老师：各位同学，大家好，我是中国人民大学附属中学的生物老师梁慧媛。今天我讲授的课程是初中生物学七年级上册光合作用吸收二氧化碳释放氧气的第2克时。通过上节课的学习，我们了解了光合作用的发现历程，归纳出光合作用的概念和反应，解释这节课我们将学习光合作用在生物圈中的意义，在农业生产中的应用，并完成相关的拓展练习。请大家准备好本节课的任务单，请观看一段科普视频，体会绿色植物光合作用释放氧气的强大能力。
学生：Butoxygenthatcomplexlifelikeuscanoperateatforlong.Soatthetopisyourheartrate.Howisthatreallyhigh?Ithinkitmightbealittlebitanxiousaboutgoinginthere.I'msure.Yourrestingheartracenotnormally92.No,Ihavebeenthinkingalotaboutit.Myvitalsignshavebeenmonitoredalongwiththeoxygenlevelsinmyblood.
学生：Nowit'stimetobesealedinsidethechamberforthenext48hours.Iwasreadytoletitbeaguy.Socanweopenthisdoor?Wishmeluck.Oh,Ismallwasn'tthat.
学生：Oxygenlevelsintheairarenormally21%.Insidethechamber,they'refarlower,justover12%.Attheseconcentrations,thecellularactivityinmybodyandbrainisstartingtoslow.Crucialstepistoseeifthe300plantsinherewithmecanproduceenoughoxygentokeepmealive.It'salltodowithawondrousabilitytheyinheritedfromthosegreenbacteria.It'sphotosynthesis,ofcourse.Ithinkwecanhavethelightson,please.Tokickstartit,youneedlight.Suddenly,thelightshit.
学生：Plantsusephotosynthesistoliveandgrow,andmostimportantlyforme,tomakeoxygen.Photosynthesisisanintricateprocessthatscienceisstilltryingtounlock,buttheprod
