The Effects of Body Mass on Metabolic Rates of Ectothermic Organisms

Abstract

We investigated the question, “Do ectotherms with a higher mass have a higher metabolic rate than ectotherms with a lower mass?” Larger organisms need more energy, overall, than small organisms. Thus we hypothesized that in ectotherms, the rate of metabolism increases as the ectotherm’s mass increases because a larger ectotherm needs more energy. We measured the rate of CO2 release in organisms of two different masses:  Madagascar hissing cockroaches (Gromphadorhina portentosa), and house crickets (Acheta domesticus).  We found that crickets have a higher metabolic rate than the cockroaches on a per gram basis.  Thus, we reject our hypothesis, and conclude that larger organisms have a lower mass specific metabolic rate.