六级-听力强化

六 主次重要信息放前主次首段转Manypeoplebut后面的内容往往是中心出现的地总结性信例：tosumup,inbrief,inparticular,allinallgenerallyspeaking重复性信息实词重文章中反复出现的term,通常是文章微观方向对比转折 举例因果关系处 解释定义建议意见强调转折对比although,though,eventhough,despite,inspiteof,however,but,yet,while,not...but...,unexpected,expected, y,fortuna 转折后面的信息为重因果关系because,for,as,since,bedueto,leadto,resultfrom,resultin,consequently定义处例words,it,as,tosay BB建议意见should,don'tyou,if中常出现，考查解决方强调mostimportant,especially,justremember,indeed举例forexample,forinstance,suchas,take...forexample通通常考查举例的目解释 eans...,thatistosay,meantthat,knownas,forshortWhat'sthelecturemainlyHowdolphinsproducethesoundstheyHowdolphinsteachtheiryoungtoidentifyTheprofessor'sexperiencewithdolphinsonaresearchboatVariouswaysdolphinscommunicatewithoneAccordingtoatheorytheprofessormentions,whydodolphinstravelsidebyTovieweachother'sbubbleToheareachother'ssignatureToavoidinterferingwithotherdolphins'sonarTokeepmothersclosetotheirWhydoestheprofessormentionthetimeshespenta ngToencouragestudentstodofieldToinformstudentsaboutapapersheToshowhowscientistscollectdataonmarineToillustratethatdolphinsaredifficulttoWe'vebeendiscussinganimalcommunication.Umtodaywe'regoingtotalkaboutdolphins.Now,dolphinsmakeawiderangeofcommunicativesoundsandalsodisplaysomethingcalledvocallearning,whichistheabilityofananimaltomodifyitsvocalizationsbasedonitsexperiencewitheachother.Ahtherearemanytypesofdolphinvocalizations.Wewestilldon'tknowtheirprecisemeanings--partly,Isuppose,becausewehaven'treallytriedthathardtofigureouttheirprecisemeanings--butwedoknowthatdolphinsareusevocalizationsasawayofcommunicatingwithoneanother.Andwe'vecategorizedtheirvocalizationsintothreetypes:whistles,clicks,andburstpulses.Thedolphinwhistlesareveryhighfrequencysounds,ahpartiallyabovetherangeofhumanhearing.What'sfascinatingis,eachdolphinhasasignaturewhistle,whichisuniquetoeachindividualdolphin.Itallowsthemtocalltoandidentifyeachother.Jennifer?FemaleKindoflikelearningsomeone'sname?So...dodolphinparentschoosenamesfortheirchildren?Well,againthat'ssomethingwedon'tknow,butwedoknowthatnotwosignaturewhistlessoundidentical.Andmembersofthesamefamily,theirsignaturewhistleshavesimilarelements.Dolphinsusethemascontactcalls--ahtheytheycalltoeachotherwhiletravelingandforaging.Ithelpskeepthegrouptogether,andhelpsmothersandchildrenfindeachother.Thinkofitlike...ahifyouweretravelingintheforestwithoneotherwhohasjustoutofsight,you'dcallout,"Areyouthere?"andtheother wouldrespond.Butiftherewereseveralpeopleintheforest,youwouldhavetocall nametocalltoIninadditiontowhistles,dolphinsproduceclicks,whichareactuallysonarorsoundwaves.Theyusetheclickstocommunicate,but,moreimportantly,tonavigateandhunt.How?Well,thesonarclicksbounceofftheobjects,andthenthedolphinsconvertthe ingsignalsintoathreedimensionalpicture...aamentalmap...ofwhat'saroundthem.Theclicksareextremelysensitiveandaccurate.Thesonarclicksareverystrong.Andthere'sthistheorythat,onereasondolphinsswimsidebysideistoavoidinterferencefromeachothers'sonarclicks.Interferencewouldbeconfusing...itwouldpreventthemfromgettinganaccuratepictureoftheirsurroundings.Ahandwhat'sinterestingis,dolphinswillturnofftheirsonarwhenanotherdolphinpassesinfront.Ahthethirdcategoryofdolphinvocalizationsisburstpulses.Theseareallthisothersoundsthedolphinmakes--squawks,squeals,barks,groans,andsoon.Burstplusesareusedtodisplayaggression,showdominance,andattractamate.Butwhistles,clicks,andburstpulsesaren'ttheonlywaysdolphinscommunicate.UmdoesanyonerememberanyotherMaleInthebook,itsaidthattheyalsoslaptheirtailsagainstthewater?Oh,and...theairthatcomesoutwhentheybreathorwhistle...the...ah...thebubblestreams?Theycancontrolhowtheairbubblescomeout?Ithoughtthatwasreallyinteresting.Yes...thebubblestreamsareveryinteresting.Dolphinscanidentifyandlocateeachotherbytheirbubblestreams,andtheycanimitatethebubblestreampatternsofotherdolphins...sortoflikesayingo.Soasyoucansee,dolphinsusemanydifferentsoundsandbehaviorstoconveymessagestoeachI'dliketolyouaboutwhenIwasagraduatestudent...and...IspentonesummeronaboatintheAtlanticOceanstudyingmarinelife.Onemorningtherewereabout25dolphinsswimmingwiththeboat.Wecouldheartheirclicksandwhistlesastheycalledtoeachother.Now,wewerethereasimpartialscientists,todoresearch,but...howcouldwenotnoticethebeautyasthebubblestreamsmadepatternsinthewaterandthedolphinsappearedtodanceandplay?It'swonderfulwhenyoudofieldworkandactuallyexperiencesomethingyou'vebeenstudyinginaclassroom.So,ifyoueverhavetheopportunity...goforit.What'sthelecturemainlyHowdolphinsproducethesoundstheyHowdolphinsteachtheiryoungtoidentifyTheprofessor'sexperiencewithdolphinsonaresearchboatVariouswaysdolphinscommunicatewithoneAccordingtoatheorytheprofessormentions,whydodolphinstravelsidebyTovieweachother'sbu