Suppose that parent-offspring similarity for tarsus length is studied in two geographically distinct sparrow populations. In the first population, the average tarsus length is 2 cm and h2 = 0.6; in the second, the average length is 2.5 cm and h2 = 0.5. From these data, can we conclude that the difference between the average tarsus lengths in the two populations has a genetic basis? Briefly explain your answer.

Explanation:

Genetic variance has a component called additive variance V(A), which is the variation due to average affects of the alleles. The h2 thus refers to the genetic component of variance that is responsible for parent-offspring resemblance. This additive portion of genotypic variance is called narrow sense heritability.

The value of h2 ranges from 0 to 1. Numerical value of 0.6 implies 60% of genetic basis, and 0.5 implies that 50% of the characters are inherited from parents. A heritability index of zero has no influence of genetic basis on the features of the offsprings. In such case environmental factors solely take responsibility. The difference in the h2 in the current scenario of sparrow populations is not a null value and also has different effects on tarsus length.

As there is a difference in h2 value of the two populations, which further has significant impact on the difference between phenotypic expression of the tarsus length, there occurs genetic basis for the variability.

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