Small changes, big gains: A curriculum-wide study of teaching practices and student learning in undergraduate biology.

A growing body of evidence has shown that active learning has a considerable advantage over traditional lecture for student learning in undergraduate STEM classes, but there have been few large-scale studies to identify the specific types of activities that have the greatest impact on learning. We therefore undertook a large-scale, curriculum-wide study to investigate the effects of time spent on a variety of classroom activities on learning gains. We quantified classroom practices and related these to student learning, assessed using diagnostic tests written by over 3700 students, across 31 undergraduate biology classes at a research-intensive university in the Pacific Northwest. The most significant positive predictor of learning gains was the use of group work, supporting the findings of previous studies. Strikingly, we found that the addition of worksheets as an active learning tool for in-class group activities had the strongest impact on diagnostic test scores. This particular low-tech activity promotes student collaboration, develops problem solving skills, and can be used to inform the instructor about what students are struggling with, thus providing opportunities for valuable and timely feedback. Overall, our results indicate that group activities with low barriers to entry, such as worksheets, can result in significant learning gains in undergraduate science.

Implantation reduces the negative effects of bio-logging devices on birds.

Animal-borne logging or telemetry devices are widely used for measurements of physiological and movement data from free-living animals. For such measurements to be relevant, however, it is essential that the devices themselves do not affect the data of interest. A recent meta-analysis reported an overall negative effect of these devices on the birds that bear them, i.e. on nesting productivity, clutch size, nest initiation date, offspring quality, body condition, flying ability, foraging behaviours, energy expenditure and survival rate. Method of attachment (harness, collar, glue, anchor, implant, breast-mounted or tailmount) had no influence on the strength of these effects but anchored and implanted transmitters had the highest reported rates of device-induced mortality. Furthermore, external devices, but not internal devices, caused an increase in 'device-induced behaviour' (comfort behaviours such as preening, fluffing and stretching, and unrest activities including unquantifiable 'active' behaviours). These findings suggest that, with the exception of device-induced behaviour, external attachment is preferable to implantation. In the present study we undertake a meta-analysis of 183 estimates of device impact from 39 studies of 36 species of bird designed to explicitly compare the effects of externally attached and surgically implanted devices on a range of traits, including condition, energy expenditure and reproduction. In contrast to a previous study, we demonstrate that externally attached devices have a consistent detrimental effect (i.e. negative influences on body condition, reproduction, metabolism and survival), whereas implanted devices have no consistent effect. We also show that the magnitude of the negative effect of externally attached devices decreases with time. We therefore conclude that device implantation is preferable to external attachment, providing that the risk of mortality associated with the anaesthesia and surgery required for implantation can be mitigated. We recommend that studies employing external devices use devices that can be borne for long periods, and, wherever possible, deploy devices in advance of the time period of interest.

The repeatability of metabolic rate declines with time.

The evolutionary causes of variation in metabolic rate within and among species are a topic of enduring interest. Variation between individuals is the raw material on which natural selection acts, and so recent years have seen an increase in the number of studies that examine the consequences of inter-individual differences in metabolic rate for organismal performance. A minimum requirement for a trait to evolve is that it must differ consistently between individuals, and these differences must be heritable. The time constancy of a trait is assessed by estimating its repeatability, which represents the ratio of the between-individual component of phenotypic variance to total phenotypic variance. A previous meta-analysis of repeatability concluded that metabolic rate is, on average, repeatable. Here, we expand on this earlier analysis by including extra data published in the intervening years and demonstrate that the repeatability of metabolic rate decreases as the interval between measurements increases.

Standard metabolic rate is associated with gestation duration, but not clutch size, in speckled cockroaches Nauphoeta cinerea.

Metabolic rate varies significantly between individuals, and these differences persist even when the wide range of biotic and abiotic factors that influence metabolism are accounted for. It is important to understand the life history implications of variation in metabolic rate, but they remain poorly characterised despite a growing body of work examining relationships between metabolism and a range of traits. In the present study we used laboratory-bred families (one sire to three dams) of Nauphoeta cinerea (Olivier) (speckled cockroaches) to examine the relationship between standard metabolic rate (SMR) and reproductive performance (number of offspring and gestation duration). We show that SMR is negatively associated with female gestation duration. Age at mating is negatively associated with gestation duration for females, and mass is negatively associated with the average gestation duration of the females a male was mated with. In addition to the results in the current literature, the results from the present study suggest that the association between metabolism and life history is more complex than simple relationships between metabolism and various fitness traits. Future work should consider longitudinal, ontogenetic as well as selective and quantitative genetic breeding approaches to fully examine the associations between metabolism and fitness.

Cockroaches that exchange respiratory gases discontinuously survive food and water restriction.

Metabolic rate and respiratory gas exchange patterns vary significantly both between and within species, even after a number of biotic and abiotic factors are taken into account. This suggests that such variation is of evolutionary importance, but the life history implications of this variation remain relatively poorly characterized. In the present study, we examine the effect of metabolic variation on starvation and desiccation resistance in the speckled cockroach Nauphoeta cinerea. We also compare the starvation and desiccation resistance of individuals that exchange respiratory gases continuously with those that breathe discontinuously. We show that metabolic rate has no effect on survival during food and water restriction, but cockroaches exhibiting discontinuous gas exchange cycles (DGCs) live longer than those that do not and those provisioned with water lived longer than those that were not. This finding represents the first demonstration that DGCs confer a fitness benefit, and supports the oldest hypothesis for the evolution of DGCs (which suggests that DGCs arose or are maintained to reduce respiratory water loss) as we also reveal reduced water loss (both respiratory and total) in cockroaches exhibiting discontinuous gas exchange.

Cockroaches breathe discontinuously to reduce respiratory water loss.

The reasons why many insects breathe discontinuously at rest are poorly understood and hotly debated. Three adaptive hypotheses attempt to explain the significance of these discontinuous gas exchange cycles (DGCs), whether it be to save water, to facilitate gas exchange in underground environments or to limit oxidative damage. Comparative studies favour the water saving hypothesis and mechanistic studies are equivocal but no study has examined the acclimation responses of adult insects chronically exposed to a range of respiratory environments. The present research is the first manipulative study of such chronic exposure to take a strong-inference approach to evaluating the competing hypotheses according to the explicit predictions stemming from them. Adult cockroaches (Nauphoeta cinerea) were chronically exposed to various treatments of different respiratory gas compositions (O(2), CO(2) and humidity) and the DGC responses were interpreted in light of the a priori predictions stemming from the competing hypotheses. Rates of mass loss during respirometry were also measured for animals acclimated to a range of humidity conditions. The results refute the hypotheses of oxidative damage and underground gas exchange, and provide evidence supporting the hypothesis that DGCs serve to reduce respiratory water loss: cockroaches exposed to low humidity conditions exchange respiratory gases for shorter durations during each DGC and showed lower rates of body mass loss during respirometry than cockroaches exposed to high humidity conditions.