Why diffusion happens in the gas exchange systems (tracheal system) of insects
2. Tissues respire using oxygen, which reduces the concentration of oxygen at the tissue
3. Oxygen moves from an area of higher concentration to lower concentration so moves from the tracheae to the tissue
4. This lowers the oxygen concentration in the tracheae so oxygen moves into the tracheae from outside the insect via the spiracles
6. Respiration produces CO2, increasing the concentration at the tissue
7. CO2 moves from an area of high concentration at the tissue to the low concentration in the tracheae
8. CO2 then moves from high concentration in tracheae to low concentration outside the insect via the spiracles