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The Effect of Different OTC Medications on the Survival Rate of Daphnia

Student Experimenter

Researched by Whitney K


The purpose of this experiment was to determine the effect of Pseudoephedrine, aspirin, and Benadryl on the heart rate of daphnia. 

I became interested in this idea when I learned about zooplankton that live in fresh and salt water. I thought that daphnia were interesting, especially because I could see their heart beating.

The information gained from this experiment could help people understand about how important it is not to dispose of wasteful product into our rivers and streams, because of the way it affects the food chain. If the zooplankton ore harmed, everything above them in the food chain will also be harmed.


My first hypothesis was that aspirin would increase the heart rate of daphnia. I based my hypothesis on an encyclopedia of medicines that said, “Aspirin can speed up the heart”.

My second hypothesis was that Pseudoephedrine would increase the heart rate of daphnia. I based my hypothesis on an encyclopedia of medicines that said, “Pseudoephedrine is a drug that speeds the heart up slightly”.

My third hypothesis was that Benadryl would decrease the heart rate of daphnia. I based my hypothesis on the common known fact that Benadryl can cause drowsiness.  


The constants in this study were: 
  •  The amount of each medications given to the daphnia.
  •  The number of seconds that are recorded to find their heart rate.
  •  The video camera I used to record their heart rate.
  •  The microscope I used to record their heart rate.
  •  The amount of time it takes to film.
  •  The place where I get the daphnia.
  •  The environment that the daphnia are stored.
  •  The type of the daphnia used.
  •  The age of the daphnia.
  •  The type of caffeine.
  •  The type of Pseudoephedrine.
  •  The type of aspirin.
  •  The type of Benadryl

The manipulated variable was the type of medication given to the daphnia. 

The responding variable was the heart rate of the daphnia after each chemical was given to them.  

To measure the responding variable I used a microscope to see the daphnia’s heart beat and a video camera to record the heart beats. I used the slow motion playback to count the heartbeats for 10.0 seconds.  


1                           Microscope
1                           Video camera
1                           Pseudoephedrine pill 
1                           Benadryl pill
1                           Aspirin Pill
1                           Video tape    
3                           Petri dishes
3                           Beakers


1. Gather all of the materials.
2. Set up equipment.
A) Put the microscope on a table.
B) Connect the microscope camera to the microscope.
C) Connect the video recorder to the MC.
3. Fill three beakers with 500 ml of room temperature water (20∞C).
4. Label each beaker:
A) Benadryl 
B) Pseudoephedrine
C) Aspirin 
5. Crush each pill into powder using a clean hammer and aluminum foil, and let dissolve in correct beaker.
6. While waiting for the pills to dissolve start control group.
7. Get a Petri dish and fill it half way with water with a large bore dropper into a second dry Petri dish.
8. Put 11-12 daphnia in just in case some die.
9. Separate the first daphnia from the group.
10. Put the first daphnia under the microscope. Write down tape counter start point.
11. Start recording once there is a clear view of the heart.
12. Stop recording after about ten seconds. Write tape counter stop point.
13. Repeat steps 9-12 with exactly 10 of the daphnia in this group.
14. Once the pills have dissolved conduct trials with all of the different chemicals.
A) Start by filling Petri dish half full of chemical solution to be tested.
B) Place 11-12 “new” daphnia into the chemical solution.
C) Repeat steps 9-13.
15. Clean up the mess.
16. Watch the video in slow motion and count all of the heartbeats per daphnia. Use the time code to determine which daphnia is in each test group.
17. Record data.
18. Graph averages.


The original purpose of this experiment was to determine the effect of Pseudoephedrine, aspirin, and Benadryl on the heart rate of daphnia. 

The results of the experiment was that the Pseudoephedrine sped the daphnia’s heart up, while the other two drugs slowed it down.


My first hypothesis was that aspirin would increase the heart rate of daphnia. This hypothesis has been rejected since the aspirin was 1.2% below the control group. 

My second hypothesis was that Pseudoephedrine would increase the heart rate of daphnia. My hypothesis was accepted since it was 0.8% higher then the control group.

My third hypothesis was that Benadryl would decrease  the heart rate of daphnia. My hypothesis was accepted since it was 4.6% lower than the control group.

The results indicate that my first two hypotheses should be accepted, but the third was rejected.

Because of the results of this experiment, I wonder if the daphnia were subjected to household detergents or cleaners if they would it have a big effect on them?

If I were to conduct this project again I would use more than ten daphnia.


When people dispose of harmful chemicals, or just plain “over the counter” pills it has a big effect on the microorganisms living in the water and other places. As larger organisms eat the tiny organisms we may eventually be eating them, and the harmful toxins we disposed of in the first place. 

An arthropod is the largest phylum of animals. Four out of five of the animal species are arthropods. Arthropods are most commonly found in freshwater and airborne environments. Their size can range from microscopic plankton to an animal seven meters long.

Arthropods have hard exoskeletons and jointed appendages. The appendages are used to feed, and defend.  Arthropods have gills, used to exchange gases. They have tracheal systems (air sacs that enter the body from the pores). An arthropod’s exoskeleton is their greatest defense from their enemy. When they start molting they are the most vulnerable. 

A crustacean is a type of arthropod and an invertebrate with a hard external shell. There are more than 42,000 known species of crustaceans around the world. Crustaceans are important members of aquatic ecology and are the basic food providers. 

There are three main body parts of a crustacean: the head, thorax, and the abdomen. Almost all adult crustaceans have a compound eye that is used to detect motion. Crustaceans can detach body parts to distract predators and have it grow back the next time they molt. Very rarely will crustaceans have a simple eye that can detect light, but not images. 

Some crustaceans will eat each other, but most eat leftover plants or the remains of animals.
Different kinds of crustaceans live in different kinds of places. Some hide in rocks or weeds, others live in sponge or coral, and some even burrow in the mud or sand. 

Daphnia are a type of crustacean and water flea. There are approximately 150 known species of Daphnia in North America. Daphnia pulex are widely used in testing water pollution. Daphnia make good test subjects since the are small, easy to get, and are transparent so that you can see everything going on inside of them.

Daphnia have one compound eye, and two antenna limbs that carry oxygen and food to their mouths. Instead of arms or fins they use their antenna to swim. They have transparent bodies, which means that you can see right through them. You can see their heart beating, without a microscope, and occasionally their food.

Daphnia are extremely tolerant of low quality water. Daphnia can also survive in low oxygen since they can photosynthesize. They can live in temperatures ranging from 64º-72º F. Daphnia are very sensitive to metal ions, copper, zinc, pesticides, detergents, bleaches, and other toxins.

One daphnia can have 13 billion babies in just 60 days. If the temperature of the water is warm the egg will hatch a female, if the temperature of the water is cold the egg will hatch a male. Sometimes the egg has a hard covering that can withstand heat, cold, and dehydration. 

The main goal of medicine is to save lives, relive pain, and keep the self-respect of sick people. Medical researchers are always searching for ways to cure and treat different diseases.

Back in the prehistoric times people thought that evil spirits and gods caused diseases. Some people in the early ages would perform surgery to release the spirits that they thought were causing common headaches.  An English physician named William Harvey conducted dozens of experiments to try and find out how blood circulates through the body. He eventually found out that the heart pumps blood throughout the body. 

Aspirin is one of the most commonly used drugs in the world. It is a white and odorless powder. 

Aspirin was made from willow bark until it was produced in a laboratory. It wasn’t until 1899 that people figured out what aspirin was used for. It was eventually known for reliving pain and fever.

Aspirin is used to: reduce headaches, relive pain (even pain from arthritis), and can bring fever down from infections. But it can irritate the stomach and cause stomach bleeding.  

Benadryl is an antihistamine drug that occurs as a white crystalline powder. It is freely soluble in alcohol and water. The chemical formula for benadryl is C17H21N0 ∑ HCI. 

 Antihistamine is a drug that treats allergies, hives, and other things caused from allergic reactions. 

Some side effects can be sedation, drying of mucous membranes, and urinary retention. 

Psedoephedrine is used to relive nasal congestion, and cough. 

Psuedoephedrine can cause: anxiety, nausea, dizziness, and sometimes hypertension (high blood pressure), headaches and palpitations. 

Being careless and just disposing of drugs or pills in the wrong way not only hurts millions of living things, but it hurts us as well.

“Aspirin” The American Medical Association Encyclopedia of Medicens. 1989. pg 137.
“Aspirin”, World Book Encyclopedia, 1998.
Bauman, Melissa. “Does Caffeine Affect the Heart Rate of Daphnia?” March 2001
“Caffeine”, Academic American Encyclopedia, 1998.
“Caffeine”, Encyclopedia Americana, 1999.
“Caffeine”, World Book Encylopedia, 2000. Page 200-201.
Clare, John.  “Daphnia: An Aquarist's Guide.” July 2002.
“Classics of Biology: DAPHNIA”
“Crustaceans”, The Animal World, 1997.
“Crustacean”, Encyclopedia America, 1998.
“Crustacean”, World Book Encyclopedia, 1998.
“Daphnia”, Academic American Encyclopedia, 1998.
“Daphnia”, Encyclopedia Americana, 1999.
“Daphnia”, World Book Encyclopedia, 2000.
“Medicine”, World Book Encyclopedia, 1998.
“Water Pollution”, World Book Encyclopedia, 2002.
“Water Flea” Academic American Encyclopedia, 1998, pg 40.


I would like to thank the following people for helping make my project possible:
  •   My dad for staying with me for 6 hours while I did my experiment.
  •   My mom for getting me all of the pills I needed.
  •   Mr. Newkirk for helping me get started and complete the project.
  •   Mrs. Helms for helping me out whenever I needed it.
  •   Mrs. Clifton for helping me with my research report.


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