What feature distinguishes amphibians from reptiles?

Amphibians are distinguished from reptiles primarily by their ability to live both in water and on land, which is a defining characteristic of their life cycle. This dual lifestyle is facilitated by their unique reproductive strategy that typically involves laying eggs in aquatic environments, where the larvae (tadpoles) develop with gills and a tail. As they mature, they undergo metamorphosis, developing lungs and limbs that allow them to transition fully to a terrestrial habitat.

In contrast, reptiles are fully adapted to life on land and have evolved various features to support this, including amniotic eggs that can be laid on land without the need for a water source to prevent desiccation. While amphibians possess four limbs, this trait is not unique to them as reptiles also have four limbs. Additionally, both amphibians and reptiles are ectothermic (cold-blooded), which means they rely on external temperatures to regulate their body heat, making this metabolic characteristic not a distinguishing factor between the two groups.