Pill Bug response to environments with varying levels of moisture
AP Biology * Solomon Oak* Periods 7 & 8
Lannawill Caruth
11/01/2018
INTRODUCTION
Pill bugs are terrestrial crustaceans. Pill bugs have gills and thus are usually restricted to damp
habitats.They are commonly found under wood, under leaf litter, under flower pots, or in damp cornes.
Their diet consists mainly of leaf litter or pieces of fruits and vegetables(Carolina Biological Supply
Co.).In this experiment we attempted to see how environmental conditions affect animal behavior. This
could be of significance for determining evolutionary relationships between the pill bug and other animals
that respond to moisture in the same way. We hoped to see how pill bugs respond when removed from
them normal environment. We hypothesized that If an even number of pill bugs were placed in two
different environment (one dry, one wet) and had the option to choose which one they remained in, more
would choose to travel to the wet one.
MATERIALS
1. Double Petri dishes (chamber with two sides and bridges)
2. 10 pill bugs
3. Water
4. Timer
5. Coffee filter paper
PROCEDURE
1. Using filter paper,plastic bowls,tape, and paper create double sided petri
dish(choice chamber)
2. Line both sides of the chamber with coffee paper
3. Add water to one side of the chamber and leave the other side dry.
4. Place 5 pill bugs on each side of the chamber.
5. Record how many pill bugs are on each side of the chamber in 60 second intervals
for 10 minutes.
DATA
Time
WET SIDE
DRY SIDE
0:00
5
5
1:00
5
5
2:00
6
4
3:00
6
4
4:00
6
4
5:00
6
4
6:00
10
0
7:00
9
1
8:00
9
1
9:00
10
0
10:00
10
0
DATA ANALYSIS
Chi-square for values on dry side
o
e
o-e
o-e^2
o-e^2/e
5 5
0
0
0
5 5
0
0
0
4 5
-1
1
.2
4 5
-1
1
.2
4 5
-1
1
.2
4 5
-1
1
.2
5
-5
25
5
1 5
-4
16
3.2
1 5
-4
16
3.2
0 5
-5
25
5
0 5
-5
25
5
0
22.2
Total
Chi-Square values of the number of pill bugs on the wet side.
o
e
o-e
o-e^2
o-e^2/e
5 5
0
0
0
5 5
0
0
0
6 5
1
1
.2
6 5
1
1
.2
6 5
1
1
.2
6 5
1
1
.2
10 5
5
25
5
9 5
4
16
3.2
9 5
4
16
3.2
10 5
5
25
5
10 5
5
25
5
Total 22.2
(Pennsylvania State University)
The chi-square calculated value is greater than chi-square. We reject the null hypothesis.
The difference between the observed and expected is statistically significant.
HANDOUT QUESTIONS
1.
Based on your graph and the introductory material, explain pill bug behavior
with respect to humidity.
a. The pill bugs prefer damp/humid areas to dry ones. This is most likely due
to the fact that they have gills
2.
Explain how the pill bug response to humidity may be advantageous.
a. Pill bugs preference for humidity might allow them to burrow into the
ground to seek humidity and find food.
3. Identify 2 more environmental factors that may affect pill bug behavior.
a.
Two environmental factors that might affect pill bug behavior are the
amount of vegetation and temperature.
4. Design an experiment to test 1 of the environmental factors that may affect pill
bug behavior.
a. An experiment to test their preference in temperature would be to add
different temperature water to the sides of the petri dish and see where the
bugs end up.
CONCLUSION
Pill Bugs show a clear preference for humid moist environments over arid
environments. This is probably due to their having gills. We were able to determine the
statistical significance because the chi-square calculated value 22.2 was greater than the
chi square critical value of 3.9. This can be advantageous because they do not have to
worry about finding food in the winter as their preference for humidity allows them to
burrow into the ground to find leaf litter. Some errors that might have affected the
results were that we had to rewrite the original instructions to construct a double petri
dish since we did not have one. A fault in the design of the original one led to u having to
transfer the bugs from one contraption to another. A few were dropped and left to walk
across the table for a bit. This change in the environment could have affected the results.
Also the temperature, humidity, and air pressure in the room varied a times and were
not closely monitored.
REFERENCES
Carolina Biological Supply Company. (2017). Pill Bug Behavior Choices. Retrieved from
https://www.carolina.com/teacher-resources/Interactive/pill-bug-behavior-choices/tr41206
.tr
Pennsylvania State University. (2018). The Chi-Square Table. Retrieved November 01, 2018,
from https://onlinecourses.science.psu.edu/stat414/node/147/