exam answer

• devise an investigation using a respirometer, to find the optimum temperature for respiration in maggots(5)

  • water baths of different temperatures are set up (10,20,30,40 and 50 degrees)
  • same species of maggots(similar age and size)of maggots in test tube, ensure same number used eg 5
  • set up respirometer and record position of coloured liquid
  • place bung on top and record distance liquid travels at 30 seconds intervals for 10 mins
  • calculate rate of respiration(speed=distance/time)
  • repeat each temperature 3 times to find mean
• devise an investigation using this apparatus to determine whether an increase of 10 degrees doubles the rate of respiration in yeast(4)

  • selection of 2 temperatures eg 20 and 30 degrees, not above optimum temp(40 degrees)
  • keep PH of solution constant and the volume of yeast constant
  • record the distance travelled by the at 30 second intervals for 5 minutes
  • calculate rate(speed=distance/time)
  • data collected during initial rate of reaction/before another factor becomes limiting
• people with a larger thorax will have a lower breathing rate as their tidal volume will be greater than those without adaptation

  devise a valid investigation,using a spirometer, to test this hypothesis(4)

  • select people with different thorax sizes
  • select people with simular fitness level, same age, same sex
  • control temperature of room
  • measure tidal volume from the spirometer trace(difference in peak to trough volume)
  • measure breathing rate as number of peaks/troughs in a set time