the 9000 or so species of sponges range in height from about 1 cm to 2m and most are marine
about 100 species live in fresh water
the body of a simple sponges resembles a sac perforated with holes
water is drawn through the pores into a central cavity the spongocoel and flows out throught a larger opening the osculum
more complex sponges contain branched canals and several oscula