There are five major kingdoms of living things: the kingdom Monera, the kingdom Protista, the kingdom Fungi, the kingdom Plantae and the kingdom Animalia. The kingdom Animalia has over 2 million species that share certain characteristics. Most animals fall into this category.
Multiple Cell Types
Living organisms in the Animalia kingdom are all multicellular, meaning they have more than one type of cell. They do not have rigid cell walls but rather have permeable membranes surrounded by fluid.
Members of the kingdom Animalia are heterotrophs, meaning they get nourishment from other organisms rather than manufacturing it themselves (as in photosynthesis).
Getting a Move On
Animals use locomotion to move about. Members of this kingdom move about using a variety of methods, from legs and fins to cilia and wings.
Most organisms in the Animalia kingdom reproduce sexually, meaning males and females mate to exchange sperm and eggs.
All Shapes and Sizes
Members of the Animalia kingdom range in size from microscopic, such as plankton, to gigantic, such as the blue whale.