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Level3unit3part1ListeningTherearemanyformsoflifeonEarth,includinghumanbeings.Lifeexistsinavarietyofconditions.Someformsoflifeliveinawateryenvironment,liketheoceans.Otherformsoflifecanbefoundinverydryareas,likedeserts.However,foranyformoflifetoexist,conditionsmustberight.Whenconditionsarenotright,thatformoflifewillbecomeextinct.Tobecomeextinctmeanstodieoutcompletely.-Whatmustberightforlifetoexist?-Conditions.-Whathappensifconditionsarenotright?–Lifecannotexist.Conditionsmustberightforlifetoexist.Millionsofyearsago,therewereformsoflifethatnolongerexist.Whenconditionschanged,theseformsoflifediedout.Oneextinctioneventhappenedabout250millionyearsago.Thiswasthelargestextinctioneventofalltime.Manyformsoflifebecameextinct.96%ofalllifeintheoceansdiedout.Mostinsectsalsobecameextinct.Thiseventhappenedoveraperiodofseveralmillionyears.-Whathappenedabout250millionyearsago?–Manyformsoflifebecameextinct.-Whathappensinanextinctionevent?–Manyformsoflifebecameextinct.Thecausesofthisextinctioneventarestillunknown.Possiblecausesincludelargevolcaniceruptionsandglobalwarming.Somescientistsbelievethattherewereseveralcauses.Theybelievethataseriesofeventscausedtheextinctions.Scientistsareworkingtobetterunderstandwhatreallyhappened.-Whatistheonepossiblecauseofthisevent?–Volcaniceruptions.Inmoderntimes,wehumansfacechangingconditions.Forhumanstolive,weneedcleanairandcleanwater.Pollutionisnowagrowingproblemaroundtheworld.Pollutionpoisonstheairandwaterthatwedependon.Pollutedairmakespeoplesickandafraidtogooutside.Pollutedwaterpoisonsourfoodsupply.Asaresult,weneverknowwhichfoodsaresafetoeat.Humanbeingscannotliveinapoisonedenvironment.Therefore,pollutionisamajorthreattoourexistence.-Whatdohumansneedtolive?–Cleanairandcleanwater.-Whatpoisonstheairandwater?–Pollution.Humansneedtemperaturestobeinacomfortablerange.Tobeinacomfortablerangemeanstobeneithertoohotnortoocold.Withglobalwarming,globaltemperaturesarerising.Astemperaturesrise,thepolaricecapswillmelt.Asthepolaricecapsmelt,oceanlevelswillrise.Areasofsomecountrieswillsoonbeunderwater.Peoplewillbeforcedtorelocatefromfloodedareas.-Astemperaturesrise,whatwillhappentothepolaricecaps?–Thepolaricecapswillmelt.-Asthepolaricecapsmelt,whatwillhappen?–Oceanlevelswillrise.Innature,evensmallchangescansometimeshavelargeeffects.It’sdifficulttopredictwhat’sgoingtohappen.Theentireecosystemthatwedependonischanging.Someofthesechangesareirreversible.Irreversiblechangescannotbeundone.-Whatcansmallchangessometimescause?–Largeeffects.-Whatishappeningtotheworld’secosystem?–Ecosystemischanging.Let’shopethathumansaresmartenoughtounderstandhowtheworldischanging.Withmoreunderstanding,wecanmakebetterchoicesaboutwhattodo.Wecanfacethechallengesofpollutionandglobalwarming.Weneedtodothisbeforeit’stoolate.ThisplanetEarthisouronlyhomeandweneedtoprotectit.-Whatchallengesdoweneedtoface?–Pollutionandglobalwarming.Weneedtoprotecttheenvironmentthatsupportsus.VocabularyMammalsarecoveredbyhairorfur,haveabackbone,andarewarmblooded.Allfemalemammalsproducemilkfortheiryoung.Reptilesarecoveredbyscales,andincludessnakes,lizardsandturtles.Reptileshaveabackboneandarecoldblooded,whichmeanstheyoftenreliedontheexternalsourceofheat.Birdsarecoveredbyfeathersandarewarmblooded.Mostbirdscanflyandmanytypesofbirdsmigrategreatdistances.Mostinsectssuchasantsandbeeshaveasmallthreepartofbodywiththreepairsoflegs.Someinsects,likemosquitoes,spreaddiseasesthatcausethedeathsofmanyhumans.Unlikeanimals,plantsgettheenergythattheyneedfromthesun.Plantsconvertlightenergy,alongwithcarbondioxideandwater,intochemicalenergy.Insectsdon’thaveabackboneandmostarecooled-blooded.Insectssuchasantsandbeesliveinwell-organizedcolonies.Mosquitoescausethedeathsofmorehumansthananyotheranimal.Mammalsincludesomeofthemostintelligentanimalsonearth,suchaselephantsandhumanbeings.Scalesandrulersareusedtomeasureweightandlength.Unitsofweightincludekilogramsandpounds,andunitsoflengthincludecentimetersandinches.Theseinstrumentsareusedtoobserveverylargeandverysmallobjects.Telescopesareusedtobyastronomersandmicroscopesareusedbybiologistsanddoctors.Theseappliancesareusedinthekitchensofalmosteveryhome.Stovesareusedtoheatfoodandrefrigeratorsareusedtokeepfoodscoolorcold.Householdtoolsliketheseareusedtobuildandrepairthings.Hammersareusedtopoundinnailsandscrewdriversareusedtoturnascow.Ifyouneedtopoundinanail,useahammer.DialogueW:doyouknowwhatdayitistoday?M:whatdoyoumean?Isitaspecialday?W:oh,soyoudon’tremember.M:rememberwhat?What’ssospecial?W:it’souranniversary.Westarteddatingayearagotoday.M:oh,really,I’msorry.-Whendidtheyfirststartdating?–Ayearago.M:justaminute.Whatdoyouthinkthisis?W:oh,it’sanecklace.M:doyoulikeit?W:yes,Ido.It’slovely,especiallytheredheart.MayIputiton?M:no,letmedoit.-Whatdidhegiveher?–Anecklace.W:soyoudidremember.M:ofcourseIremembered.It’saveryspecialdayforbothofus.W:Ihavesomethingforyoutoo.M:youdo?W:yes,butitwillhavetowaituntillater.M:oh,Ican’twait.Tellmewhatitis.-Whatwouldhavetowaituntillater?–She’sgoingtogivehimagift.Doyouknowwhattodayis?W:canyouguesswhatitis?M:couldyougivemeahi