RP1

• Caffeine


  A stimulant which increases heart rate by increasing release of excitatory neurotransmitters
• Daphnia


  • Water fleas with a translucent body through which the heartbeat can be observed
  • Used to measure the effect of caffeine on heart rate
• Equipment


  • Daphnia
  • Cavity slides
  • Dropping pipettes
  • Distilled water
  • Caffeine solution
  • Cotton wool
  • Test tubes
  • Stop clock
  • Filter paper
  • Optical microscope
• Method


  1. Dilute caffeine solution with distilled water to produce different concentrations

  2. Place cotton wool on cavity slide, add one water flea

  3. Use filter paper to absorb water around flea

  4. Add a few drops of distilled water to slide

  5. Use stop clock to time a minute and record number of heartbeats

  6. Repeat experiment, replacing distilled water with caffeine solution
• Do not use a coverslip to prevent conditions from becoming anoxic
• Hazards


  • Biohazard - Contamination
  • Broken glass - Cuts from sharp object
• Safety Precautions


  • Use disinfectant; wash hands with soap after handling Daphnia
  • Take care when handling glassware; keep away from edge of desk
• Emergency Procedures


  • Seek assistance
  • Elevate cuts; apply pressure; do not remove glass from wound; seek medical assistance
• Graph


  Plot a graph of heart rate against caffeine concentration
• It is important to treat the Daphnia ethically during the experiment and release them back into a stream/pond afterwards