In the scientific classification of living beings, animals (Animalia) or metazoans (Metazoa) constitute a kingdom that brings together a wide group of organisms that are eukaryotic, heterotrophic, multicellular and tissue (except poriferous). It is characterized by its wide capacity for movement, by not having a chloroplast or a cell wall, and by its embryonic development; that goes through a blastula phase and determines a fixed body plan (although many species can undergo later metamorphosis such as arthropods).