• 2022-05-27
    Passage9
    EvolutionoftheSharkTheshark,whateverelseitmightbe,isalmostuniquelysuccessful.Accordingtofossilevidence,theearliestshark-likecreaturesprowledtheworld’soceans450millionyearsago—longbeforetheageofdinosaurs.Comparedtothis,man’sspanofacoupleofmillionyearsisamereflashofatigershark’stail.
    Evolutionisthegrindinglyslowprocesswhichrewardssuccessby“survivalofthefittest”.Organismsbestsuitedtoexploittheirenvironmentsurvivetobreed,producingmorelikethemselves.Thoselesssuitedtotheirsurroundingsfailtoprosperandsimplydieout.Ifanenvironmentchanges,whichmaymeanchangesinpredators*orfoodsupply,aswellasphysicalsurroundings,aspeciesmayneedtoadaptifitistosurvive.
    Whathappensinpracticeisthatoneormoreofthemyriadtinydifferencesthatoccurnaturallyinapopulationbecomeanadvantageordisadvantage.Ifthecharacteristicisanasset,thecreaturepossessingitismorelikelytosurviveandpassitontothenextgeneration.Ifitisnot,theindividual,andthecharacteristic,aremorelikelytodieout.Humans,forinstance,althoughallpartofthesamespecies,comeinmanyshapesandsizes.Althoughmodemman’scapacitytochangehisenvironmenthasreducedhisneedtoadapttoit,someofthesecouldbecomemoreorlessadvantageousifoursurroundingsweretochange.
    Althoughtheshark’senvironment,thesea,hasprobablybeenmoreconstantthantheone-thirdoftheglobethatisland,sharks,too,haveundergoneinnumerablechangesoverthemillennia.AsNatureexperimentedtofindherperfectfish,thereweremanysuccessesbutprobablymanymoredeadends.Someofthesearepreservedinlayersofancientrock,the“fossilrecord”,fromwherepaleontologists**laterunearththem.
    *predator:捕食其他动物为生的动物
    **paleontologist:古动物学家
    (2005年5月试题)
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