The Effects of Stimulants and Depressants on Daphnia – Lab 10 Extension
Objective: To learn to identify stimulants and depressants by their effect on the heart rate of Daphnia
Materials: - Culture of Daphnia magna - Solutions of: - Cotton o Caffeine - Depression slides o Epinephrine - Pipettes o Ethyl Alcohol - Daphnia form and structure sheet o Nicotine - Stopwatch
Procedure 1. Obtain a depression slide and cover slip.
2. Using a pipette, draw up 1-2 daphnia from the culture dish. Using the Daphnia dropper, catch a large Daphnia and place it in the depression slide along with some of the Daphnia water. Observe it under the stereoscope on low light so that you can familiarize yourself with the location of the Daphnia's heart and also the rest of its anatomy. Turn the light off when you are not directly observing the Daphnia as the light warms them, causing their heart rate to increase. Let the Daphnia get used to its life in the depression slide for two minutes before putting a cover slip on top of it to hold it in place.
3. Time the heart rate. To do this, have your partner use the stopwatch and tell you when to begin counting. Count for 10 seconds. Enter this heart rate in the Data Tables and compute the heart rate per minute by multiplying by 6.
4. Repeat this procedure 2 more times and find the average heart rate of a Daphnia. Enter this information into the data table.
5. Remove the cover slip and sponge off the liquid around the Daphnia by putting a corner of a piece of Kleenex into the liquid. Be careful not to sponge up the Daphnia. Add a drop of caffeine solution to the Daphnia. Wait one minute for the solution to be absorbed, and compute the average heart rate as performed above. Enter whether the caffeine is a stimulant to depressant. If, after observing your Daphnia and recording your observations, you see that its heart is still beating, put your Daphnia into the beaker of water labeled “Tested Daphnia.” Clean our your slide.
6. Obtain another daphnia. Computer the average heart rate.
7. Repeat steps 2-6, using the epinephrine, ethyl alcohol, and nicotine. Fill out the data tables as your work through the different substances.
Control Heart Rate Per Min (x6) Treated with Caffeine Heart Rate per min (x6) Heart rate/10 sec. Trial 1 Heart rate/10 sec Trial 1 Trials 2 Trial 2 Trial 3 Trial 3 Average heart rate per Average heart rate per minute minute Stimulant or Depressant Control Heart Rate Per Min (x6) Treated with Heart Rate per min (x6) Epinephrine Heart rate/10 sec. Trial 1 Heart rate/10 sec Trial 1 Trials 2 Trial 2 Trial 3 Trial 3 Average heart rate per Average heart rate per minute minute Stimulant or Depressant
Control Heart Rate Per Min (x6) Treated with Ethyl Heart Rate per min (x6) alcohol Heart rate/10 sec. Trial 1 Heart rate/10 sec Trial 1 Trials 2 Trial 2 Trial 3 Trial 3 Average heart rate per Average heart rate per minute minute Stimulant or Depressant
Control Heart Rate Per Min (x6) Treated with Nicotine Heart Rate per min (x6) Heart rate/10 sec. Trial 1 Heart rate/10 sec Trial 1 Trials 2 Trial 2 Trial 3 Trial 3 Average heart rate per Average heart rate per minute minute Stimulant or Depressant
Post – lab 1. Which substances were stimulants, which were depressants?
2. Would it be safe to conclude these substances would have similar effects in humans? Explain.
3. There are many substances in your body that act as stimulants and depressants. Propose a situation where your body might need a stimulant. Propose a situation where your body might need a depressant.
4. Why was it necessary to start with a new Daphnia after each substance?
5. Design an experiment that would test the effect of temperature on a daphnia.
Extension – Research Paper
Research the effects of caffeine, nicotine, alcohol, and epinephrine on the human heart and body. Explain the reaction they have in the human body, and explain WHY they cause that reaction. Are they vasodilators or vasoconstrictors? What is happening in your circulatory system when a human uses these substances? Then, compare that information to your findings on how these substances affect daphnia.