Animal

• Main Author: Walter J. Bock
• Format: Reference Entry
• Language: English
• DOI: 10.1036/1097-8542.035200

Any living organism taxonomically assigned to the classification kingdom known as Animalia. Members of the kingdom Animalia—that is, animals (see illustration)—possess certain characteristics that distinguish them from organisms belonging to the other kingdoms—Plantae, Fungi, Protista, and Monera (in certain systematic schemes, the Monera kingdom is replaced by the Archaea and Bacteria kingdoms). However, there is no single criterion that can be used to distinguish all animals from all other organisms. Unlike plants, for example, animals usually lack chlorophyll and the ability to manufacture foods from raw materials available in the soil, water, and atmosphere. Animal cells are usually delimited by a flexible plasma or cell membrane rather than a cell wall composed either of cellulose or chitin, as are the cells of most plants. Animals generally are limited in their growth, and most have the ability to move in their environment at some stage in their life history. Animal kingdom Cell membrane Chlorophyll Plant Plant kingdom