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Lecture 17

BGYB51H3 Lecture 17 Notes Nov 5

Biological Sciences
Course Code
Maydianne Andrade

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BGYB51H3 Lecture Notes
-selection differential is the mean value of trait between successful breeders and whole
S = P* - P
-if S>0, increase in trait value, if S<0 decrease in trait value, S=0 mean trait value
-larger values of S, stronger selection occurring
-the closer S is to the population mean, weak selection
-R is the evolutionary response to selection
R = O* - O
-O means that there is no evolutionary change and is an estimate from P
O* - O rise R
h2 = ______ =____ =___ R = h2S
P* - P run S
-heritability is the response to the selection divided by the selection differential
-even if strong selection, if heritability is low there is low direction of change in offspring
-relative fitness is the number of surviving offspring divided by mean number of surviving
-selection gradient is the relation between trait value and fitness
-selection gradient is more commonly measured than selection differential
S = selection gradient/variance
-coevolution is when interacting species experience reciprocal evolutionary change due to
natural selection imposed by each on the other
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