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Sample Coral Reefs Worksheet
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Coral Reefs

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¹     Coral reefs are home to more than 25% of all marine life, yet they only cover a very small fraction of the ocean floor -- less than 0.2%, to be exact! The degree of biodiversity we observe in coral reefs is not unique. On land, at least 50% of all the plant and animal species can be found in an ecosystem that represents merely about 7% of Earth's surface area. That ecosystem is called a rain forest. It's no wonder that we often nickname coral reefs "rainforests of the sea."
 
²     Coral reefs are made of corals (also called polyps). And, contrary to our intuition, corals are animals, not plants. There are microscopic plants that live within the animal tissues (a symbiotic relationship). The animals benefit from the energy that the plants provide through photosynthesis. The plants are protected within the coral tissues and gain nutrients from animal wastes. These tiny plants are called zooxanthellae and are responsible for much of the color seen in reef corals.
 
³     There are two types of corals -- hard corals and soft corals. Hard corals secrete calcium carbonate that later becomes limestone. When they die, they leave their chalky, horny skeletons behind to form the framework of coral reefs. Over time, as living polyps grow on top of dead ones, coral reefs get bigger and taller. They expand at a rate of 0.16-7.8 inches a year.

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