Coral reef communities include many different organisms that must compete for resources such as space and light. A. In order to keep from being overgrown, the different species of coral kill each other's polyps, or live in different local habitats within the reef community. B. Competition among the different species of corals is more intense than that between corals and other coral reef inhabitants. C. Predation shapes reef structure by getting rid of competitors of corals, but coral polyps themselves are also eaten, as are many reef inhabitants. D. Coral reefs are divided into a shallow upper portion and a deeper lower portion with branching corals dominating in the lower portion. E. Grazing by fishes and urchins prevents algae and seaweeds from overgrowing the corals, although damselfish exclude grazers from some areas. F. Fish and invertebrate corallivores are the most common cause of coral colony destruction, followed by tropical storms and damage by humans.