Flexi Says: The phylum Porifera contains the earliest invertebrates: the sponges. There are about 8,550 living sponge species. Sponges are benthic, sessile aquatic animals, meaning they live attached to the ground or other surface beneath the water. Most species of sponges live on the ocean floor or on coral reefs. However, many species live in freshwater environments such as lakes and rivers.
