Sponge

Sponges, the members of the phylum Porifera, are a basal animal clade as a sister of the Diploblasts. They are multicellular organisms made up of jelly-like mesohyl sandwiched between two thin layers of cells. Their bodies are covered in holes and channels that allow water to flow through them.

Unspecialized cells in sponges have the ability to change into other cell types and frequently migrate between the mesohyl and the major cell layers. The neurological, digestive, and circulatory systems are absent in sponges. In order to get food, and oxygen, and to remove waste, the majority of organisms rely on keeping a continual water flow through their bodies. Sponges were the first to branch off the evolutionary tree from the last common ancestor of all animals, making them the sister group of all other animals.