Question

Tadpoles of frog can be made to grow as giant sized tadpoles. if they are

(a) administered antithyroid substance like thiourea

(b) administered large amounts of thyroxine

(c) reared on a diet rich in egg Yolk

(d) reared on a diet rich in both egg yolk and glucose.

Answer 1

Correct option (a) administered antithyroid substance like thiourea

Explanation :

Thyroxine, the principal hormone, of thyroid gland, is required for tissue differentiation and metamorphosis (the rapid transformation from the larval to the adult form) in amphibians. So in the presence of antithyroid substance, (that inhibits the synthesis of thyroid hormone) e.g., thiourea, tadpoles remain in the larval stage indefinitely. Thiourea is an organic compound of carbon, nitrogen, sulphur and hydrogen, with the formula CSN₂H₄ or (NH₂)₂CS. It is similar to urea, except that oxygen atom is replaced by a sulphur atom.