Investigating the Role of an Inquiry-Based Biology Lab Course on Student Attitudes and Views toward Science.

Students' academic experiences can influence their conceptualization of science. In contrast experts hold particular beliefs, perceptions, opinions, and attitudes about science that are often absent in first-year undergraduate students. Shifts toward more expert-like attitudes and views have been linked to improved student engagement, critical-thinking ability, conceptual understanding, and academic performance. In this study, we investigate shifts in attitudes and views toward science by students in four biology classes with differences in student enrollment, academic support, and instruction. We observe significant, positive effects of enrollment in a guided-inquiry lab course and academic performance on the percentage of expert-like student attitudes and views at the end of term. We also identify variation in two aspects of student attitudes and views: 1) confidence and interest and 2) understanding and acceptance. In particular, enrollment in the lab course boosts student confidence and interest in scientific inquiry in the short term, even for students with low academic performance or little English-language experience. Our results suggest that low-performing students in particular may require additional opportunities for experiential learning or greater academic support to develop expert-like perceptions of biology as a science.

Development of the Statistical Reasoning in Biology Concept Inventory (SRBCI).

We followed established best practices in concept inventory design and developed a 12-item inventory to assess student ability in statistical reasoning in biology (Statistical Reasoning in Biology Concept Inventory [SRBCI]). It is important to assess student thinking in this conceptual area, because it is a fundamental requirement of being statistically literate and associated skills are needed in almost all walks of life. Despite this, previous work shows that non-expert-like thinking in statistical reasoning is common, even after instruction. As science educators, our goal should be to move students along a novice-to-expert spectrum, which could be achieved with growing experience in statistical reasoning. We used item response theory analyses (the one-parameter Rasch model and associated analyses) to assess responses gathered from biology students in two populations at a large research university in Canada in order to test SRBCI's robustness and sensitivity in capturing useful data relating to the students' conceptual ability in statistical reasoning. Our analyses indicated that SRBCI is a unidimensional construct, with items that vary widely in difficulty and provide useful information about such student ability. SRBCI should be useful as a diagnostic tool in a variety of biology settings and as a means of measuring the success of teaching interventions designed to improve statistical reasoning skills.

Development of the Biological Experimental Design Concept Inventory (BEDCI).

Interest in student conception of experimentation inspired the development of a fully validated 14-question inventory on experimental design in biology (BEDCI) by following established best practices in concept inventory (CI) design. This CI can be used to diagnose specific examples of non-expert-like thinking in students and to evaluate the success of teaching strategies that target conceptual changes. We used BEDCI to diagnose non-expert-like student thinking in experimental design at the pre- and posttest stage in five courses (total n = 580 students) at a large research university in western Canada. Calculated difficulty and discrimination metrics indicated that BEDCI questions are able to effectively capture learning changes at the undergraduate level. A high correlation (r = 0.84) between responses by students in similar courses and at the same stage of their academic career, also suggests that the test is reliable. Students showed significant positive learning changes by the posttest stage, but some non-expert-like responses were widespread and persistent. BEDCI is a reliable and valid diagnostic tool that can be used in a variety of life sciences disciplines.

Longitudinal Study of Student Attitudes in a Biology Program.

This is among the first longitudinal studies to report student attitudes across 4 yr of a university program. We found that the attitudes of students in biology become significantly more expert-like from the first year to the fourth year of the program, that is, there was a significant positive shift in students' overall percent favorable scores from 64.5 to 72%, as opposed to the expert response, which averaged 90%. There was a significant positive shift for the real world connection category (78-85%), the enjoyment (personal interest) category (74-82%), and the conceptual connections/memorization category (66-74%). Moreover, there was a significant correlation between students' overall percent favorable scores and performance (cumulative grade point average) at the end, but not at the beginning, of the fourth year, with high-performing students having significantly more expert-like attitudes than low-performing students. The correlation between percent favorable score and performance was the strongest for the problem solving: synthesis and application category, in which the highest-performing students finished their fourth year with 90% favorable compared with 35% favorable for the lowest-performing students. A comparison of these results with previously reported results and their implications for teaching are discussed.

Development of a meiosis concept inventory.

We have designed, developed, and validated a 17-question Meiosis Concept Inventory (Meiosis CI) to diagnose student misconceptions on meiosis, which is a fundamental concept in genetics. We targeted large introductory biology and genetics courses and used published methodology for question development, which included the validation of questions by student interviews (n = 28), in-class testing of the questions by students (n = 193), and expert (n = 8) consensus on the correct answers. Our item analysis showed that the questions' difficulty and discrimination indices were in agreement with published recommended standards and discriminated effectively between high- and low-scoring students. We foresee other institutions using the Meiosis CI as both a diagnostic tool and an instrument to assess teaching effectiveness and student progress, and invite instructors to visit http://q4b.biology.ubc.ca for more information.

The Colorado Learning Attitudes about Science Survey (CLASS) for use in Biology.

This paper describes a newly adapted instrument for measuring novice-to-expert-like perceptions about biology: the Colorado Learning Attitudes about Science Survey for Biology (CLASS-Bio). Consisting of 31 Likert-scale statements, CLASS-Bio probes a range of perceptions that vary between experts and novices, including enjoyment of the discipline, propensity to make connections to the real world, recognition of conceptual connections underlying knowledge, and problem-solving strategies. CLASS-Bio has been tested for response validity with both undergraduate students and experts (biology PhDs), allowing student responses to be directly compared with a consensus expert response. Use of CLASS-Bio to date suggests that introductory biology courses have the same challenges as introductory physics and chemistry courses: namely, students shift toward more novice-like perceptions following instruction. However, students in upper-division biology courses do not show the same novice-like shifts. CLASS-Bio can also be paired with other assessments to: 1) examine how student perceptions impact learning and conceptual understanding of biology, and 2) assess and evaluate how pedagogical techniques help students develop both expertise in problem solving and an expert-like appreciation of the nature of biology.

Metabolic responses to light in monkey photoreceptors.

PURPOSE: Transient changes in intraretinal oxygen tension (PO(2)) in response to light stimuli were studied in order to understand the dynamics of light-evoked changes in photoreceptor oxidative metabolism. METHODS: PO(2) changes during illumination were recorded by double-barreled microelectrodes in the outer part of the perifoveal retina in five macaques (Rhesus and Cynomolgus) and were fitted to a single exponential equation to obtain the time constant (tau) and maximum PO(2) change. RESULTS: At the onset of light, PO(2) increased at all illuminations in all animals. The magnitude of the light-evoked PO(2) change increased with increasing illumination over 3-4 log units but decreased in all animals at the maximum illumination. The median time constant of the PO(2) change (tau) was 26 sec and was not correlated with illumination. The time constant for the return to darkness was similar for illuminations below rod saturation. Since O(2) diffusion is fast over the short distance from the choroid to the inner segments, tau reflects the time course of the underlying change in oxidative metabolism. CONCLUSIONS: Previous results suggested that two competing processes influence the change in photoreceptor oxidative metabolism with light, Na(+)/K(+) pumping and cyclic guanosine monophosphate (cGMP) turnover. Because a single exponential fitted the PO(2) data, it appears that these processes have time constants that differ by no more than a few seconds in primate. In monkeys, tau is longer than previously reported values for cat and rat. Longer time constants are related to larger photoreceptor volume, possibly because metabolic rate is controlled by intracellular Na(+), and a change in intracellular Na(+) after the onset of illumination occurs more slowly in larger photoreceptors. The "metabolic threshold" illumination that reduced oxygen consumption by about 10% is approximately the same as the illumination that closes 10% of the light-dependent cation channels that are open in the dark.

Effects of photocoagulation on intraretinal PO2 in cat.

PURPOSE: To test the hypothesis that intraretinal Po(2) increases after photocoagulation. METHODS: Anesthetized cats underwent retinal argon laser photocoagulation. At least 4 weeks after treatment, Po(2)-sensitive microelectrodes were used to record intraretinal Po(2) profiles from healed photocoagulation lesions in anesthetized cats breathing air. Histopathologic examination of the retinas was used to confirm that the photoreceptors were destroyed and that the inner retinal layers were preserved, though somewhat disorganized, as in human panretinal photocoagulation (PRP). RESULTS: The retina and tapetum were thinner in the lesioned retina than in the nonphotocoagulated retina. Average Po(2) across the inner 50% of the retina was higher (22 +/- 10 mm Hg) in photocoagulated retina than in untreated retina (14 +/- 7 mm Hg; P < 0.01; n = 13 cats). The minimum Po(2) was also significantly higher, whereas choroidal Po(2) was significantly lower in the photocoagulated retina than in untreated retina. No significant difference was found in the preretinal vitreous. After lesions, inner retinal Po(2) could also be maintained above zero, even in the absence of retinal circulation. CONCLUSIONS: Previous measurements showed increased Po(2) in the preretinal vitreous of rabbits and pigs (but not cats) after photocoagulation of the outer retina. These intraretinal measurements in cats provide further evidence for a chronic increase in inner retinal Po(2) in lesioned areas during air breathing.

Oxygen distribution and consumption in the macaque retina.

The oxygen distribution in the retina of six anesthetized macaques was investigated as a model for retinal oxygenation in the human retina in and adjacent to the fovea. P(O2) was measured as a function of retinal depth under normal physiological conditions in light and dark adaptation with O(2) microelectrodes. Oxygen consumption (Q(O2)) of the photoreceptors was extracted by fitting a steady-state diffusion model to P(O2) measurements. In the perifovea, the P(O2) was 48 +/- 13 mmHg (mean and SD) at the choroid and fell to a minimum of 3.8 +/- 1.9 mmHg around the photoreceptor inner segments in dark adaptation, rising again toward the inner retina. The P(O2) in the inner half of the retina in darkness was 17.9 +/- 7.8 mmHg. When averaged over the outer retina, photoreceptor Q(O2) (called Q(av)) was 4.6 +/- 2.3 ml O(2).100 g(-1).min(-1) under dark-adapted conditions. Illumination sufficient to saturate the rods reduced Q(av) to 72 +/- 11% of the dark-adapted value. Both perifoveal and foveal photoreceptors received most of their O(2) from the choroidal circulation. While foveal photoreceptors have more mitochondria, the Q(O2) of photoreceptors in the fovea was 68% of that in the perifovea. Oxygenation in macaque retina was similar to that previously found in cats and other mammals, reinforcing the relevance of nonprimate animal models for the study of retinal oxygenation, but there was a smaller reduction in Q(O2) with light than observed in cats, which may have implications for understanding the influence of light under some clinical conditions.

Retinal arterial occlusion leads to acidosis in the cat.

This study investigated the changes in pH during retinal artery occlusion by means of extracellular H+ concentration ([H+]o) measurements in the retina under both air and 100% O2 ventilation. Occlusion was produced in intact anesthetised cats by pressing with a probe onto a retinal artery. [H+]o profiles were recorded across the retina with pH sensitive microelectrodes. The average inner retinal [H+]o increased during occlusion, resulting in an acidification of as much as 0.10 pH units, even under 100% O2 ventilation. The inner retinal H+ profile magnitude decreased during occlusion due to impaired clearance. The average outer retinal H+ profile magnitude also increased even though outer retinal H+ production did not increase during occlusion. This might be due to H+ diffusion from the inner retina to the outer retina, which is opposite to the flux in the normal retina. After reperfusion, [H+]o returned to its preocclusion value. In conclusion, arterial occlusion leads to acidification of the retina. Enhanced oxygenation during occlusion did not decrease this acidification. This may explain why increasing PO2 in the retina by enhanced O2 breathing improves retinal function during and after occlusion, but does not totally reverse the effect of occlusion.

Hyperoxia promotes electroretinogram recovery after retinal artery occlusion in cats.

PURPOSE: This work assessed the hypotheses that (1) hyperoxia is preferable to air breathing during retinal arterial occlusion, (2) hyperoxia during occlusion is beneficial in promoting recovery from arterial occlusion, and (3) hyperoxia has value even if it is delayed relative to the onset of the occlusion. METHODS: Reversible branch retinal artery occlusion was produced by pressing with a glass probe onto an artery emerging from the superior part of the optic disc in the retina of anesthetized cats. During 2-hour occlusion episodes, the cats breathed 100% O(2), 1 hour of air and 1 hour of 100% O(2), 1 hour of air and 1 hour of 70% O(2), or air. Intraretinal ERGs were recorded before, during, and after the occlusion. RESULTS: Hyperoxia during occlusion preserved intraretinal b-wave amplitude at 86% +/- 12% of normal; longer durations of increased oxygenation maintained the b-wave at higher levels during occlusion and increased the probability of b-wave recovery after occlusion; higher O(2) content in the breathing gas increased b-wave amplitude during recovery; and hyperoxia during occlusion decreased the time it took for the b-wave to recover after the occlusion. CONCLUSIONS: Hyperoxia is preferable to air breathing during retinal arterial occlusion not only for maintaining b-wave amplitude during occlusion, but also for providing a shorter recovery time and better percentage recovery after the end of the occlusion. Even if it is not possible to begin hyperoxia at the onset of occlusion, it may still be valuable.

A morphologically structured model for penicillin production.

A morphologically structured model is proposed to describe penicillin production in fed-batch cultivations. The model accounts for the effects of dissolved oxygen on cell growth and penicillin production and variations in volume fractions of abiotic and biotic phases due to biomass formation. Penicillin production is considered to occur in the subapical hyphal cell compartment and to be affected by availability of glucose and oxygen. As it stands, the model provides a wide range of applicability in terms of operating conditions. The model has been tested for various conditions and has given satisfactory results. A series of glucose feeding profiles have been considered to demonstrate the capabilities of the proposed model. It is concluded that the model may be valuable for the interpretation of experimental data collected specifically for metabolic flux analysis during fed-batch cultivation because the elements of measured specific production rates are determined from measurements of the concentrations of the components and their mass balances. The proposed model may be further used for developing control strategies and model order reduction algorithms.