Transport in Animals

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  • Transport in Animals
    • Surface to Volume Ratio
      • Small animals have a large surface area to volume ratio
      • Once an  Animal has several layer of cells, any O2 or Nutrients diffusing in from the outside will be used up by the outer cells. The O2 and Nutrients will not reach tht cells deeper within the body
      • In Larger Animals, the surface to volume ration is smaller, the surface area is not large enough to supply all the O2 etc needed by the cells.
    • Circulatory Systems
      • Single
        • Fish have a single circulatory System. The blood flows like this.... Heart -> Gills->Body -> Heart
        • Disadvantages
          • The Blood pressure is reduced as plood passes through the tiny capillaries of the gills
            • This means it will not flow very quickly to the rest of the body
              • This limits the rate at which O2 and Nutrients are delivered to respiring tissues
      • Double
        • Mammels have a double circulatory system. One circit carries blood to the lungs to pick up O2 (Pulmonary  Circulation )
          • The other circuit carries the O2 and nutrients around the body to the Tissues (Systematic Circulation)
        • Advantages
          • The heart can increase the pressure of the blood after it has passed through the lungs, so bloos flows more quickly to the body tissues
          • The Systematic Circulation can carry blood at a higher pressure than the pulmonary circulation
          • The Blood Pressure must not be too high in the Pulmonary circulation, otherwise it may damage the delicate cappilaries in the lungs
    • Features of a good transport system
      • An Effective Transport System will include:
        • A Fluid or medium to carry nutreints and O2 around the body - Blood
        • A Pump to create pressure that will push the fluid around the body - Heart
        • Exchange surfaces that enablt O2 and Nutrients to enter the blood and to leave it again where they are needed.
      • An Efficient Transport System will include:
        • Tubes or Vessels to carry the blood
        • Two Circuits - Oe to pick up O2 and another to deliver O2 to the tissues.


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