UPSC CAPF AC 2021 Paper

Coral reefs are large underwater structures composed of the skeletons of colonial marine invertebrates called coral. The coral species that build reefs are known as hermatypic, or "hard," corals because they extract calcium carbonate from seawater to create a hard, durable exoskeleton that protects their soft, sac-like bodies.
Coral Reefs need following factors for their growth
- Corals need to grow in shallow water where sunlight can reach them.
- Corals rarely develop in water deeper than 165 feet ( 50 meters).
- Corals generally live in water temperatures of 23°-25°C.
- Corals need saltwater to survive and require a certain balance in the ratio of salt to water.
- The best known and largest example of a Coral reef is the great barrier reef in the Australian.