Biology Required Practicals

• Tips for answering practical questions

  • Identify the independent variable (the thing you change)
  • Identify the dependent variable (the thing that changes as a result)
  • Identify the control variables (things you keep the same)
  • State the equipment used for each measurement
  • Discuss safety precautions like using goggles, gloves, etc.
  • Discuss the accuracy of measurements and how to reduce errors/uncertainties
  • Discuss taking multiple/repeat measurements to calculate a mean
• Microscopy


  1. Use a scalpel and tweezers to prepare a thin layer of onion skin

  2. Add a drop of iodine to stain the cells

  3. Place a cover slip on top

  4. Place the slide on the microscope stage

  5. Start with the shortest objective lens and use the coarse and fine focus knobs to bring the specimen into focus

  6. Change to a higher magnification objective lens and refocus if needed

  7. You can use a graticule (tiny ruler) to measure cell size in micrometers
• Osmosis


  1. Cut equal-sized cylinders from the same vegetable using a cork borer

  2. Dab off excess water and weigh the cylinders

  3. Place the cylinders in test tubes with different concentrations of sugar solution

  4. After a set time, remove the cylinders, dab off excess water, and reweigh

  5. Calculate the percentage difference in mass for each cylinder

  6. Plot the percentage change in mass against solution concentration to find the concentration with no osmosis
• Enzymes


  1. Measure out a set volume of the enzyme (amylase) and substrate (starch) solutions

  2. Mix them together and start a timer

  3. Every 10 seconds, remove a sample and test it with iodine to see if the starch has been broken down

  4. Record the time taken for all the starch to be broken down

  5. Repeat this using different temperatures or pH values

  6. Plot the time taken against temperature or pH and identify the optimum conditions
• Food tests


  1. Grind solid food samples and add distilled water to create a solution

  2. Test for starch by adding iodine (turns black/dark purple)

  3. Test for glucose/simple sugars by adding Benedict's solution and heating (color change)

  4. Test for proteins by adding biuret reagent (turns purple)

  5. Test for lipids by adding ethanol and then adding to water (goes cloudy)
• Photosynthesis


  1. Use pondweed submerged in water in an inverted test tube or measuring cylinder

  2. Cut the stem at an angle and add sodium hydrogen carbonate to promote oxygen release

  3. Measure the distance between the light source and pondweed

  4. Wait 1 minute for photosynthesis to reach a constant rate

  5. Count the bubbles or measure the volume of oxygen made

  6. Repeat at different distances and plot the results against distance