Transport in Animals

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  • Transport in Animals
    • Surfaces for Exchange
      • Special surfaces are needed because all living cells need certain substances to keep them alive
        • Proteins - growth and repair
        • Fats - make membranes, energy store
        • Glucose - energy source
        • Water - involved in lots of reactions
        • Oxygen - aerobic respiration
        • Minerals - maintain water potential, help enzyme action and metabolism
      • all living cells must be able to remove waste products from metabolic activities : CO2, O2, other wastes like urea/ammonia (excess nitrogen)
      • Organisms can absorb these substances from the surrounding environment or make them in their cytoplasm ( as part of cell metabolism)
      • Single celld/small organisms can exchange gases/nutrients/ wastes  via diffusion accross the outer surfaces
        • they have a large surface area to volume ratio, so the process is quick enough for the cells to survive
      • Multicellular/Large Organisms have small surface area to volume ratios and need more supplies to maintain life
        • they are unable to get all that they need from diffusion on the outer surface as they would die before enough got to their inner cells
          • they therefore require a transport system to move substances around the body quickly
      • Good Exchange Surfaces
        • Large Surface area - more space for molecules to pass through
        • fresh supply of molecules on one side - concentration gradient maintained
        • thin barrier - reduce diffusion distance
        • Removal of required molecules on one side to keep concentration low - maintain concentration gradient
      • EXAMPLES
        • Walls of alveoli in lungs
        • Small intestine - nutrients absorbed
        • root hairs of plants - water + minerals
    • Transport Systems
      • Good features
        • exchange surfaces to enable O2 and nutrients to enter blood and leave where needed
        • a pump for pressure to push fluid around body - HEART
        • A fluid/medium to carry nutrients/O2 around the body - BLOOD
        • Tubes/Vessels to carry blood
        • 2 curcuits - one to pick up O2 and one to deliver O2
      • Needed if they are large, with a small surface area to volume ration and have a high level of activity
        • SA:V ratio is affected by shape - long and thin vs short and fat. Thick is necessary for organisms to be large - for strength need bones/range of tissues
          • SA:V ratio must be small as V increases whilst SA doesn't
        • Level of Activity - if an animal is very active it requires a good supply or nutrients and oxygen to supply the energy for movement/warmth
      • Single Circulatory
        • Blood flows from the heart to the oxygen supply and then to the body and heart again.
          • .E.G. Fish - heart, gills, body, heart
        • In fish, the blood pressure is reduced as blood passes through tiny capillaries in the gills so it will not flow as quickly to the rest of the body - thus limiting the rate that oxygen/nutrients can be delivered to respiring tissues
      • Double Circulatory
        • 2 separate curcuits - one takes blood to lungs to pick up O2 (pulmonary circulation) and other carries oxygen filled blood/nutrients around the body (systemis circulation)
        • Mammels: heart, body, heart, lungs, heart
        • the systemic circulation can carry blood at a higher pressure than the pulmonary circulation
          • the heart can increase the pressure of the blood after it has been through the lungs so blood flows more quickly through the body tissues
        • the blood pressure must not be too high in the pulmonary circulation or it could damage delicate capillaries
      • Mammels - active animals and need to maintain their body temperature
        • both the energy for activity and the heat are needed require energy from food
        • An efficient circulatory system is needed to deliver O2 and nutrients quickly to the parts of the body where they are needed - the blood can be made to flow more quickly by increasing the blood pressure created by the heart


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