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The Theory of Evolution

Darwin

NotesPt.2

Charles Darwin

– Darwinwasbornin1809inEngland.

– HewasfromastrongChristianfamily.

– Age16,Darwinwassentbyhisfathertostudymedicine

– HeleftandenrolledatCambridgetobecomeaclergyman– Acareerthatallowedhimtopursuehisinterest inbecoming anaturalist

– Helovedscience&decidedtotakeseveralvoyagesaround theworldtostudy.– At22,hesetoutontheHMSBeagle

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Charles Darwin

– Proposedawayhowevolutionworks– Howdidcreatureschangeovertime?Bynaturalselection

– Collectedalotofevidence tosupporthisideas

Voyage of The H.M.S. Beagle

– 1831– 1836– Darwintookhisship,theH.M.SBeaglearoundtheworldtostudytherocks(geology),flora(plants)andfauna(animals)aroundtheworld.

– HeendedupintheGalapagosIslandsinthePacificOcean.

– Hesawmanystrangecreaturesandstudiedthemovermanyyears.

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Voyage of The H.M.S Beagle

– Stopped inGalapagosIslands– 500milesoffcoastofEcuador

Galapagos

– MostofanimalsontheGalápagoslivenowhereelseinworld,buttheylook likespecieslivingonSouthAmericanmainland.

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What Was Found?

–Darwinfound…manyuniquespecies– GiantGalapagosTortoise

– RedFootedBooby

– GalapagosIguana

– GalapagosFinches

–ManyofDarwin’sobservationsmadehimwonderwhy?

Giant Galapagos Tortoise

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What Was Found?

– Differentshellsontortoisesondifferentislands

– Darwinasked:– Istherearelationshipbetweentheenvironmentandwhatananimallookslike?

Red Footed Booby

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Galapagos Iguana

Galapagos Finches

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Darwin’s Finches

– Eachislandhadauniquespecies,eachwithadifferentbeaksizeandshape– Therewere14differentspeciesoffinches(birds) ontheGalapagosIslands,thatareuniquetothatarea.

– Darwinhypothesizedthatfinchesfromthemainlandcouldhaveevolved intoseparatespecieson theislandbynaturalselection

Darwin’s Finches

– Asthebirdswithsmallerbeaksdiedoff,thebirdswithlargerbeakscontinued toeatthefoodandmate/haveoffspring.

– The“largebeak”geneswerepassedontotheseoffspring,andeventuallyallthefincheshadlargebeaks,becausethe“smallbeak”genewaswipedoutofthepopulation.

– Thefincheshaveevolvedovermanygenerationstobettersurviveintheenvironment.

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Darwin’s Finches

– Darwin’sConclusions:– Variations inBeaks

– differencesinbeaksintheoriginalflock

– adaptationstofoodsavailableonislands

– NaturalSelection fortheMostFit

– overmanygenerations,thefincheswereselectedforspecificbeaks&behaviors

– OffspringInheritSuccessfulTraits– accumulationofwinningtraits:bothbeaks&behaviors

– SeparateintoDifferent Species

present day Armadillosancient Armadillo

More Evidence for Darwin

– DarwinfoundEvidenceinfossilsthatcreatureshavechangedovertime.

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Darwin’s View of Evolution

– Giraffesthatalreadyhavelongneckssurvivebetter

– Leavemoreoffspringwhoinherittheirlongnecks– Variation

– Selection&Survival

– Reproduction&Inheritanceofmorefittraits

Darwin Came Up With Two Main Points

1. DescentwithModification

2. NaturalSelection

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Darwin and Descent with Modification

–DarwinFound– Thedifferencesbetweenspeciesoffincheswereassociatedwiththedifferentfoodtheyate.

– Allfinchescamefromoneancestorbuteventuallyovertimenatureselectedfordifferentspecieswithdifferentbeaks.

Darwin and Natural Selection

“Survival of the Fittest”–NaturalSelection isalsoknownas“survivalofthefittest”.– Thismeansthatthestrongestofthespecies,theoneswiththebestnaturaldefenses,ortheoneswiththemostadvantageousvariations,willsurvive.

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Natural Selection Requirements

1. Variation- Individualsinapopulationhavedifferences

2. Heritability- Variationsareinheritedfromparents

3. Overproduction - Populationsproducemoreoffspringthancansurvive

4. ReproductiveAdvantage- Somevariationsalloworganismstohavemoreoffspringthanotherorganisms.

Natural Selection and Differential Survival

– Onlyalimitedamountoforganismsineachpopulationcansurvive.

– Sothetraitsthatareleftinthatpopulationcaneitherhelpthepopulationtosurvive&thrive&thereforeevolve,orharmit&causeittobecomeextinct.

– Whatmightlimitpopulationsize?– AccesstoFood– Predators– Sunlight– Space– Water

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Let’s Think…

–Canyouthinkofaphysicaltraitthatwouldgiveanorganismanadvantageinobtainingoneoftheselimitingfactors?– AccesstoFood

– Predators

– Sunlight

– Space

– Water

Variation In Moths

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What gives this moth an advantage?

Let’s Think…

–Whatwould happenifpollutionmadetreesdarker?

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Darker Moths Become More Common!

Is this Evolution?

– Yes,itisbecauseevolutionworksonpopulations

– Evolution:Achangeinapopulationovertime.