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首页 古代文学诗集

古代文学诗集.ppt

古代文学诗集

用户3640045230
2013-11-07 0人阅读 举报 0 0 暂无简介

简介:本文档为《古代文学诗集ppt》,可适用于领域

PrinciplesofEvolutionPrinciplesofEvolutionHowDidEvolutionaryThoughtEvolveEarlybiologicalthoughtdidnotincludetheconceptofevolutionExplorationofnewlandsrevealedastaggeringdiversityoflifeFossildiscoveriesshowedthatlifehadchangedoverTimeSomescientistsdevisednonevolutionaryexplanationsforfossilsAfewscientistsspeculatedthatlifehadevolvedwithtimeGeologyprovidedevidencethatEarthisexceedinglyoldSomepreDarwinbiologistsproposedmechanismsforevolutionDarwinandWallaceproposedamechanismofevolutionDarwinstudiedagroupofcloselyrelatedspeciesoffinchesontheGalapagosIslandsEachspeciesspecializesineatingadifferenttypeoffoodandhasabeakofcharacteristicsizeandshape,becausenaturalselectionhasfavoredtheindividualsbestsuitedtoexploiteachfoodsourceefficientlyAsidefromthedifferencesintheirbeaks,thefinchesarequitesimilarPrinciplesofEvolutionhttp:wwwhygycom衬塑复合管涂塑复合管钢塑复合管消防涂覆钢管http:wwwucomaLargegroundfinch,beaksuitedtolargeseedsSmallgroundfinch,beaksuitedtosmallseedsWarblerfinch,beaksuitedtoinsectsdVegetariantreefinch,beaksuitedtoleavesHowDoesNaturalSelectionWorkHowDoesNaturalSelectionWorkModernGeneticsconfirmedDarwin’sassumptionofinheritanceNaturalSelectionmodifiespopulationsovertimeFossilsprovideevidenceofevolutionarychangeovertimeComparativeAnatomygivesevidenceofDescentwithModificationHomologousstructuresprovideevidenceofCommonAncestryFunctionlessstructuresareinheritedfromancestorsManyorganismshavevestigialstructuresthatservenoapparentfunctionThe(a)salamander,(b)whale,and(c)snakeallinheritedhindlimbbonesfromacommonancestorthebonesremainfunctionalinthesalamanderbutarevestigialinthewhaleandsnakeHowDoWeKnowThatEvolutionHasOccurredHowDoWeKnowThatEvolutionHasOccurredSomeanatomicalsimilaritiesresultfromevolutioninsimilarenvironmentsEmbryologicalsimilaritysuggestscommonancestryModernbiochemicalandgeneticanalysesrevealrelatednessamongdiverseorganismsConvergentevolutioncanproduceoutwardlysimilarstructuresthatdifferanatomicallyThewingsof(a)insectsand(b)birdsandthesleek,streamlinedshapesof(c)sealsand(d)penguinsareexamplesofsuchanalogousstructuresTheearlyembryonicstagesofa(a)lemur,(b)pig,and(c)humanshowstrikinglysimilaranatomicalfeaturesWhatIstheEvidenceThatPopulationsEvolvebyNaturalSelectionWhatIstheEvidenceThatPopulationsEvolvebyNaturalSelectionControlledBreedingModifiesOrganismsEvolutionbyNaturalSelectionOccursTodayWhenfewerpredatorsarepresent,brightercolorationcanevolveNaturalSelectioncanleadtopesticideresistanceExperimentscandemonstrateNaturalSelectionSelectionactsonrandomvariationtofavorthetraitsthatworkbestinparticularenvironmentsDogdiversityillustratesartificialselectionAcomparisonof(a)theancestraldog(thegraywolf,Canislupus)and(b)variousbreedsofmoderndogsArtificialselectionbyhumanshascausedagreatdivergenceinsizeandshapeofdogsinonlyafewthousandyearsHowArePopulations,Genes,andEvolutionRelatedHowArePopulations,Genes,andEvolutionRelatedGenesandtheenvironmentinteracttodeterminetraitsThegenepoolisthesumofthegenesinapopulationEvolutionisthechangeovertimeofallelefrequencieswithinapopulationTheequilibriumpopulationisahypotheticalpopulationthatdoesnotevolveWhatCausesEvolutionWhatCausesEvolutionMutationsarethesourceofGeneticVariabilityMutationsarerare,butimportantMutationsarenotGoalDirectedMutationsoccurspontaneouslyGeneflowbetweenpopulationschangesAlleleFrequenciesAllelefrequenciesmaydriftinsmallpopulationsPopulationsizemattersApopulationbottleneckIsanexampleofGeneticDriftPopulationbottlenecksreducevariationTheEffectofPopulationSizeonGeneticDriftEachcoloredlinerepresentsonecomputersimulationofthechangeovertimeinthefrequencyofalleleAina(a)largeor(b)smallpopulationinwhichtwoalleles,Aanda,wereinitiallypresentinequalproportions,andinwhichrandomlychosenindividualsreproducedPopulationBottlenecksReduceVariation(a)ApopulationbottleneckmaydrasticallyreducegeneticandphenotypicvariationbecausethefeworganismsthatsurvivemaycarrysimilarsetsofallelesBoth(b)thenorthernelephantsealand(c)thecheetahpassedthroughpopulationbottlenecksintherecentpast,resultinginanalmosttotallossofgeneticdiversityWhatCausesEvolutionWhatCausesEvolutionIsolatedfoundingpopulationsmayproducebottlenecksMatingwithinapopulationIsalmostneverrandomAllgenotypesarenotequallybeneficialAntibioticresistanceevolvesbynaturalselectionPenicillinresistanceillustrateskeypointsaboutevolutionAHumanExampleoftheFounderEffectAnAmishwomanwithherchild,whosuffersfromasetofgeneticdefectsknownasEllis–vanCreveldsyndrome(shortarmsandlegs,extrafingers,and,insomecases,heartdefects)ThefoundereffectaccountsfortheprevalenceofEllis–vanCreveldsyndromeamongtheAmishresidentsofLancasterCounty,PennsylvaniaACompromiseBetweenOpposingPressures(a)Amalegiraffewithalongneckisatadefiniteadvantageincombattoestablishdominance(b)Butagiraffe'slongneckforcesittoassumeanextremelyawkwardandvulnerablepositionwhendrinkingThus,drinkingandmale–malecontestsplaceopposingevolutionarypressuresonnecklengthHowDoesNaturalSelectionWorkHowDoesNaturalSelectionWorkNaturalselectionstemsfromunequalreproductionNaturalselectionactsonphenotypesSomephenotypesreproducemoresuccessfullythanothersAnenvironmenthasnonlivingandlivingcomponentsCompetitionactsasanagentofselectionBothpredatorandpreyactasagentsofselectionSexualselectionfavorstraitsthathelpanorganismmateSelectioncaninfluencepopulationsinthreewaysDirectionalselectionshiftscharactertraitsinaspecificdirectionStabilizingselectionactsagainstindividualswhodeviatetoofarfromtheaverageDisruptiveselectionadaptsindividualswithinapopulationtodifferenthabitatsThreeWaysthatSelectionAffectsaPopulationOverTimeAgraphicalillustrationofthreewaysnaturalandorsexualselection,actingonanormaldistributionofphenotypes,canaffectapopulationovertimeInallgraphs,thebeigeareasrepresentindividualsthatareselectedagainstthatis,donotreproduceassuccessfullyasdotheindividualsinthepurplerange

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