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Background
The phylum Porifera is made up of mostly marine sponges, although 150 species live in fresh water. A total of 5,000 species are found all over the world. Sponges have a system of pores and canals, specialized cells and a skeleton made up of spicules and protein collagen. Sponges eat food, usually bacteria and plankton, that drifts into their pores and canals by water movement created by small, moving tendrils on its body. Sponges reproduce both sexually and asexually.
Calcarea
The most primitive group of Porifera are those found in the calcarea class. The calcarea sponges have three body types: simple tubes (asconoid), bigger tubes with tendrils and canals in its tissue (syconoid), and the bigger and most complex sponges (leuconoid). The skeleton of sponges in this class has individual calcium carbonatees spicul. These sponges are mostly found in shallow, topical waters. However, one type of calcarea sponge thrives at a sea depth of 13,000 feet.
Hexactinellida
Organisms in the hexactinellida class are also known as "glass sponges." They have siliceous spicules. These structures have four or six rays that meet at at right angles, similar to a toy jack. Hexactinellidas cannot contract like some other sponge types can. About 500 species live in deep waters, although a few species live in shallower polar areas. Hexactinellid sponges were recently found to have formed huge reefs off the coast of Canada near British Columbia.
Demospongiae
The demospongiae type is the most diverse sponge class, and 90 percent of sponges fall under this classification. These sponges are found in a variety of habitats, from shallow intertidal pools to the depths of the ocean floor. All freshwater sponges are in the demospongiae class. Their skeletons are either spongin fibers or siliceous spicules, and their spircules do not form right angles. Many sponges in this class are brightly-colored and can be yellow, red, purple, green and orange.