Why would exhaled air or air near a fern plant have a different concentration of carbon dioxide than classroom air?

Answer 1

Air is altered by respiration (in animals) and photosynthesis (in plants). When humans breathe in classroom air, its contains about 21% oxygen and 0.03% carbon dioxide. In the lungs, oxygen is removed from the air and taken into the blood. The oxygen is used in the process of respiration to release energy from food. One of the waste products of respiration is carbon dioxide. At the same time as we absorb oxygen into the blood, carbon dioxide passes from the blood into the air in the lungs. The air we breathe out (exhaled air) therefore contains less oxygen and more carbon dioxide than normal clasroom air. During photosynthesis plants use up carbon dioxide and produce oxygen. Therefore, near a plant which is photosynthesising, the level of carbon dioxide could be reduced because it is being removed by the plant. For a simple comparison of inhaled and exhaled air see: http://www.bbc.co.uk/schools/ks3bitesize/science/Biology/gas_3.shtml For an experiment demonstrating carbon dioxide production see: http://www.biotopics.co.uk/humans/inhaledexhaled.html For an introduction to photosynthesis see: http://www.bbc.co.uk/schools/gcsebitesize/biology/greenplantsasorganisms/0photosynthesisrev1.shtml