Turtles are classified as reptiles due to their distinct characteristics and physiological traits. Unlike amphibians, turtles have dry, scaly skin that prevents water loss, making them well-adapted for life on land. Their skin structure is significantly different from that of amphibians, which typically have moist skin that allows for gas exchange and is essential for their survival in aquatic environments.
Moreover, turtles lay hard-shelled eggs, a trait associated with reptiles. This reproductive strategy allows them to protect their eggs from desiccation and predation in terrestrial environments. In contrast, amphibians generally lay soft, jelly-like eggs in water, where their offspring undergo a life cycle that involves a metamorphosis from a water-dwelling larval stage to an adult form.
Another key difference lies in their circulatory systems. Turtles, like other reptiles, possess a more advanced heart structure that supports their adaptation to a variety of habitats, from aquatic to highly terrestrial. They are also ectothermic, which means that their body temperature is regulated through environmental conditions, a characteristic shared with other reptiles, while amphibians typically require a more moist environment to thrive.
In summary, turtles belong to the reptile category because of their scaly skin, egg-laying methods, and other physiological traits that distinguish them from amphibians.