7.  Many traits vary more or less continuously over a wide range. For example, height, weight, shape, color, reproductive rate, metabolic activity, etc., vary quantitatively rather than qualitatively. Continuous variation can often be represented by a bell-shaped curve, where the “average” phenotype is more common than the extremes. Discontinuous variation describes the easily classifiable, discrete phenotypes of simple Mendelian genetics: seed shape, auxotrophic mutants, sickle-cell anemia, etc. These traits often show a simple relation between genotype and phenotype, although discontinuous traits such as affected versus not-affected for a disease condition can also exhibit complex inheritance.

9.  The mean is 4.7 bristles, the variance is 1.11 bristles², and the standard deviation is 1.05 bristles.

12.  The breeder cannot be assured that this population will respond to selective breeding even though the broad-sense heritability is high. Broad-sense heritability is the ratio of the genetic variance to the phenotypic variance. The genetic variance is the sum of the additive and dominance variances. Only additive variance is transmitted from parent to offspring. Dominance variance is not transmitted from parent to offspring. If all the genetic variance in the population is dominance variance, then selective breeding will not succeed.

18.  = [(9.8 + 10.8)/2] − 9.6 = 0.7 mm, = 0.79 × 0.7 = 0.55 mm, = 9.6 + 0.55 = 10.15 mm

23.  V_e = 3.5 g², V_g in population B is 21.0 − 3.5 = 17.5 g², H² = 17.5/21.0 = 0.83.