Grey Seal pups are weaned (begin to consume adult diet) at 3-4 weeks of age. We
ID: 151418 • Letter: G
Question
Grey Seal pups are weaned (begin to consume adult diet) at 3-4 weeks of age. We want to determine whether time to weaning is a heritable trait. A population of 400 grey seal pups takes an average time of 26 days to reach weaning. We select ten grey seal pups that reached weaning earliest; their average time to weaning is 19 days. Those 10 fastest-weaning pups are later bred. We watch to see the time to weaning of their offspring; the average time weaning is 22 days.
Calculate the selection differential. 2 pts.
Calculate the response to selection. 2 pts.
Calculate heritability (h2). 2 pts.
Interpret the heritability of weaning time in grey seal pups from above. 2 pts.
Explanation / Answer
Solution:
In this question, we need to find out how is the inheritance of the weaning period in Grey seals. The population has a mean weaning period of 26 days. The 10 fastest weaning parents had weaning period of 19 days. The difference in the mean of population and the mean of selected fastest parents is called Selection differential.
So Selection differential (S)= 26 - 19 = 7 days
The selection response is how much gain you make when mating the selected parents. It is equal to the difference between the mean of the offsprings of selected parents (22) and the mean of the population (26).
so, selection response (R) = 26 - 22 = 4 days
The response to selection is related to heritability as : R = h^2. S
where h is heritability
rearranging the formula: h^2 = R / S
h = square root of R / S
h = root of 4/7
h = 0.75
The heritabiliy is 0.75 in the above case. This indicates strong heritability and the trait will repond positiely for selection. The seals can be bred to shorten the weaning time with very high chance of heritability.
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