CTET 2 Math and Science Feb 2015 Paper

Larva of frog is called tadpole.Larva undergoes series of gradual changes called metamorphosis in order to become adult.To start metamorphosis Iodine is needed by the thyroid gland to produce hormone thyroxine. If iodine is lacking in water then metamorphosis cannot take place and tadpole cannot change into frog.You can add iodine in water or you can directly feed tadpoles on thyroid gland of some other animal.This will lead to change of tadpoles into frogs.