Transport in animals

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  • Transport in animals
    • Factors that affect the need for a transport system.
      • Size
        • Once an organism has several layers of cells, any oxygen or nutrients diffusing in from the outside will be used up by the outer layers of cells.
      • Surface-area-to-volume ratio
        • Small animals have a larger surface area to volume ratio than large animals.
        • The surface area-to-volume ratio is affected by the animal's shape.
      • Level of activity
        • Releasing energy from food by respiration requires oxygen.
        • If the organism is fairly active, its cells will need good supplies of nutrients and oxygen, to supply the energy for movement.
    • Features of a good transport system.
      • A fluid to carry nutrients and oxygen around the body.
      • A pump to create pressure that will push the fluid around the body.
      • Exchange surfaces that enable oxygen and nutrients to enter the blood and for waste products to be removed.
      • Tubes or vessels to carry the blood.
      • Two circuits - one to pick up oxygen and another to deliver oxygen to the tissues.
    • Single and double circulatory systems.
      • Single circulatory systems
        • Occur in Fish.
        • Heart, Gills, Body, Heart
      • Double circulatory systems
        • Occur in mammals.
        • Pulmonary circulation is when one circuit carries blood to the lungs to pick up oxygen.
        • Systemic circulation is when one circuit carries the oxygen and nutrients around the body to the tissues.
        • Heart, body, heart, lungs, heart.
    • Advantages of a double circulation system.
      • In the Fish single circulatory system.
        • The blood pressure is reduced as blood passes through the tiny capillaries of the gills.
          • This means the blood won't flow very quickly to the rest of the body
            • This limits the rate at which oxygen and nutrients are delivered to respiring tissues.
      • In the mammal double circulatory system.
        • The heart can increase the pressure of the blood after it has passed through the lungs, so blood flows more quickly to the 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 capillaries in the lungs.


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