Rates of Respiration for Species Exhibiting Different Activity Levels


Chelsea Wencl and Alice Shallcross


CU Boulder, Fall 2006


         We tested respiration rates in two species (crickets and isopods) exhibiting different levels of activity.  Since crickets are more active than isopods, they need to create more ATP to maintain that level of activity.  ATP production during aerobic cellular respiration will generate CO2 as a by product and therefore, the level of activity will be correlated with the rate of respiration.  Thus, we hypothesize that the rate of respiration will be greater in crickets than in isopods.

         To test this hypothesis, we placed the organisms in a chamber and measured the change in CO2 concentration inside the chamber.  The gas chamber was connected to a CO2 probe, which was connected to a computer that recorded the levels of CO2.  We allowed the system to equilibrate for three minutes and collected data for seven minutes.  We did this three times for the crickets and repeated the procedure for the isopods.  Different individuals were used for each replication and before each trial we weighed each group of either crickets or isopods.  Since crickets are more active than isopods, we predict the rate of CO2 production will be greater for crickets than isopods.

         After running a T-test assuming unequal variance, we found the p-value to be 0.067, which is greater than our alpha value of 0.05.  This shows that there was not a significant difference between the rate of respiration for the crickets and isopods.  Although our results are marginally consistent with our hypothesis (the levels of CO2 increased at a faster rate for the crickets in all three trials), the T-test does not support this claim and we find no evidence that the level of activity greatly influences the rate of respiration. 

         There are several reasons for the lack of support for our hypothesis from our data.  Since the isopods are much smaller than the crickets, the CO2 levels might have been more accurate if we had used a larger sample of isopods in each trial.  If the future, we would like to use insects of the same relative size in order to eliminate the potential error due to variations in size.  In comparison to past experiments, we found a similar lack of support for our hypothesis.  In “Do faster moving crickets respire more than slower moving earthworms?” Raese et al. performed a similar experiment and had a p-value of 0.073.  Since the p-values are close to 0.05, more research is needed to conclusively determine if the rate of respiration is different in organisms exhibiting different levels of activity.