Required Practicals

  • Created by: harrypj03
  • Created on: 03-03-19 19:30
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  • AQA GCSE Biology: Required Practicals
    • Using a microscope
      • Method: Collect sample, remove inner skin of onion, place on slide, add iodine as stain, drop coverslip on
        • Place on stage, lowest objective lens, turn coarse focus, turn fine focus, increase magnification
          • Magnification= image size / object size
    • Osmosis in plants
      • Method: Create potato cylinders of same mass. Place into 3 different solutions (pure, slightly salty, v. salty), leave for 30 mins, dry, reweigh
        • Find change in mass. Decide is solution is hypertonic (mass increase), hypotonic (mass decrease) or isotonic (same)
      • Keywords: Hypotonic - solution w/ lower conc. than something else (water moves away) Isotonic - solution w/ same conc. (no change) Hypertonic - solution w/ higher conc. (water moves towards)
    • Food tests
      • Starch Carbohydrate
        • Grind food, add iodine
          • Yellow red --> Blue black = present
      • Sugar Carbohydrate
        • Grind food, add Benedict's, heat
          • Blue --> Brick red  = present
      • Protein
        • Grind food, add biuret
          • Blue --> purple = present
      • Lipids
        • Grind, add ethanol
          • Clear --> cloudy white layer = present
            • HAZARD: Ethanol = flammable & harmful
    • Impact of pH on amylase
      • Method: add a range of pH buffers to 5 test tubes half-filled with amylase. Add starch solution. Swirl to mix, and start timer. Every 30s, remove some from each mixture and add to each spotting tile
        • Add iodine solution to the drops made, and if drop turns yellow-red to blue-black, amylase hasn't yet worked. Repeat until iodine hasn't turned blue black, record time.
          • Optimum pH is that which didn't turn blue-black first
    • Bacterial Growth
      • Method: separate an agar plate into sections. Label each section as a different antibacterial. Dip a small paper disk into each antibacterial, then place gently into agar gel
        • Make sure one paper disk is left clean as a control. Leave agar in 25?c for a week, record zones of inhibition. Largest area of zone = best antibacterial
    • Rate of Photosynthesis
      • Method: Place pondweed in boiling tube. Record temperature of water. Place lamp 15 cm away, could how many bubbles are produced per minute
        • Repeat this, increasing the distance from the lamp. The fact that increasing distance decreases rate of photosynthesis shows that light intensity is a factor
    • Reaction times
      • Method:  Split test group into two. Give one group water and one coffee. Hold a ruler between the finger and thumb at 0cm. Without warning, drop the ruler. Record how many cm it takes to catch the ruler
        • Repeat and find the average for each group. Compare to show the effect of caffeine on reaction times
    • Plant hormones & responses
      • Method: get two Petri dishes. Place cotton wool pad and add a small amount of water. Scatter a few cress seeds, and place each dish in different levels of light (one in light from only one angle and one from light at all angles)
        • The plant with light from one direction will grow in that direction, showing phototropism.
    • Distribution & abundance
      • Method: Choose a habitat and calculate its total area. Divide the habitat into co-ordinates, then randomly select a series of co-ords. Place the quadratic in tis area, and count the number of organism in the area.
        • Calculate the average number of organism per 1m^2 quadrat, and multiply by the area of the habitat to find an estimate for the total number of organisms.
    • Rates of decomposition
      • Method: prepare 6 test tubes with 5cm^3 of full fat milk. In a different 6 tubes, add 3cm^3 of lipase. Add 5 drops of Cresol red to the milk tubes, it should turn purple.
        • Heat each pair of milk and lipase in different temperature water baths. Leave until temperature reaches that of the bath. Add each pair together and record time for cresol red to turn yellow.
          • The different temperatures show the affect of temperature on decomposition.


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