CharlesDarwin0 LivedinEngland0 1809-1882

0 1831-1836:Beagle’sfive-yearvoyagemappingthecoastlineofSouthAmerica

0 1859:OntheOriginofSpeciesbyMeansofNaturalSelection

0 EVOLUTIONà explainshowmodernorganismsevolvedoverlongperiodsoftimethroughdescentfromcommonancestors

OntheOriginofSpeciesbymeansofNaturalSelection

0 PublishedbyDarwinin1859(158yearsago)

0 Twomajorclaims:0 ThespeciespresentonEarthtodaydescendedfromancestralspecies

0 Naturalselectionisthemechanismforevolution

0 NaturalSelectionleadstoevolutionaryadaptation.

0 Individualswithbeneficialheritabletraitsleavemoreoffspring,therefore,thefrequencyofthosetraitsincreasesinthepopulationovergeneration

0 Evolution– changesinapopulation’sgeneticcompositionovertime.

Darwinchallengedtraditionalviews

0 Prevailingview=Earthwasonlyafewthousandyearsold,speciesoforganismswereunchanging,createdbyGod

Historicalcontext0 Aristotle(384-322B.C.)– alllivingformscouldbearrangedonascaleofincreasingcomplexity=scala naturae

0 speciesarepermanentandperfectanddonotevolve

0 NaturalTheology– 1700s0 BasedonOldTestamentcreationstory0 SpecieswereindividuallydesignedbyGodanddonotevolve0 Taxonomy=scienceofclassification

0 SoughttoclassifythespeciesthatGodhadcreated0 Linnaeus(1707-1778)– taxonomyshowedGod’sorganization

Historicalcontext(continued)0GeorgesCuvier(1769-1832):paleontologist;feltchangesinfossilsatdifferentstrataduetocatastrophism.

0 Somecatastrophe(floodordrought)destroyedlargenumbersofspeciesatatime

0Hutton:(1726-1797):gradualism;profoundchangecantakeplacethroughthecumulativeeffectofslowbutcontinuousprocesses.

0 Earth’sgeologicfeaturesexplainedbymechanismscurrentlyoperatingintheworld.

Historicalcontext(continued)0 CharlesLyell(1797-1875):uniformitarianism;basicgeologicalprocesses(wind,rain,erosion,etc.)havenotchangedthroughoutEarth’shistory.

0 DarwinreasonedthatEarthmustbeolderthan6000years

Otherscientistssuggestthatevolutionoccurs

0 Lamarck’stheoryofevolution:theoryofevolutionbasedontheideathatmodificationacquiredduringlifeofanorganismpassedtooffspring.

0 Wallace:alsodevelopedtheoryofevolutionbasedonnaturalselectionin1858;thispushedDarwintopublishhisfindings

AcquiredCharacteristicsList the characteristics that you believe you have always had. For example, you may have brown eyes or curly hair.

InheritedCharacteristicsList your acquired characteristics. For example, you may have learned how to play a musical instrument.

0 JeanBaptisteLamarck– proposedtheoryofevolutionbasedongrowingfossilrecord

0 Suggestedthatorganismscouldchangeduringtheirlifetimesbyselectivelyusingornotusingvariouspartsoftheirbodies.

0 Suggestedthatindividualscouldpasstheseacquiredtraitsontooffspring,enablingspeciestochangeovertime0 Publishedideasin1809–yearDarwinwasborn

LamarckwasINCORRECTbecause:1. Organismsdonothaveaninborndrivetobeperfect

2. Evolutiondoesnotmeanthatovertimespeciesbecomes“better” somehow

3. Evolutiondoesnotprogressinpredetermineddirection

4. Traitsacquiredbyorganismsduringlifetimecannotbepassedontooffspring

Lamarckgaveussomegoodstufftoo!0 Lamarckwasoneof1st totryto

explainevolutionscientificallyusingnaturalprocesses

0 Recognizedlinkb/worg’senvironmentandbodystructures

Darwin’sresearch0 CharlesDarwin(1809-1882)0 VoyageoftheHMSBeagle– 1831

0missiontocharttheSouthAmericancoastline0 Observations:

0 Adaptationsofplantsandanimalsweresimilarinsimilarenvironments0 Geologicchange(forexampleduetoearthquake)indicatedthatEarthwasmucholderthan6000years.0 GeographicdistributionofunusualspeciesonGalapagosindicateddescentwithmodification

BlueFootedBoobies

ArtificialSelection• ArtificialSelection:selectivebreedingofdomesticatedplantsandanimalstoproduceoffspringwithgenetictraitsthathumansvalue

• natureprovidesvariation,humansselectvariationsthatareuseful.

• Example:afarmerbreedsonlyhisbestlivestock

ArtificialSelection0 Humanshavebeenmodifyingspeciesforthousandsofyears

0 Darwinsawthisbeingdonewithdogs0 Heobservedthataspeciescouldbechangedalotinashortperiodoftime

0 Thoughtthatthesamethingcouldbehappeninginnatureataslowerpace

Differences

NaturalSelection ArtificialSelection

0 Traitsthataremorebeneficialintheorganismsenvironmentbecomemorecommoninthepopulation

0 Humanschoosethetraitsthatbecomemorecommoninthepopulation

WhatDarwinKnew0 WhatdidDarwin(andscience)know?0 TheEarthisREALLYold0 4.6BillionYears

0 TheEarthhaschangedovertime0 Mountainsandvalleysformed0 Riverschangecourse0 Watererodesland

0 Humanscanchangeorganismsthroughbreeding

0 OrganismshaverapidPopulationGrowth0 Darwinrealizedmostorganismsdon’tsurviveandreproduce…

0 ???Whichindividualssurviveandwhy???

WhatDarwindidn’tknow0DNAandGenetics0Knewthattraitswerepassedfromparenttooffspring0Didn’tknowHOW

StruggleforExistence0 Ifmoreindividualsareproducedthancansurviveàmembersofapopulationmustcompetetoobtainfood,livingspace,andotherlimitednecessitiesoflife

0Called:StruggleforExistence

0Whichindividualscomeoutontopofstruggle?

VariationandAdaptation0 Individuals have natural variations among

heritable traits0 Some variants are better

suited to life in their environment than others0 Predatory species that are

faster, longer claws, sharper teeth à catch more prey

0 Prey species that are faster, better camouflaged àavoid being caught

SomeVariationsareFavorable0Adaptation - anyheritablecharacteristicthatincreasesanorganism’sabilitytosurviveandreproduce0 Bodypartsorstructures0bear’sclaws0bodycolorà camouflageormimicry

0 Physiologicalfunctions0aplantcarryingoutphotosynthesis

0 Behaviors0avoidancestrategiespreyuse0craneflappingwings

Darwin’sTheoryofNaturalSelection

� Animalsondifferentislandsareindifferentpopulations� GalapagosIslandsweremostlikelycolonizedbyasinglefinchspeciesfromSouthAmerica¡ Singlespeciesadaptedtothevariedhabitatsontheislands¡ Todaywehave13differentspeciesoffinch

¡ DifferbyBeakShape÷ WHY?

Darwin’sObservationsOverproduction Variation

0 BasedonMalthus’ Idea,Darwinrealizedthatspeciestendtoproduceexcessoffspring

0 limitresources+excessoffspring=competition0 NotEveryoneSurvives!

� Differencesamongmembersofthesamespecies

�Mostvariationisheritable¡ Siblingslookmorelikeeachotherthantheydootherpeople

Darwin’sObservations

NaturalSelectionandSpeciesFitness

0Overtime,naturalselectionresultsinchangesintheinheritedcharacteristicsofapopulation.0Thesechangesincreaseaspeciesfitness0 survivalrate

SummaryofDarwin’sTheoryTheProcess

1. Organismsdiffer;variationisinherited2. Organismsproducemoreoffspringthansurvive

3. Organismscompeteforresources4. Organismswithadvantagessurvivetopassthoseadvantagestotheirchildren

5. Speciesalivetodayaredescendedwithmodificationsfromcommonancestors

SummaryofDarwin’sideas0 Naturalselectionreferstothedifferentialsuccessinreproductionwhichresultsinadaptationsofpopulationsoforganismstotheirenvironment

0 Naturalselectionoccursfromtheinteractionbetweentheenvironmentandtheinherentvariabilityinapopulation0 Variationsinapopulationarisebychance0 Naturalselectionisnotachancephenomenon,sinceenvironmentalfactorssetdefinitecriteriaforreproductivesuccess