biology paper one core practicals

• microscopy core practical

  • peel off thin layer of onion using forceps
  • mount layer onto the microscope slide, make sure the layer lies flat
  • add a drop of iodine stain to stain the cells
  • place coverslip on slowly, making sure no air bubbles are trapped
  • rotate objective lens so that the low power is in line with the stage
  • turn the course focus so that the stage is close as close to the objective lens as possible
  • place microscope slide in the centre of the stage
  • focus slide
  • record image then rotate the objective lens so that the high power is in line with the stage
• osmosis core practical

  • use a cork borer to cut out 5 identical potato cylinders
  • trim the cylinders using a sharp knife and ruler to be same lengths
  • measure and record the lengths and mass of each cylinder
  • measure equal quantities of the sugar solution and add to the boiling tube making sure to label them
  • add a potato cylinder to each tube
  • leave cylinders overnight in a test tube rack
  • remove cylinders and lightly pat dry
  • measure the lengths and mass of each cylinder and calculate the percentage change
• food test core practical

  • take a food sample and then crush it diluted water and with a pestle and mortar
  • add the paste into a beaker and add more distilled water. stir the solution
  • filter it and then add dish soap to solution in order to break down cell walls
• photosynthesis core practical

  • take a boiling tube and place it away from a Lightsource e.g. lightbulb
  • fill boiling tube with sodium hydrogen carbonate solution - the solution releases carbon dioxide which is needed for photosynthesis
  • put a piece of pondweed into boiling tube with the cut end at the top
  • leave for 5 minutes to ensure it has acclimated to the conditions in the boiling tube
  • start a stopwatch and count the number of bubbles produced in one minute
  • repeat 2 more times to calculate a mean
  • repeat experiment by increasing distance of boiling tube from light