as well as shells, what other parts of marine organisms need carbon and calcium to form?

Coral skeletons are the other key structures that need both carbon and calcium to form, in addition to shells.

What they are made of

• Many marine organisms build hard parts from calcium carbonate, a mineral that uses calcium and carbon from seawater.

• Corals use this calcium carbonate to create rigid skeletons that support the living coral polyps and form reefs over time.

Why corals need carbon and calcium

• Reef‑building corals take in dissolved calcium ions and carbonate (a carbon‑containing ion) from seawater to precipitate calcium carbonate skeletons.

• These skeletons provide long‑term structure and protection for the colony, similar to how shells protect mollusks.

Quick classroom-style answer

• Question: As well as shells, what other parts of marine organisms need carbon and calcium to form?
• Answer: Coral skeletons , which are made of calcium carbonate using calcium and carbon from seawater.

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