Gas Exchange🫁

• What stimulates the spiracles to open?

  Carbon dioxide increase causes the spiracles to open
• Explain what causes oxygen concentration in the trachea to fall when the spiracles are open?

  The oxygen is used in respiration so it diffuses from the trachea to the tissues, so oxygen is unable to enter
• The insect lives in dry conditions. Suggest an advantage of the spiracle movements shown in the diagram ?

  By opening and closing they are reducing water loss
• Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of the insect. Why?

  The rhythmic movement helps the air move in and out by diffusion , mainiting the diffusion gradient as well as more oxygen enters quicker
• Abdominal pumping is an adaption found not in many insects. Explain how their small size enables gas exchange to be efficient without abdominal pumping?

  Their small size gives them a large surface area volume ratio for efficient gas exchange as well as a shorter diffusion distance
• The insect opens if spiracles at a lower frequency suggest an advantage of this?

  Reduces water loss
• The ends of tracheoles connect directly with the insects muscle tissue and are filled with water which gets absorbed. ReNovak of water increases the rate of diffusion of oxygen between the tracheoles why?


  Gases diffuse better in air than water
• Explain how the structure of a gil makes oxygen uptake efficient?

  Lamallae are thin and have loads of blood capillaries for a short diffusion pathway
• water containing dissolved oxygen flows over the gill in the opposite direction to the blood flow inside. Explain why this arrangement is important for efficient uptake?

  Maintains the concentration gradient for the net movement of particles down a concentration gradient

  counter current across the whole length of lamallae so the fish gets more oxygen
• Suggest an advantage to the fish of this one way flow over it’s gills

  Maintains the concentration gradient by having a constant flow of oxygen
• Advantage of counter current flow

  Constantly maintains a concentration gradient, by the diagram showing the countercurrent of blood and water

  As the amount of oxygen is higher in water than blood so more oxygen will diffuse into the blood!
• Explain how the waxy cuticle reduces water loss

  Waxy cuticle covers the whole cell surface prevents water loss by evaporation
• Explain how one of the other labelled parts reduces water loss

  The stoma closed when the shape is flaccid which reduces the area for evaporation
• Describe how a student could use an eyepiece graticule to determine the mean diameter of stomata

  Put a portion of leaf under the microscope and use eyepiece graticule to measure the length of the stomata

  Calibrate the eyepiece graticule against the stage micrometer

  Calculate a mean
• Explain why producing ABA may help these spcies survive in dry conditions

  Less stomatal opening so less water loss by diffusion

  More water available for metabolic reactions
• How might LAM13 protect plants against infection?


  Closes spores so infection cannot enter the organism