Daphnia on Drugs

Prepared by Joan K. McLaughlin-Johnston

This laboratory is an enjoyable, safe, hands-on learning experience for students. As a consequence of its adapted cooperative learning format and constructivist procedural setup, it addresses many learning styles and ability levels that may be present in a diverse classroom population.


How do various chemicals affect the heart rate of a Daphnia?


microscope medicine dropper depression slide
coverslip paper towel stopwatch
calculator Daphnia coffee solution
tea solution aspirin solution cigarette solution
scotch solution sleeping pill solution adrenalin solution


1. When students have completed reading the written directions, have them prepare a data table to record their observations.
2. Assign each team a specific chemical to test.
3. Use the medicine dropper to withdraw a Daphnia from the container in which it is stored. Place the Daphnia together with a few drops of water from the container into a well in the depression slide. Cover the Daphnia with a coverslip.
4. Observe the Daphnia under low power. Locate the heart using the diagram provided. Locate the various organs labeled.
5. Using your stopwatch, record how many heartbeats you can count in one minute. Record the heartrate in your data chart.
6. Repeat for two additional trials. Record your data. Calculate the average heartrate of your daphnia.
7. Use the medicine dropper to transfer two drops of assigned chemical to one edge of the coverslip. Draw the chemical across the specimen by placing a piece of paper towel at the opposite edge of the coverslip.
8. Determine the effects of the chemical on the heartbeat by repeating steps #4 and #5.
9. Prepare a graph of the data you have collected on the heartbeat both before and after exposure to the chemical assigned.


1. Describe the Daphnia's heartrate.
2. What was the Daphnia's heart rate before exposure to the chemical?
3. What was the Daphnia's heart rate after exposure to the chemical?


1. What effect did the chemical have upon the Daphnia's heart rate?
2. What do we call drugs that cause an increase in heart rate in humans?Reference
3. What do we call drugs that cause a decrease in heart rate in humans?Reference
4. Describe the graphs of the data collected, what do they indicate about the heart rates?
5. Using either the Teacher or Student Topic links from our web page "Effects of Drugs on the Nervous System" design a route to trace the movement of the specific drug (chemical) you worked with today through the human nervous system. Be creative, use diagrams, pictures (your own/off web) to support your ideas.

PROJECT (topics)

  1. Design a psychoactive drug:
    1. Name it
    2. Tell its purpose
    3. How will it be introduced into the body
    4. Which part of the nervous system is its target site
    5. Where are its receptor cites
    6. List any beneficial/harmful effects

  2. Roleplay a neuron in synapsis:
    1. You can use students as chemicals
    2. You can design your own chemical diagrams
      • Name and color code chemicals
      • Show proper sequence of events
      • Include a stimulus and a response
      • Identify location in the nervous sysem

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