What is an Amphibian?
Frogs, toads and salamanders are all amphibians. They hatch from eggs and grow gills so they can breathe in water. Amphibians then develop fins and tails to help them swim. As their life cycle progresses their bodies change. They grow legs and lungs then move out of the water onto land.
Amphibians are cold-blooded. This means when their environment is cold they are slows and sluggish. When their environment warms up they warm up become more active.
If frogs only had legs on one side of their body they would be lopsided and unable to hop. Bilateral symmetry helps amphibians move efficiently so they can avoid predators, catch food and swim well.