Volume 6, Spring 2008 - Saddleback College

Fall 2007 Biology 3A Abstracts
with the equation of the line and the R 2 value (Fig 2).
The slope of the line represented the metabolic rate in
different units. The slope (ppm/sec) was multiplied by
the total time the roaches remained in the container to
make the value a measurement only of CO 2 per million
molecules of air:
Slope ppm/sec Time sec = [CO 2 ] ppm
To determine the number of moles of CO 2
within the volume of air in the container, a ratio was
set between the ppm of CO 2 per million molecules of
air:
Parts of CO 2 = Moles of CO 2
Parts of Air Moles of Air
The moles of CO 2 were applied to the Ideal Gas Law to
calculate the volume (L) of CO 2 :
PV = nRT V = nRT
P
The volume of CO 2 produced was converted
to milliliters (mL), divided by the body mass (g) of
each roach, and divided by the duration of the trial
(sec), ultimately yielding the metabolic rate (mL/g/sec)
or (mLg -1 sec -1 ). Calculations were applied to all
roaches and their averages for the three temperatures.
Results
A one way ANOVA test with replication
(ANOVA simple factor) was conducted since there
were three groups to account for. There were
differences between the MR means for the three
temperatures (Figure 1). Standard deviation represents
the probability of the subjects’ results within a group
skewing from a projected mean value (Figure 2). The
combined p-value 2.068 10 -3 is less than the critical
value ( = 0.05). A post hoc test was performed by
GraphPad Software to determine if there was a
considerable difference and between which groups.
Paired p-values—room temperature vs. hot, room
temperature vs. cold, hot vs. cold—are greater than =
0.05, therefore the null hypothesis was not rejected and
the conclusion cannot be drawn stating there is an
association between temperature and metabolic rate.
Mean Metabolic Rate (m L/g/sec)
CO2 Concentration (p p m )
0.00009
0.00008
0.00007
0.00006
0.00005
0.00004
0.00003
0.00002 3500
0.00001
3000
0
2500
2000
1500
1000
500
Figure 2 Mean metabolic rates with corresponding
standard deviation values: room temperature was
3.770 10 -5 ml/g/sec 1.355 10 -5 ; cold
temperature was 2.497 10 -5 ml/g/sec 2.157 10 -
5 ; hot temperature was 6.755 10 -5 ml/g/sec
2.484 10 -5 .
y = 1.2545x + 850.1
R 2 = 0.9984
y = 0.7764x + 916.18
Temperature (C)
R 2 = 0.9848
Room Hot Cold
y = 0.3476x + 1482.4
R 2 = 0.8836
0
400 600 800 1000 1200 1400 1600 1800 2000
Time (sec)
23C 39C 10C Linear (39C) Linear (23C) Linear (10C)
Figure 1 Comparison of average metabolic rates of
roaches from three variables. Elevated temperature
was the highest with 6.755 10 -5 mL/g/sec 9.39
10 -6 (se); room temperature was 3.770 10 -5
mL/g/sec 4.79 10 -6 (se), elevated; and cold
46
Saddleback Journal of Biology
Spring 2008
temperature was 2.497 10 -5 mL/g/sec 8.15 10 -6
(se).
Figure 3 Comparison of averaged data from three
temperatures showing slopes and correlation values.
Slopes values converted to mL/g/sec from ppm/sec
represent metabolic rates.
Discussion
G. portentosa rely mainly on carbohydrate
synthesis (Weins & Gilbert, 1995) to provide energy
for metabolism. The measurements of the volume of
carbon dioxide (VCO 2 ) during cockroaches’ calm
states and graphed slopes (ppm/sec) could be converted
into metabolic rate in relation to body masses and the
amount of time they respired (ml/g/sec). The volume of
CO 2 is equal to the volume of oxygen (VO 2 ) because