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S2200108Checkboxes&RelatedQuestionTypesATheunderwaterworldholdsmanychallenges.movement.ThedensityS2200108Checkboxes&RelatedQuestionTypesATheunderwaterworldholdsmanychallenges.movement.ThedensityofwatermakesitdifficultThemostbasicoftheseisforanimalstomove.Forwardmovementisacomplexinteractionofunderwaterforces.Additionally,wateritselfhasmovementStrongcurrentscarryincrediblepowerthatcaneasilysweepcreaturesaway.Thechallengestoaquaticmovementresultinavarietyofswimmethods,usedbyawiderangeofanimals.Theresultisadazzlingunderwaterballet.BFishrelyontheirskeleton,fins,andmusclestomove.Theprimaryfunctionoftheskeletonistoaidmovementofotherparts.Theirskullactsasafulcrum(支点)andtheirjvertebraeactaslevers.Thevertebralcolumnjconsistsofaseriesofvertebraeheldtogetherbyligaments,butnotsotightlyastopreventslightsidewaysmovementbetweeneachpair:ofvertebrae.Thewholespineis,therefore,flexible.Theskullistheonlytrulyfixedpartofafish.ItdoesnotmoveinUnderseamovementTrue/False/NGListofHeadingsSummaryParagraphMatchingMatchingMultipleChoicesPassageBackgroundsS2.海底 （环境类）andoffitselfbutactsasapointofstabilityforotherbones.Theseandoffitselfbutactsasapointofstabilityforotherbones.Theseotherboneasleverscausemovementofthefish’sbody.CWhilethebonesprovidethemovement,themusclessupplythepower.Atypicalfishhashundredsofmusclesrunninginalldirectionsarounditsbody.Thisiswhyafishcanturnandtwistandchangedirectionsquickly.Themusclesoneachsideofthespinecontractinaseriesfromheadtotailanddowneachsidealternately,causingawave-likemovementtopassdownthebody.Suchamovementmaybeverypronouncedinfishsuchaseels,buthardlyperceptibleinotherse.g.mackerel.Thefrequencyofthewavesvariesfromabout50/mininthedogfishto170/mininthemackerel.Thesidewaysandbackwardthrustoftheheadandbodythewaterresultsintheofthewaterpushingthefishsidewaysandforwardsinadirectionopposedtothethrust.Whenthecorrespondingsetofmusclesontheothersidecontracts,thefishexperiencesasimilarforcefromthewateronthatside.Thetwosidewaysforcesarcequalandopposite,unlessthefishismakingaturn,sotheycancelout,leavingthesunofthetwoforwardforces.DThemusclesinvolvedinswimarcoftwomaintypes.Thebulkofafishsbodyiscomposedoftheso-calledwhitemuscle,whilethemuchsmallerareasattherootsofthefinsandinastripalongthecenterofeachflankcompriseredmuscle.Theredmusclereceivesagoodsupplyofbloodandcontainsamplerqutiesoffatandglycogen,thestorageformofglucose,whichisusedformostday-to-dayswimmovements.Incontrast,thewhitemusclehasapoorbloodsupplyandfewenergystores,anditisusedlargelyforshort-term,fastswim.Itmightseemoddthatthebodyofananimalwhichadaptsadaptedsoefficientlytoitsenvironmentshouldbecomposedalmostentirelyofatypeofmuscleitrarelyuses.However,thishugeauxiliarypowerpackcarriedbyafishisofcrucialsignificanceifthelifeofthefishisthreatened--byapredator,forinstance--becauseitenablesthefishtoswimrapidlyawayfromdanger.EThefinsarethemostdistinctivefeaturesofafish,composedofbonyspinesprotrudingfromthebodywithskincoveringthemandjoiningthemtogether,eitherinawebbedfashion,asseeninmostbonyfish,ormoresimilartoaThefinsarethemostdistinctivefeaturesofafish,composedofbonyspinesprotrudingfromthebodywithskincoveringthemandjoiningthemtogether,eitherinawebbedfashion,asseeninmostbonyfish,ormoresimilartoaflipper,asseeninsharks.Theseusuallyserveasameansforthefishtoswim.Butitmustbeemphasizedthattheswimmovementsareproducedbythewholeofthemuscularbody,andinonlyafewfishdothefinscontributeanypropulsiveforce!Theirmainfunctionistocontrolthestabilityanddirectionofthefish:aswaterpassesoveritsbody,afishusesitsfinstothrustinthedirectionitwishestogo.FFinslocatedindifferentplacesonafishservedifferentpurposes,suchasmovingforward,turning,andkeeanuprightposition.Thetailfin,initsfinallash,maycontributeasmuchas40percentoftheforwardthrust.Themedianfins,thatis,thedorsal,analandventralfins,controltherollingandyawingmovementsofthefishbyincreasingtheverticalsurfaceareapresentedtothewater.Thepairedfins,pectoralandpelvic,actashydroplanesandcontrolthepitchofthefish,causingittoswimdownwardsorupwardsaccordingtotheangletothewateratwhichtheyaeldbytheirmuscles.Thepectoralfinslieinfrontofthecentreofgravityand,beingilymobile,arechieflyresponsibleforsendingthefishupordown.Thepairedfinsarealsothemeansbywhichthefishslowsdownandstops.GTheswimspeedoffishisnotsofastasonewouldexpectfromwatchingtheirjrapidmovementsinaquariaorponds.Tunaseemtobethefastestat44mph,troutarerecordedasdoing23mph,pike20mphforshortburstsandroachabout10mph,whilethemajorityofsmallfishprobablydonotexceedor3mph.Manypeoplehaveattemptedtomakeaccuratemeasurementsofthespeedatwhichvariousfishswim,eitherbythemoverknowndistancesintheirnaturalswimfourgroups:butpossessenvironmentorbydeterminingtheirperformanceinman-channels.Fromthesestudies,wecanbroadlycategorisefishinto“sneakrs，suchaseesthatarewlycapaleofslwspeedssomestayingpower;“stayers",thatcanswimquitefastoverlongperiods;“sprinters”thatcangeneratefastburstsofspeed(e.g.pike);and“crawlers”thataresluggishswimmers,althoughtheycanaccelerateslightly(bream,forexample).HOnetypeofsailfisharesluggishswimmers,althoughtheycanaccelerateslightly(bream,forexample).HOnetypeofsailfishisconsideredtobethefastestspeciesoffishovershortdistances,achieving68mphoverathree-secondperiod,andanglershaverecordedspeedsinexcessof40mphoverlongerperiodsforseveralspeciesoftuna.Oneislikelytoconsiderafish’sswimcapabilitiesinrelationtoitssize.However,itisgenerallytruethatasmallfishisamoreableswimmerthanamuchlargerone.Ontheotherhandintermsofspeedinperhourabigfishwill,allotherthingsbeingequal,beabletoswimfasterthanasmallerfish.Questions14-19TheingPassagehas8paragraphsA-H.Whichparagraphcontainsthefollowinginformation?WritethecorrectletterA-H,inboxes14-19onyouranswersheet.14categorizationsoffishbyswimspeedanexampleoffishcapableofmaintainingfastswimhowfishcontrolstabilityfrequencyofthemusclemovementoffishforalongtime18amechanicalmoffishskeleton19energystoragedevicesinafishQuestions20-23Thediagrambelowgivesinformationaboutfishfinsandtheirpurposes.CompletethediagramwithNOMORETHANTHREEWORDSfromthepassageforeachblank.Writeyouranswersinbo