Question

Which is useful in metamorphosis of tadpoles into frogs?
A. Aldosterone
B. Thyroxine
C. Pituitary
D. Oxytocin

Answer 1

This hormone is secreted by thyroid gland. In case of frogs, the thyroid gland is present between the eyes.

Complete answer:
Metamorphosis is a developmental mechanism through which the animal evolves internally after birth or hatching, requiring a marked and relatively sudden transition in the configuration of the animal's body by cell growth and differentiation. Any insects, mollusks, amphibians, crustaceans, fish, cnidarians, tunicates, and echinoderms are metamorphosed, often followed by a shift in their nutritional source or behaviour. Animals can be classified into species that undergo full metamorphosis, incomplete metamorphosis, or no metamorphosis.
With frogs and toads, after a few days, the outer gills of the newly hatched tadpole are replaced with a gill sac, and the lungs are easily developed. The front legs are shaped under the gill pouch, and the hind legs are visible a few days later. There is typically a longer stage after that, during which the tadpole survives off vegetarian diets. Tadpoles use a relatively long, spiral-shaped intestine to ingest the meal.
Quick changes in the body can be detected as the diet of the frog changes entirely. The horny tooth ridges with spiral-shaped mouth are reabsorbed along with the spiral intestine. The animal grows a wide mouth, and the gills dissolve along with the gill pocket. The eyes and legs expand steadily, the tongue is shaped, and all this is followed by the related changes in the neural networks. All this will happen in around a day, because it's a metamorphosis. It is not until a few days later that the tail is reabsorbed due to the higher concentrations of thyroxine needed for tail resorption.

Thus, the correct answer is option B. i.e., Thyroxine.

Note: The thyroid gland found in the frog secretes a hormone called thyroxin. It is a hormone that is necessary for growth and development. It controls the gene expression from which it helps to turn tadpoles into frog.