Darwin’s Observations Darwin’s Voyage (7.3 Voyage of the ... · 1. What qualities of a good scientist did Darwin display on the voyage? 2. Describe Darwin’s key observations

Darwin’sObservationsDarwin’sVoyage(7.3VoyageoftheHMSBeagle)

1. WhatqualitiesofagoodscientistdidDarwindisplayonthevoyage?2. DescribeDarwin’skeyobservationsregardingthedistributionoffossils.3. WhatdidthechangeincoastlinefollowinganearthquakeleadDarwintodiscover?4. DarwinwassurprisedbythespecieshefoundontheGalapagosIslands.

a) Whatotherspeciesdidtheyremindhimof?

b) What is theconnectionbetweenthetypesofnativeanimalsonthe island,andtheirability tocross theopenocean?

Darwin’sObservationsandHypotheses InJuly1837Darwinbeganwritinghisfirstnotebook,the“transmutationofspecies”.

• Markedthebeginningofhisinvestigationsontheevolutionofspecies• Realized that the patterns he observed regarding the distribution of both ____________ and ____________

species,wereevidencethatspeciesmighthaveevolvedEachkeyobservationregardingthespeciesfoundontheGalapagosIslandsmatchedwithhiscorrespondinghypothesisforallremoteislands,basedonthetheorythatspeciesevolve:

Observations HypothesesManyspeciesofplants,birds,insects Onlythosekindsoforganismsareabletoreachremoteislandsby

crossingalargewatermassNonativeamphibiansandfewmammals Amphibiansandmostmammalsareunabletocrosslargewater

massesandwillnotbefoundonremoteislandsManyuniquespeciesfoundnowhereelse Overtime,ancestralspecieshaveevolvedintonewgeographically

isolatedspeciesUniquespeciesmostcloselyresemblespeciesonnearestcontinentallandmass

Uniquespeciesaredescendantsofancestralspeciesfromthenearestcontinentallandmassesandexhibitsomesimilarities

ThefollowingobservationsprovidedDarwinwithevidencethatspecieshad________________overtimeandthatspeciesappearedtoshareacommon___________________.#1Biogeography DarwinwassurprisedbytheunusualassortmentofspecieshefoundontheIslands.Darwin’sobservationsoflivingandfossilizedspecieslaidthefoundationforthescienceofbiogeography.

Biogeography=

Darwin considered evolution to be the best explanation forwhy isolated islands hadmany species thatwere foundnowhereelse,andwhythesespeciesborearesemblancetospeciesonthenearestcontinentallandmass.Hypothesis=

HomologousandAnalogousFeatures Iflivingthingsarerelatedtoeachother,thenweshouldexpecttofindevidenceforsuchrelationshipsbyexaminingtheiranatomy.Darwinwasstruckbythemanycasesinwhichsimilarstructuresoftwoorganismscouldhaveentirelydifferentfunctions.Homologousfeatures=

Healsoobservedfeaturesthatmaybefunctionallysimilar,butnotstructure.Analogousfeatures=

Darwinconcludedthat:

• Organismswithhomologousfeatures________________sharedamorerecentcommonancestor• Thosewithanalogousfeaturesare__________________toshareacommonancestor

VestigialFeaturesandAnatomicalOddities Vestigialfeatures=

Forexample,Darwinobservedthat:

• Dogshaveavestigialtoe;althoughtheboneremains,nopresentpurpose• Pigs’feethavetwowell-developeddigits;theothersarevestigial• Horsesonlyhaveoneenlargeddigit;othersarevestigialorhavebeenlostcompletely

Manyanatomicalodditiesalsosuggestedanevolutionarypast.Forexample:• Uplandgeeseandfrigatebirds,forexample,havefullywebbedfeet,butneverenterwater.• Hipbonesareusedtotransferbodyweighttothehindlegs.Theexistenceofthesebondsinmodernwhalesis

compellingevidencethatthesemammalsevolvedfromancestorsthathadhindlegs.

Vestigialfeaturescouldbeexplainedasevolutionarybaggage= CompetitionwithinPopulations Theanatomicalfeaturesofspecies,biogeography,&fossilrecordsprovidedDarwinwithevidenceofevolution.Breedersofdomesticatedplantsandanimalsrepeatedlyshowedthatbehaviorandappearancecouldbechangedbyartificiallyselectingindividualswithfavoredtraitstobetheparentsofeachnewgeneration.

• Recognizedthatallspeciespossess________________variationsthatcanbe___________tochangethespecies• Wonderedifnature,likehumans,mightalsobeableto________certainindividualsinapopulationoverothers

Hefoundhisanswerinamathematicalessayonpopulation,writtenbyThomasMalthusin1798.Malthusstatedthat:

• “Innature,bothplantsandanimalsproducefar______________offspringthanareabletosurvive.”• Allpopulationswere_________________insizebytheirenvironment(e.g.foodsupply)

Darwinrealizedseveralimplicationsthishadforindividualswithinpopulations.Heconcludedthat:

• Thereis____________________forsurvivalbetweenmembersofthesamespecies• Inthisstruggletosurvive,themost________________traitsare_________________bysucceedinggenerations