What is a Coral?

.....The dictionary says, "A hard stony substance made by certain marine coelenterates as an external skeleton, typically forming large reefs in warm seas". Coral reefs are found in shallow, tropical marine waters. .Colonial Coral reefs are aragonite structures made of living organisms. Cnidarians secrete an exoskeleton of calcium carbonate (limestone). There are mostly very little nutrients in the waters. Coral reefs are biomes. They are also in danger of becoming extinct. The reefs can be found all through the year. Coral reefs can be found on the coast of Australia. They can also be found in the waters of the Philippines, in the Indian Ocean, the Red Sea, and in the Caribbean. Coral reefs can be found on the Gulf of Mexico.
..... All reefs are made of polyps or simply corals. The coral reefs live together in colonies. Corals that built reefs are called hard coral or stony coral. Coral polyps are about the size of a pencil eraser. There are at least 800 different species of stony coral. Except for rain forests, a coral reef has more living organisms than any other Ecosystem. The waste products that the coral reproduce become food for other organisms. Lots of colorful fish inhabit the coral reefs.
...... Many of the fish have special adaptations for their reef environments. For example, parrotfish they have beaklike front teeth that they use to scrape off algae. Algae from the hard coral is a parrotfish’s main food. Moray eels have long, thin bodies that enable them to hide in limestone cracks, from which they catch passing prey. Reefs also provide homes for reptilians. Sea turtles have paddle like flippers for swimming in the sea. Even invertebrates (animals without backbones) live in the reefs. This includes clams, crabs, lobsters, sea anemones, sea stars, sponges, and octopuses. Very unusual plants called, sea grass grow in many of the reef areas. The sea grass is very much like real grass only they are in no way related. Unlike a lot of plants, sea grass can survive under water. Coral reefs are very helpful to us as humans, even the sand of the beaches. Some of the sand was literally made by the corals from the reefs. Some scientist believe that the coral reefs help regulate the temperature. The creatures of the reef may help keep the planetway too warm.