These include muscles, which are able to contract and control locomotion, and a nervous system, which sends and processes signals. With a few exceptions, most notably the sponges (Phylum Porifera), animals have bodies differentiated into separate tissues. They are also distinguished from plants, algae, and fungi because their cells lack cell walls. They are heterotrophic, generally digesting food in an internal chamber, which distinguishes them from plants and algae. Animals are eukaryotic and usually multicellular (although see Myxozoa), which separates them from bacteria and most protists. Īnimals have several characteristics that set them apart from other living things. A common usage of the term may be limited to so-called lower animals (as in "brutes" or "beasts") and refer to humans only in a contemptuous or humourous context. The word "animal" comes from the Latin word animal, of which animalia is the plural, and is derived from anima, meaning "vital breath" or " soul".
More specifically, animals can be defined as heterotrophic eukaryotes without cell walls, which move through a blastula stage in early development. Their body plan becomes fixed as they develop, usually early on in their development as embryos, although some undergo a process of metamorphosis later on. In general they are multicellular, capable of locomotion, responsive to their environment, and feed by consuming other organisms. Superphylum Lophotrochozoa (trochophore larvae / lophophores)Īnimals are a major group of organisms, classified as the kingdom Animalia or Metazoa.Superphylum Ecdysozoa (shed exoskeleton).