Core Practical 1

• What type of substance is caffeine in humans?

  Stimulant
• How does caffeine affect heart rate in humans?

  It increases heart rate by increasing neurotransmitters
• What organism is used to measure the effect of caffeine on heart rate?

  Daphnia
• Why are Daphnia chosen for this experiment?

  They have a translucent body for observation
• What equipment is needed for the caffeine experiment?

  • Daphnia
  • Cavity slides
  • Dropping pipettes
  • Distilled water
  • Caffeine solution
  • Cotton wool
  • Test tubes
  • Stop clock
  • Filter paper
  • Optical microscope
• What are the steps in the method for the caffeine experiment?

  1. Dilute caffeine solution with distilled water.
  2. Place cotton wool on a cavity slide and add Daphnia.
  3. Use filter paper to absorb water around the flea.
  4. Add distilled water without a coverslip.
  5. Time for one minute and record heartbeats.
  6. Repeat with caffeine solution.
• What should be done to restrict Daphnia's movement during the experiment?

  Add cotton wool on the cavity slide
• Why should a coverslip not be used in the experiment?

  To prevent conditions from becoming anoxic
• How long should the heartbeats be timed for?

  One minute
• What is the purpose of repeating the experiment with caffeine solution?

  To compare heart rate with distilled water
• What are the hazards and safety precautions in the experiment?

  Hazards:

  • Biohazard contamination
  • Broken glass

  
  

  Safety Precautions:

  • Use disinfectant and wash hands after handling Daphnia
  • Handle glassware carefully and keep it away from edges
• What should be done in case of a biohazard contamination emergency?

  Seek assistance
• What is the risk level associated with biohazard contamination?

  Low
• What should be done if broken glass causes cuts?

  Elevate cuts and apply pressure
• What should be plotted on a graph in this experiment?

  • Heart rate
  • Caffeine concentration
• What conclusion can be drawn from the experiment regarding caffeine and heart rate?

  Caffeine increases heart rate by stimulating neurotransmitters
• What ethical consideration should be taken when using Daphnia in experiments?

  Release them back into a stream/pond
• What happens to Daphnia's heart rate as caffeine concentration increases?

  • Heart rate increases
  • Due to increased release of stimulatory neurotransmitters