F13 lecture 21 v2

G 120 y 00205x 02469 r 008578 relave tness

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Unformatted text preview: gene,c varia,on for the phenotype Three elements of phenotypic evolution by natural selection Phenotypic variation VP Consistent relationship between fitness and phenotype Some of the phenotypic variation is heritable h2 Chicago school approach •  developed at U. Chicago in 1970s •  natural selec,on is depicted as in last slide, graph B –  phenotype on X axis, fitness on Y axis •  useful to standardize the phenotype –  subtract the mean from each individual value –  divide each residual value by the phenotypic standard devision σ e.g. y- axis = “fitness” •  as we discussed earlier in the course – very difficult to quan,fy •  Chicago approach = life,me reproduc,on (# offspring produced) –  used mostly in theory –  most empirical work uses “fitness proxy” • ...
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