For this experiment we tested the effects of different adrenalin concentrations (0.001%; 0.01%; 0.1%) on the daphnia flea. The daphnia was placed on a slide with cover slip in order to examine its heartbeat by using the microscope.
Aim
In this Lab we will study the effect of different concentrations of adrenalin on the heart rate daphnia, the water flea.
It is expected to recognize a threshold of the daphnia in its reaction the three different adrenalin concentrations, in terms of heart rate.
Background
The endocrine system works with the nervous system to regulate and coordinate body functions. While the nervous system works quickly and sends messages directly to specific body parts, the endocrine system takes a longer time to produce a longer-lasting effect.
The system operates by releasing chemical messengers called hormones into the bloodstream, which travel throughout the body. Eventually the hormone reaches a target organ or tissue to cause an effect. Growth and development, sexual maturation and reproduction, metabolism and homeostasis are some of the processes regulated by endocrine gland secretions. Endocrine effects can last hours, days, or even years.
Adrenalin is a hormone secreted by the adrenal glands that helps the body deal with stress. It produces the emergency, or “fight or fight,” response and is secreted when sudden stress such as fear, pain, anger, or extreme physical exertion requires a burst of energy. Adrenalin causes increases in metabolic rate, breathing rate, heart rate, blood pressure, sweating and even blood clotting. It is a convenient hormone to study because its effect is relatively swift.
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Materials required
Materials list
Daphnia culture, medicine dropper, slides, cover slips, bristles or threads, paper and pencil, paper towels, aquarium water, “recovery” beaker, dropper bottles containing adrenalin in various concentrations, microscope.
Method
1) With a clean medicine dropper, remove a daphnia from the aquarium. Place it in a small drop of aquarium water on the center of a slide. Add two bristles or thread to the slide to limit the movement of the animal. Then place the cover slip over daphnia. Your setup should look like that in Figure 1.
Figure 1
2) With the low-power objective, locate the transparent heart of the daphnia. It is a beating found almost midway in the back. See Figure 2. Observe the animal for a few minutes until it calms down.
Figure 2
3) Determine the heartbeat rate over a 15-second period. Your partner should tell you when to start and stop counting. If the heart is beating too fast count every other beat and multiply by two. Another method of counting is to tap a pencil on a clean sheet of paper each time the heart beats. After 15 seconds, count the number of pencil marks.
Trial 1
a. Record the number of heartbeats per 15 seconds in Table 1. Multiply this number by 4 to get the number of heartbeats per minute. Record this number in Table 1.
4) Repeat Step 3 two more times.
Trials 2 and 3
b. Record the number of heartbeats per 15 seconds and the number of heartbeats per minute in Table 1. Average the heartbeats per minute and record this number.
5) Place a drop of the 0.001% adrenalin solution next to the edge of the cover slip. Touch a piece of paper towel to the other side of the cover slip to draw the solution through. Add a second drop and draw it through in the same manner. Wait about 20 seconds. Count the number of heartbeats in 15 seconds.
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Trial 4
c. Record your result in Table 1.
6) Repeat your count of heartbeats two more times.
Trials 5 and 6
d. Record your results in Table 1. Average the heartbeats per minute and record this number.
7) Repeat Step 5 and 6 above using the 0.01% adrenalin solution.
Trials 7-9
e. Record your results in Table 1. Average the heartbeats per minute and record this number.
8) Repeat Steps 5 and 6 above using the 0.1% adrenalin solution.
Trials 10-12
f. Record your results in Table 1. Average the heartbeats per minute and record this number.
9) Return your daphnia to the “recovery” beaker designated by your teacher. (Do not return it to the daphnia aquarium.)
g. Complete Table 1 by reporting your averages to your teacher for class average determination.
Data Collection and Data Analysis
Table 1
Condition Trial Beats/15s Beats/min Average Beats/min Class Average Beats/min
Aquarium Water 1 60 240 285 268
2 90 360
3 64 256
0.001% Adrenalin 4 59 236 152 236
5 47 188
6 46 184
0.01% Adrenalin 7 57 228 205 229
8 52 208
9 45 180
0.1% Adrenalin 10 67 268 280 298
11 66 264
12 77 308
Analysis
After having followed the procedures and completed all steps, the results have been noted down in Table 1. At the beginning the heart rate was still quite high, probably due to the fact, that the daphnia was nervous and scared after being removed from its previous location. Later on in the experiment the heart rate even decreased up to the point where we were using the 0.1% adrenalin concentration. After having added the strongest concentration, there must have been some threshold which was over come, because the heart rate rose noticeably from about 152 and 205 to 280; this is a clear positive change in heart beat.
Questions or Discussion
1. How would you expect adrenalin to affect daphnia? – It will probably have no effect with the 0.001% concentration of adrenalin, but I expect to already see a increase in heart rate by maybe a 0.01% adrenalin concentration. This will only be the case, if its threshold lies at this level.
2. At what concentration did the adrenalin seem to take effect (threshold level?) – This occurred with the 0.1% concentration of adrenalin. One could see quite quickly, that the heartbeat rate had increased only b looking at it through the microscope.
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3. How do your results compare with the class average? – Our results differed a bit more from the overall class average at the point where we measured the heartbeat after taking the daphnia out of the aquarium. This might have been due to our impatiens at the beginning of the lab.
4. How much concentrated is 0.1% adrenalin than 0.001% adrenalin? – 0.001 x 100= 0.1% Therefore we have a 100x stronger concentration of adrenalin from 0.001% to 0.1%.
5. Why did you not return your daphnia to the original culture dish (aquarium) after the activity? – This was due to the fact that we had already used these daphnias for our experiment and were therefore contaminated. If one would have added them back into the aquarium, the other daphnias would have gotten affected due to the other, added daphnias adrenalin. This would have contaminated all the other daphnias and make the further lab procedures impossible to complete.
Conclusion
As expected, the daphnias threshold could be identified. This was at 0.1% concentration of adrenalin where a clear increase in heartbeat could be identified.
The overall design of the lab was done quite well. There were basically no problems and misunderstandings of the procedures.
The only suggestion one could make for this and future lab is to always remind the students to shakeup their chemicals before using them. This is because most chemicals settle at the bottom of the containers, after having stood for a while. By shakingup the container again, the chemicals will spread evenly in the solution their in and will therefore also give you relevant results for your Lab.
