reptile

Reptiles are a class of cold-blooded, air-breathing vertebrates that includes snakes, lizards, turtles, crocodilians, and the tuatara. They are characterized by dry, scaly skin and an ectothermic metabolism that relies largely on external environments to regulate body temperature.

Reptiles breathe with lungs and reproduce sexually through internal fertilization. Most species lay eggs with tough or leathery shells, but some give birth to live young. Reptiles occur in a wide range of habitats, including deserts, forests, freshwater, and seas.

The major living groups are Testudines (turtles and tortoises), Squamata (lizards and snakes), Crocodylia (crocodilians), and Rhynchocephalia (the tuatara). Body plans vary from limbless snakes to armored turtles and long-snouted crocodilians.

Physiology includes adaptations for water conservation, such as tough skin and efficient kidneys. Many reptiles exhibit temperature-dependent sex determination and rely on basking or shade to control body temperature. Diet ranges from carnivorous to omnivorous, with some herbivorous lizards and turtles.

Ecology and human interactions: reptiles occupy important ecological roles as predators and prey; they are also kept as pets, used in research, and sometimes come into conflict with humans. Numerous species are threatened by habitat loss, hunting, pollution, and climate change, leading to conservation concerns.