The Effect of Substrate On Pillbug Habitat Selection
by Mrs. Culver
3rd period
July 28th, 2008
Partners:
Mrs. Crozier
Mrs. Bond
Mrs. Kenyon
Mrs. Gazda
AIM
Statement of the Problem/Causal Question:
What substrate do pillbugs select prefer as their habitat?
Pillbugs typically like natural humus as their substrate for their habitat, but what would
happen if you changed their habitat to cut grass or wood chips? Cut grass or wood chips
are typically found as aesthetic borders in yards. Sometimes digging in these areas you
will find pillbugs.
Hypothesis Statement:
If Pillbugs prefer the natural humus chamber, then they will stay in the natural humus
chamber at least 80% of the time after the first 10 minutes of experimentation. This will
happen because in nature this is what they use for their habitat.
Experimental Design:
Title: The Effect of Substrate on Pillbug Habitat Selection
Hypothesis: If Pillbugs prefer the natural humus chamber, then they will stay in the
natural humus chamber at least 80% of the time after the first 10 minutes of
experimentation. This will happen because in nature this is what they use for their habitat.
Natural Humus Wood Chips Cut Grass
10 pillbugs/chamber
10 thirty-second trials (# pillbugs/chamber/30sec)
Independent Variable (IV): Type of substrate (the natural environment in which an
organism lives, or the surface or medium on which an organism grows or is attached)
Groups
Trials
Dependent Variable (DV): Time in habitat chamber
Control: Chamber with natural humus substrate
Constants:
1.
2.
3.
4.
5.
Moisture level of substrate
Temperature in chamber
Amount of Food
Lack of predation
Size of chamber
MATERIALS
*chambers
* 30 pillbugs
*fresh cut grass
* natural humus
*wood chips
* paper
*pencil/pen
* data table
*graph paper
* computer
*excel program
* word program
PROCEDURES
1) Observe behavior of pillbugs
2) Ask questions
3) Define a problem
4) Write a hypothesis statement
5) Make a list of materials and procedures
6) Sketch experiment set up
7) Create the experimental design
8) Prepare a choice chamber
9) Cover the bottom of each chamber with either wood chips, cut grass or natural humus
10) Transfer ten pillbugs from the stock culture into each choice chamber
11) Cover the chambers
12) Count and record how many pillbugs are in each chamber every 30 seconds for I0
minutes
13) Graph results
14) Analyze results
15) Conclude whether hypothesis statement is supported or not supported.
16) Discuss lab suggestions or improvements
RESULTS/EVIDENCE:
Data Table:
Title: The Effect Of Substrate On Pillbug Habitat Selection
(IV): Type of
Substrate
(DV): Time in Habitat Chamber # of pillbugs/Chamber
Trials
Trial 1 (30 sec)
Trial 2 (60 sec)
Trial 3 (90 sec)
Wood Chips
7
8
7
Cut Grass
13
6
5
Natural Humus
10
16
18
This data table shows the number of pillbugs per chamber and the length of time
spent in each substrate type.
Graph:
Substrate Preference in Pill Bugs
30
#
of
Pi
ll b
ug
s.
25
20
15
10
5
0
0
30
60
90 120 150 180 210 240 270 300
Time (secs)
Wood Chips
Cut Grass
Natural Humus
This graph shows the number of pillpugs per chamber and the length of time spent in
each substrate type.
Data Analysis: On average 20 pillbugs spent a majority of their time in the natural humus
chambers, on average 6 pillbugs spent a majority of their time in the wood chip chambers, and on
average 4 pillbugs spent a majority of their time in the cut grass chambers.
Conclusions:
The claim that if Pillbugs prefer the natural humus chamber, then they will stay in the
natural humus chamber at least 80% of the time after the first 10 minutes of
experimentation. This is supported because the evidence shows that on average 20
pillbugs spent a majority of their time in the natural humus chambers, on average 6
pillbugs spent a majority of their time in the wood chip chambers, and on average 4
pillbugs spent a majority of their time in the cut grass chambers. During the experiment
each trials results varied slightly. This could be due to a draft in the room at the time of
the experiment. For future experimentation, it is suggested to control the movement of
air in the room. In addition, it would be interesting to test and compare the pillbugs
reaction to synthetic materials versus natural humus, cut grass and wood chips.