Required practicles

• Reaction time required practical

  1. Ruler drop test

  2. Person A drops ruler

  3. Person B catches ruler

  4. Measure distance ruler fell

  5. Convert distance to reaction time

  6. Repeat 3 times

  7. Calculate mean reaction time

  8. Change caffeine factor

  9. Repeat experiment with 10 other people
• Reaction time practical


  • Difficult to measure with stopwatch
  • Use ruler drop test instead
• Factors that could affect reaction time

  • Caffeine
  • Distractions
  • Tiredness
• Control variable


  Holding ruler at same height each time
• Reaction time


  • Faster if ruler falls through short distance
  • Slower if ruler falls through longer distance
• Organism distribution required practical

  1. Random sampling

  2. Transect
• Random sampling


  • Estimate population size
  • Avoid bias
• Random sampling method


  1. Measure out area

  2. Divide into numbered squares

  3. Use random number generator to select squares

  4. Place quadrat on selected squares

  5. Count organisms in quadrats

  6. Calculate mean organisms per quadrat

  7. Estimate total organisms in area
• Quadrat


  Small area used for sampling
• Increasing number of squares sampled increases reliability of population estimate
• Percentage cover


  Measure coverage of organisms like lichen rather than counting individuals
• Transect method


  1. Lay transect line

  2. Place quadrats at intervals

  3. Count organisms in quadrats

  4. Measure environmental factor (e.g. light intensity)

  5. Repeat at intervals along transect
• For tall vegetation, count plants touching transect line instead of using quadrats
• Transects can measure vertical distribution as well as horizontal
• Measuring plant growth using a transect

  1. Identify plants touching the transit line

  2. Measure plant height along the transect
• When measuring plant growth vertically, the process is the same as a horizontal transect
• Plant growth required practical


  Use fast-growing seeds like mustard or cress
• Investigating how light intensity affects plant growth


  1. Set up petri dish with seeds

  2. Vary distance between light source and petri dish

  3. Measure plant height
• Independent variable


  • Distance between light and petri dish
• Dependent variable


  • Height of plants
• Control variables


  • Number of seeds, power of lamp, type of seed, water volume, temperature
• Investigating how direction of light affects plant growth

  1. Keep light distance constant, vary direction of light source

  2. Measure direction of plant growth
• Independent variable


  • Direction of light source
• Dependent variable


  • Direction of plant growth
• Control variables


  • Number of seeds, power of lamp, type of seed, water volume, temperature, distance between lamp and seeds
• Investigating how angle of petri dish affects plant growth


  1. Set up petri dishes at different angles

  2. Measure direction of plant growth
• Independent variable


  • Angle of petri dish
• Control variables


  • Direction of light source, light intensity
• Shoots respond to gravity and grow upwards
• Investigating how temperature affects rate of decay


  1. Set up 3 water baths at different temperatures

  2. Add lipase to milk and sodium carbonate solution

  3. Measure time for colour change
• Independent variable


  • Temperature
• Dependent variable


  • Rate of decay
• Control variables


  • Volume of lipase, volume of milk, volume of sodium carbonate
• Rate of decay equation


  Rate = 1000 / time