生物专业英语课件.docx

生物专业英语课件.docx

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生物专业英语课件

Biology:

TheScienceofOurLives

Biologyliterallymeans"thestudyoflife".Biologyissuchabroadfield,coveringtheminuteworkingsofchemicalmachinesinsideourcells,tobroadscaleconceptsofecosystemsandglobalclimatechange.Biologistsstudydetailsofthehumanbrain,thecompositionofourgenes,andeventhefunctioningofourreproductivesystem.Biologistsrecentlyallbutcompletedthedecipheringofthehumangenome,thesequenceofdeoxyribonucleicacid（DNA）basesthatmaydeterminemuchofourinnatecapabilitiesandpredispositionstocertainformsofbehaviorandillnesses.DNAsequenceshaveplayedmajorrolesincriminalcases（O.J.Simpson,aswellasthereversalofdeathpenaltiesformanywrongfullyconvictedindividuals）,aswellastheimpeachmentofPresidentClinton（thestainatleastdidnotlie）.Wearebombardedwithheadlinesaboutpossiblehealthrisksfromfavoritefoods（Chinese,Mexican,hamburgers,etc.）aswellasthepotentialbenefitsofeatingotherfoodssuchascookedtomatoes.Informercialstoutthebenefitsofmetabolism-adjustingdrugsforweightloss.ManyAmericansareturningtoherbalremediestoeasearthritispain,improvememory,aswellasimproveourmoods.

Canabiologybookgiveyoutheanswerstothesequestions?

No,butitwillenableyoulearnhowtosiftthroughthebiasesofinvestigators,thepress,andothersinaquesttocriticallyevaluatethequestion.Tobehonest,fiveyearsafteryouarethroughwiththisclassitisdoubtfulyouwouldrememberallthedetailsofmeatbolism.However,youwillknowwheretolookandmaybealittleabouttheprocessofsciencethatwillallowyoutomakeaninformeddecision.Willyoubeascientist?

Yes,inaway.Youmaynotbeformallytrainedasasciencemajor,butyoucanthinkcritically,solveproblems,andhavesomeideaaboutwhatsciencecanandcannotdo.Ihopeyouwillbeabletotelltheshoefromtheshinola.

ScienceandtheScientificMethod

Scienceisanobjective,logical,andrepeatableattempttounderstandtheprinciplesandforcesoperatinginthenaturaluniverse.ScienceisfromtheLatinword,scientia,toknow.Goodscienceisnotdogmatic,butshouldbeviewedasanongoingprocessoftestingandevaluation.Oneofthehoped-forbenefitsofstudentstakingabiologycourseisthattheywillbecomemorefamiliarwiththeprocessofscience.

Humansseeminnatelyinterestedintheworldwelivein.Youngchildrendrivetheirparentsbattywithconstant"why"questions.Scienceisameanstogetsomeofthosewhysanswered.Whenweshopforgroceries,weareconductingakindofscientificexperiment.IfyoulikeBrandXofsoup,andBrandYisonsale,perhapsyoutryBrandY.Ifyoulikeityoumaybuyitagain,evenwhenitisnotonsale.IfyoudidnotlikeBrandY,thennosalewillgetyoutotryitagain.

Inordertoconductscience,onemustknowtherulesofthegame（imagineplayingMonopolyandhavingtodiscovertherulesasyouplay!

Whichispreciselywhatonedoeswithsomecomputerorvideogames（beforebuyingthecheatbook）.Thescientificmethodistobeusedasaguidethatcanbemodified.Insomesciences,suchastaxonomyandcertaintypesofgeology,laboratoryexperimentsarenotnecessarilyperformed.Instead,afterformulatingahypothesis,additionalobservationsand/orcollectionsaremadefromdifferentlocalities.

Stepsinthescientificmethodcommonlyinclude:

1.Observation:

definingtheproblemyouwishtoexplain.

2.Hypothesis:

oneormorefalsifiableexplanationsfortheobservation.

3.Experimentation:

Controlledattemptstotestoneormorehypotheses.

4.Conclusion:

wasthehypothesissupportedornot?

Afterthisstepthehypothesisiseithermodifiedorrejected,whichcausesarepeatofthestepsabove.

Afterahypothesishasbeenrepeatedlytested,ahierarchyofscientificthoughtdevelops.Hypothesisisthemostcommon,withthelowestlevelofcertainty.Atheoryisahypothesisthathasbeenrepeatedlytestedwithlittlemodification,e.g.TheTheoryofEvolution.ALawisoneofthefundamentalunderlyingprinciplesofhowtheUniverseisorganized,e.g.TheLawsofThermodynamics,Newton'sLawofGravity.Scienceusesthewordtheorydifferentlythanitisusedinthegeneralpopulation.Theorytomostpeople,ingeneralnonscientificuse,isanuntestedidea.Scientistscallthisahypothesis.

Scientificexperimentsarealsoconcernedwithisolatingthevariables.Agoodscienceexperimentdoesnotsimultaneouslytestseveralvariables,butratherasinglevariablethatcanbemeasuredagainstacontrol.Scientificcontrolledexperimentsaresituationswhereallfactorsarethesamebetweentwotestsubjects,exceptforthesingleexperimentalvariable.

Consideracommonlyconductedsciencefairexperiment.Sandywantstotesttheeffectofgangstarapmusiconpeaplantgrowth.Sheplaysloudrapmusic24hoursadaytoaseriesofpeaplantsgrownunderlight,andwateredeveryday.Attheendofherexperimentsheconcludesgangstarapisconducivetoplantgrowth.Herteachergradesherprojectverylow,citingthelackofacontrolgroupfortheexperiment.Sandyreturnstoherexperiment,butthistimeshehasaseparategroupofplantsunderthesameconditionsastherappingplants,butwithsoothingLedZeppelinsongsplaying.Shecomestothesameconclusionasbefore,butnowhasabasisforcomparison.Herteachergivesherprojectabettergrade.

TheoriesContributingtoModernBiology

Modernbiologyisbasedonseveralgreatideas,ortheories:

1.TheCellTheory

2.TheTheoryofEvolutionbyNaturalSelection

3.GeneTheory

4.Homeostasis

RobertHooke（1635-1703）,oneofthefirstscientiststouseamicroscopetoexaminepondwater,corkandotherthings,referredtothecavitieshesawincorkas"cells",Latinforchambers.MattiasSchleiden（in1838）concludedallplanttissuesconsistedofcells.In1839,TheodoreSchwanncametoasimilarconclusionforanimaltissues.RudolfVirchow,in1858,combinedthetwoideasandaddedthatallcellscomefrompre-existingcells,formulatingtheCellTheory.Thusthereisachain-of-existenceextendingfromyourcellsbacktotheearliestcells,over3.5billionyearsago.Thecelltheorystatesthatallorganismsarecomposedofoneormorecells,andthatthosecellshavearisenfrompre-existingcells.

Figure1.JamesWatson（L）andFrancisCrick（R）,andthemodeltheybuiltofthestructureofdeoxyribonucleicacid,DNA.Whileamodelmayseemasmallthing,theirdevelopmentoftheDNAmodelfosteredincreasedunderstandingofhowgeneswork.ImagefromtheInternet.

In1953,AmericanscientistJamesWatsonandBritishscientistFrancisCrickdevelopedthemodelfordeoxyribonucleicacid（DNA）,achemicalthathad（then）recentlybeendeducedtobethephysicalcarrierofinheritance.CrickhypothesizedthemechanismforDNAreplicationandfurtherlinkedDNAtoproteins,anideasincereferredtoasthecentraldogma.InformationfromDNA"language"isconvertedintoRNA（ribonucleicacid）"language"andthentothe"language"ofproteins.Thecentraldogmaexplainstheinfluenceofheredity（DNA）ontheorganism（proteins）.

Homeostasisisthemaintainenceofadynamicrangeofconditionswithinwhichtheorganismcanfunction.Temperature,pH,andenergyaremajorcomponentsofthisconcept.Theromodynamicsisafieldofstudythatcoversthelawsgoverningenergytransfers,andthusthebasisforlifeonearth.Twomajorlawsareknown:

theconservationofmatterandenergy,andentropy.Thesewillbediscussedinmoredetailinalaterchapter.Theuniverseiscomposedoftwothings:

matter（atoms,etc.）andenergy.

Thesefirstthreetheoriesareveryacceptedbyscientistsandthegeneralpublic.Thetheoryofevolutioniswellacceptedbyscientistsandmostofthegeneralpublic.However,itremainsalighteningrodforschoolboards,politicians,andtelevisionpreachers.Muchofthisconfusionresultsfromwhatthetheorysaysandwhatitdoesnotsay.

DevelopmentoftheTheoryofEvolution

Modernbiologyisbasedonseveralunifyingthemes,suchasthecelltheory,geneticsandinheritance,FrancisCrick'scentraldogmaofinformationflow,andDarwinandWallace'stheoryofevolutionbynaturalselection.Inthisfirstunitwewillexaminethesethemesandthenatureofscience.

TheAncientGreekphilosopherAnaxiamander（611-547B.C.）andtheRomanphilosopherLucretius（99-55B.C.）coinedtheconceptthatalllivingthingswererelatedandthattheyhadchangedovertime.Theclassicalscienceoftheirtimewasobservationalratherthanexperimental.AnotherancientGreekphilosopher,AristotledevelopedhisScalaNaturae,orLadderofLife,toexplainhisconceptoftheadvancementoflivingthingsfrominanimatemattertoplants,thenanimalsandfinallyman.Thisconceptofmanasthe"crownofcreation"stillplaguesmodernevolutionarybiologists（SeeGould,1989,foramoredetaileddiscussion）.

Post-Aristotlean"scientists"wereconstrainedbytheprevailingthoughtpatternsoftheMiddleAges--theinerrancyofthebiblicalbookofGenesisandthespecialcreationoftheworldinaliteralsixdaysofthe24-hourvariety.ArchbishopJamesUssherofIreland,inthelate1600'scalculatedtheageoftheearthbasedonthegeneologiesfromAdamandEvelistedinthebiblicalbookofGenesis.AccordingtoUssher'scalculations,theearthwasformedonOctober22,4004B.C.ThesecalculationswerepartofUssher'sbook,HistoryoftheWorld.Thechronologyhedevelopedwastakenasfactual,andwasevenprintedinthefrontpagesofbibles.Ussher'sideaswerereadilyaccepted,inpartbecausetheyposednothreattothesocialorderofthetimes;comfortableideasthatwouldn