Protection of certain species is a very controversial topic. Many species like the mountain lion or jaguar that are near extinction in certain areas, are threats to human life. Another reason is that they could off set the food chain when they come back and be stonger than ever. For example the mountian lion could eat out the thriving white tail deer population which was struggling because of the mountain lion. And many people rely on white tail deer for food.
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Food is the most important source of chemical energy for living things. The chemical energy in food is converted, or changed, by the body into moving mechanical energy and heat energy. People have invented ways to use the chemical energy of substances to power machines.
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17: Mitochondria and Chloroplasts
19: The cell membrane is a double-layered sheet called a lipid bilayer. It affects the content of the cell because it controls what goes in and out of the cell.
