Final answer:
Reptiles adapted to life on land through the development of keratin scales to prevent water loss and the evolution of the amniotic egg, which can be laid on land and protects the embryo from desiccation.
Step-by-step explanation:
Reptiles exhibit major adaptations that support a terrestrial lifestyle, substantially different from their amphibian ancestors. Two significant adaptations include their specialized skin and the development of the amniotic egg.
Reptile skin is covered in keratin scales that minimize water loss, unlike the permeable skin of amphibians. These scales act as a barrier, making reptiles less dependent on moist environments. Additionally, reptiles utilize uric acid to excrete nitrogen waste, which conserves water and allows them to inhabit arid regions.
Above all, the development of the amniotic egg marks a pivotal adaptation. This type of egg contains amniotic membranes that shield the embryo from dehydration and other environmental challenges. Unlike amphibian eggs that must remain in water, amniotic eggs can be laid on land, thus frees reptiles from the need to return to aquatic habitats for reproduction.
One of the major adaptations of reptiles that support a life out of water is the development of scaly skin. These scales, made of protein keratin and waxy lipids, prevent water loss from the skin. Reptiles also have lungs for breathing air, unlike amphibians who can use their skin for respiration. Another adaptation is the ability to excrete nitrogen in the form of uric acid paste, which helps conserve body water. Additionally, reptiles lay shelled, amniotic eggs that protect the embryo from harsh conditions on land.