Practicals

• GCSE biology required practicals for AQA

  • Microscopy
  • Osmosis
  • Enzymes
  • Food tests
  • Photosynthesis
  • Reaction times
  • Quadrats
  • Microbiology
  • Germination
  • Decay
• 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)
  • Describe the equipment used for measurements
  • Discuss safety precautions like using goggles, gloves, etc.
  • Discuss ways to improve accuracy and reduce errors (e.g. taking repeat measurements, using proper techniques)
  • Use bullet point format to clearly communicate points
• Microscopy


  1. Prepare a thin layer of onion skin

  2. Place on microscope slide and add iodine stain

  3. Place cover slip

  4. Start with lowest magnification objective lens

  5. Use coarse and fine focus to bring specimen into focus

  6. Switch to higher magnification objective if needed
• Micrometre


  Unit of measurement equal to 10^-6 metres
• Osmosis


  1. Cut equal-sized cylinders from vegetable

  2. Remove ends to expose permeable surface

  3. Place in test tubes with different sugar solution concentrations

  4. After set time, remove, dab dry, and reweigh

  5. Calculate percentage change in mass

  6. Plot against solution concentration to find concentration with no osmosis
• Enzymes


  1. Measure volume of enzyme and substrate solutions

  2. Mix together and start timer

  3. Every 10 seconds, remove sample and test for presence of substrate using iodine

  4. Record time until no colour change (endpoint)

  5. Repeat with different temperatures or pH values

  6. Plot time against temperature/pH and identify optimum
• Food tests


  1. Grind solid food in water to make a solution

  2. Test for starch using iodine

  3. Test for glucose/simple sugars using Benedict's solution

  4. Test for proteins using Biuret reagent

  5. Test for lipids by adding ethanol then water
• Photosynthesis


  1. Set up pond weed in inverted test tube or measuring cylinder

  2. Cut stem at angle and add sodium hydrogen carbonate

  3. Measure distance from light source

  4. Wait 1 minute for photosynthesis to reach constant rate

  5. Count bubbles or measure oxygen volume in 1 minute

  6. Repeat at different distances

  7. Plot bubbles/oxygen against distance
• Reaction times


  1. Hold ruler between partner's finger and thumb

  2. Drop ruler without warning and have partner catch it

  3. Calculate reaction time using equation of motion
• Quadrats


  1. Use random number generator to choose quadrat positions

  2. Count organism in each quadrat

  3. Calculate mean number per quadrat

  4. Multiply by total area to estimate population
• Biotic factors


  Factors related to living things that affect population density
• Abiotic factors


  Non-biological factors that affect population density
• Microbiology


  1. Spot different bacterial cultures on agar and observe growth

  2. Spread culture to make a lawn and add antibiotic discs

  3. Use aseptic techniques to prevent contamination
• Germination


  1. Place seeds on damp cotton wool in Petri dish

  2. Observe root growth (geotropism) and shoot growth (phototropism)
• Decay


  1. Measure volume of milk/cream

  2. Add sodium carbonate and phenolphthalein indicator

  3. Add lipase enzyme

  4. Measure time for solution to decolorize at different temperatures

  5. Plot time against temperature to find optimum
• GCSE biology required practicals for AQA

  • Microscopy
  • Osmosis
  • Enzymes
  • Food tests
  • Photosynthesis
  • Reaction times
  • Quadrats
  • Microbiology
  • Germination
  • Decay
• 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)
  • Describe the equipment used for measurements
  • Discuss safety precautions like using goggles, gloves, etc.
  • Discuss ways to improve accuracy and reduce errors (e.g. taking repeat measurements, using proper techniques)
  • Use bullet point format to clearly communicate points
• Microscopy


  1. Prepare a thin layer of onion skin

  2. Place on microscope slide and add iodine stain

  3. Place cover slip

  4. Start with lowest magnification objective lens

  5. Use coarse and fine focus to bring specimen into focus

  6. Switch to higher magnification objective if needed
• Micrometre


  Unit of measurement equal to 10^-6 metres
• Osmosis


  1. Cut equal-sized cylinders from vegetable

  2. Remove ends to expose permeable surface

  3. Place in test tubes with different sugar solution concentrations

  4. After set time, remove, dab dry, and reweigh

  5. Calculate percentage change in mass

  6. Plot against solution concentration to find concentration with no osmosis
• Enzymes


  1. Measure volume of enzyme and substrate solutions

  2. Mix together and start timer

  3. Every 10 seconds, remove sample and test for presence of substrate using iodine

  4. Record time until no colour change (endpoint)

  5. Repeat with different temperatures or pH values

  6. Plot time against temperature/pH and identify optimum
• Food tests


  1. Grind solid food in water to make a solution

  2. Test for starch using iodine

  3. Test for glucose/simple sugars using Benedict's solution

  4. Test for proteins using Biuret reagent

  5. Test for lipids by adding ethanol then water
• Photosynthesis


  1. Set up pond weed in inverted test tube or measuring cylinder

  2. Cut stem at angle and add sodium hydrogen carbonate

  3. Measure distance from light source

  4. Wait 1 minute for photosynthesis to reach constant rate

  5. Count bubbles or measure oxygen volume in 1 minute

  6. Repeat at different distances

  7. Plot bubbles/oxygen against distance
• Reaction times


  1. Hold ruler between partner's finger and thumb

  2. Drop ruler without warning and have partner catch it

  3. Calculate reaction time using equation of motion
• Quadrats


  1. Use random number generator to choose quadrat positions

  2. Count organism in each quadrat

  3. Calculate mean number per quadrat

  4. Multiply by total area to estimate population
• Biotic factors


  Factors related to living things that affect population density
• Abiotic factors


  Non-biological factors that affect population density
• Microbiology


  1. Spot different bacterial cultures on agar and observe growth

  2. Spread culture to make a lawn and add antibiotic discs

  3. Use aseptic technique to prevent contamination
• Germination


  1. Place seeds on damp cotton wool in Petri dish

  2. Observe root growth (geotropism) and shoot growth (phototropism)
• Decay


  1. Measure volume of milk/cream

  2. Add sodium carbonate and phenolphthalein indicator

  3. Add lipase enzyme

  4. Measure time for solution to decolorize at different temperatures

  5. Plot time against temperature to find optimum