Maintaining Atmospheric Composition

glucose + oxygen energy + carbon dioxide + water The Carbon Cycle The carbon cycle is one of the ways in which the composition of the atmosphere is maintained. The carbon cycle shows how carbon (often in the form of carbon dioxide) is moved from place to place around the Earth. For your exams you only need to know 3 ways in which carbon dioxide is added to, or removed from, the atmosphere. They are: Respiration This is where oxygen (breathed in from the air) reacts with glucose (taken in as food) to produce energy. Carbon dioxide is produced as a waste product, along with water vapour. glucose + oxygen energy + carbon dioxide + water

2. Combustion This is where fuels, such as petrol, natural gas and coal, are burned in air. They react with (use up) oxygen and produce carbon dioxide and water vapour. fuel + oxygen carbon dioxide + water Photosynthesis This is the opposite to respiration. All green plants take in carbon dioxide and water. They produce glucose as well as oxygen gas as a waste product. energy carbon dioxide + water glucose + oxygen

These three processes keep the levels of oxygen, and more importantly carbon dioxide, at constant levels. Questions: Give two processes which increase the level of carbon dioxide in the atmosphere. Give one process which decreases the level of carbon dioxide in the atmosphere. Combustion and respiration Photosynthesis

It would increase since carbon dioxide is a product of combustion. 3. What would happen to the level of carbon dioxide in the atmosphere if more fuels were burnt. Explain your answer. What would happen to the levels of carbon dioxide in the atmosphere if thousands of square miles of forest were cut down. Explain your answer. It would increase since carbon dioxide is a product of combustion. It would increase since there are less plants available to convert carbon dioxide into oxygen via photosynthesis.