<span>Metamorphic rocks form by existing rocks join together under high heat and pressure. Examples of metamorphic rocks are marble, schist, slate, and quartzite. Metamorphic rocks formed when the minerals are chemically changed due to heat and pressure. They are often seen near magma but they do not melt like igneous rock.</span>
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The coral provides the algae with a protected safe environment (a home) and compounds they need for photosynthesis. The algae in return, produce oxygen and help the coral to remove wastes. Most importantly, zooxanthellae supply the coral with glucose, glycerol, and amino acids, which are the products of photosynthesis.