These eggs have a protective shell, and are laid out of water. The shell is porous to air, and may be flexible or calcareous (hard).The calcareous shell prevents the egg from desiccation. The eggs contain all the food the embryo needs to develop into a hatchling. As a result, the amphibian's larval stage, the tadpole, is not needed by reptiles or birds. The special membranes that support these eggs are typical traits of all amniotes, including mammals.