2023学年完整版Unit3Underthesea备课资料6

Unit3Underthesea备课资料OceanicseahorseFragileandmystical,theoceanicseahorse(Hippocampuskuda)isprobablywhatyouseewhenyoucloseyoureyesandthinkofseahorses.Whilenotthemostexoticspeciesofseahorse,itisaclassicrepresentationofabeautifulandfascinatingfish.You’llseemanytypesofseahorsesatShedd.Oceanicseahorsesmaybeyellow,deepred,brown,orblackandmaybeblotchedorbanded.Theycanreachabout7inchesinadulthood.Theoceanicseahorseisalsoknownasthecommonseahorse,butthesadtruthisthatallseahorsesarebecominglessandlesscommon.Andit’spreciselytheirethereal,otherworldlycharmthathasgottenthemintotrouble.We’vebeenenchantedbythesecreaturesformillennia.FrompractitionersofancientChinesemedicinetotouristsinFlorida,we’vebelievedtheirmagicgaveuswondrousthings—arthritiscures,loveelixirs,evenkeychains.Now,becauseofthat,theyfaceahighriskofextinctioninthewild.Seahorsescannotproduceenoughoffspringtoreplacethehugenumbersfishedformedicines,petsandsouvenirs.Thereareseveralreasonsforthis.First,theyaremonogamous,andifoneofthepairiscaptured,itcantakealongtimefortheremainingpartnertomateagain.Second,thestrikingringedarmorthatprotectsseahorsesfrommanypredatorsdoesnotdevelopuntilthey’readultssoperhapsonlytwoinathousandjuvenileseahorsesreachadulthood.GreenSeaTurtle—CharacteristicsNameGreenSeaTurtlesgettheirnamefromthecoloroftheirbodyfat,whichisgreenfromthealgaeorgrassestheyeat.TheHawaiianGreenSeaTurtlepopulation,isknownbyitsHawaiiannameHonuHistoryGreenSeaTurtlesarereptileswhoseancestorsevolvedonlandandreturnedtotheseatolive.ThefirstturtlesappearedduringtheTriassicperiod,245to208millionyearsago.FossilsfortheearliestknownseaturtlesappearintheLateJurassicperiod,208to144millionyearsago.Turtlesareoneofthefewspeciesthatwatchedthedinosaursevolveandbecomeextinct.Asreptiles,seaturtlespossessthefollowingtraits:*Theyarecold-blooded,meaningtheygettheirbodyheatfromtheenvironment.*Theybreatheair.*TheirskinisscaleStatusNow,scientistsrecognizesevenspeciesofthesemarinereptiles.Therecognizedseaturtlespeciesareasfollows:Greens,Hawksbill,Kemp’sRidley,OliveRidley,Loggerhead,FlatbackandLeatherback.TheLoggerheadSeaTurtleislistedasthreatened,theFlatbackislistedasvulnerable,andallotherspeciesarelistedasendangered.GreenSeaTurtlepopulationsofHawaiiarethreatenedandprotectedinHawaiiunderstatelaw.PopulationsofGreenSeaTurtlesoffthecoastofFloridaandthePacificcoastofMexicoarelistedasendangered.GreenSeaTurtlesareprotectedbythefederalEndangeredSpeciesAct,andlistedundertheConventiononInternationalTradeofEndangeredSpecies(CITES).CITESmakesitillegaltoimportorexportturtleproducts.ShellInadditiontotheirreptiliantraits,allspeciesofturtlesexcepttheLeatherbackhaveevolvedabonyoutershell,whichprotectsthemfrompredators.TheLeatherbackistheonlysoft-shelledseaturtleandisinafamilybyitself.Theshellcoversthedorsal(back)andventral(belly)surfacesofaseaturtle.Thedorsalportionoftheshellisthecarapaceandiscoveredwithscale-likestructurescalledscutes,whiletheventralportionoftheshellisknownastheplastron.Expertscanidentifyspeciesofseaturtlesbythenumberandpatternofscutesonthecarapace.Theshellisconsideredthemosthighlydevelopedprotectivearmorofanyvertebratespecies.Whilemostlandturtlescanretracttheirheadsintotheirshellsforaddedprotection,seaturtlescannotandtheirheadsremainoutatalltimes.ColorGreenSeaTurtleshavegreenflesh.Thecarapaceisolivebrowntoblack,whiletheplastronispaleyellowtocreamywhite.Thecarapaceismolted,variegatedincolor.RarelywillyoufindaGreenSeaTurtlewithasolidcoloredshell.Counter-shadingoftheshellconcealstheturtlefrompredators,makingitdifficulttodistinguishthedarkcarapacefromtheseafloorandthelightplastronfromthelightersky.SizeGreenSeaTurtlesashatchlingsweighaboutanounceandhaveacarapacelengthof2inches.Asexuallymaturegreenseaturtleweighs200-350poundswithacarapacelengthoffeet.Adultsgrowtoacarapacelengthoffeetandweighanaverageof400pounds.OneofthelargestturtlesthateverlivedfromtheLateCretaceausperiod,144to65millionyearsago,reachedalengthof-13feet.LifespanThelifespanofseaturtlesisnotknown.ItisbelievedthatGreenSeaTurtlesreachsexualmaturityaroundtheageof25yearsandcanliveupto80yearsofage.Thelongperiodofmaturationhelpstoexplainwhyittakesturtlessomanyyearstorecoverfromapopulationdecline.ShapeSeaturtlesarewonderfull