Coral reefs are formed of coral colonies. Many thousands of coral polyps are connected together to form a coral colony. These colonies are of many shapes and colors. Corals are divided into groups according to their respective shapes (e.g. braching, massive). On a visit to a nearby reef, you can discover the kinds of coral in your area.
Coral polyps can reproduce sexually, by producing eggs and sperm which fuse (join) to form a larva or the baby coral animal (planula-many planula are called planulae) that drifts in the sea until it finds a hard, stable surface (like dead corals) to settle on and grow. The above process is referred to as spawning. Different organisms compete with corals for space for settlement and growth (e.g. algae and sponges). Reef animals like parrot fish, limpets, chitons, and sea urchins feed on plants and sponges that grow on dead coral, thus creating free space for new corals to settle and grow.
Corals also reproduce by budding (asexual reproduction). Small buds appear on the body of the adult polyp, grow larger, and break off from the parent body. They then move off to produce their own limestone and help the colony increase in size.
