Porifera are the some of the longest existing and some of the simplest multi-cellular animals. Sponges is mainly a water-filtering system. They do not move and feed of food particles floating around in the water. All poriferans also have a canal system through which water is pumped. Sponges are just cells that surround a water filled space, have no nervous system, and have no tissues or organs. Sponges do not have a distinct circulatory system, have no definite symmetry and can reproduce sexually and asexually. Rather than have an inner layer that circulates sea water throughout the sponge that allows them to have the nutrients necessary for their survival.
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