Amphibians are a class of their own under the umbrella of vertebrates as are mammals, reptiles, birds and fish. They are cold-blooded which means they can not regulate their own body temperature from within, they need to rely on their surroundings to either warm or cool their bodies just like reptiles do. When they are too cool they become relatively inactive and need to find a warmer environment to increase their body temperature. They breath through their skin; their skin is actually very thin and permeable to gases which allows oxygen directly in and carbon dioxide out. Frogs also have a simple set of lungs but they are not adequate to supply enough oxygen on their own. Since the amphibians skin is so thin it is covered with a type of mucus for protection and that is why they live near water and moist places so they can prevent their skin from drying out. Amphibians also go through a type of metamorphosis, meaning their bodies transform from one form to another during the growing stages.
Amphibians include frogs (and toads), salamander’s and caecilians. Additionally there were diplocaulus, ladyrinthaods and anthracosauria which are all extinct. Australian amphibians only include frogs, which umbrella’s the one introduced toad.