Most scientists recognize 8 species of these marine reptiles. Experts can identify each by the number & pattern of scutes ( horny plates) on the carapace ( top shell). Sea turtle species range in length from about 53 cm (21 in.) Up to 1.9 m (6 ft.) Males & females are about the same size. Sea turtles share characteristics with other reptiles: they are cold blooded, they breathe air ,and have scaly skin. Sea turtles cannot retract their limbs or head into their shells as land turtles can. Diets vary greatly among sea turtles species. Green sea turtles & black sea turtles feed on seagrasses and algae. Loggerheads, and olive ridleys strong jaws can crush carbs,shrimps, & molluscs. Leather backs prey only on jellyfish & other soft-bodied animals. In general, sea turtles do not come out onto land ,except females when they nest. Most nest during the warmest months, returning to the same beaches year after year. 200 eggs, each the size of a ping pong ball. The incubation period for most species is 45 to 70 days. All 8 sea turtle species are listed as either endangered or threatened. Despite several management measures to preserve sea turtles, their future is still in question, due to a number of natural & human- related factors such as hunting and pollution.