Gas exchange

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  • Created by: rhiglynn
  • Created on: 05-03-16 20:44
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  • Gas Exchange
    • Adaptations of a gas exchange surface
      • Large surface area
      • Have a short diffusion pathway
      • Maintains a steep conc gradient by moving external or internal mediums
    • Single celled organisms exchange gases across their body surface
      • Absorb and release gases out of their outer surfaces via diffusion.
        • They have a large surface area, a thin surface and a short diffusion pathway- no need for gaseous exchange system.
    • Fish use a counter current flow system.
      • Water, containing oxygen, enters the fish through its mouth and passes out through the gills
        • Each gill is made up of lots of thin plates called gill filaments, which give a big surface area for exchange of gasses
          • Gill filaments are covered in lamellae, which increase the surface area even more.
            • The lamellae have lots of blood capillaries and a thin surface layer to speed up diffusion
              • Blood flows through the lamellae in one direction and water flows out in the opposite. This maintains a large concentration gradient between the water and the blood
    • Insects use tracheae to exchange gases.
      • Insects have tracheae for gas exchange.
        • Air moves in via spiracles
          • O2 travels down a concentration gradient towards the cell
            • The tracheae branch off in to smaller tracheoles which have thin, permeable walls- o2 goes directly to the respiring cells.
              • CO2 from the cells, moves down from its own concentration gradient towards the spiracles to be realised into the atmosphere.
                • Insects use rhythmic abdominal movements to move air in and out of the spiracles.
    • Dicotyledonous plants exchange gases at the surface of the Mesphyll Cells
      • Plants need CO2 for photosynthesis and o2 for respiration
        • the mesophyll cells have a large surface area
          • Gases moves out of the stomata.
            • The stomata can open and close if the plant is losing too much water the guard cells close the stomata.


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