Sponge dissection - by Susan Cascio Phylogeny and general characteristics of the Sponge Sponges are the most primitive of all multicellular animals. They are classifed as Parazoans, meaning beside the animals, and are in the Phylum Porifera. These animals lack true tissue, which is a characteristic that all other animal phyla have.
Sponges are sessile animals that live in fresh or salt water.
There are approximately 5000 salt water species and 150 fresh water species. Most sponges, except for a few deep sea species, live in shallow water attached to rocks, submerged timbers, shells, coral, or in sand or mud bottoms. Sponge structure is unique in that it is constructed around a series of canals. Sponges lack any kind of specialized organs but instead have well-developed connective tissue. Specialized cells within the connective tissue carry out different functions.