What are the three classes of Porifera?
Calcarea (400 spp. calcium carbonate spicules, tend to be small and tubular or vase-shaped) Demospongiae (95% of spp, very diverse, spongin and silicaceous spicules, include "bath sponges") and Hexactinellida (nearly all deep-sea spp, mostly vase- and funnel-shaped ranging from 7.5cm-1.3m)