gas exchange in animals

• simple organisms do not require specialised gas exchange system


  Because they can exchange gases across the body surface
• Skin

  • earthworms use their skin as a gas exchange surface
  • they have blood vessels very close to the surface of the skin
  • they ensure that their skin is moist to aid the diffusion of gases

  
• tracheal system

  • insects use this system, as they have an exoskeleton that prevents them from being able to use their skin as a gas exchange surface
  • they have opening in their exoskeleton called spiracles

  
• How spiracles work

  • oxygen enters the organism through the mouth or the spiracles and travels through the tracheoles to the cells.
  • carbon dioxide is also removed through the spiracles via diffusion
  • this is often aided by rhymical movements of the abdomen or thorax