10 air purifying plants for cleaner house Question of the Week: Why are sea sponges considered animals? UCL Researchers in Museums The 22 Safest Plants to Keep Around Pets Garden Betty sea sponge, an aquatic animal belonging to the phylum Porifera. Sponges are simple, multicellular animals that are sessile, meaning they attach themselves to the seabed or other surfaces. They are filter List Of Nonflowering Plants