Which organism is classified under the phylum Porifera?

The organism classified under the phylum Porifera is the sponge. The defining characteristics of Porifera include being multicellular, having a porous body structure, and lacking true tissues and organs. Sponges are simple animals that rely on the flow of water through their bodies for feeding, respiration, and excretion. They have specialized cells called choanocytes that help in filtering food particles from the water. This simplicity and unique skeletal structure made of spicules or protein fibers are distinctive features that set sponges apart from other animal groups such as corals (which belong to Cnidaria), jellyfish (also in Cnidaria), and starfish (which are echinoderms). Understanding these classifications and characteristics helps highlight the biological diversity within the animal kingdom.