Members of Porifera have several pores on their surfaces called as [[1]] and a single large opening called as [[2]].

Members of Porifera have several pores on their surfaces called "Ostia". Ostia are tiny openings in the body wall of sponges that allow water to flow into the sponge. Water enters the sponge through the Ostia and then flows out through a single larger opening called the osculum. The movement of water through the sponge allows the sponge to filter out small particles of food and oxygen from the water, which are then absorbed by specialized cells within the sponge. The ostia are an important part of the sponge's feeding and respiratory system.