L4——U2——1/4listening
Earthformsandextinction
A
1. Theearthwasformedaboutfourpointsixbillion(46亿)yearsago. 2. Thefirstlifeappearedaboutabillion(10亿)yearslater.
3. Thefirstplant-likedidn’tappearuntilaroundtwobillion(20亿)yearsago. 4. Untilaboutfivehundredeightymillion(五亿八千万)yearsagolifeformsweresmallandmicroscopic(极小的，微小的). 5. Sincethattime,lifehasevolved(进化)intomanydifferenttypesorspecies. 6. Howeverscientistsestimate(估计)thatmorethanninetyninepercent（99%）ofthemarenowextinct(灭绝的). B 1. Therehavebeenseveralextinction(绝种)eventsinthehistoryoftheearth. 2. Inanextinctioneventsmanylifeformsorspeciesoflifedieout. 3. Thecausesofmassextinctioneventsareunsolvedmysteries(未解之谜). 4. Theseeventsarenotpredictable(预告)andcanhappenatanytime. 5. Scientiststhinkthatsomeofthemwerestartedbyasteroidimpacts(影响，碰击或者装机)orvolcaniceruptions(火山爆发). 6. Eventslikethis,canchangetheglobalconditionsthatlifedependson. C 1. Onemajorextinctioneventhappenedaboutsixty-sixmillion(6600万)yearsago. 2. Thateventmayhavebeenstartedbyalargeasteroidthathittheearth. 3. Asaresult,thedinosaursandabouthalfofallspecies(物种，种类，类型)ontheplanetdieout. 4. Whentheasteroidshittheearth,itstartedachainofevents. 5. Achainofeventsisaseriesofeventslinkedtogetherlikeachain.
D
1. Thisparticularchainofeventshappenedoveraperiodofmonthsandyears.
2. Whentheasteroidhittheearth,itcausedahugecloudofdusttoentertheatmosphere. 3. ThiscloudofdustblockedtheSunanddarkenedtheEarthformanymonths. 4. Withoutenoughsunlight,plantsandplant-eatinganimalsquicklydied.
5. Withthedeathsofsomanyplantsandanimals,thefoodchaincollapsed. 6. Thisledtothedeathsofmanymorespecies.
E
1. Massextinctioneventshaveplayedanimportantpartintheevolution(演变，发生，进化论)oflife.
2. Infact,someextinctioneventshavehelpedtoaccelerate(加快，加速)evolution. 3. Forexample,somemammals(哺乳动
物)livedthroughtheageofthedinosaurs,buttheycouldn’tcompete(竞争). 4. Whenthedinosaurswereremoved,themammalswereabletocompetemoresuccessfully. 5. Oncetheycouldcompete,mammalsevolvedtoahigherstate. 6. Withoutextinctionevents,perhapswewouldn’tbeheretoday. Existence(存在) F 1. Scientistsestimate(估计，预测)thattherehavebeenatleastfivemassextinctions(五次大灭绝)inthelastfivehundredfortymillionyears. 2. Theyalsobelievethatwehaveenteredanewextinctionevents. 3. Speciesarebecomingextinctatamuchfasterratethanbefore. 4. Insteadofasteroidsorvolcaniceruptionsthecurrent(最近的)eventsistheresultofhumanactivities. 5. Humanactivitiesforexamplehaveledtoglobalwarming. G 1. globalwarmingistheresultofanincreaseincarbongases(含碳气体)inouratmosphere. 2. Thesegasestrapheat(阻碍热量排放)fromthesun,sotheEarthisgettingwarmer. 3. Asaresult,sealevelsarerisingandweatherpatterns(气候模式)arechanging. 4. Inaddition(另外),wehumansaredestroyingthehabitats(动物的栖息地)ofmanyplantsandanimals.
5. Cuttingdownforestsandpollutingriversdestroythehabitatsofmanyformsoflife.
H
1. Thereisnolongeranydoubtthatthisishappening.
2. Species(物种，类型)oflifearedisappearingatanincreasingrate. 3. Globaltemperaturesarerisingandweatherpatternsarechanging. 4. Scientistsarewarningusthatfastactionisnecessarytosaveourfuture.
5. Ifwedon’tact,wemaygothewayofthedinosaurs. 练：
1. (读)thisnewextinctioneventiscausedbyhumans. 2. It’swhenanasteroidcollideswithsomething. 3. AnasteroidhittheEarthandstartedachainofevents. 4. Withtheriseintemperature.Thepolaricecapsaremelting.
L4——U2——1/4vocabulary Bodyorgan2andhumanbeingevolution(进化) A 1. Thebody’scirculatory(循环的)systemincludestheheartandbloodvessels(血管). 2. Theheartpumpsbloodtoallpartsofthebodythroughanetwork(网络，网状物)ofarteries(动脉)andveins(静脉). 3. Thedigestsystem(消化系统)breaksdown(分解)andabsorbed(吸收)foodintothebody. 4. Itsuppliestheenergythatthebodyneedsforgrowthandrepair. 5. Afterdigestion,excess(超重，超量)foodisturnedintowasteandeliminated(排除，消除)fromthebody. 6. Thenervoussystemsincludethebrain,spinal(脊柱的)cord(脊髓)andnerves. 7. Thisisyourbodiescontrolsystem. 8. Itcontrolsyourmuscles(肌肉)andorgans(器官)includingyourcirculatory(循环)anddigest(消化)system. 9. Therespiratory(呼吸的)systemincludesthenoseandlungs. 10.Itbringsairandoxygenintothebodyandremovescarbondioxide(二氧化碳). 11.Thelungsarewhereoxygenentersthebloodstream(血流，体内循环的血液)and(二氧化碳)carbondioxide(二氧化物)isremoved.
12.Theimmune(免疫的)systemprotectsthebodyagainstinfections(传染，感染，传染病)anddiseases.
13.Sneezing(打喷嚏)andfeverareexampleofhowtheimmunesystemworks. 14.Ifaninfectioninvades(侵入)thebodytheimmunesystemattacks(攻击)it. 练：
1.Thebloodvessels(血管)thatcarryoxygen-richbloodfromtheheartarecalledarteries(动脉).
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