TOEFL Vocabulary Quiz #1: Core Words

Coral reefs occupy less than one percent of the ocean floor, yet they harbor nearly a quarter of all known marine species. The structures themselves are built by tiny animals called polyps, which deposit thin layers of calcium carbonate over thousands of years. These formations provide shelter and feeding grounds for fish, crustaceans, and countless smaller organisms. Because so many species depend on them, damage to a single reef can disturb food webs across a wide area.