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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 to 1 people frequently. But these fish2 perform a 2 service for earths waters and for human beings. Yet business and sport fishing3 are threatening their 3 Some sharks are at risk of disappearing from 4 Warm weather may influence both fish and shark activity. Many fish swim near coastal areas 5 their warm waters. Experts say sharks may follow the fish into the same areas, 6 people also swim. In fact, most sharks do not purposely charge at or bite humans. They are thought to mistake a person 7 a 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 the 8 when 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 and 9 produced by animals. These powerful 10 help sharks fred their food. Sharks eat fish, any 11 sharks, and plants that live in the ocean. Medical researchers want to learn more about the sharks body defense, and immune 12 against disease. Researchers know that sharks 13 quickly from injuries. They study the shark in hopes of finding a way to fight human disease. | 
