An ecological approach to restructuring school biology

As a follow-up to the human-centred and cybernetic structuring principles described by Kattman and Schaefer in J. Biol. Educ. 10 (3), an ecological structuring principle is discussed. This principle takes the dynamic and reciprocal relationships between man and his environment as the basis of his existence. The reciprocal relationships are characterized as the biological capacity for self-preservation, reproduction, and adaptation. Several examples from a teaching syllabus are given to illustrate this approach.     

The Quiet Revolution: A New Synthesis of Biological Knowledge

A method is described for preparing thin-layer chromatography plates for use in the classroom. Glass plates are coated with adsorbent using a technique which is cheap, rapid and reliable and which avoids the need for expensive, commercially-available apparatus. It can be adapted to preparative use. The main adsorbent described is silicic acid H and G but other adsorbents such as cellulose can be spread by the same method. Points to watch for in setting up plates for thin-layer chromatography and applying solute samples are discussed.     

Studying the activities of microorganisms in soil using slides

Two implanted slide techniques are described by which the activity of proteolytic bacteria and the growth of algae in the soil can be readily studied by school students using simple apparatus and methods. Variations are suggested for studying the effects of agricultural practices and environmental conditions on the soil bacteria and algae.     

Testosterone increases repertoire size in an open-ended learner: An experimental study using adult male European starlings (Sturnus vulgaris)

Song in songbirds is a learned secondary sexual behavior, first acquired during a sensitive phase of juvenile development, which is affected by hormones such as testosterone (T). While the latter has received much attention, the potential involvement of T in the adult repertoire changes observed in a number of species is much less understood. Yet, this may prove essential to understand the role of song as a sexually selected trait. We therefore performed a T-implantation experiment during the non-breeding season (when T is basal), using adult male European starlings (Sturnus vulgaris), a songbird species in which song repertoire size (and composition) changes seasonally and increases with age. Repertoire size increased rapidly in T-males, but not in control males, indicating a role for T in repertoire size changes. This increase resulted from a lower proportion of dropped song types in T-males than in control males, while the proportion of added song types did not differ between both groups. Interestingly, the observed repertoire turnover (adding and removing song types from the repertoire) in both groups, suggests that elevated plasma T levels were not essential for changes in repertoire composition (contrary to repertoire size). Finally, T-males (but not control males) significantly increased their song rate, while neither group showed a significant change in their song bout length and phrase repetition rate. Taken together, our results suggest a role for T in adult song learning and provide new insights into the information content of repertoire size and song bout length as sexually selected traits.     

A Simple and Accurate Method for the Study of Water Movement across Amphibian Skin

Ethical principles have long been associated with biological phenomena. A review of some of the different forms this has taken in the past and of issues which are arising currently suggests that ethics should be taught as part of biological education within a framework of history, futures study, training in clear thinking and the development of empathy.     

Improving achievement through problem-based learning

In this study, the effect of problem-based learning on students' academic achievement and performance skills in a unit on he human excretory system was investigated. Sixty-one 10th grade students, from two full classes instructed by the same iology teacher, were involved in the study. Classes were randomly assigned as either the experimental or the control group and were pre- and post-tested to determine their academic achievement and performance skills before and after the treatment. The experimental group was taught with problem-based learning while the control group received traditionally-designed biology instruction. Results showed that although there was no pre-existing difference between two groups, students instructed with problem-based learning earned significantly higher scores than those instructed with traditionally-designed biology instruction — in terms of academic achievement and performance skills. Students in the experimental group appeared to be more proficient in the use and organisation of relevant information, in constructing knowledge and moving toward better conclusions.     

Properties of the biosurfactant produced byBacillus licheniformis strain JF-2

Summary The activity of the biosurfactant produced byBacillus licheniformis strain JF-2 was quantified using a unit defined as the amount of the acid-precipitated biosurfactant that lowered the surface tension by 10 mN/m. One unit was equivalent to 37 g/ml of the acid-precipitated biosurfactant. Acid precipitation was very effective in the removal of the biosurfactant from the spent medium. Among the solvents tested methanol was the most efficient in extracting the surfactant activity from acid-precipitated material. Thin-layer chromatography of the acid-precipitated biosurfactant revealed four components, two of which contained a lipid moiety and one of which contained an amino group. The methanol-soluble fraction also contained these four components. Studies suggested that all four components were needed for full activity. The lowest interfacial tensions against octane were observed when NaCl concentrations were 50 g/l or greater. Calcium concentrations greater than 25 g/l significantly increased the interfacial tension     

Plasticity in flower size as an adaptation to variation in pollinator specificity

1. Mutualisms, including plant-pollinator interactions, are an important component of ecosystems. 2. Plants can avoid the costs of variation in pollinator benefit by maintaining specificity. 3. We hypothesise a novel mechanism to ensure specificity, which takes advantage of the cognitive abilities of specific pollinators to exclude non-specific flower visitors. 4. Inflorescences of the tropical vine genus Psiguria produce flowers at regular intervals, with subsequent flowers smaller than predecessors. 5. The principle pollinators, Heliconius spp., possess an excellent spatial memory. 6. Therefore, decreasing flower size may ensure specific pollination: once Heliconius individuals have learnt the location of an inflorescence they will return, but inconspicuous flowers should reduce visits by non-specific pollinators with poorer spatial memories. 7. We tested the predictions of this hypothesis with field experiments in Panama. We confirmed that flowers on inflorescences are smaller than their predecessors. 8. Paired experiments showed that larger flowers attracted more pollinators and that the presence of an initial large flower increased subsequent visitation by Heliconius spp. to small flowers, indicating learning behaviour. 9. These results suggest that learning behaviour and decreasing flower size maintain visits from specific pollinators while reducing those from non-specific pollinators. We propose this as a novel mechanism for promoting pollinator specificity and discuss its ecological significance.