WJEC biology gas exchange

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  • Created by: rachel
  • Created on: 08-05-13 12:47
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  • Gaseous exchange
    • Fish
      • surface = gills
        • many folds providing large S.A. and specialised
      • 2 main groups
        • cartilaginous fish- skeleton is cartilage
          • Blood and sea water parallel flow (in gill capillaries) = inefficient
        • Bony fish- bone skeleton
          • Gills covered by flap (operculum)
          • counter current flow - blood in gill capillaries flow in opposite direction to water
            • increases efficiency- D gradient maintained through out
    • mammals (humans)
    • plants
    • insects
    • other examples
    • respiratory surfaces- evolved diffusion in and out of cells take place rapidly and efficiently
      • large S.A:Vol
      • thin- diffusion pathway short
      • permeable
    • increase size
      • unicellular organisms    *Diffusion over whole body surface *Large SA:Vol  *Thin and moist membrane *short D paths
      • multicellular evolved special gaseous exchange mechanisms with surfaces generally  located inside organism. Ventilation needed- moving air over surface


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