Members of phylum porifera are unique among animals because they contain __ distinct tissue layers.

Phylum Porifera contains sponges that have cellular level of organization so the cells in sponges are not organized into specialized tissue, therefore, tissue level of organization is absent in sponges while other animals contain tissue and a higher level of organization.

Therefore, members of Porifera are unique in animals as they contain zero distinct tissue layers due to lack of tissue level of organization.

Sponges contain different cells that performs different function so the cells are specialized in sponges and are organized loosely. Most sponges are asymmetrical and contain pores called Ostia for the passage of water.