Question

question # 21 1 point besides glass (silica), spicules of sponges are made of ____________ & ____________.

Explanation:

Sponge spicules can be made of calcium carbonate and spongin besides silica. Calcium - carbonate spicules are common in some sponge species, and spongin is a protein - like substance that also forms part of the skeletal structure in certain sponges.

Answer:

calcium carbonate, spongin