Organization of the Animal Body
Animals are characteristically multicellular heterotrophs whose cells lack cell walls. At some point during their lives, animals are capable of movement. In the most commonly encountered animals, this stage is the adult, although some animals (corals) have sessile (nonmobile) adult phases and mobile juvenile forms. Animal and plant evolutionary history both show the development of multicellularity and the move from water to land (as well as secondary adaptation back to water).
Animals developed external or internal skeletons to provide support, skin to prevent or lessen water loss, muscles that allowed them to move in search of food, brains and nervous systems for integration of stimuli, and internal digestive systems.
Most animals have a life cycle with a preadult stage, a predominance of the diploid stage, and a series of embryonic developmental stages.
Label: animalia, body, organization
