Question

What are the three layers of a mollusk shell, from outer to inner?

Answer 1

The three layers of a mollusk shell are the outer periostracum, middle prismatic layer, and inner nacre layer. The mantle beneath the shell secretes these layers, and the radula is a feeding organ unique to mollusks.

Step-by-step explanation:

The three layers of a mollusk shell, from outer to inner, are:

1. The Periostracum - This is the outermost layer, made of a protein called conchiolin. It serves as a protective layer, guarding the rest of the shell from predators and acidic environments.
2. The Prismatic layer - Located beneath the periostracum, this is a middle layer composed mainly of calcium carbonate. It provides strength and rigidity to the shell.
3. The Nacre or mother-of-pearl layer - This is the innermost layer, directly in contact with the mollusk's body. It is smooth and lustrous, reducing friction between the shell and the soft body of the mollusk.

The mantle, which is the tissue beneath the shell, secretes the substances to form these layers and creates the shell over time. Mollusks also have a unique feeding organ called the radula, with teeth made of chitin, used for scraping or shredding food.