofgutparasites.ln1972RichardWrangham,aresearcherattheGombeStreamReserveinTanzania,noticedthatchimpanzeeswereeatingtheleavesofatreecalledAspilia.Thechimpschosetheleavescarefullybytestingthemintheirmouths.Havingchosenaleaf,achimpwouldfolditintoafanandswallowit.Someofthechimpswerenoticedwrinklingtheirnosesastheyswallowedtheseleaves,suggestingtheexperiencewasunpleasant.Later,undigestedleaveswerefoundontheforestfloor.

Dr.Wranghamrightlyguessedthattheleaveshadamedicinalpurpose-thiswas,indeed,oneoftheearliestinterpretationsofabehaviourpatternasself-medication.However,heguessedwrongaboutwhatthemechanismwas.Hisandeverybodyelse'sassumptonwasthatAspiliacontainedadrug,andthissparkedmorethantwodecadesofphytochemicalresearchtotrytofindoutwhatchemicalthechimpswereafter.BuintheI990s,chimpsacrossAfricahadbeenseenswallowingtheleavesof19differentspeciesthatseemedtohavefewsuitablechemicalsincommon.Thedrughypothesiswaslookingmoreandmoredubious.

ItwasDr.Huffmanwhogottothebottomoftheproblem.Hedidsobywatchingwhatcameoutofthechimps,ratherthanconcentratingonwhatwentin.Hefoundthattheegestedleaveswerefullofintestinalworms.ThefactorcommontoallI9speciesofleavesswallowedbythechimpswasthattheywerecoveredwithmicroscopichooks.Thesecaughtthewormsanddraggedthemfromtheirlodgings.

Followingthatobservation,Dr.Engelisnowparticularlyexcitedabouthowknowledgeofthewaythatanimalslookafterthemselvescouldbeusedtoimprovethehealthoflivestock.Peoplemightalsobeabletolearnathingortwoandmay,indeed,alreadyhavedoneso.Geophagy,forexample,isacommonbehaviourinmanypartsoftheworld.ThemedicalstallsinAfricanmarketsfrequentlyselltabletsmadeofdifferentsortsofclays,appropriatetodifferentmedicalconditions.

AfricansbroughttotheAmericasasslavescontinuedthistradition,whichgavetheirownersonemoreexcusetoaffecttodespisethem.YetasDr.Engelpointsout,Rwandanmountaingorillaseatatypeofclayrathersimilartokaolinite一themainingredientofmanypatentmedicinessoldoverthecounterintheWestfordigestivecomplaints.Dirtcansometimesbegoodforyou,andtobeassickasaparrotmayafterall,beastatetobedesired.

1Dr.EngeIhasbeenengagedinanimalself-medicationresearchsincetenyearsago.2Sometimesanimalshavetotravelalongdistanceinorderhuntforplantfor3Duetothepreferenceofnaturaldiet,birdslikemacawareseeneatingclay.4Dr.Engelisquiteexcitedaboutresearchonanimalmedicationforreformingdrugsfor

Theresearchanimalself-medicationhasbeensupportedbymuchevidence.Oneofthemiscalled10 ，acommonsoil-consumingbehavioracrossanimalspecies,Thisbehaviorisduetotheearth,especiallyclay,peopleinAfricatake11totreatvariousdiseases.Anotherrelevantoneisaboutchimpsthateatleaveswith12structurecanneutralizethe13contentoftheirdiet.Similarly,tasteprobably,butwithmedicinalvalueduetotheirspecial

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Birdmigrationistheregularseasonalmovement,oftennorthandsouthalongawaybetweenbreedingandwinteringgrounds,undertakenmanyspeciesofbirds.Migration,whichcarrieshighcostsinpredationandmortality,isdrivenprimarilybyavailabilityoffood.Thetypeofmigrationconsistsshort-distance,medium-distanceandlong-distance.

Birdshavemanyuniquedesignfeaturesthatenablethemtoperformsuchamazingfeatsofendurance.Theyareequippedwithlightweight,hollowbones,intrica ydesignedfeathersprovidingbothliftandthrustforrapidflight,navigationsystemssuperiortoanythatmanhasdeveloped,andaningeniousheatconservingdesignthat,amongotherthings,concentratesallbloodcirculationbeneathlayersofwarm,waterproofplumage,leavingthemfittofacelifeintheharshestofclimates.Theirrespiratorysystemshavetoperformefficientlyduringsustainedflightsataltitude,sotheyhaveasystemofextractingoxygenfromtheirlungsthatfarexceedsthatofanyotheranimal.Duringthelaterstagesofthesummerbreedingseason,whenfoodisplentiful,theirbodiesareabletoaccumulateconsiderablelayersoffat,inordertoprovidesufficientenergyfortheirlongmigratory

Thefundamentalreasonthatbirdsmigrateistofindadequatefoodduringthewintermonthswhenitisinshortsupply.ThisparticularlyappliestobirdsthatbreedinthetemperateandArcticregionsoftheNorthernHemisphere,wherefoodisabundantduringtheshortgrowingseason.Manyspeciescantoleratecoldtemperaturesiffoodisplentiful,butwhenfoodisnotavailabletheymustmigrate.However,intriguingquestions

Onepuzzlingfactisthatmanybirdsjourneymuchfurtherthanwouldbenecessaryjusttofindfoodandgoodweather.Nobodyknows,forinstance,whyBritishswallows,whichcouldpresumablysurviveequallywelliftheyspentthewinterinequatorialAfrica,insteadflyseveralthousandsoffurthertotheirpreferredwinterhomeinSouthAfricaCapeProvince.Anothermysteryinvolvesthehugemigrationsperformedbyarcticternsandmudflat-feedingshorebirdsthatbreedclosetoPolarRegions.Ingeneral,thefurthernorthamigrantspeciesbreeds,thefurthersouthitspendsthewinter.Forarcticternsthisnecessitatesanannualroundtripof .Yet,enroutetotheirfinaldestinationinfar-flungsouthernlatitudes,alltheseindividualsoverflyotherareasofseeminglysuitablehabitatspanningtwohemispheres.Whilewemaynotfullyunderstandbirds'reasonsforgoingtoparticularplaces,wecanmarvelattheirfeats.

Oneofthegreatestmysteriesishowyoungbirdsknowhowtofindthetraditionalwinteringareaswithoutparentalguidance.Veryfewadultsmigratewithjuvenilesintow,andyoungstersmayevenhavelittleornoinklingoftheirparents'appearance.Afamiliarexampleisthatofthecuckoo,whichlaysitseggsinanotherspecies'nestandneverencountersitsyoungagain.Itismindbogglingtoconsiderthat,onceraisedbyitshostspecies,theyoungcuckoomakesitownwaytoancestralwinteringgroundsinthetropicsbeforereturningsingle-handedlytonorthernEuropethenextseasontoseekoutamateamongitsownkind.Theobviousimplicationisthatitinheritsfromitsparentsaninbuiltroutemapanddirection-findingcapability,aswellasamentalimageofwhatanothercuckoolooksIike.Yetnobodyhastheslightestideaastohowthisis

Mountingevidencehasconfirmedthatbirdsusethepositionsofthesunandstarstoobtaincompassdirections.Theyseemalsotobeabletodetecttheearth'smagneticfield,probablyduetohavingminutecrystalsofmagnetiteintheregionoftheirbrains.However,truenavigationalsorequiresanawarenessofpositionandtime,especiallywhenlost.Experimentshaveshownthatafterbeingtakenthousandsof overanunfamiliarlandmass,birdsarestillcapableofreturningrapidlytonestsites.Suchphenomenalpowersaretheproductofcomputinganumberofsophisticatedcues,includinganinbornmapofthenightstartsandthepulloftheearth'smagneticfield.

Howthebirdsusetheir"instruments"remainsunknown,butonethingisclear:seetheworldwithasuperiorsensoryperceptiontoours.Mostsmallbirdsmigrateatnightandtaketheirdirectionfromthepositionofthesettingsun.However,aswellasseeingthesungodown,theyalsoseemtoseetheplaneofpolarizedduetoflyingforlongperiodslightcausedbyi