Amphibians are cold-blooded vertebrates with a unique life cycle, transitioning from aquatic larvae to terrestrial adults. Frogs, toads, salamanders, and newts are common examples. Their distinguishing feature is permeable skin, enabling respiration in water and air. Amphibians serve as environmental indicators due to their sensitivity to ecosystem changes. They reproduce through external fertilization and adapt to diverse habitats, though they are susceptible to habitat degradation and climate variations.