1. How Humans Exchange Gasses By: Ashar

2. Gas Exchange  Gas exchange occurs in two locations. It occurs as external respiration in the lungs, where CO2 defuses out of the blood and O2 into the blood and internal respiration in all living cells in the body. CO2 leaves the cell and O2 enters the cell to the mitochondria mainly for respiration.

4. Why do we need Gas Exchange Systems  The larger the object, the smaller the surface area it had for each unit of volume. In multi-cellular organisms, this means there will be more and more cells will not be in direct contact with the air or will not be near enough to the surface to receive oxygen and expel carbon dioxide through direct diffusion.Prokaryotes only have one or few cells so they don't have this problem. So the gas exchange system is required for a more effective exchange of gas for all the cells in the body.

5. Bibliography  http://answers.yahoo.com/question/index?qid=200906 02200453AABpr2S http://answers.yahoo.com/question/index?qid=200906 02200453AABpr2S  http://faculty.stcc.edu/AandP/AP/imagesAP2/respirat ion/alvexch.jpg http://faculty.stcc.edu/AandP/AP/imagesAP2/respirat ion/alvexch.jpg  http://wiki.answers.com/Q/Gas_exchange_in_humans _and_mammalshttp:// http://wiki.answers.com/Q/Gas_exchange_in_humans _and_mammalshttp://  positivepsychologynews.com/ppnd_wp/wp- content/uploads/2008/12/thank-you.jpg