The term sponge derives from the Ancient Greek word σπόγγος ( spóngos 'sponge'). Sponges were possibly the first to branch off the evolutionary tree from the last common ancestor of all animals, which would make them the sister group of all other animals.
Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes. Sponges do not have complex nervous, digestive or circulatory systems like humans. Sponges have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells. Sponges, the members of the phylum Porifera ( / p ə ˈ r ɪ f ər ə/ meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts.
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