1) In an experimental population of flour beetles, the body length shows a conti

Question

1) In an experimental population of flour beetles, the body length shows a continuous distribution with a mean of 6.8 mm. A group of males and females with body length of 9 mm are removed and interbred. The body lengths of their offspring average 7.6 mm. From these data calculate the heritability in the narrow sense for body length in this population.

2) Grant and Grant have been studying a population of finches for several years and have determined that the average bill depth is 8.6mm and that the narrow sense heritability of this trait is 0.75. During their study, a major drought reduced the food supply and only hard seeds were left (which required deeper bills). The year after the drought the researchers measured new juvenile birds and found that the new average bill depth was 11.4 mm. What must have been the average bill depth of the birds that survived the drought to breed?

Explanation / Answer

h2 = R/S , where h2 = narrow sense heritability

R= response to selection = X next generation - X before selection = 9 - 6.8 = 2.2

S = selection differential = X after selection - X before selection = 7.6 - 6.8 = 0.8

h2 = 2.2 / 0.8 = 2.75

2. Given h2 = 0.75; X before selection = 8.6 mm ; X next generation = 11.4mm; X after selection = ?

0.75 = 2.8 / X after selection - 8.6

X after selection - 8.6 = 2.8/0.75 = 3.73

X after selection = 3.73 + 8.6 = 12.33

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