Phylum Porifera Name: This phylum contains one of the oldest organisms, SPONGES, which date back to the Cambrian period. Sponges are in the phylum Porifera because they have pores all over their body. They were once thought to be plants because they are sessile but are now grouped as animals because they are MULTICELLULAR, HETEROTROPHS that contain SPECIALIZED CELLS with NO CELL WALL.
Sponges can reproduce sexually, keeping their eggs inside their body and releasing sperm into surrounding water. An amebocyte of another sponge collects the sperm and takes it to the egg. Once fertilized, the zygote develops into a larva that swims away to settle and grow elsewhere. Asexually, sponges bud or produce gemmules, which are amebocytes surrounded by spicules that grow into new sponges. This happens in unfavourable conditions.
Sponges interact with their environment despite their sessile nature. They have symbiotic relationships with non-animals such as blue-green algae, which provide it with oxygen. They also provide shelter for marine animals, are a food source for snails, starfish and fish, and they recycle old shells on the ocean floor.
Sponges produce chemicals that are toxic to many organisms to protect themselves. Humans now use these chemicals in antibiotics.
Form and Function Sponges belong to the phylum Porifera and live in fresh or marine environments. They are so different from all other animals that they were once thought to be plants. They barely move, have no specialized tissues or organ systems and have nothing that resembles a mouth or a gut. Because sponges are sessile, they have to find a way to catch food without moving and fend off predators since it is basically a “sitting duck”. Sponges are filter feeders that sift microscopic particles of food from the water. The body of a sponge has pores (holes) all over it. It is designed so that water flows in through the pores to a central cavity and out. This allows for the movement of water to serve as the respiratory, excretory and internal transport system.