Final answer:
Many amphibians breathe through gills during their larval stage and by lungs when adult. They also utilize cutaneous respiration, absorbing oxygen through their moist skin. This combination allows amphibians to respire in both aquatic and terrestrial environments.
Step-by-step explanation:
There are two primary ways in which many amphibians can breathe. The first method is through gills, particularly when they are in their larval stage, such as with tadpoles. However, as amphibians grow, they develop another breathing mechanism involving lungs for respiring on land.
Unlike mammals, amphibians have more primitive lungs and lack a fully developed diaphragm which makes lung breathing less efficient. Consequently, they also utilize cutaneous respiration, which involves absorbing oxygen directly through their moist skin. This dual mode of breathing is essential as amphibians live both in water and on land during their life cycle.
Specifically, with frogs, the air is collected in a pouch below their throat before being pushed into the lungs by muscle contraction, which differs from the inhalation process in humans and other mammals where a diaphragm aids the process.
Salamanders, on the other hand, may retain their gills throughout their lives in some species, allowing them to breathe underwater effectively. Most amphibians must keep their skin moist, often with mucus, to facilitate the absorption of oxygen through their skin - a critical aspect of their unique respiratory abilities.