Reproduction in marine turtles (Cheloniidae, Dermochelyidae) occurs within three general constraints. First, nesting must occur during conditions which "are conducive to adult activity". Second, nesting must occur during conditions which facilitate embryonic development and survival. Third, hatchlings must emerge into conditions that "are conducive to their survival". The seven species of sea turtles that reproduce on beaches around the world, Dermochelys coriacea (leatherback turtle), Chelonia mydas (green turtle), Caretta caretta (loggerhead turtle), Eretmochelys imbricata (hawksbill turtle), Lepidochelys olivacea (olive ridley), L. kempi (Kemp's ridley), and Natator depressus (flatback turtle), share a common life cycle with only minor variation. As a consequence of their food and habitat requirements, adult sea turtles are unevenly distributed throughout the circumglobal tropical and subtropical seas. Marine turtles do not begin to breed at a uniform or minimum size. The major aspects of reproduction are very similar among the seven species of sea turtles as a result of similarities in both morphological and ecological constrain.