1. Amphibians Amphibians lead double lives—one in water and one on land. Many begin life with gills, then develop lungs as they age. They are vertebrate animals that include frogs, toads, salamanders, and newts as well as odd, wormlike caecilians (seh-SILL-yuns). They are cold-blooded, using the environment to regulate their body temperature. Early amphibians were the first animals to leave the sea and venture onto land.

2. Metamorphosis Amphibians from gills to lungs Adult frog eggs Tadpole(larva)

3.  Respiration: tadpole: gills adult frog: lungs Circulation: tadpole two-chambered heart adult frog three-chambered heart Homeostasis: Ectotherm (animal that has variable body temperature and gets its heat from external sources) Life Functions