How Instructors Can Enhance Biology Students' Motivation, Learning, and Grades through Brief Relevance Writing and Worked-Example Interventions.

The high failure rate of students in "gateway" science, technology, engineering, and mathematics (STEM) courses has been a persistent problem for biology programs nationwide. Common wisdom contends that addressing this problem requires major curricular overhauls. While desirable, such large systematic changes are often expensive or impractical. We propose an alternative approach: supplementing the regular instruction with brief online modules targeting specific cognitive (learning) and motivational mechanisms. We conducted an intervention study to test the effects of different combinations of cognitive and motivational modules on undergraduate introductory biology students' learning, motivation, achievement, and intentions to remain in science. Introductory biology students at three research universities were randomly assigned to a no-treatment control condition or one of several combinations of cognition motivation modules. In this article, we describe the modules that are easiest for instructors to integrate with existing course content: worked examples (demonstrations of biology problem solving) and relevance writing (brief open-ended writing assignments about connections of biology concepts to one's life). Increased student engagement in these modules led to higher motivation, biology reasoning, and course grades. These findings support the effectiveness of delivering brief online supplemental modules on students' success in introductory biology courses. This easily implemented intervention can utilize online tools such as Blackboard, Canvas, or Moodle and provides an option when major changes to course instruction are not practical.

Constructional morphology within the head of hammerhead sharks (sphyrnidae).

The study of functional trade-offs is important if a structure, such as the cranium, serves multiple biological roles, and is, therefore, shaped by multiple selective pressures. The sphyrnid cephalofoil presents an excellent model for investigating potential trade-offs among sensory, neural, and feeding structures. In this study, hammerhead shark species were chosen to represent differences in head form through phylogeny. A combination of surface-based geometric morphometrics, computed tomography (CT) volumetric analysis, and phylogenetic analyses were utilized to investigate potential trade-offs within the head. Hammerhead sharks display a diversity of cranial morphologies where the position of the eyes and nares vary among species, with only minor changes in shape, position, and volume of the feeding apparatus through phylogeny. The basal winghead shark, Eusphyra blochii, has small anteriorly positioned eyes. Through phylogeny, the relative size and position of the eyes change, such that derived species have larger, more medially positioned eyes. The lateral position of the external nares is highly variable, showing no phylogenetic trend. Mouth size and position are conserved, remaining relatively unchanged. Volumetric CT analyses reveal no trade-offs between the feeding apparatus and the remaining cranial structures. The few trade-offs were isolated to the nasal capsule volume's inverse correlation with braincase, chondrocranial, and total cephalofoil volume. Eye volume also decreased as cephalofoil width increased. These data indicate that despite considerable changes in head shape, much of the head is morphologically conserved through sphyrnid phylogeny, particularly the jaw cartilages and their associated feeding muscles, with shape change and morphological trade-offs being primarily confined to the lateral wings of the cephalofoil and their associated sensory structures.

Feeding anatomy, filter-feeding rate, and diet of whale sharks Rhincodon typus during surface ram filter feeding off the Yucatan Peninsula, Mexico.

The feeding anatomy, behavior and diet of the whale shark Rhincodon typus were studied off Cabo Catoche, Yucatan Peninsula, Mexico. The filtering apparatus is composed of 20 unique filtering pads that completely occlude the pharyngeal cavity. A reticulated mesh lies on the proximal surface of the pads, with openings averaging 1.2mm in diameter. Superficial to this, a series of primary and secondary cartilaginous vanes support the pads and direct the water across the primary gill filaments. During surface ram filter feeding, sharks swam at an average velocity of 1.1m/s with 85% of the open mouth below the water's surface. Sharks on average spent approximately 7.5h/day feeding at the surface on dense plankton dominated by sergestids, calanoid copepods, chaetognaths and fish larvae. Based on calculated flow speed and underwater mouth area, it was estimated that a whale shark of 443 cm total length (TL) filters 326 m(3)/h, and a 622 cm TL shark 614 m(3)/h. With an average plankton biomass of 4.5 g/m(3) at the feeding site, the two sizes of sharks on average would ingest 1467 and 2763 g of plankton per hour, and their daily ration would be approximately 14,931 and 28,121 kJ, respectively. These values are consistent with independently derived feeding rations of captive, growing whale sharks in an aquarium. A feeding mechanism utilizing cross-flow filtration of plankton is described, allowing the sharks to ingest plankton that is smaller than the mesh while reducing clogging of the filtering apparatus.

Phylogeny of hammerhead sharks (Family Sphyrnidae) inferred from mitochondrial and nuclear genes.

Hammerhead sharks (Family Sphyrnidae) get their name from their laterally expanded, dorsal-ventrally compressed head, a structure referred to as the cephalofoil. Species within the family vary for head size and shape and for body size in ways that are functionally significant. Here we infer the phylogeny for all species within the family based on analysis of mitochondrial and nuclear genes amounting to 6292 base pairs. Mixed model Bayesian analysis of the concatenated data and Bayesian estimation of the species tree (BEST) converged on the same topology of the relationships. Shimodaira-Hasegawa tests revealed that all previously proposed hypotheses could be refuted by the data. The new hypothesis for the group suggests that the ancestor of all extant sharks was large (>200 cms) and that small body size probably evolved twice at different times and places. Moreover, the results suggest that once the cephalofoil evolved, it underwent divergent evolution in different lineages presumably in response to unique selective regimes.

Bite force and performance in the durophagous bonnethead shark, Sphyrna tiburo.

Bite force, a measure of performance, can be used to link anatomical form and function. Earlier studies have shown bite force to have a significant influence on dietary constraints and ontogenetic shifts in resource utilization. The bonnethead shark, Sphyrna tiburo, is a durophagous member of the family Sphyrnidae. Its diet in South Florida waters consists almost entirely of blue crabs, which are crushed or ingested whole. This abundant coastal predator's feeding mechanism is specialized for the consumption of hard prey, including a modified biting pattern and molariform teeth. The goals of this research were to (1) characterize the mechanical function of the feeding mechanism of S. tiburo through biomechanical modeling of biting and in vivo bite force measurements; (2) compare the bite force of S. tiburo with those of other fishes; and (3) identify functional constraints on prey capture by comparing the bite force of S. tiburo with the fracture properties of its primary prey item, blue crabs. Maximum theoretical bite force ranged from 25.7 N anteriorly to 107.9 N posteriorly. S. tiburo has the second lowest mass specific bite force for any fish studied to date, and its posterior mechanical advantage of 0.88 is lower than other durophagous chondrichthyans, indicating that this independent evolutionary acquisition of durophagy was not accompanied by the associated morphological changes found in other durophagous cartilaginous fishes. Blue crab fracture forces (30.0-490.0 N) range well above the maximum bite force of S. tiburo, suggesting that prey material properties functionally constrain dietary ecology to some degree.

Functional morphology of the feeding apparatus, feeding constraints, and suction performance in the nurse shark Ginglymostoma cirratum.

The nurse shark, Ginglymostoma cirratum, is an obligate suction feeder that preys on benthic invertebrates and fish. Its cranial morphology exhibits a suite of structural and functional modifications that facilitate this mode of prey capture. During suction-feeding, subambient pressure is generated by the ventral expansion of the hyoid apparatus and the floor of its buccopharyngeal cavity. As in suction-feeding bony fishes, the nurse shark exhibits expansive, compressive, and recovery kinematic phases that produce posterior-directed water flow through the buccopharyngeal cavity. However, there is generally neither a preparatory phase nor cranial elevation. Suction is generated by the rapid depression of the buccopharyngeal floor by the coracoarcualis, coracohyoideus, and coracobranchiales muscles. Because the hyoid arch of G. cirratum is loosely connected to the mandible, contraction of the rectus cervicis muscle group can greatly depress the floor of the buccopharyngeal cavity below the depressed mandible, resulting in large volumetric expansion. Suction pressures in the nurse shark vary greatly, but include the greatest subambient pressures reported for an aquatic-feeding vertebrate. Maximum suction pressure does not appear to be related to shark size, but is correlated with the rate of buccopharyngeal expansion. As in suction-feeding bony fishes, suction in the nurse shark is only effective within approximately 3 cm in front of the mouth. The foraging behavior of this shark is most likely constrained to ambushing or stalking due to the exponential decay of effective suction in front of the mouth. Prey capture may be facilitated by foraging within reef confines and close to the substrate, which can enhance the effective suction distance, or by foraging at night when it can more closely approach prey.