B4 Organising plants and animals

• What is the function of blood plasma?

  Transports blood cells, platelets and dissolved substances around the body

  
• What is the function of the red blood cell?

  Carries oxygen around the body

  
• How is the red blood cell adapted for its role?

  They have a biconcave disc which gives a large surface area/volume ratio to absorb more oxygen

  
• What is the function of white blood cells? (lymphocytes and phagocytes)


  They help protect the body against infection.

  Lymphocytes form antibodies against microorganisms. Phagocytes engulf and digest invading bacteria and viruses.

  
• Explain how platelets help the blood to clot and produce a scab

  1)Enzyme controlled reactions - convert fibrinogen into fibrin.

  2)Produces network of protein fibres which captures red blood cells and platelets to form a jelly-like clot.

  3)The clot dries and hardens to form a scab - This protects the new skin as it grows and stops bacteria entering the body through the wound.

  
• What is the function of the arteries in the body?

  Carries blood away from the heart under high pressure around the whole body. Almost all of them carry oxygenated blood.

  
• What is the function of the veins in the body?

  Carries blood into the heart at low pressure. Almost all of them carry deoxygenated blood.

  
• What is the function of capillaries in the body?


  A huge network of tiny vessels linking the arteries to the veins. Where substances such as oxygen and glucose are exchanged between the blood and the body's cells.

  
• Compare the structure of arteries, veins and capillaries and explain how these adaptations allow them to perform their functions in the body

  Arteries stretch slightly as blood flows through them (felt as a pulse). Small lumen. Thick walls of elastic and muscle fibres.

  
  

  Veins often have valves to prevent the backflow of blood as it moves back to the heart. Large Lumen and relatively thin walls.

  
  

  Capillary walls only one cell thick to allow substances to diffuse into and out of the surrounding cells. The diameter of the lumen is just a little bigger than a red blood cell.

  
• Explain why blood vessels in humans are arranged in a double circulatory system

  It makes our circulatory system very efficient. Fully oxygenated blood returns to the heart from the lungs. The blood can then be sent off to different parts of the body at high pressure, so more areas of your body can receive fully oxygenated blood quickly.

  
• Name the 4 main chambers of the heart

  left atrium, right atrium, right ventricle, left ventricle

  
• Describe the flow of blood through the heart naming the vessels and chambers in order

  Blood flows into the two atria from the vena cava and the pulmonary vein. The aria contract, pushing the blood into the ventricles. The ventricles contract, forcing the blood into the pulmonary artery and the aorta, and out of the heart. The blood then flows to the organs through arteries, and returns through veins. The atria fill again and the whole cycle starts over.

  
• Why does the heart contain valves?

  Prevents back flow of blood

  
• Why is the muscular wall of the left ventricle bigger than the right?

  It has a bigger job and has to pump blood further

  
• What is a stent?

  Placement of a mesh wire device to hold an artery open and prevent restenosis

  
• Explain how a stent can be used to treat heart problems

  They make sure that blood is passing through the arteries; this keeps the heart beating

  
• Explain how Doctors can use bypass surgery where stents cannot work

  They replace the narrow or blocked coronary arteries with bits of veins from other parts of the body. This works for badly blocked arteries where stents can't help. The surgery is expensive and involves the risk associated with a general anaesthetic.

  
• What are statins?


  Statins are prescribed to reduce cholesterol levels and this slows down the rate at which fatty material is deposited in the coronary arteries. They can reduce the risk of a heart attack or stroke.

  
• What are the advantages and disadvantages of using mechanical valves as a replacement for leaky heart valves?


  Advantage - Lasts a long time

  Disadvantage - Need to take medicine for the rest of your life to prevent blood clotting around it

  
• What are the advantages and disadvantages of using biological valves as a replacement for leaky heart valves?

  Advantage - Patient doesn't need any medication

  Disadvantage - Only lasts about 12 - 15 years

  
• What is an artificial pacemaker?

  A device that uses electrical impulses to regulate the beating of the heart or to reproduce the rhythm of the heart beat.

  
• What is an artificial heart?

  Mechanical devices that pump blood for a person whose own heart has failed

  
• Explain how the movement of the ribs and diaphragm can cause inhalation

  When the diaphragm moves down and contracts, the rib muscles contract and the rib cage moves up. This gives the chest an increased volume and lower pressure which allows air to be drawn into the lungs.
• Explain how the movement of the ribs and diaphragm can cause exhalation

  When the diaphragm moves down and contracts, the rib muscles relax and ribcage moves down, decreasing volume inside chest, higher pressure in chest and air is forced out of the lungs.
• Describe the pathway of air into the body

  The air that you breath goes through your trachea, this splits into two tubes called bronchi, one tube going to each lung. It then splits into smaller tubes called bronchioles, they end at small bags called alveoli and go into the bloodstream.

  
• Describe the differences in composition of inhaled and exhaled air

  Inhaled air is 21% oxygen, exhaled air is 16% oxygen (used in respiration)

  Inhaled air is 0.04% carbon dioxide, exhaled air is 4% carbon dioxide (produced in respiration)

  Both inhaled and exhaled air are around 78% nitrogen, this is because nitrogen is not used by the body.
• Describe how the alveoli are adapted for gas exchange

  Folded membrane to increase the surface area for diffusion

  Very thin wall to give a short distance for the diffusion pathway

  Good blood supply maintains the concentration gradient for diffusion

  Ventilation moves air in and out and helps maintain a steep concentration gradient
• What is the role of epidermal tissues in plants?

  Covers the surfaces and protects them, transparent.
• What is the function of mesophyll tissues in plants?

  To carry out photosynthesis, many chloroplasts.

  
• Describe the function of the plant organs; leaves, stem and roots

  Leaves - photosynthesis.

  Stem - support leaf and flowers.

  Roots - absorb water and minerals from soil.
• What is a vascular bundle in a plant?

  Contains xylem and phloem
• Describe the structure of a leaf (you may want to include a diagram)

  
• What is translocation?


  The movement of sugars through phloem in plants
• What is transpiration? Describe the transpiration stream


  Transpiration is the loss of water from a plant by evaporation.

  Movement of water from the roots to the leaves through the xylem vessels. Water then evaporates from the leaves through the stomata.
• What causes the guard cells to open the stomata?

  The guard cells open stomata to allow carbon dioxide to diffuse into the leaf (for photosynthesis).

  When the plant has enough water the guard cells are swollen, this causes the stomata opening to appear between the cells.
• What causes the guard cells to close to stomata?

  If the guard cells are flaccid (not much water) then the stomata are closed.
• Describe how to carry out a practical to estimate the number of stomata on a leaf. Include the maths for a circular field of view and a square field of view

  1) Use nail varnish to cover an area of the leaf. Allow the nail varnish to dry, then peel it off and place it on a microscope slide.

  2) Place the slide onto the microscope stage and bring the image into focus.

  3) Count the number of stomata in the field of view.

  4) Calculate the area of the field of view (πr2 for a circle, width x length for a square).

  5) Divide the number of stomata seen by the area of the field of view. This will tell you the number of stomata per mm2. Multiply this by the area of the leaf for the final estimation.
• Describe and explain how light intensity effects transpiration rate

  High light intensity causes water to evaporate from the leaf at a quicker rate, this will increase transpiration. This is because the stomata are open to allow carbon dioxide to diffuse into the plant for photosynthesis.
• Describe and explain how wind speed effects transpiration rate

  Windy conditions increase the rate of evaporation and also maintain a steep concentration gradient from the inside of the leaf to the outside by removing water vapour as it diffuses out. This will increase the rate of transpiration.
• Describe and explain how humidity effects transpiration rate

  Water vapour diffuses more rapidly into dry air than into humid air because the concentration gradient is steeper. So high humidity would decrease the rate of transpiration.