Sponges or poriferans (Latin: porus "pore" and ferre "to bear") are animals of the phylum Porifera, with about 5000 species known across the world. Sponges are primarily marine, but around 150 species live in fresh water. Sponges have cellular-level organization, meaning that that their cells are specialized so that different cells perform different functions, but similar cells are not organized into tissues and their bodies are a loose aggregation of different kinds of cells. This is the simplest kind of cellular organization found among parazoans.
There are three classes of porifera: