Paper 2

• Reaction times

  1. Hold a ruler between your lab partner's finger and thumb with the zero mark in line with them

  2. Drop the ruler without warning and have your partner catch it as fast as they can

  3. Calculate the reaction time using the equation t = sqrt(2s/a) where s is the distance fallen and a is acceleration due to gravity

  4. Repeat multiple times and calculate the mean reaction time
• Quadrats

  1. Place multiple tape measures along the length and width of the field, forming a large grid.

  2. Use a random number generator to generate 10 pairs of random coordinates.

  3. Place quadrats at those coordinates and count how many dandelions are found in each quadrat.

  4. Calculate the mean number of dandelions per m2.

  5. Estimate the total population size using our mean number of dandelions per m2 and the total area of the field.
• Microbiology

  1. Spot different bacterial cultures on agar in a petri dish and observe how they grow

  2. Spread a culture over the agar to make a lawn and then add antibiotic discs

  3. Use aseptic technique - sterilize equipment, work near a Bunsen flame, etc.

  4. Measure the diameters or areas of the bacterial colonies or antibiotic inhibition zones
• Germination

  1. Place seeds on damp cotton wool in a petri dish

  2. Leave the dish upright in the dark and observe the roots growing downwards (geotropism)

  3. Allow a small amount of light in and observe the shoot growing towards the light (phototropism)
• Decay

  1. Measure out a volume of milk or cream and add sodium carbonate and phenolphthalein indicator

  2. Add the enzyme lipase and use a water bath to control the temperature

  3. Time how long it takes for the solution to decolorize as the milk decays

  4. Plot the time taken against temperature and identify the optimum temperature
• Transects

  1. A transect line (usually a tape measure) is laid out in a straight line between the lake and woodland.
  2. Quadrats are placed at regular intervals along the transect line. 
  3. The abundance of dandelions is measured by counting the number of dandelions in each quadrat along the transect line, from the lake to the woodland.
  4. Steps 1-3 are repeated using new transect lines (these must be parallel to the first). By using multiple transect lines, the data gathered is more representative of the area.