Sponges: Phylum Porifera

The poriferans, also known as sponges, are animals from the phylum Porifera.  In most biology textbooks they are treated as the first group because of their relatively primative organization. In fact, most scientists consider them the be the simplest animals. They are sessile, mostly marine, and filter feeders.  They pump water through their bodies to filter out particulate mater in the water.

Sponges have no true tissues and lack muscles, nerves and internal organs.  In fact they show similarities to colonial choanoflagellates. Sponges may represent a kind of evolutionary jump from unicellular to multicelluar organisms.  But, we should be wary as some evidence suggests that their simplified form developed secondarily.  

 There are more than 5,000 forms of modern sponges.  They are found from the intertidal zone to the depths of the ocean.

The earliest sponges come from the Neoproterozoic Era.