Metabolic ecology is a conceptual area covered in most general ecology and some physiology courses, and includes important principles such as the allometric scaling and temperature-dependence of metabolic rates. The learning of these concepts by undergraduate students may be facilitated by inquiry-based exercises, in which students manipulate data to explore relationships between body size, temperature and metabolic rates. We developed a critical thinking exercise for an undergraduate general ecology course to facilitate student learning of metabolic ecology. Students were given field-derived data on nitrogen N and phosphorus P excretion rates of over 200 individual fish, as well as fish body mass and environmental temperature. Using these data and working in groups, students tested two general hypotheses of metabolic theory: 1) excretion rates show negative allometry, specifically that log(excretion rate) scales with log(body mass) with an exponent near 0.75; and 2) excretion rates increase with temperature with a Q10 near 2. One challenge for students was dealing with simultaneous variation in the two independent variables, temperature and body size: because data were derived from the field, rates could not be measured at equally-spaced, controlled temperatures, and the range of body sizes available varied among dates. Therefore, students had to devise ways of quantifying allometric scaling exponents using multiple temperatures, and estimating Q10 using fish of multiple body sizes.
Results/Conclusions
The student groups took a variety of approaches to estimate allometric scaling exponents and Q10, but in general most groups employed logical, valid methods. Students learned that the hypotheses were generally supported, but that there is a substantial “noise” in these relationships when they are derived from data from the field, where conditions cannot be precisely controlled. In general, there was more convergence among approaches for estimating scaling exponents than for estimating Q10. Assessments of the exercise revealed that most of the students felt that the exercise was challenging, helped them understand the metabolic ecology concepts, and improved their quantitative skills.
