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
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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
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