Gas exchange

• Gas Exchange Structures in Animals and Plants


  • Microscopic structures: alveoli in mammals and leaf structure in plants
  • Macroscopic structures: respiratory systems in a range of animals
• Gas Exchange in Fish


  1. Gulp water through mouth

  2. Pump water over gill arches

  3. Capillary networks in gill filaments take oxygen from water and release carbon dioxide

  4. Water passes out through gill cover
• Gases have low solubility in water so their concentration in water is much lower than their concentration in air
• Gas Exchange in Insects


  1. Pores called spiracles with valves to regulate opening and closing

  2. Spiracles lead to tracheal tubes which carry air directly to cells

  3. Tracheal tubes held open by chitin

  4. Trachea branch into smaller tracheoles to create large surface area for gas exchange

  5. Tracheoles bring air directly to and from cells
• Blood is not involved in the transport of gases in an insect