Evolution__3rd_Edition

252 PART 2 / Evolutionary Genetics
Study and review questions
1 Review the reasons why characters that are influenced
by a large number of genetic and/or environmental
effects will show a normal distribution.
2 Suppose the average spine length in a population of
porcupines is 10 in and we take a number of individuals
with 12 in spines and mate each with a random member
of the population. The offspring grow up with spines of
average length 10.5 in. What is the additive effect of
those 12 in porcupines?
3 Here are measurements, or estimates, of the
phenotypic values and their additive genetic
components in a population of nine porcupines.
(a) Calculate V P , V A , and h 2 . (b) What would you
predict the average spine length would be in the next
generation if porcupines eight and nine were used to
produce it?
4 Imagine we are selecting porcupines to make them
pricklier. The heritability of prickliness is 0.75. Average
prickliness before selection is 100 (and the standard
deviation is also 100). The average prickliness of the
porcupines who produce the next generation is 108.
What will the prickliness of the next generation be?
5 If a character is subject to stabilizing selection, how
might the genotype–phenotype relationship for it
evolve?
6 Suppose there is stabilizing selection on a character
controlled by eight gene loci, and the optimum individual
should have six positive genes and 10 negative genes.
What will happen through time to a population that
initially contains individuals of two sorts: those that
are +++–––––/+++––––– and those that are
++++++––/––––––––?
Individual 1 2 3 4 5 6 7 8 9 V P V A h 2
P −10 −5 −5 0 0 0 +5 +5 +10
A −4 −2 −2 0 0 0 +2 +2 +4
..