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Pillbug Experiment Presentation
Transcript of Pillbug Experiment Presentation
Maya Foster, Laura Kanji, and Emily Yang
Materials and Methods
10 pillbugs and sowbugs (approximately five of each species)
2 petri dishes, taped together with a tunnel cut out of the side
1 circle wet paper towel
1 circle dry paper towel
Black construction paper
1. For the first experiment, place a wet paper towel in one side of the petri set-up and a dry paper towel in the other.
2. Place 5 pillbugs on each side of the set-up.
3. Loosely cover petri dishes with lids to prevent the bugs from escaping.
4. Allow bugs to move around freely within the dishes for ten minutes, counting and recording the number of bugs on each side every thirty seconds.
5. For the second experiment, remove the paper towels and dry the petri dishes. Loosely tape black paper over one of the petri dishes, so it acts as a lid and there is room for the bugs to crawl under it. Do not block the tunnel.
6. Place the pillbugs in the set-up, putting 5 under the black paper if possible. If this is not possible, allow 5 to crawl under the paper, then begin taking data.
7. Record the number of pillbugs on each side every thirty seconds for ten minutes.
Cut a small hole in the side of each petri dish and tape together to form a tunnel, then place wet paper towel on one side and dry paper towel on the other:
Experiment 1: Wet versus dry environment. Dampened the paper towel on one side to make half of the environment wetter than the other.
Experiment 2: Light versus dark environment. Covered half of the set-up with black paper to make it darker than the other half.
Pill Bug Behavioral Lab Analysis: Investigating Pill Bug Behavioral Responses to Moist vs. Dry Environments and Light vs. Dark Environments
1. Do pill bugs prefer wet or dry environments?
2. If the pillbugs and sowbugs have the choice to choose between a dark or light environment, they will choose the dark area.
Pill bugs and sow bugs are terrestrial isopods that belong to the Classic Crustacea family. This means they have gills, in which they use for respiration, and have other related body parts similar to their marine crustacean counterparts. Pill bugs are also cold-blooded organisms. These organisms can be found under rocks, logs, and rotting tree bark in moist, dark areas outside. A pill bug's diet consist of wood and leaf debris.
There are two kinds of behaviors these animals exhibit. They are taxis (curling into a ball) and kinesis (scurrying in no particular direction). Taxis is a behavior in response to a stimulus with a specific orientation either away or towards that stimulus. Kinesis is a random movement that is not oriented toward or away from a stimulus. These behaviors were investigated during this lab, ultimately to determine which type was exhibited with each experimental stimuli.
Because of the nature of the pill bugs' habitat, which is usually moist and dark to keep them from dehydrating, we predicted that they will prefer similar environments.
We calculated Chi-Square using data from 3 minutes to 10 minutes because in experiment one, the pill bugs were continuously escaping during the first three minutes, and in experiment 2, we started with ten pillbugs on the light side (since we could not put them under the black paper without hurting them) and it took three minutes for the numbers to even out.
. "BioJunction." AnimalBehavior. N.p., n.d. Web. 13 Sept. 2014. <http://www.biologyjunction.com/Lab%2011%20animal%20behavior.htm>.
2. Bozeman Science. "Chi-squared Test."
YouTube, 13 Nov. 2011. Web. 14 Sept.2014
3. "Pillbugs." Pillbugs. N.p., n.d. Web. 13 Sept. 2014. <http://www3.northern.edu/natsource/INVERT1/Pillgu.htm>
2. How does the presence of light affect a pill bug's preference of a given environment?
1. If the pillbugs and sowbugs have the choice to choose between a wet environment and a dry environment, they will choose the wet environment
Observe effects of the presence of a light source (light versus dark) on pill bug behavior
Diagram of pill bug body structure
Observe the effects that dry soil versus wet soil has on pill bug behavior
(We chose this because pill bugs respire through gills and need water in order to prevent dehydration).
(We chose this because they live in environments absent of the sun, such as under rocks and in soil).
The reason for the results in Experiment 1 might be that not enough time was allowed for the pill bugs to calm down in the new environment, as they seemed to be very uneasy in both trials, continuously attempting to escape instead of exploring the chambers. The escapes lead to discontinuities in our data. In Experiment 2 a pill bug was stuck on the tape for about 2 minutes, causing some disturbance.
Also, counting them at exactly 30 seconds intervals proved to be challenging, for there are so many things to take care of. Miscounting, although a human error, would not be too surprising for this experiment.
To improve the experiment, we would give the bugs more time to calm down before starting the time.
We should also have done more trials because more data means more accuracy. We should have divided up our jobs better (one person keeping track of time, one person counting, etc.) so there is less confusion. Furthermore, we should have done a better job cover up the chambers with other petri dishes so the bugs can't escape and wouldn't get stuck on the tape :)
Sources of Error
Wet/Dry: Chi Square > 3.84 to reject null hypothesis
Average in the wet (3-10 mins): 6.2
Average in the dry (3-10 mins): 3.8
Chi-Square = [(6.2-5.0)2/5.0+(3.8-5.0)2/5.0] = 0. 58
Accept the null hypothesis!
Light/Dark: Chi Square > 3.84 to reject null hypothesis
Average in the light (3-10 mins): 1.7
Average in the dark (3-10 mins): 8.3
Chi-Square = [(1.7-5.0)2/5.0+(8.3-5.0)2/5] = 4.4
Reject the null hypothesis!
Average in the light (3-10 mins): 1.2
Average in the dark (3-10 mins): 8.8
Chi-Square = [(1.2-5.0)2/5+(8.8-5.0)2/5] = 5.8
Reject the null hypothesis!
One possible avenue for further research can be the effect of light on the dehydration of pill bugs. If they avoid light this much, how would light actually hurt them? (How much of an effect it would have?)
Average in the wet (3-10 mins): 4.5
Average in the dry (3-10 mins): 5.5
Chi-Square = [(4.5-5.0)2/5.0+(5.5-5.0)2/5.0]= 0.1
Accept the null hypothesis!
Note that in the first three minutes of the first trial, literally every single pill bug was escaping, leading to blanks in these places.
In both trials of experiment 1, we failed to reject the null hypothesis, thus our observed values have no statistical difference from the expected value, contradicting our hypothesis that pill bugs would show preference of the wet chamber. In fact, the average number of pill bugs in the wet chamber was smaller than the dry chamber in trail 2 while larger in trial 1, thus we cannot conclude overall whether they prefer the dry chamber or the wet chamber from this experiment.
In both trials of experiment 2, we succeeded in rejecting the null hypothesis, proving that there is a preference for the dark environment, supporting our hypothesis. It is also interesting to note that we obtained more accurate results in the second trial of both experiments.
We concluded that the actions of pill bugs was kinesis as well because their paths follow no distinctive pattern.
We were able to obtain more accurate data in the second experiment than the first.
We did not have data, thus the graph starts from 2.5 minutes.
This trial was much easier than the first since less of them attempted to escape. The numbers continued to fluctuate, however.
*We started this trial with 6 pill bugs on the dark side and 4 on the light.