Bigger Is Not Better: The Effect of Body Size on Metabolic Rate

Jillian Gore, Heber Garcia, Shelby Gentry, Dani Kirsch


According to the popular saying, bigger is better, but is that true when it comes to metabolic rate? We decided to test if body size affects metabolic rate with crickets, Acheta domestica, and Madagascar hissing cockroaches, Gromphardorhina portenosa. We hypothesize that the cockroaches will have a slower metabolic rate than the crickets because the cockroaches surface area to volume ratio is smaller, therefore the cockroaches will not produce as much CO2 as the crickets.  We ran ten, five minute trials with eight cockroaches in a large respiration chamber and eight crickets in a small chamber, and then measured the carbon dioxide output. The crickets produced on average 626ppm of CO2 whereas the cockroaches produced 361ppm. Our findings concluded that our hypothesis was supported, because the crickets, with a larger surface area to volume ratio, expelled more CO2 than the cockroaches, with the smaller surface area to volume ratio, therefore, the cockroaches have a slower metabolic rate.

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