The Effects of Drugs on Daphnia
Activity: Book based Life science
Grade level: 6th
Introduction:
Drugs are chemicals that make our body react differently than they normally do.
Drugs are classified into two types. These types are called stimulants and depressants.
Stimulants cause body functions to increase or go faster than they were before the drug
was taken. Depressants cause body functions to decrease or go slower than they were
before the drug was taken. Some of the body functions that drugs effect are the number
of times the heart beats, the number of breathes taken, the energy level a person has and
the amount a person sweats. In the lab today, we will be using a stimulant and a
depressant.
The chosen stimulant for the lab is Caffeine. Caffeine appears in many soft
drinks, coffee, tea, chocolate and other things. Since caffeine is a stimulant, it will cause
an increase in the body functions. Caffeine is very common, but it is also very powerful.
The chosen depressant for the lab is Chamomile. Chamomile is a flower that
contains chemicals that act as a depressant. Chamomile has been used for centuries to
soothe and calm. It is usually brewed as a tea.
The animal used in this lab is daphnia. Daphnia have also been called the water
flea because they are completely aquatic. They cannot leave water, if they do they will
die. Daphnia have a multiple number of cells in their bodies, just like we do. The effects
of the drugs can be viewed by watching and counting the heartbeat of the daphnia.
Purpose:
This lab will introduce students to daphnia. The lab will also have students
realize the effect drugs can have on an organism. Also, the students will be able to
identify drug as stimulants or depressants. This decision will be based on the effect the
drugs have on an organism.
Equipment and Materials:
Microscope
daphnia
96 well microplate
strong coffee
4- thin stem pipettes
strong Chamomile tea
Stopwatch, or clock with seconds on it
water
Safety:

Do not trip over the extension cords.
Procedure: The effects of Caffeine
1. Use the thin stemmed pipette to put 10 drops of water in well B7 of the
microplate. Make sure the water is room temperature.
2. Put one daphnia into well B7 of the microplate. Use the pipette that is labeled
for the daphnia container.
3. Set the microscope on low power.
4. Place the well microplate on the microscope stage underneath the lens.
5. Find and observe the heartbeat of the daphnia.
6. Have one person count the number of heartbeats, while another group member
is watching the clock. Count the heartbeats for 10 seconds. Write this
number down in the data table, in the Caffeine section under Daphnia and
water.
7. Using the pipette labeled caffeine, add one drop of coffee to the same well
with the daphnia.
8. Observe the heartbeat again. Count the number of heartbeats for 10 seconds.
Write this number down in the data table under Daphnia, water and Caffeine.
9. Put the daphnia into the container labeled Daphnia and Caffeine.
The Effects of Chamomile:
1. Use the thin stemmed pipette to put 10 drops of water in well B8 of the
microplate. Make sure the water is room temperature.
2. Put one daphnia into well B8 of the microplate. Use the pipette that is labeled
for the daphnia container.
3. Set the microscope on low power.
4. Place the well microplate on the microscope stage underneath the lens.
5. Find and observe the heartbeat of the daphnia.
6. Have one person count the number of heartbeats, while another group member
is watching the clock. Count the heartbeats for 10 seconds. Write this
number down in the data table under Daphnia and water in the Chamomile
section.
7. Using the pipette labeled chamomile, add one drop of tea to the same well
with the daphnia.
8. Observe the heartbeat again. Count the number of heartbeats for 10 seconds.
Write this number down in the data table under the chamomile in the space for
Daphnia, water and Chamomile.
9. Put the daphnia into the container labeled Daphnia, and Chamomile.
10. Once you have done both samples, find the number of heartbeats that Caffeine
changed. Then find the number of heartbeats that the Chamomile changed.
Data Table
The Effects of Drugs on Daphnia
Name: _______________________________
Date: ______________
Daphnia and Caffeine from well B7:
Daphnia and water
Number of heartbeats in ten seconds: _______________
Daphnia, water and caffeine
Number of heartbeats in ten seconds: _______________
Number of heartbeats changed by caffeine: ___________________
Daphnia and Chamomile from well B8:
Daphnia and water:
Number of heartbeats in ten seconds: ________________
Daphnia, water and Chamomile:
Number of heartbeats in ten seconds: ________________
Number of heartbeats changed by Chamomile: _______________
Questions:
1. Which drug caused the greatest change in the number of heartbeats?
2. a. What do you think will happen to the number of heartbeats in the daphnia,
if the amount of caffeine in the coffee is increased?
b. What do you think will happen to the number of heartbeats in the daphnia,
if the amount of Chamomile in the tea is increased?
3. a. How could the amount of Caffeine in the coffee be increased?
b. How could the amount of Chamomile in the tea be increased?
Teacher’s Notes
The Effect of Drugs on Daphnia
Lab time: 40 minutes
Preparations:
Time: 15 minutes
T: Daphnia are small multicellular organisms that look a little like a teardrop
with two eyes, and two legs out front. They are completely aquatic
organisms that must remain in some type of liquid their entire life.
T: During the lecture time for the lab, concentrate on the drugs and the effect
it should have on organisms, especially if this lab is being used in
conjunction with a health unit.
T: Brew the cup of coffee with twice the recommended amount of grounds.
Along the same lines, brew the cup of tea with twice the recommended
amount of tea. Brew these samples the day before the lab. Bring both the
solutions to room temperature and then refrigerate until the next day.
T: On the day of the lab, pull the solutions out of the refrigerator and let them
warm up to room temperature before use. If room temperature in the
solution is not reached, the effect of temperature will be tested, instead of
the effect of the drug on the organisms.
V: The van can supply microscopes, daphnia and needed materials upon
request.
Answers to Questions:
1. Which drug caused the greatest change in the number of heartbeats?
Caffeine should produce better results.
2. a. What do you think will happen to the number of heartbeats in the daphnia,
if the amount of caffeine in the coffee is increased?
The more caffeine the faster the heart rate. Which also means a higher
number of heartbeats.
b. What do you think will happen to the number of heartbeats in the daphnia,
if the amount of chamomile in the tea is increased?
The stronger the drug the more the effect. Which in this case results in a
slower heart rate.
3. a. How could the amount of Caffeine in the coffee be increased?
Increase the amount of coffee grains used when brewing. Or an amount of
water could be evaporated off.
b. How could the amount of Chamomile in the tea be increased?
Brew the tea longer, use another tea bag, or evaporate some water off
Considerations:
One consideration would be to change the drugs to accommodate specific lecture
material. Many different and common drugs can be used. It is recommended to stick
with two different kinds of drugs though.
Another consideration would be to use brine shrimp instead of daphnia. Brine
shrimp can get fairly large. If brine shrimp are used, count the number of swimming
strokes instead of the number of heartbeats. One way to define the stroke of the brine
shrimp would be to count every time the front end of the fin starts the stroke.
Source:
Russo, Tom (1996) Consumer Microchemistry: Student and Teacher’s Manual. Theta
Technologies. pages 71-73, 111-112.