Question

If thyroid extract is added to the water containing tadpole, it will

• A. Retard metamorphosis
• B. Hasten metamorphosis
• C. Tadpole larva remains in the larvel stage
• D. None of these occur

Answer 1

The correct option is B

Hasten metamorphosis

If thyroid extract is added to the water containing tadpole, it will hasten metamorphosis. There is an additional function of the thyroid gland that is unique to amphibians—thyroid hormones are needed for the metamorphosis of the larvae into adults. If the thyroid gland is removed from a tadpole, it will not change into a frog. Conversely, if an immature tadpole is fed pieces of a thyroid gland, it will undergo premature metamorphosis and become a miniature frog.