The correct option is (c).
Explanation
Metamorphosis and Hormonal Regulation
Metamorphosis is a biological process involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. In amphibians and insects, this process is strictly regulated by the endocrine system.
Statement 1 is Correct
The transformation of a larva into an adult through drastic physiological and morphological changes is called metamorphosis. This phenomenon is characteristic of the life cycles of insects (e.g., silkworms transforming into moths) and amphibians (e.g., tadpoles transforming into frogs).
Statement 2 is Incorrect
In frogs, metamorphosis is controlled by the hormone thyroxine, which is produced by the thyroid gland. Insulin is a hormone produced by the pancreas that regulates blood glucose levels; it does not control metamorphosis.
Statement 3 is Correct
Thyroxine is an iodinated hormone, meaning its production requires iodine. For tadpoles, which are aquatic, the water they inhabit must contain sufficient iodine. If the water is iodine-deficient, the thyroid gland cannot produce thyroxine, and the tadpoles will fail to transform into adult frogs.
Key Takeaway:
Metamorphosis in frogs is driven by the hormone thyroxine, the synthesis of which is dependent on the availability of iodine in the environment.