Gas Exchange

HideShow resource information
View mindmap
  • BY2 - Gas Exchange
    • Gas Exchange Surface
      • Properties
        • Thin - short diffusion pathway
        • Moist - gases dissolve on the surface before diffusing in.
        • Large surface area to volume ratio.
          • Faster rate of diffusion.
      • Why have multicellular organisms developed specialised gas exchange surfaces?
        • Higher metabolic rates means a greater demand for oxygen.
          • Skin would not be an efficient gas exchange surface as the diffusion pathway is to long.
        • Small surface area to volume ratio - diffusion of gases would be too slow.
    • Amoeba
      • Unicellular organism
      • Cell membrane = gas exchange surface
        • Thin
        • Moist
          • Lives in water
        • Diffusion of gases occurs over whole body surface.
        • Low demand for oxygen.
        • Large surface area to volume ratio.
    • Earth Worm
      • Gas exchange surface = Skin
        • Although multicellular, the organism has a low metabolic need for oxygen.
        • Elongated body shape provides a large surface area to volume ratio.
          • Increases rate of diffusion.
          • Modest oxygen demand - slow moving so low oxygen levels needed for metabolism.
      • Mucus released onto skin keeps it moist.
      • Blood capillaries carry oxygen and carbon dioxide to maintain concentration gradient.
        • Respiratory pigment - Carries oxygen.
        • Closed blood system.
    • Fish
      • Gas exchange surface = Gill filaments.
        • Advantage of being in water
          • Water prevents gills from collapsing.
            • Maintains a large surface area for diffusion.
      • Cartilaginous Fish
        • Skeleton is mainly cartilage.
        • Gas exchange involves parallel flow.
          • Blood in the gills travels in the same direction as the water flowing over them.
          • Gas exchange is relatively inefficient.
        • e.g. Sharks
      • Boney Fish
        • Skeleton is made of bone.
        • Gas exchange involves counter current mechanism.
          • Blood in the gill capillaries flow in the opposite direction to the water flowing over the gills.
          • More efficient gas exchange.
          • Highly efficient for gas exchange because the concentration gradient is maintained against the entire length of the gill filament.
        • e.g. Mackerel
      • Gill Features
        • Gill plates/lamella and filaments give a large surface area for diffusion.
        • Good blood supply - maintains concentration gradient.
          • Thin gill filaments - provides a short diffusion pathway.
        • Counter-current flow.
      • Ventilation
        • Needed to provide a fresh supply of oxygen.
          • Maintains concentration gradient for diffusion of gases.
        • Water needs to be forced over the gill filaments by pressure differences to increase efficiency.
          • Pressure moves from high pressure to a lower pressure so BREATHING IN forces water over the gills.
        • Breathing In/Inspiration.
          • Opposite happens with breathing out/expiration.
      • Difficulties getting oxygen from the water
        • The water is less dense so less oxygen is dissolved.
  • Why have multicellular organisms developed specialised gas exchange surfaces?
    • Higher metabolic rates means a greater demand for oxygen.
      • Skin would not be an efficient gas exchange surface as the diffusion pathway is to long.
    • Small surface area to volume ratio - diffusion of gases would be too slow.
  • Blood capillaries carry oxygen and carbon dioxide to maintain concentration gradient.
    • Respiratory pigment - Carries oxygen.
    • Closed blood system.
  • Inefficient because only 50% of oxygen leaves the water and diffuses into the blood.
    • This is because a concentration gradient is not maintained across the entire length of the gill filament.
    • Gas exchange involves parallel flow.
      • Blood in the gills travels in the same direction as the water flowing over them.
      • Gas exchange is relatively inefficient.
  • 1. Mouth opens
    • 2. Operculum closes.
      • 3. Floor of mouth lowers.
        • 4. Volume inside mouth cavity increases.
          • 5. Pressure inside mouth cavity decreases.
            • 6. Water moves IN.
    • Breathing In/Inspiration.
      • Opposite happens with breathing out/expiration.
  • Metabolically active.
    • Much slower diffusion rates.
    • Difficulties getting oxygen from the water
      • The water is less dense so less oxygen is dissolved.

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Gas exchange resources »