Question

Tadpoles of frogs 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

Hint: Frogs are short-bodied, tailless amphibians i.e. they live both on the ground as well as underwater, and composing the group Anura. Their habitat involves a permanent source of moisture to survive or reproduce such as ponds, rivers, etc.

Complete answer:
Metamorphosis in frogs is a gradual change from larval life to an adult form involving structural, physiological, behavioral, and biochemical changes. In frogs, metamorphosis is controlled via hormone i.s. thyroxine which is essential for physiological and biochemical changes during frogs metamorphosis. Amphibian metamorphosis is under the control of neuroendocrine. Iodine an essential element of the thyroid hormone controls the metabolism; if iodine is deficient in the diet then the thyroid gland may produce insufficient hormones that affect the process of metamorphosis.
Amphibian’s egg which is a huge egg contains a moderate amount of yolk, which is a nutrient-rich portion of the egg. Its main function is to provide food for the development of the embryo acting as a stored food material. They are rich in vitamins, minerals, or proteins.
If we inject thyroid extracts in tadpoles then it accelerates the mechanism of metamorphosis due to the constitution of iodine in the thyroid hormone, while if we inject the tadpole with an antithyroid substance like thiourea (which results in amphibians size) inhibit the mechanism of metamorphosis resulting in the growth of tadpoles to a giant-size frog.

Hence, the correct answer is option (A).

Note: Thiourea has been used in the treatment of the excessive activity of the thyroid gland (hyperthyroidism). One such giant size frog is the Goliath frog also known as the goliath bullfrog or giant slippery frog of West Africa.