Kelly Fox, age 10, of Sarasota, Fla., for her question:

IS THE SAND DOLLAR A PLANT OR AN ANIMAL?

The cookie shape sand dollar we find on the beach is the remains of a sea dwelling animal. When living, his stony round center was covered with a layer of muscle and skin. The skin was rough and bumpy and in some cases covered with prickles to discourage the sand dollar's hungry enemies.

This flat, roundish sea dweller enjoys life in shallow water near the shores, where he likes to bury or partly bury himself in the sand. He takes in water with food and oxygen through openings. His five sided pattern is seen on his bony remains. He feeds on floating scraps, including live and dead plants and animals. When the tide washes him up on the beach, he dies. His surface skin soon decays, the prickles fall away  and all that remains is a dollar shape cookie of calcium material.