Practicals

• Biology practical: Microscopy


  Thin layer of onion skin placed on a microscope slide using a scalpel and tweezers, add a drop of iodine to stain the cells, place a cover slip on top, adjust the microscope's light or mirror, start with the shortest objective lens, use coarse and fine focus knobs to bring specimen into focus, use a graticule to measure cell size in micrometers
• Biology practical: Osmosis


  Cut equal size cylinders from a vegetable, remove non-permeable skin, dry the surface, weigh the cylinders, place in test tubes with different sugar concentrations, wait a set time, reweigh the cylinders, calculate the percentage difference in mass for each cylinder, plot against solution concentration to find the concentration at which no osmosis occurs
• Biology practical: Enzymes

  Determine the optimum temperature or pH for an enzyme using amylase and starch, change the independent variable (temperature or pH), measure the time taken for starch to be broken down
• Experiment procedure for starch breakdown

  Measure out a set volume of the amylase and starch solutions using a syringe or measuring cylinder, mix together, start the timer, remove a bit of the mixture every 10 seconds and put a drop in the spotting tile dimple with iodine, repeat every 10 seconds until there is no color change, record the time, repeat at different temperatures using a water bath, measure the temperature with a thermometer, or change to a different pH buffer solution
• Experiment procedure for testing nutrients in foods

  Grind solid food using a pestle and mortar, add distilled water to create a solution, test for starch by adding iodine solution (turns black or dark purple if starch is present), test for glucose and simple sugars by adding Benedict's solution and heating using a water bath (color changes from blue to green, yellow, or orange depending on sugar content), test for protein with Biuret reagent (turns from blue to purple in the presence of protein), test for lipids by adding cold ethanol and observing if the solution goes cloudy
• Experiment procedure for photosynthesis

  Determine the relationship between light intensity and rate of photosynthesis using pond weed submerged in water, cut the stem at an angle, add sodium hydrogen carbonate to promote oxygen release, measure the distance between the light source and pond weed, acclimatize the pond weed in the dark, start counting bubbles or measure the volume of oxygen made, repeat at different distances, plot bubbles or volume of oxygen against distance
• Reaction time experiment procedure

  Hold a ruler between lab partner's finger and thumb, drop it without warning for partner to grab as fast as possible, calculate reaction time using Newton's equation of motion, consider acceleration due to gravity, do repeats and calculate means, introduce independent variables like distractions or stimulants to see how reaction time changes
• Quadrat experiment procedure

  Use a quadrat to estimate the population of an organism in an area, choose grid positions randomly using a number generator, place the 1m square quadrat
• Using a quadrat to estimate the population of an organism in an area

  1. Use a random number generator to choose grid positions in the area to place the 1m² quadrat over

  2. Count the number of the chosen organism inside each grid position

  3. Sample 10% of the total area to give an accurate estimate

  4. Calculate the mean number per square meter

  5. Multiply this by the total area in square meters to estimate the total population
• Combining a quadrat with a transect


  1. Move the quadrant up the transect 1m at a time

  2. Plot population density against distance

  3. Create a graph to visualize the population density variation
• Factors affecting population density
• Microbiology practicals

  1. Spot different bacteria cultures on agar in a petri dish and observe their growth over time

  2. Spread a culture all over the agar to make a lawn and test antibiotics

  3. Ensure sterile technique by flaming equipment before use

  4. Incubate for a number of days

  5. Measure diameters of colonies or areas with no bacteria

  6. Germination process with seeds on damp cotton wool in a Petri dish

  7. Decay experiment with milk, sodium carbonate, phenolphthalein, and lipase enzyme

  8. Use a water bath to control temperature and a stop clock to measure time taken for decolorization

  9. Plot times against temperature to observe the rate of reaction