Amphibians lay their eggs in water, and young amphibians tend to resemble small fish.
The tadpole, or newborn frog, is born and lives in water. It has a tail that allows it to swim like a fish. It also has gills so that it can breathe under water. As the tadpole grows into a frog, it loses its gills and tail, and develops legs for moving on land. Most amphibians can both walk and swim in water.
Depending on the species of amphibian, breathing can take place in gills, lungs, the lining of the mouth, the skin, or some combination of these.
In Amphibians body temperature changes with its environment. In cold climates, amphibians hibernate during the winter.
The Earth has lots of different environments that support animal and plant species. Changes in an environment can have a negative impact on certain species' ability to survive.
There is an extreme cold in winter in the polar region. Food is not available in winter in the polar region. So the polar animals lie down without moving about during winter. Their respiration and heartbeat are slowed down. The animals utilize the fat already stored in the body for the essential activities, as no food is available afresh. This state of living is called hibernation or winter sleep. Again in summer, they move about actively. So the polar bear adapts itself suitably to the environment.