1. Evolutionary theory predicts the direction and magnitude of evolutionary change Change in trait mean (phenotype) of a population from one generation to the next Change in allele frequency (genotype) from one generation to the next

2. What will beak size be in the next generation? Selection differential = S = 10.1mm – 9.4mm = 0.7mm Response to selection = R = 9.7mm – 9.4mm = 0.3mm

3. The “breeder’s equation” R = S x h 2 h 2 = 0.77 Predicted R = 0.7mm x 0.77 = 0.5mm Observed R = 0.3mm Estimated heritability from parent/offspring regression = 0.77 Realized heritability = R/S = 0.43 How might these discrepancies be explained, and how might the explanation(s) be tested experimentally?

4. Heritability from Falconer and Mackay, Quantitative Genetics Cattle Pigs Chickens Mice Drosophila Egg number Body weight Litter size Weight gain Food conversion Back-fat Milk yield Butterfat % Body weight Tail length Litter size Egg number Egg weight Body weight Ovary size Body size Bristle number What does this tell us?