Required Practicals

• Reaction times?

  • hold ruler between person's thumb and index finger, lined up with 0cm mark
  • drop without warning and record distance dropped before caught
  • repeat to calculate mean
  • Introduce a variable such a before and after taking coffee or distractions to see its effect on reaction time
• Quadrats?

  • Place 1m^2 quadrat in random grid positions in area (using random number generator to remove bias)
  • count organisms present in the area
  • to observe variation in population density over distance, move quadrat along a transect and record number per m^2
  • calculate the mean number per m^2, then multiply by total area to give an estimate of the total population
• Germination?

  • Put cress seeds on damp cotton wool in a petri dish
  • Allow to germinate in a dark environment (place in a cupboard or a box)
  • If observing root growth, stand dish on its side. After a few days, you should observe the geotropism
  • You can also turn 90 degrees and check again to see a bend in roots
  • If observing shoot growth, allow a bit of light to enter through a hole and measure shoot height every day
• Decay?

  • Measure volume of whole milk (5cm^3) or cream using a syringe or measuring cylinder
  • put in a test tube
  • add sodium carbonate
  • add the indicate phenolphthalein, which is turns from white to pink for a pH over 8.3
  • use a water bath to change temperature, measured using a thermometer in the test tube
  • add the enzyme lipase (5cm^3) and start the stopwatch
  • record the time taken for the indicator to decolourise (white).
  • repeat this for different temperatures
  • An increase temperature will increase the rate of decay up to the point at which the enzymes denature