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Sharks Perform a Service for Earths Waters It is hard to get people to think of sharks as anything but a deadly enemy1. They are thought to1people frequently. But these fish2 perform a2service for earths waters and for human beings. Yet business and sport fishing3 are threatening their3Some sharks are at risk of disappearing from 4 Warm weather may influence both fish and shark activity. Many fish swim near coastal areas5their warm waters. Experts say sharks may follow the fish into the same areas, 6people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person7a sea animal, such as a seal or sea lion. That is why people should not swim in the ocean when the sun goes down or comes up. Those are the8when sharks are looking for food. Experts also say that bright colors and shiny jewelry may cause sharks to attack. A shark has an extremely good sense of smell4 It can find small amounts of substances in water, such as blood, body liquids and9produced by animals. These powerful10help sharks fred their food. Sharks eat fish, any11 sharks, and plants that live in the ocean. Medical researchers want to learn more about the sharks body defense, and immune12against disease. Researchers know that sharks13quickly from injuries. They study the shark in hopes of finding a way to fight human disease. Sharks are important for the worlds14They eat injured and diseased fish. Their hunting activities mean that the numbers of other fish in ocean waters do not become too15.This protects the plants and other forms of life that exist in the oceans. | 
