B4 Organising Plants and Animals


B4.1: The Blood

  • the blood, blood vessels and heart make up the circulatory system which transports substances to and from body cells. 
  • plasma has blood cells suspended in it and transports proteins and other chemicals around the body.
  • red blood cells contain haemoglobin that binds to oxygen to transport it from the lungs to tissues.
  • white blood cells help protect the body from infection.
  • platelets are cell fragments that start the clotting process at wound sites. 
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B4.2: The Blood Vessels

  • blood flows around the body in the blood vessels.
  • the main types of blood vessel are arteries, veins and capillaries.
  • substances diffuse in and out of the blood in the capillaries. 
  • the valves prevent backflow, ensuring that blood flows in the right direction.
  • humans have a double circulatory system. 
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B4.3: The Heart

  • the heart is an organ that pumps blood around the body.
  • heart valves keep the blood flowing in the right direction.
  • stents can be used to keep narrowed or blocked arteries open.
  • statins reduce cholestorol levels in the blood, reducing the risk of coronary heart disease.
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B4.4: Helping the Heart

  • damaged heart valves can be replaced using biological or mechanical valves.
  • the resting heart rate is controlled by a group of cells in the right atrium that form a natural pacemaker. 
  • artifical pacemakers are electrical devices used to correct irregularities in the heart rhythm.
  • artifical hearts are occasionally used to keep patients alive while they wait for a transplant or for their heart to rest as an aid to recovery. 
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B4.5: Breathing and Gas Exchange

  • the lungs are in your chest cavity, protected by your ribcageand separated from your abdomen by the diaphragm. 
  • the alveoli provide a very large surface area and a rich supply of blood capillaries. this means gases diffuse in and out of blood as efficiently as possible.
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B4.6: Tissues and Organs in Plants

  • plant tissues are collections of cells specialised to carry out specific functions.
  • the structure of the tissues in plant organs is related to their functions.
  • the roots, stem and leaves frm a plant organ system for the transport of substances around the plant. 
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B4.7: Transport Systems in Plants

  • plants have separate transport systems.
  • xylem tissue transports water and mineral ions from the roots to the stems and leaves.
  • phloem tissue transports dissolves sugars from the leavesto the rest of the plant, including the growing regions and storage organs.  
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B4.8: Evaporation and Transpiration

  • the loss of water vapour from the surface of leaves is known as transpiration.
  • water is lost through the stomata which open to let in carbon dioxide for photosynthesis.
  • the stomata and guard cells control gas exchange and water loss. 
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B4.9: Factors Affecting Transpiration

  • factors that increase the rate of photosynthesis or increase stomatal opening will increase the rate of transpiration.
  • these factors include: temperature, humidity, air flow, and light intensity.
  • transpiration is more rapid in hot, dry, windy, or bright conditions. 
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