Required practicals

• RP1: Microscopy

  Peel a thin onion epidermal layer using forceps.

  Place the peeled layer on a slide with water, ensuring flat positioning.

  Apply 2 drops of iodine solution to stain the cells.

  Gently position a cover slip, avoiding air bubbles.

  Place the slide on the microscope stage, select low power objective, and use coarse adjustment for initial focus.

  Switch to high power objective, repeat focusing process, using the fine adjustment knob for detailed observation.
• RP2: Microbiology

  1. Spray the bench you are working on with disinfectant then wipe dry with paper towels.

  2. On the bottom of the agar plate (not the lid) mark with a wax pencil / permanent marker:

  a. 3 segments

  b. a dot in the middle of each segment

  c. your initials, date, name of bacteria as seen below

  3. Wash your hands with antibacterial handwash.

  4. Place the different antiseptics onto different filter paper discs.

  5. Lift the lid of the agar plate at an angle carefully and use forceps to place each filter paper disc onto the dots. Note down the antiseptic applied to each zone.

  1. Tape the lid onto the agar plate securely, but loosely enough that oxygen can still reach the bacteria.

  6. Place the agar plate in the incubator at 25°C for 48 hours
• Safety RP2

  Disinfect the bench you are working on

  Wash your hands with antibacterial hand wash

  Keep incubator at 25 degrees in a school setting to prevent harmful pathogens growing
• How do you calculate the clear area zones? RP2

  Measure the diameter of the clear zones after 48 hours using a ruler. Take a second measurement at 90 degrees from your first measurement and take a mean for the diameter.

  Do not remove the lid when taking measurements.

  Record the results in a table as seen below. The area of the clear zones can be calculated using the formula pie x r squared
• How do you test for starch? Any changes? (RP4: Food Tests)

  1. Put some food sample in a test tube

  2. Add a few drops of iodine solution

  The colour should be from browny-orange to blue/black
• How do you test for lipids? Any changes? What type of test is this called? Any safety precautions? (RP4: Food Tests)

  1. Add a few cm3 of ethanol to the food sample

  2. Pour this mixture into a test tube of equal volumes of distilled water

  3. If lipids are present, a white emulsion is formed on the surface of the mixture

  Wear eye protection for safety. Ethanol is highly flammable and harmful
• How do you test for reducing sugars? Any changes? (RP4: Food Tests)

  1. Add an equal volume of Benedict's Solution to the food sample in a test tube

  2. Place the test tube in a rack into a hot water baths for a few minutes.

  3. If a reducing sugar is present, a brick red substance will form
• How do you test for proteins? Any changes? (RP4: Food Tests)

  1. Add a few drops of Biuret's reagent to the food sample in a test tube

  2. Shake the solution to mix and wait a few minutes

  3. If protein is present, the solution turns form blue to purple
• RP06 Photosynthesis

  1. Place a test tube rack containing a boiling tube 10 cm away from the light source, measured using the ruler.

  2. Fill the boiling tube with a fixed volume of sodium hydrogen carbonate solution.

  3. Place the cut pondweed into the boiling tube with the cut end at the top. Gently push the pondweed down with the glass rod.

  4. Leave the boiling tube to rest for 5 minutes.

  5. Start the stopwatch and count the number of bubbles produced in one minute.

  6. For each light intensity/distance, repeat the count twice more and take a mean.

  7. Record in a table as seen below.

  8. Repeat steps 1-7 for 3 more distances (20, 30, 40 cm) of the boiling tube from the light source.

  9. Plot a graph of the rate of photosynthesis (given by the no. of bubbles) against light intensity

  (using the inverse square law, light intensity = 1/distance? between pondweed and light source).
• RP07 Reaction Times

  1. Sit down on the chair and place your forearm of your weaker/non-dominant hand on the table with your hand hanging over the end of the table.

  2. Have your partner hold a ruler with the bottom end in between your fingers so you can practice holding the ruler with 2 fingers.

  3. Have your partner hold the ruler and remove your fingers.

  4. Have your partner hold the ruler in line so that the 0 mark is level with the top of your thumb.

  5. Your partner will drop the ruler without telling you beforehand, and you will catch the ruler as quickly as you can.

  6. Note and record the number level with the top of your thumb after you have caught the ruler in a table such as below.

  7. Repeat the test at least 5 times.

  8. Swap places with your partner and repeat steps 1-7.

  9. Find reaction times by using a conversion table to convert the ruler measurements.
• RP08 Plant responses

  1. Pour a fixed volume of water into 3 petri dishes and add cotton wool.

  2. Place 10 seeds in each petri dish.

  3. Place the petri dishes in a warm location eg. incubator, not to be disturbed.

  4. Allow time for the seeds to germinate. If necessary, add more water to the petri dishes (same volume for each dish).

  5. If not all the seeds have germinated into seedlings, remove any excess ones so that the petri dishes have the same number of seedlings.

  6. Place one petri dish in full sunlight by a window. Place a second petri dish in partial sunlight. Place a third petri dish in darkness in a cupboard.

  7. Use a ruler to measure the height of each seedling every day for at least a week. Record in a table as seen below.

  8. Find the mean height of the seedlings each day.
• RP09 Field Investgation (Use random sampling to estimate the population size of a plant species.)

  1. Use a random number generator to obtain 2 numbers, which are to be used as coordinates to find a location on the 2 tape measures set up.

  2. Set down the quadrat at the coordinates.

  3. Count and record the number of the required plant species in the quadrat.

  4. Repeat steps 1-3 to take 9 more samples.

  5. Estimate the population size using this formula:

  area sampled / total area x number of plant species counted
• RP09 Field Investigation (Use continuous sampling with a transect line to investigate the effect of variation in a factor on the distribution of a plant species)


  1. Write down a hypothesis of the effect of a change in an abiotic factor (eg. light intensity) on the distribution of the plant species.

  
  

  2. Lay down a tape measure from the base of a tree to an open area of ground/ along a location with an ecological gradient.

  
  

  3. Place the quadrat along the 'O' end of the tape measure, with one corner touching the 'O' mark.

  
  

  4. Count the number of plants and record it in a table as seen below.

  
  

  5. Place the quadrat 5 m up the tape measure and repeat step 3.

  
  

  6. Repeat step 4 at 5 m intervals until you reach the end of the transect line.

  
  

  7. Gather data from your class to find the mean number of plants at each point along the transect.

  
  

  8. Plot a graph of 'number of plants' against the ecological gradient that is observed as the distance along the transect line increases. Compare your results to your hypothesis.
• RP10: Decay

  Prepare 3 beakers of full fat milk and measure the initial pH reading with a pH probe

  Put each beaker in a place of different temperature by placing them into separate water baths : Beaker 1 - 0 degrees celsius, Beaker 2 - 30 degrees Celcius Beaker 3 - 80 degrees celsius

  Measure the pH of each beaker of milk for 6 days, beaker 2 will have the lowest ph as it is at optimal conditions for the enzymes, neither 1 nor 3 will have much change if any