Final answer:
The frog's life cycle starts with a larval stage known as a tadpole, which has gills and lives in water, followed by metamorphosis that prepares them for terrestrial adult life with developed lungs, limbs, and adapted digestive system.
Step-by-step explanation:
The life cycle of frogs involves a larval stage that occurs in water; commonly known as a tadpole, which possesses gills for under-water breathing, a tail, and lacks limbs. As they grow, tadpoles undergo a process called metamorphosis, in which they develop limbs, their tails recede, and they form lungs, preparing them for adult life on land. Some species of frogs showcase unique reproductive behaviors, such as the frogs in the genus Eleutherodactylus, whose eggs bypass the tadpole stage and develop directly into froglets, with parental care at times being provided.
During metamorphosis, significant physiological transformations take place: gills and the lateral line system are replaced by lungs, the long-finned tail disappears, and the tadpole develops into a carnivorous adult frog with four limbs and a short predator gut. These changes allow the frog to leave the aquatic environment and live on land.