Question

If a trace of thyroid extract is added to water containing tadpoles, it will

• A. Slow down the metamorphosis
• B. Hasten the metamorphosis
• C. Keep them as tadpoles
• D. Kill the tadpoles

Answer 1

Answer: (B)

Iodine serves as limiting factor in metamorphosis and removal of animal’s thyroid gland make halts the metamorphosis forever as thyroid hormones are rich in iodine. This makes option C incorrect. Thus, injection of thyroid extracts in tadpoles hastens the metamorphosis because of being rich in iodine content. This makes options A and D incorrect and option B correct.