The digestive system of Porifera (sponges)
Sponges (Porifera) are a group of simple aquatic invertebrates that include glass sponges, demisponges, and calcareous sponges. Adult sponges live attached to hard rocky surfaces like shells. There are about 5,000 living species are classified in the phylum Porifera, which is composed of three distinct groups. These groups consist of the following: Hexactinellida (glass sponges), the Demospongia, and the Calcarea (calcareous sponges). All species of sponges digest food the same way. The inside of the phylum is basically covered with cells that have one function, to absorb all the nutrients of the food as the food passes through the system. The food goes through the cells by cilia into the stomach.