BIOLOGY 130 Chapter Notes - Chapter 6: Heritability, Theodosius Dobzhansky, Biogeography

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27 Apr 2016

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Evolution

If: 

❖Variation:individualswithinaspeciesdifferintheirtraits(includingbehavior)

❖Heritability:offspringresembleparents(geneticinfluenceontraits)

❖EffectonSuccess:sometraitsmakeindividualsmorelikelytosurvive,breed,and

leavemanydescendants.

Knifes 

Then: 

❖Successfulindividualsineachgenerationwilltendtohavecertaintraits.

❖Greaterandgreaterproportionofindividualswillexhibitthosetraitsovertime

(successivegenerations)



LogicalstructureofDarwin’sHypothesis



1) Organism’scouldincreasetheirnumbersgeometrically,buttheydon’t.

**thereforetheremustbea“struggleforexistence”**

2) Variationexistsamongindividualsineveryspecies.

3) Manysuchvariationscanbetransmittedfromparentstooffspring

4) VariationsthatresultingreatersurvivalandreproductionwillincreaseIfrequency

astimepasses.

(Resultinginchangesinpopulation.)



Evolution:genefrequencychangeinapopulation((changeovertime)).Onlyhappensto

populations.



Evolutionisnotthesameasnaturalselection.



“NaturalSelectionisatoneandthesametimeablindandcreativeprocess.”–Theodosius

Dobzhansky



Creative:newforms,newspeciesarecreated.

Blind:ithasnogoal,noforethought,thenewspeciesandadaptationsjustfalloutfrom

differentialsurvival.



❖Complexstructuresaretheresultofmany,many……tinystepsoverlongperiodsof

time.

❖Naturalselectionhasbeendiversifyinglifefor3.5billionyears.

❖ArtificialSelection:Variantsdepend.Humansarecausingachangeinreproduction.



Waspsaregettingbigger.Isitevolutionvianaturalselection?Waspsthatsurvivedthe

winterswerebigger,theyalsohadmorebabiesthanthesmallerwasps.Waspsarean

invasivespecies.



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BIOLOGY 130 Chapter Notes - Chapter 6: Heritability, Theodosius Dobzhansky, Biogeography

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