Gas exchange

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  • Created by: emma
  • Created on: 10-03-14 21:52
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  • Gas exchange
    • Insects
      • Limit water loss
        • Waterproof covering over body
        • Small surface area to volume ratio
      • Movement of oxygen
        • O2 enters spiracles into tracheae then spiracle closes
          • O2 diffuses through tracheae into tracheoles
            • O2 delivered directly to tissue (short diffusion distance)
      • Oxygen diffusion
        • Tissues respire using O2
          • O2 moves from high conc to low from tracheae to tissue
            • Lowers O2 conc in tracheae so O2 moves into tracheae from outside spiracles
      • Carbondioxide
        • Respiration produces CO2 increasing conc at tissue
          • CO2 moves from a high to low conc from tissue to tracheae
            • Then from high to low con from tracheae to outside spiracle
    • Fish
      • Many lamellae and many filaments for large surface area
      • Thin epithelium for short diffusion distance
      • Counter current maintains concentration gradient between blood and water
        • Blood flow and water in opposite directions
          • ensures diffusion can take place across entire gill surface
    • Plants
      • Adaptations of leaf
        • Flat (large surface area)
        • Stomata pores allow air into leaf
        • Air spaces in leaf provide a short diffusion distance
      • Diffusion of CO2
      • Diffusion of O2
        • Mesophyll cells produce O2 in photosynthesis
          • O2 diffuses into air spaces from cell (high to low conc)
            • Increases O2 conc in air spaces so O2 diffuse from air spaces to air through stomata
      • Xerophytic
        • Reduce number of stomata
          • Less surface area for water loss
        • Hairs to trap water vapour
          • Reduce concentration gradient
        • Rolled leaves
          • Reduce concentration gradient
        • Leaves reduced to spines
          • Less surface area for water loss
        • Thick waxy cuticles
          • Increased diffusion distance
    • Single celled organisms
      • Diffusion for gas exchanges
      • Have large surface area to volume ratio


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