Metabolic rate is commonly thought to scale with body mass to the 3/4 power as a result of universal body design constraints. However, recent comparative work has shown that the metabolic‐scaling slope may vary significantly among species and higher taxa, apparently in response to different lifestyles and ecological conditions, though the precise mechanisms involved are not well understood. To better understand these underappreciated ecological effects and their causes, it is important to control for extraneous phylogenetic and environmental influences. We demonstrate how this may be done by comparing the ontogenetic scaling of resting metabolic rate among populations of the same species (the amphipod Gammarus minus) in mid‐Appalachian freshwater springs with similar, relatively constant environmental conditions, except for the varying presence of the predatory fish Cottus cognatus. We found that populations of G. minus exhibit significantly lower metabolic‐scaling slopes (0.54–0.62) in three freshwater springs with C. cognatus than in two springs without these fish (0.76–0.77). We tested multiple hypothetical causes for these population differences. Our results best supported the hypothesis that metabolic scaling was influenced by the effects of size‐selective predation on the ontogeny of growth, a metabolically expensive process. The body size scaling of growth is significantly less steep in the populations inhabiting springs with vs. without fish, thus paralleling the interpopulation differences in metabolic scaling. Prematurational growth of G. minus is as high or higher in the fish springs, whereas postmaturational growth is significantly lower, often approaching zero. Similarly, the amphipods in the fish springs tend to have higher metabolic rates at small sizes, but lower metabolic rates at large sizes, compared to those in the fishless springs. Our results do not support other hypothetical causes of the interpopulation variation in metabolic scaling, including differential scaling of cell size or low‐metabolism body components (fat and mineralized exoskeleton), or possible effects of other environmental factors associated with the presence of fish. However, fish‐induced population differences in adult behavioral activity may influence metabolic scaling in G. minus, a possibility under current study. We conclude that ecological factors may significantly influence metabolic scaling, contrary to common belief.

This study investigated the impact of three commonly used cardiovascular model-assisted activities on student learning and student attitudes and perspectives about science. College students enrolled in a Human Anatomy and Physiology course were randomly assigned to one of three experimental groups (organ dissections, virtual dissections, or plastic models). Each group received a 15-min lecture followed by a 45-min activity with one of the treatments. Immediately after the lesson and then 2 mo later, students were tested on anatomy and physiology knowledge and completed an attitude survey. Students who used plastic models achieved significantly higher overall scores on both the initial and followup exams than students who performed organ or virtual dissections. On the initial exam, students in the plastic model and organ dissection treatments scored higher on anatomy questions than students who performed virtual dissections. Students in the plastic model group scored higher than students who performed organ dissections on physiology questions. On the followup exam, when asked anatomy questions, students in the plastic model group scored higher than dissection students and virtual dissection students. On attitude surveys, organ dissections had higher perceived value and were requested for inclusion in curricula twice as often as any other activity. Students who performed organ dissections were more likely than the other treatment groups to agree with the statement that "science is fun," suggesting that organ dissections may promote positive attitudes toward science. The findings of this study provide evidence for the importance of multiple types of hands-on activities in anatomy laboratory courses.

The valves of oysters act as a physical barrier between tissues and the external environment, thereby protecting the oyster from environmental stress and predation. To better understand differences in shell properties and predation susceptibilities of two physiologically and morphologically similar oysters, Crassostrea virginica and Crassostrea ariakensis, we quantified and compared two mechanical properties of shells: hardness (resistance to irreversible deformation; GPa) and compressive strength (force necessary to produce a crack; N). We found no differences in the hardness values between foliated layers (innermost and outermost foliated layers), age class (C. virginica: 1, 4, 6, 9 years; C. ariakensis: 4, 6 years), or species. This suggests that the foliated layers have similar properties and are likely composed of the same material. The compressive force required to break wet and dry shells was also not different. However, the shells of both six- and nine-year-old C. virginica withstood higher compressive force than C. virginica shells aged either one or four, and the shells of C. ariakensis at both ages studied (4- and 6-years-old). Differences in ability to withstand compressive force are likely explained by differences in thickness and density between age classes and species. Further, we compared the compressive strength of differing ages of these two species to the crushing force of common oyster predators in the Chesapeake Bay. By studying the physical properties of shells, this work may contribute to a better understanding of the mechanical defenses of oysters as well as of their predation vulnerabilities.