Porifera

Sponges are multicellular animals with unspecialized cells. They form skeletons built with spicules. The chemical composition of skeletons is calcium carbonate, silica and/or spongin. According to the complexity of body structure they are divided into the three basic groups: asconoid, syconoid and leuconoid. They are filter feeders, the water is ejected through the main aperture – osculum. The oldest records come from the Precambrian. Presently they inhabit all water environments.

## Keywords
multicellular animals, Phylum Porifera, Precambrian - Recent