Respuesta :

A shell is considered as biotic (living) because it is a hard, rigid covering of many animals such as snail, sepia, pila, turtles, sea urchins. A shell is protective outer layer of these soft bodied animals. Shells are made of calcium carbonate in the form of  calcite or aragonite crystallized in an organic matrix. Shells of other animals are composed of chitin, bone or cartilage. That's why a shell is considered as biotic (living).

Sunnygary

Answer:

The correct answer is "because it came from something living".

Explanation:

In biology, a shell is defined as a protective structure of mollusks and crustaceans. A shell is considered to be biotic because it came from something living. Shells are not in fact alive as they are made of calcium carbonate and in some cases α-chitin, two non living materials. However, since mollusks and crustaceans are living beings, shells are considered biotic.

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