Amphibians are a class of animals that are characterized by several distinct features:

  1. They are vertebrates - this means they have a backbone.

  2. They are cold-blooded - their body temperature is regulated by their environment.

  3. They have moist, permeable skin - this allows them to breathe through their skin and absorb water.

  4. They undergo metamorphosis - they typically begin life as aquatic larvae and then transform into adult forms that can live on land.

  5. They lay their eggs in water - most amphibians have external fertilization, meaning that the eggs are fertilized outside of the female's body.

  6. They have a three-chambered heart - this means that their circulatory system is less efficient than that of mammals and birds.

  7. They are found in a wide range of habitats - including freshwater, saltwater, and terrestrial environments.

  8. They are an important indicator species - as they are sensitive to changes in their environment, they can help scientists monitor the health of ecosystems.