北极熊英文介绍PPT课件

.,1,Thelargestterrestrialcarnivorousanimal,Polarbear,.,2,somepicturesaboutPolarbear,.,3,ThepolarbearisabearnativelargelywithintheArcticCircleencompassing（围绕，包围;）theArcticOcean,itssurroundingseasandsurroundinglandmasses.Itistheworldslargestlandcarnivore（食肉动物）andalsothelargestbear,.,4,PolarbearsInitsexistentspace,itisthetopmostfoodchain.Ithasthickfatandhairtostaywarm,itswhiteappearanceonwhitesnowisgoodprotectivecoloration,anditcanonlandandsea,soitcancatchfoodinthearcticinthisextremelyharsh（严酷的）climate.,.,5,Ecologicalrole,Thepolarbearistheapexpredator（顶端食肉动物）withinitsrange.Severalanimalspecies,particularlyArcticFoxesandGlaucousGulls,routinelyscavenge（清除）polarbearkills.Therelationshipbetweenringedseals（环斑海豹）andpolarbearsissoclosethattheabundanceofringedsealsinsomeareasappearstoregulate（调节）thedensity（密度）ofpolarbears,whilepolarbearpredationinturnregulatesdensityandreproductivesuccessofringedseals.TheevolutionarypressureofpolarbearpredationonsealsprobablyaccountsforsomesignificantdifferencesbetweenArcticandAntarcticseals.,.,6,BecausepolarbearsplayanimportantroleinArcticenvironment,scientistsfeelthatpolarbearcanbeagoodindicatorofthehealthofArcticenvironment.So,wecansaythatbyprotectingpolarbears,weareprotectingthewholeArcticecosystem.,.,7,Globalwarminghasanimpactontheice.,Theiceismeltingquicklyinnorthandsouthpole.Andthathaveabadinfluenceonpolarbears.Duetotheglobalwarming,Arcticicebegantomelt,thepolarbearshomehasbeendestroyed,thepreyisalsoacorrespondingreductionin,.,8,Polarbearsareindanger,wemusttakemeasurestoprotectthekindofbeautifulandlovelyanimal.Becauseitisthetreasureofnature.,.,9,Physicalcharacter,Thepolarbearsclawsareshortandstocky.,theteetharelargerandsharper,Polarbearfurconsistsofdenseunderfurandguardhairs.,nose,.,10,Appearance,smallhead,smallearsandroundnecklong,wide,footandlegandpalmarehirsutegoodswimmerblackskin,.,11,Habitat,Marinemammal(becauseitspendsmanymonthsoftheyearatsea).Arcticringoflife,.,12,HuntingandDiet,Themostcarnivorousmemberofthebearfamily(mostofitsdietconsistsofringedandbeardedseals)ExcellentsenseofsmellRingedandbeardedsealswildfoodsandplants,.,13,Thepolarbearsmostcommonhuntingmethodiscalledstill-hunting.,Thebearusesitsexcellentsenseofsmelltolocateasealbreathinghole,andcrouches（蹲）nearbyinsilenceforasealtoappear.Whenthesealexhales,thebearsmellsitsbreath,reachesintotheholewithaforepaw,anddragsitoutontotheice.Thepolarbearkillsthesealbybitingitsheadtocrushitsskull.createinthesnow.,.,14,Thepolarbearalsohuntsbystalking（跟踪）sealsrestingontheice:Uponspottingaseal,itwalkstowithin100yd(91m),andthencrouches.Ifthesealdoesnotnotice,thebearcreeps（缓慢前进）towithin30to40feet(9.1to12m)ofthesealandthensuddenlyrushesforthtoattack.Athirdhuntingmethodistoraid（突袭）thebirthlairs（巢穴）thatfemaleseals,.,15,Reproductionandlifecycle,CourtshipandmatingtakeplaceontheseaiceinAprilandMayAmalemayfollowthetracksofabreedingfemalefor100km(62mi)ormoreafterfindingherengageinintensefightingwithothermalesovermatingrights,fightswhichoftenresultinscarsandbrokenteethPolarbearshaveaenerallypolygynousmatingsystem,.,16,Maternitydenning（穴居）andearlylife,Aftermating,thefertilizedeggremainsinasuspendedstateuntilAugustorSeptember.BetweenNovemberandFebruary,cubsarebornblind,coveredwithalightdownfur,andweighinglessthan0.9kg(2.0lb),.,17,Lifeexpectancy,Polar