PORIFERA:
Porifera are multicellular organisms which have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl contracted between two thin layers of cells. Sponges have unspecialized cells that can transform into other types and which often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food, oxygen and remove wastes.Some sponges also deposit exoskeletons that lie completely outside their organic components. For example sclerosponges("hard sponges") have huge calcium carbonate exoskeletons. These exoskeletons are deposited by the pinacocytes which form the animals' skins.
Porifera are multicellular organisms which have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl contracted between two thin layers of cells. Sponges have unspecialized cells that can transform into other types and which often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous, digestive or circulatory systems. Instead, most rely on maintaining a constant water flow through their bodies to obtain food, oxygen and remove wastes.Some sponges also deposit exoskeletons that lie completely outside their organic components. For example sclerosponges("hard sponges") have huge calcium carbonate exoskeletons. These exoskeletons are deposited by the pinacocytes which form the animals' skins.