required practicals

• Method

  1. Dilute the caffeine solution with distilled water to produce several different concentrations.
  2. Place some cotton wool (to restrict movement) on a cavity slide. Add one large water flea.
  3. Use filter paper to absorb the water around the flea.
  4. Then use a dropping pipette to add a few drops of distilled water to the slide. Do not use a coverslip to prevent conditions from becoming anoxic.
  5. Use a stop clock to time a minute and record the number of heartbeats.
  6. Repeat the experiment, replacing the distilled water with a caffeine solution.