# CAPT Lab Report - Daphnia Heart Rate

```09/29/19
Biology I - Period 7/8
Lab Report - Daphnia Heart Rate
Problem Definition:
This report centers around the experimentation of Daphnia, small organisms with clear
and visible organs who are able to react in such a way that is expressive of the environment
they are in. Our job was to investigate how different water temperatures would affect the heart
rate (BPM) of Daphnia. Our variables are reflective of our needs for this project. Our
independent variable was of course, the temperature of the water we were testing our specimen
in. (These temperatures, as we later discover turn out to be for 15 celsius for cooled water, 22
celcius for room temperature water, and 33 celsius for heated water). Meanwhile, our
dependent variable, was in turn, the average heart rate of our specimen after being placed in
the exact temperature of the water. We ran five trials with such intentions. Our hypothesis reads
as so - We predicted that if water temperature alters whilst the specimen,( in our case - the
Daphnia) is located in it, then cold water (15&deg;C), will decrease it significantly from the controlled
heart rate (at 22 &deg;C - room temperature water) and hot water (33 &deg;C) will increase it significantly
from the controlled heart rate of (22 &deg;C - room temperature water). This is because not receiving
enough heat will slow the heart down to conserve energy, whilst overheating requires the body
to generate energy to cool itself off and increases the heart rate to accomplish so. What sources
this claim is the ability of the human body to regulate homeostasis when faced with temperature
changes. Taking these observations, we applied them to our predictions and proceeded to run
such trials with results to confirm or not confirm in mind.
Experimental Design:
The design of this experiment was structured in such a way to accommodate the findings
of the results we required to test our hypothesis. We had a precise procedure to use - with set
materials, control aspects - and a clear definition of independent and dependant variables.
Independent Variables:
The temperature of the water used to maintain the Daphnia in - 15&deg;C for cooled water,
22&deg;C for room temperature water, 33 &deg;C for heated water.
Dependent Variables:
The heart rate (BPM) of the Daphnia after being placed in cooled water, room
temperature water, and heated water.
Control:
The average heart rate of Daphnia when observed in room temperature pond water.
Constants:
-
Beats to time test ratio
-
Equipment used
-
Liquid type
-
Trials ran
Materials:
-
Live Specimen (Daphnia)
-
5.3 ounce Chobani Yogurt Cup
-
40 mL beaker
-
Faucet (to obtain heated water)
-
Glass Coverslip
-
Ice Cubes
-
Indented Slide
-
Microscope
-
Observation Sheet
-
Pencil/Pen
-
Pipette
-
Room Temperature Pond Water
-
Timer
-
Thermometer
Room Temperature Trials :
1. Obtain a 40 mL beaker
2. Fill the beaker with room temperature pond water to the 20 mL line.
3. Measure the temperature of the water (using celsius)
4. Use a pipette to grab the specimen (Daphnia) from the designated jar
5. Gently squirt Daphnia into indented slide (which holds the room temperature water)
6. Cover with glass coverslip
7. Place indented slide onto microscope stage.
8. Locate heart of Daphnia
9. Count and record heart beats per 15 seconds (Multiply for BPM results)
10. Repeat until all five trials are complete
Cold Temperature Trial :
1. Remove indented slide from microscope stage
2. Obtain the 5.3 ounces Chobani yogurt cup
3.
Fill cup halfway with water and place ice cubes in
4.
Use pipette to grab Daphnia from indented slide and place it into a beaker of pond water
5. Place beaker into cup
6. Wait until the temperature of the water in the beaker is 15&deg;C.
7. Use pipette to grab Daphnia and place onto indented slide (containing cooled water)
8. Cover the slide with a glass slip
9. Place indented slide onto microscope stage
10. Locate heart of Daphnia
11. Count and record heart beats per 15 seconds (Multiply by 4 for BPM) and record
12. Repeat until all five trials are complete
Hot Temperature Trial:
1. Remove indented slide from light microscope stage
2. Obtain a 5.3 Chobani yogurt cup
3. Fill cup half way with warm tap water (dump a bit of water out if it gets too cool and add
more hot water)
4.
Place beaker into cup
5. Wait until the temperature of the water in the beaker is 33&deg;C
6.
Use pipette to grab Daphnia and place onto indented slide (which contains heated
water)
7. Cover the slide with a glass coverslip
8.
Place indented slide onto microscope stage
9. Locate heart of Daphnia
10. Count and record heart beats per 15 seconds (Multiply for BPM results)
11. Repeat until all five trials are complete
Data:
Room Temperature Trials (15 &deg;C)
Trial
Temperature
Beats- 15 sec
BPM
#1
22&deg;C
47 beats
188 beats
#2
22&deg;C
43 beats
172 beats
#3
22&deg;C
46 beats
184 beats
#4
22&deg;C
42 beats
168 beats
#5
22&deg;C
44 beats
176 beats
Average beats per 15 seconds in 22&deg;C water : 44.4 beats
Average beats per minute in 22&deg;C water : 177. 6 beats
Room Temperature Trials (22 &deg;C)
Trial
Temperature
Beats - 15 sec
BPM
#1
15&deg;C
34 beats
136 beats
#2
15&deg;C
36 beats
144 beats
#3
15&deg;C
35 beats
140 beats
#4
15&deg;C
35 beats
140 beats
#5
15&deg;C
33 beats
132 beats
Average beats per 15 seconds in 15&deg;C water : 34.6
Average beats per minute in 15&deg;C water : 138.4 beats
Heated Temperature Trials (33 &deg;C)
Trial
Temperature
Beats - 15 sec
BPM
#1
33&deg;C
50 beats
200 beats
#2
33&deg;C
51 beats
204 beats
#3
33&deg;C
50 beats
200 beats
#4
33&deg;C
52 beats
208 beats
#5
33&deg;C
49 beats
196 beats
Average beats per 15 seconds in 33&deg;C water : 50.4
Average beats per minute in 33&deg;C water : 201.6 beats
Conclusion:
The conclusions that can be drawn from this experiment are evident. The hypothesis we
presented at the beginning of our experiment is valid and supported by the evidence we have
gathered. ​(We predicted that if water temperature alters whilst the specimen,( in our case - the
Daphnia) is located in it, then cold water (15&deg;C), will decrease it significantly from the controlled
heart rate (at 22 &deg;C - room temperature water) and hot water (33 &deg;C) will increase it significantly
from the controlled heart rate of (22 &deg;C - room temperature water). This is because not receiving
enough heat will slow the heart down to conserve energy, whilst overheating requires the body
to generate energy to cool itself off and increases the heart rate to accomplish so). T
​ he
difference between the water temperatures and the heart rate averages supports our
hypothesis.
The cooled water, at 15 &deg;C, was 7 degrees cooler than the constant temperature, whilst
the heated water, at 33 &deg;C, was 11 degrees warmer than the constant temperature. The
constant temperature maintained at 22&deg;C. When under constant temperature (room
temperature), the Daphnia’s heart rate remained at a rate of 177. 6 beats per minute. However,
when exposed to cooler temperatures (15 &deg;C), the Daphnia’s heart rate slowed to 138.4 beats
per minute. That lowered the BPM of the Daphnia by 39.2 beats. Afterwards, the trial was run
with heated water (33 &deg;C), which increased the Daphnia’s heart rate to 201.6 beats per minute.
This was 24 beats above the control. Using this found data, one can conclude that the increase
of water temperature is directly correlated with the increase of Daphnia BPM.
I believe our drawn conclusion is valid. Our hypothesis is supported by our data, with the
average Daphnia BPM of cooled water being under the average Daphnia BPM under room
temperature water, whilst the average Daphnia BPM under heated water being above that. We
used precise constants such as water type, compared to a control, and took great care to record
data at the most precise time intervals. Our independent variable directly impacted our
dependent variable in the way we predicted it too. All aspects of the experiment were controlled
and monitored. Although not perfect, the lab was carried out with minimal interference and
turned out to be very successful.
While our experiment was conducted with great precision, there are many minor yet
impact details we must examen. While I believe that our conclusion is valid, it can certainly be
improved upon. The amount of trials we did were nowhere near enough to how many could
have been done to truly capture the most precise intervals of change in the experiment.
Occasionally, we would have to restart a trial due to human error, which would prolong the
exposure of different water temperatures to the specimen. This added stress of increased time
spent could have easily been a part of the reason our results developed the way they did. Other
aspects out of our control also may have affected the results taken from such an experiment.
For example, the sudden passing of our first specimen after it had given birth under the
microscope could easily be taken as an outside factor that impacted the experiment. The use of
two different creatures could have easily been a large aspect of the impacted data. If we were to
run the lab through once more, I believe we would be much more likely to find more precise
conclusions if we could spend more time on running more trials, making sure our timing is as
constant as it should be and picking reliable specimen.
All that being said, I did thoroughly enjoy this lab and the report that followed.
Researching the homeostasis of living things is quite interesting and the experiment run was
easy to execute and got clear results. Daphnias are fascinating little things, aren’t they?
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