Gas Exchange in Humans

• Gas exchange

  • gas exchange is the exchange of gases between an organism and the environment
  • organisms take in oxygen for aerobic respiration through the process of gas exchange
• Respiration in Unicellular organisms


  • unicellular organisms such as amoebae have large surface area to volume ratio
  • oxygen can be exchanged efficiently between the organism and the surrounding water by diffusion through the cell membrane, so special gas exchange system is not needed
• Respiration in large organisms

  • larger organisms have smaller surface area to volume ratio since their external surface is thickened for protection and to prevent water loss
  • special organs such as lungs or gills are used for gas exchange
  • the organs have enlarged surface areas and thin coverings, so to increase the rate of absorption of oxygen and removal of carbon dioxide from the body