gas exchange in insects

• insects have an exoskeleton made of hard fibrous material for protection and a waterproof lipid layer to prevent water loss
• insects do not have lungs instead the have a tracheal system
• adaptations to prevent water loss

  • small surface area : volume ratio, less space for water to evaporate from
  • waterproof exoskeleton
  • spiracles where gas can enter and leave which opens and closes to reduce water loss
• spiracles (tracheal system)

  • round , valve-like openings
  • run along the abdomen
  • leads into the trachea
• trachea ( treacheal system)

  • network of internal tubes
  • have rings within to keep them open and provide strength
• tracheoles (tracheal system)

  • trachea branches into smaller tubes called tracheoles
  • these extend to all the respiring tissues
• 3 methods of moving gas

  1. simple diffusion , due to the concentration gradient between the tracheoles and the atmosphere
• 3 methods of moving gases

  2. gas exchange in mass transport . an insect contracts and relaxes their abdomen muscles to move gases fast and in larger quantity
• 3 methods of moving gases

  3. when the insects are in flight , their cells respire anaerobically producing lactate which lowers water potential and makes water move from the tracheoles into the cells. this decreases the volume in the tracheoles and air is drawn in
• adaptations for diffusion

  • large number of fine tracheoles - increases surface area
  • walls of tracheoles are thin and short - short diffusion pathway
  • use of oxygen and production of carbon dioxide sets up steep diffusion gradient
• what's the differences in the human tracheal system and an insects?

  1. A human trachea is obviously much bigger than an insect trachea.

  To be precise, scientists say that a human trachea has a much bigger diameter and  length than an insect trachea.

  2. Humans only have one trachea, whereas insects have many tracheae. 

  3. A human trachea branches into bronchi. 

  An insect trachea branches into tracheoles.

  4. A human trachea is supported by cartilage, whereas an insect trachea is supported by chitin. 
• Give 2 way insects are adapted to limit water loss

  1. the exoskeleton is waterproof
  2. the spiracles can open and close
• how does gas exchange occurs in the tracheoles?

  • oxygen enters through the spiracles
  • diffuses across the trachea
  • into the tracheoles
  • dissolves in tracheal fluid
  • enters muscle
• what happens to the tissue fluid during flight?

  absorbed so there's air in the tracheoles so oxygen diffuses faster
• what are the trachea and tracheoles supported by

  chitin