Recall Questions

• How is air supplies to the respiring tissues in an insect?

  Through the tracheoles
• Where does air enter the tracheal system in an insect?

  Down the concentration gradient - oxygen used by respiring tissues, creates a diffusion gradient. Oxygen diffuses from the atmosphere along the trachea to the cells
• The ends of tracheoles in insects are filled with tracheal fluid. What is the function of this fluid?

  Allows gases to dissolve and then diffuse into the cells
• How can insects increase ventilation?

  By contracting muscles on each section of the abdomen - this pushes on the tracheals and therefore creates pressure
• When an insect is active, what changes occur in the insect to increase their oxygen supply?

  Air is actively pumped by movements of the abdomen and thorax - this creates a pressure gradient to draw more oxygen in and push more carbon dioxide out.

  Also, more spiracles are open to allow more gases to diffuse in and out