Gas Exchange in Fish and Insects

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  • Created by: Jasmine
  • Created on: 19-02-16 20:15
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  • Gas Exchange in Fish and Insects
    • Gas Exchange in Fish
      • Structure of Gills
        • Water(plus oxygen) enters the fish through the mouth and passes out the gills
        • Each gill has gill filaments which provide a large SA for exchange of gases
        • Gill filaments are covered in gill plates (secondary lamellae) which also increases the SA
          • Have lots of blood capillaries with a thin layer of cells to increase the rate of diffusion between water and blood
        • Each gill is supported by a gill arch which have an artery and vessels for oxygenated and deoxygenated blood
      • Counter Current System
        • Blood flows through the gill plates in one direction whereas the blood flows in the complete opposite direction
        • Water always has a slightly higher concentration of O2 when flowing next to blood which has a slightly lower concentration of O2
          • This maintains the concentration gradient so equilibrium is not reaches
          • Ensures that as much oxygen as possible will diffuse from the water into the blood
    • Ventilation in Fish
      • 1) Fish opens its mouth to the floor of the buccal cavity
      • 2) Volume of buccal cavity increases which decrease the pressure so water is sucked in
      • 3) When mouth closes the buccal cavity is raised so the volume decreases and the pressure increases
        • The increase in pressure is what forces the water out of the cavity and across the gill filaments
      • Opperculum- a bony flap which protects the gills
        • Increase in pressure forces the opperculum out and allows water to leave the gills
    • Gas Exchange and Ventilation in Insects
      • Insects has microscopic air filled pipes called tracheae
      • Air moves in through pores called spiracles
        • CO2 moves down concentration gradient and out the spiracles
        • They use abdominal movements to change volume of their bodies- helps pump air in and out of spiracles
      • Oxygen travels down concentration gradient to cells
      • Trachaea to tracheoles to individual cells
        • Tracheoles have permeable walls. They also have a fluid with the oxygen diffused into it


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