All of the biology required practicals

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Cards (12)

  • 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)
    • 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 take a thin layer of onion skin
    2. Place it on a microscope slide and 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 filled 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 (same as the concentration in the cells)
  • Enzymes

    1. Measure out a set volume of the enzyme (e.g. amylase) and substrate (e.g. 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. For solid foods, grind them in water to make 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 indicates amount of sugar)
    4. Test for proteins by adding biuret reagent (turns purple)
    5. Test for lipids by adding ethanol and then water (cloudy solution indicates lipids)
  • 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 the pondweed
    4. Count the bubbles of oxygen released or measure the volume of oxygen made in a set time
    5. Repeat at different distances and plot the results against distance (should be a curve due to inverse square law)
  • 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 they catch it as fast as they can
    3. Calculate the reaction time using the distance fallen and acceleration due to gravity
    4. Repeat multiple times and calculate the mean reaction time
    5. Can also test how reaction time changes with an independent variable like distractions or stimulants
  • Quadrats

    1. Use a random number generator to choose grid positions to place the quadrat
    2. Count the number of the chosen organism inside each quadrat
    3. Sample 10% of the total area to get an accurate estimate
    4. Calculate the mean number per square meter and multiply by the total area to estimate the population
    5. Can also use a transect line to see how population density varies with distance
  • Microbiology

    1. Spot different bacterial cultures on agar and observe how they grow over time
    2. Or spread a culture over the agar to make a lawn and put drops of antibiotics or paper discs soaked in them
    3. Use aseptic technique - sterilize equipment by passing through a Bunsen flame
    4. Open dishes only briefly towards the Bunsen flame to prevent contamination
    5. Secure lids with minimal tape to allow air flow for aerobic respiration
    6. Measure the diameters or areas of the bacterial colonies or antibiotic inhibition zones
  • Germination

    1. Place seeds (e.g. cress) on damp cotton wool in a Petri dish
    2. Leave in the dark and observe the roots growing downwards due to geotropism
    3. Allow a small amount of light and observe the shoot growing towards the light due to 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 maintain a set temperature
    3. Time how long it takes for the solution to decolorize as the milk decays
    4. Repeat at different temperatures and plot the time taken against temperature (should be a curve with an optimum)