Are the features of a plant or an animal that fit it for its environment and aid for in its survival. These may be characteristics of shape, color, habits, or internal organization. A tadpole, for example, breathes by means of gills; it is adapted for life in the water. But the tadpole develops into a frog which has lungs as part of its adaptation for life on land. Unrelated plants and animals may become similar in appearance as a result of being adapted to the same way of life. Wings of insects, birds, and bats differ in structure but the perform the same function. A streamlined body shape is characteristic of swimming animals, such as sharks and porpoises (mammals), and also of flying animals, such as birds and insects. Members of a group of animals or plants may be adapted to such varied habitats that their relationship is not easily recognized. Worm lizards, for example, are burrowing reptiles. Unlike other lizards, they do not have legs and their scales are modified to form rings around their bodies. They look like earthworms. This is a protective adaptation. Some plants are adapted to grow only in the sun; others only in the shade. Some have roots that grow deep into soil to get water; other have fibrous root systems near the surface. Cacti have needle-like leaves, through which little water is lost, and thick stems for storing water. Sometimes an animal or a plants becomes so limited as a result of its changes. Monarch Butterfly larvae, for example, feed exclusively on milkweeds, they cannot survive. Animals or plants that do not have special needs are the most widely distributed. Man can adapt himself to many environments.