Required biology’s practicals

• Eyepiece


  The part of the microscope that you look into
• Objective lenses


  The lenses on the microscope that have different magnification numbers
• Calculating magnification


  Multiply the objective lens number by the eyepiece number
• Preparing a slide


  1. Spread cells on slide

  2. Add dye (e.g. iodine)

  3. Add cover slip
• Viewing a slide


  1. Start with lowest magnification objective lens

  2. Use coarse focus wheel

  3. Use fine focus wheel

  4. Draw image without shading
• Magnification calculation


  Magnification = Image size / Real size
• Osmosis is the movement of water from a dilute solution to a concentrated solution through a partially permeable membrane
• Osmosis practical


  1. Cut vegetable pieces of similar size

  2. Weigh pieces

  3. Place in different sugar solutions

  4. Leave for 24 hours

  5. Reweigh pieces

  6. Calculate percentage change in mass
• Osmosis practical results


  • Increase in mass for dilute solutions
  • Decrease in mass for concentrated solutions
  • Graph shows point where no change in mass (equal internal and external concentrations)
• Enzyme activity practical


  1. Heat water bath to 37°C

  2. Add amylase and pH buffer to boiling tube

  3. Add starch and start timer

  4. Every 30 seconds, take sample and add to iodine-containing well on spotting tile
• Iodine turns black when it reacts with starch
• Iodine test for starch

  1. Add a couple of drops of iodine to each well

  2. Iodine turns orange-brown
• Amylase enzyme test


  1. Add 5 cm³ of starch to boiling tube

  2. Start stopwatch

  3. Take samples every 30 seconds

  4. Add samples to wells

  5. Wells turn black at first, then brown, then orange
• Rate of reaction


  Calculated as 1000 / time (seconds)
• Food tests


  • Starch (iodine test)
  • Sugar (Benedict's test)
  • Protein (Biuret test)
• Measuring rate of photosynthesis

  1. Cut 10 cm of pond weed

  2. Submerge in water in boiling tube

  3. Clamp tube

  4. Measure bubbles produced in 1 minute at different distances from lamp

  5. Repeat at 40 cm, 30 cm, 20 cm, 10 cm
• Variables


  • Independent: Distance lamp to pond weed
  • Dependent: Bubbles per minute
  • Control: Pond weed type, length, lamp power, temperature
• Inverse square law for light intensity only applies to A-level
• For GCSE, know that as distance increases, light intensity decreases
• Investigating effect of antibiotics on bacteria

  1. Prepare uncontaminated bacterial cultures

  2. Seed agar plates with E.coli and Streptococcus

  3. Place paper discs with different antibiotics on plates

  4. Incubate plates

  5. Measure zone of inhibition around each antibiotic disc
• Zone of inhibition


  Area around antibiotic disc where no bacteria are able to grow
• Antibiotics are specific - different antibiotics work better on different bacteria