Natural Selection and Hardy Weinberg Equilibrium (7 points)
Let's say that in the sea otter two alleles at a single locus determine coat
thickness. The alleles (T and t) are co-dominant, so that heterozygotes have
medium coats with homozygote TT otters having thick coats and homozygote tt
otters having thin coats.
In this population of the sea otter, the following coat thicknesses were recorded:
Thick coat: 20 Medium coat: 60 Thin coat: 20 TOTAL: 100
a. Is this population in Hardy Weinberg Equilibrium? SHOW YOUR WORK!
YOUR FULL NAME:
b. As you may know, sea otters were hunted to near extinction for the early 19th
Century fur trade. Let's say that fur traders were selective in their hunting of the
sea otter population such that they harvested mostly otters with thick or medium
coats, but did not kill otters with thin coats. In this population, there was selective
mortality of the sea otters such that none of the thick-coated sea otters survived,
while 20% of the medium-coated sea otters and all of the thin-coated sea otters
survived to reproduce. Given the early 19th Century hunting pressures, what are
the relative fitness values, w, of the three genotypes?
c. What mode of selection is happening in the population?
d. Draw a simple graph to show how the frequency of the T allele will change
over generations in a population with starting frequency of the T allele = 0.8 and
with the selection against individuals caused by hunting (as in b.). LABEL BOTH
AXES!
