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Lecture 8

ANTH 201 Lecture Notes - Lecture 8: Falkland Islands Wolf, Thylacine, Darwinius


Department
Anthropology
Course Code
ANTH 201
Professor
Susanne Cote
Lecture
8

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PhylogeneticsandTaxonomy
ImplicationsofSpeciation
● Newspeciesoriginatebysplittingfromancestralspecies
● Stillsharemanysimilaritieswithancestralgroup,and/orwithsisterspecies
● Allowsustosortspeciesintonestedgroupsofsimilar/relatedspecies
NamingandSortingSpecies
● Systematics
○ Constructionofphylogenies(familytrees)
○ Determineevolutionaryrelationshipsamongspecies,genera,families,ect
● Taxonomy
○ Usingphylogeniestonameandclassifyorganisms
Phylogeny
● Evolutionaryrelationshipsamongspecies
● Hierarchicalfamilytreewithdescendantsbranchingofffromancestors
● Importanceofphylogeny:
○ 1)Basisforidentificationandclassification(taxonomy)
■ e.g.howmanyspeciesinagenus,family,ect
○ 2)Helpsexplainwhyaspeciesevolvedcertainadaptationsandnotothers
■ Understandwhenandwhereinthefamilytreecertaintraitsevolved
■ e.g.knucklewalkingoccursinthechimpsandgorillasbutnotinhumans
■ Becausehumansandchimpsaretheclosestrelatives:
● A)Knucklewalkingwaseitherpresentintheancestortoallthree
● B)Orknucklewalkingdevelopedindependentlyingorillasand
chimps
● 

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○ 3)Deducefunctionoftraitsbycomparisonwithotherspecies
■ Thecomparativemethod
● Doesatraitexistforitsperceivedcurrentfunctionoronly
becauseitwasinheritedfromthecommonancestor?(i.e.isitan
adaptation?)
● Havetocontrolforphylogenytodeterminefunction
● Exampleonpage96oftextbookofgroupsizeand
arboreality/terrestriality
● e.g.groupsizeandhabitatpreferenceinprimates(hypothetical
example)
■ Getustoasktherightquestionsthroughunderstandingtheevolutionary
historyofthegroups
■ 
Howdoweconstructtrees?
● Traditionalmethodslookedatoverallsimilaritiesamongspecies
○ Includesbothancestraltraits(plesiomorphies)
■ “primitive”or“plesiomorphic”
■ Occurinlastcommonancestor
○ Derivedtraits(apomorphies)
■ “apomorphic”
■ Newlyevolvedtraitssincethetimeofthelastcommonancestor
● Modernmethodsrelyonsharedderivedcharacteristicstodeterminerelationships
○ Sharedderivedtraits=synapomorphies
● Cladistics
○ Membersofagroupshareacommonevolutionaryhistory,andare“closely
related”,recognizedbysharinguniquefeaturesnotpresentindistantancestors
Cladistics
● Step1:Chooseatrait
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○ Arecharactershomologousoranalogous?
○ Homologyiswhatweareseeing
■ Similartraitssharedbetweenorganismsbecausetheyshareacommon
ancestor
■ e.g.frogsandlizardshavethesamebonesoftheforelimbbecausethe
commonancestortoallreptilesandamphibianshadthesesamebones
■ 
AnalogousTraits
● Similartraitsinorganismsduetosimilarfunctionratherthancommonancestry
● Throughconvergentevolution
● Convergenttraitsdon’thelptoestablishrelationships
● 
Whatelsemakesagoodtrait?
● Homologous(i.e.shared)
● Objective/quantifiable
● Variesmorebetweenthanwithinspecies
● Independent(notcorrelatedwithothertraits)
Cladistics
● Step2:Determinepolarityoftrait
○ Sharedderivedtraits(AKAsynapomorphies)telluswhoourclosestrelativesare
○ Sharedprimitivetraits(AKAsymplesiomorphies)can’thelpusdeterminewho
ourclosestrelativesare
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