以冬眠为话题的英语作文
Hibernationismorethansleep.Itisaverydeepsleep.Theanimal'stemperaturedropstojustoverzerocentigrade,anditsheartbeatsveryslowly.Peoplewhofindhibernatinganimalsasleepoftenthinkthattheyaredead:thebodyfeelsverycold,andthecreaturemaybreatheonlyonceeveryfiveminutes.Ahibernatinganimalcannotfeelanypain.Youcantouchit,orevenpullitstail,withoutcausingittomoveorwakeup.Initshibernatingstateitcanevenliveinapoisonousatmosphereforalongtimewithoutanyilleffect.
Hibernatinginthisway,theanimalcansleepallthroughthewinter.Youmightwonderhowitmanagestolivewithouteatingforsomanymonths.Theanswerliesintwofacts.Thefirstisthatithasstoredsuppliesoffatinitsbodyduringthesummerandautumn.Thesecondisconnectedwiththemainusethebodymakesoffood--tosupplytheenergyformovement.Wehaveseenthathibernatinganimalreducesmovementtofarbelowtheordinarylevel.Eventhemovementsoftheheartandlungsaregreatlyreduced.Theanimalhardlymakesanymovement,hardlyuseanyenergy,andhardlyneedsanyfood.
Someanimals,includingsomebearsonlyhalfhibernate.Thatistosay,theysleepduringthewinter,buttheirsleepisnotdeepandtheirbodytemperaturedoesnotdrop,astheyarewarm-bloodedanimals.Intheantumnthebeareatsandeatsandbeesveryfat.Hishairgrowslonger.Soonhehasathickcoveringoffatandfur.InNovemberhefindsaplacetoliedownandgoestosleep.Onwarmwinterdayshemaythinkspringhasarrived;hegetsupandwalksaround.Whenheseesthatthesnowisstillthickontheground,hequicklygoestosleepagain.