Reptiles

Reptiles are a class of amniote vertebrates that includes turtles, snakes, lizards, crocodilians, and the tuatara. They are characterized by dry, scaly skin that helps limit water loss, and by ectothermy, meaning their body temperature largely depends on the surrounding environment. Most reptiles have lungs and internal fertilization, and most lay eggs on land with leathery or calcified shells, though some species give birth to live young.

Modern reptiles are divided into four living orders: Testudines (turtles and tortoises), Squamata (lizards and snakes), Crocodylia (crocodilians), and Rhynchocephalia (tuataras). Snakes are derived from legged lizards; turtles show diverse shell forms and habitats; crocodilians are semi-aquatic carnivores with a distinctive anatomical design; tuataras have unique skull features and a slow life history.

Ecology and behavior vary widely. Reptiles occupy habitats from deserts to tropical forests and oceans. Diet ranges from herbivory in some tortoises to carnivory and omnivory in many lizards and snakes; sea turtles and marine iguanas feed in marine environments. Many species exhibit diverse reproductive and parental strategies, with most reproducing sexually and laying eggs, while some give birth to live young. Temperature can influence the sex of offspring in certain groups.

Evolution and distribution: Reptiles first appeared hundreds of millions of years ago and diversified alongside other vertebrates through the Mesozoic era. Today they are found on all continents except a few polar regions, occupying a broad range of ecological niches.

Conservation: A substantial number of reptile species are threatened by habitat loss, climate change, hunting, and invasive species. Conservation efforts focus on habitat protection, regulation of trade, and, where needed, captive breeding and reintroduction programs.