daphnia heart rate lab
name:
Objective: ​
You will compare the effects of different drugs on the heartbeat of Daphnia. You will
classify the drugs as stimulants or depressants, and compare the effects of these drugs to the human
body.
Introduction:​
How do stimulants and depressants affect heart rate? When chemicals (drugs) are
ingested they are carried through the body by the blood. While such chemicals sometimes act on the
brain centers that control your heartbeat, they also affect the heart directly. Daphnia (see diagrams),
or water fleas, are small enough to be studied under a microscope and transparent enough that we
can see the heart beating. ​
Daphnia hearts respond in much the same way as human hearts.
Background Research: ​
In order to fully understand this experiment, you will first need to find out
about the drugs you will be administering to the daphnia. The drugs we will use will be ​
alcohol
(ethanol), sleeping pills, aspirin, nicotine, and caffeine​
. Discuss with your partner what is meant
by the terms “stimulant” and “depressant”.
Anatomy of Daphnia:
http://pulse.pharmacy.arizona.edu/9th_grade/culture_cycles/science/handouts/daphnia_named.jpg
Video of Daphnia Heartbeat:​
There are TWO things “twitching” in the video - the legs and the heart
of the Daphnia. When you look at your Daphnia we are looking for the top oval shaped structure. In
the video the bottom things twitching are its legs.
https://www.youtube.com/watch?v=2g-04Uk0ut0
Procedure:
1. One partner should keep time (30 seconds) while the other partner watches/counts the
heartbeat of the daphnia.
2. To get the heartbeat ​
per minute​
- take the heartbeat counted in #1 and multiply by 2. Enter
data into chart below.
3. Obtain a daphnia - your teacher will show you how the first time. The daphnia will be drawn
into a pipet with some of its water and placed on a depression slide. Place the slide under the
microscope and find the heart.
4. In order to determine the effect a drug has on the heart rate, you first need to determine the
un-drugged heart rate. This is the CONTROL GROUP! Find the heart and determine the heart
rate as decided in step #1. Repeat this ​
2 more times for a total of 3 trials.​
Average the three
trials together and record as your control heart rate below.
5. Decide on which drug you will test first and make a hypothesis as to whether the daphnia
heart rate will increase, decreases, or not affect the heart rate. Administer the drug to the
same daphnia you got the control rate for. Use ​
only one drop of the drug solution​
.
6. Wait 2 minutes to allow the drug to absorb into the daphnia’s system and then count the
heart rate again for 30 seconds.
7. Multiply the amount of heart beats by 2 to get the number of beats per minute and record
your data. ​
Repeat this process for two more trials and then determine the average for
the EXPERIMENTAL heart rate of this drug.
8. Take this daphnia to “rehab”. It will be taken to live out its life in peace in a lovely sunlit
aquarium. Do not use this daphnia for future tests.
9. Obtain a new daphnia and repeat the entire experiment using a different drug.
Data:
Drug Used
Control 1
Control 2
Control 3
Control Average
Experimental 1
Experimental 2
Experimental 3
Experimental Average
Control 1
Control 2
Control 3
Control Average
Experimental 1
Experimental 2
Experimental 3
Experimental Average
Control 1
Control 2
Control 3
Control Average
Experimental 1
Experimental 2
Experimental 3
Experimental Average
Control 1
Control 2
Control 3
Control Average
Experimental 1
Experimental 2
Experimental 3
Experimental Average
Control 1
Control 2
Control 3
Control Average
Experimental 1
Experimental 2
Experimental 3
Experimental Average
CAFFEINE
Hypothesis:
ASPIRIN
Hypothesis:
SLEEPING PILLS
Hypothesis:
ALCOHOL
Hypothesis:
NICOTINE
Hypothesis:
Results:​
Answer the following questions with COMPLETE SENTENCES.
1.
2.
3.
4.
Which drugs caused the heart rate to increase?
Which drugs caused the heart rate to decrease?
Which drugs had no effect on the heart rate?
Were your predictions correct? Did you get any surprising results - did a stimulant slow a
heart rate, for example?
5. What factors might cause these surprises (consider differences among the daphnia)?
6. Were all of the control heart rates the same? Would you expect them to be the same? Why or
why not?
7. List some sources of random error or human error from this experiment.
8. Why do you think different people react differently to the same medications. (example: two
people are on the same medication, but they are reacting differently to the medicine.)
9. What is a stimulant?
10. What is a depressant?
11. What ​
could​
happen when two or more of these drugs are consumed at the same time?