COVID-19 and “natural” experiments arising from physical distancing: a hypothetical case study from chronobiology

ABSTRACT

With countless “natural” experiments triggered by the COVID-19-associated physical distancing, one key question comes from chronobiology: “When confined to homes, how does the reduced exposure to natural daylight arising from the interruption of usual outdoor activities plus lost temporal organization ordinarily provided from workplaces and schools affect the circadian timing system (the internal 24 h clock) and, consequently, health of children and adults of all ages?” Herein, we discuss some ethical and scientific facets of exploring such natural experiments by offering a hypothetical case study of circadian biology.     

Quantitative trait loci influencing protein and starch concentration in the Illinois Long Term Selection maize strains

A study was initiated to determine the number, chromosomal location, and magnitude of effect of QTL (quantitative trait loci or locus depending on context) controlling protein and starch concentration in the maize (Zea mays L.) kernel. Restriction fragment length polymorphism (RFLP) analysis was performed on 100 F₃ families derived from a cross of two strains, Illinois High Protein (IHP), X Illinois Low Protein (ILP), which had been divergently selected for protein concentration for 76 generations as part of the Illinois Long Term Selection Experiment. These families were analyzed for kernel protein and starch in replicated field trials during 1990 and 1991. A series of 90 genomic and cDNA clones distributed throughout the maize genome were chosen for their ability to detect RFLP between IHP and ILP. These clones were hybridized with DNA extracted from the 100 F₃ families, revealing 100 polymorphic loci. Single factor analysis of variance revealed significant QTL associations of many loci with both protein and starch concentration (P < 0.05 level). Twenty-two loci distributed on 10 chromosome arms were significantly associated with protein concentration, 19 loci on 9 chromosome arms were significantly associated with starch concentration. Sixteen of these loci were significant for both protein and starch concentration. Clusters of 3 or more significant loci were detected on chromosome arms 3L, 5S, and 7L for protein concentration, suggesting the presence of QTL with large effects at these locations. A QTL with large additive effects on protein and starch concentration was detected on chromosome arm 3L. RFLP alleles at this QTL were found to be linked with RFLP alleles at the Shrunken-2 (Sh2) locus, a structural gene encoding the major subunit of the starch synthetic enzyme ADP-glucose pyrophosphorylase. A multiple linear regression model consisting of 6 significant RFLP loci on different chromosomes explained over 64 % of the total variation for kernel protein concentration. Similar results were detected for starch concentration. Thus, several chromosomal regions with large effects may be responsible for a significant portion of the changes in kernel protein and starch concentration in the Illinois Long Term Selection Experiment.     

Fluctuations in a coastal dune grassland due to fluctuations in rainfall: Experimental evidence

Experiments with rainfall on a dune grassland near Oostvoorne, the Netherlands with Festuco-Galietum as the main syntaxon are described. Both increase in rain through additional watering and decrease in rain through catchment are presented to plots belonging to the xerosere and the mesosere. Clear changes in the floristic composition are the result, even after only two years. Typical Festuco-Galietum species are promoted by high rainfall, species of open habitat such as Corynephorus canescens are promoted by drought. The results are discussed against the background of long term permanent plot observations in the area and a relation with rabbit grazing intensity is supposed.Nomenclature of vascular plants follows Heukels-van Ooststroom (1975) Flora van Nederland 18 ed., Woiters-Noordhoff, Groningen; Nomenclature of syntaxa follows Westhoff & den Held (1969). Plantengemeenschappen in Nederland, Thieme, Zutphen.Field work in 1978 was carried out with Frans Bongers and Marc de Lyon, in 1979 with Marc de Lyon, Picter Meeuwissen and Guiljo van Nuland, all then MSc. students at the Division of Geobotany. Their help and the advice of Dr. Peter van der Aart, Institute of Ecological Research, Oostvoorne, are acknowledged.     

Density-related mortality of the flour beetle,Tribolium confusum duval

Life tables were constructed to assess the relative importance of some factors causing mortality of Tribolium confusum and to gauge their response to increasing population density. Observations focussed on three population densities (100, 400 and 800 individual/8 g medium) from the egg to the adult stage. The medium was not renewed in order to maximize predatory interactions. Generation mortality at densities 100, 400 and 800 was 42%, 50% and 74% respectively, i. e. density-dependent. Mortality in the first 10 days was also density-dependent reaching a maximum of 27% at density 800: predation by small larvae on eggs seemed the principal causative factor. The overall pattern of larval mortality was density-independent. Data on the mortality of pupae and callows were ultimately consistent with an inversely density-dependent pattern. Apparently, only mortality occurring within the first 10 days was capable of population regulation.     

“互联网+”背景下“微生物学实验”课程的改革与实践

"互联网+"技术应用于教育使高校教学在教学场景、教师角色和学生学习特点等方面发生巨大变化。为适应"互联网+"时代的教学特点以及学生个性化学习和创新能力培养的需要,将智慧教学工具引入到"微生物学实验"课程教学以及在互联网学习平台上建设在线开放课程。雨课堂教学工具将智能手机转变为学生的学习工具,提高了学生学习的积极性、加强了师生间的互动、实现了教学效果的及时反馈,学生的学习数据有助于教师更客观地评价学习效果和更好地开展个性化教学。其次,在江苏省在线课程中心平台上开展了江苏省在线开放课程"微生物学模块化实验"的建设工作。课程建设需及时更新教学理念,提高教师参与课程建设的积极性;加强在线开放课程建设的岗前培训;课程内容应考虑大学生的学习特点、制作成本和学习成本等因素。在线课程的建设为开展翻转课堂教学和混合式教学提供支撑条件,为"互联网+"背景下的"微生物学实验"教学改革奠定基础。     

Diversity and beyond: plant functional identity determines herbivore performance

1. Recent biodiversity studies have addressed various community-level effects of biodiversity change, but the number of studies on specific biotic interactions is still rather limited. An open question in the context of plant-insect-herbivore relationships is how diversity impacts the population ecology of individual species. 2. In the present study, we explored the relationship between plant species diversity and the performance and fitness of a generalist herbivore, the meadow grasshopper Chorthippus parallelus Zetterstedt (Orthoptera, Gomphocerinae). A total of 1620 fourth-instar nymphs of this insect were captured and transferred to cages (10 females and 10 males per cage) on 81 experimental grassland communities in plots containing one to 60 plant species within the Jena biodiversity experiment. 3. Median survival of grasshoppers in the experiment was 14.5 days. Survival was independent of plant species richness and number of plant functional groups in the communities, but increased if plant communities contained grasses. Plant species richness and plant functional group richness had no effect on the number of oothecae laid by females or the number of hatchlings in the next generation. 4. Functional group composition of the plant communities affected most fitness measures. Grass presence increased the number of oothecae laid by females from 0.78 +/- 0.21 to 3.7 +/- 0.41 per female, and the number of hatchlings in the next generation from 4.0 +/- 1.3 to 16.6 +/- 2.4. Certain combinations of plant functional groups increased grasshopper survival. 5. The findings indicate that the fitness of C. parallelus is influenced more by plant functional group identity than by plant species richness. In the absence of grasses, grasshoppers performed better if more than just one functional group of plants was present. We call this a 'rescue effect' of plant functional group richness.     

Root exudate cocktails: the link between plant diversity and soil microorganisms?

Higher plant diversity is often associated with higher soil microbial biomass and diversity, which is assumed to be partly due to elevated root exudate diversity. However, there is little experimental evidence that diversity of root exudates shapes soil microbial communities. We tested whether higher root exudate diversity enhances soil microbial biomass and diversity in a plant diversity gradient, thereby negating significant plant diversity effects on soil microbial properties. We set up plant monocultures and two‐ and three‐species mixtures in microcosms using functionally dissimilar plants and soil of a grassland biodiversity experiment in Germany. Artificial exudate cocktails were added by combining the most common sugars, organic acids, and amino acids found in root exudates. We applied four different exudate cocktails: two exudate diversity levels (low‐ and high‐diversity) and two nutrient‐enriched levels (carbon‐ and nitrogen‐enriched), and a control with water only. Soil microorganisms were more carbon‐ than nitrogen‐limited. Cultivation‐independent fingerprinting analysis revealed significantly different soil microbial communities among exudate diversity treatments. Most notably and according to our hypothesis, adding diverse exudate cocktails negated the significant plant diversity effect on soil microbial properties. Our findings provide the first experimental evidence that root exudate diversity is a crucial link between plant diversity and soil microorganisms.     

实验教学改革条件下医学微生物学实验考核评价体系的构建与实践

配合医学微生物学科实验教学改革的实施,建立以实验全过程管理为基础,以合理评价指标为核心,以科学评价学生综合实验能力为目标的实验考核评价体系。分层次考核学生的基本技能掌握情况、科学的实验思想,及综合性探究性实验的能力。通过调查表及访谈结果可以看出,考核评价体系能够科学地反映学生的实验能力、综合能力,具有传统的实验考核评价体系不可比拟的优越性。     

“微生物学实验”混合式教学实践与评价

生命科学的本科教学中,实验教学是举足轻重的一个部分。本文以"微生物学实验"课程为研究对象,利用互动网站进行线上线下混合式教学,评价学生的学习效果和规律,探索生命科学实验类课程采用混合式教学的效果,并探讨推广可能性。在连续三年的教学实践中,统计分析各维度数据,发现在混合式教学模式下,绝大部分学生都具有主动自学的能力。同时,实验课程中的深度和广度都有所提升。学习规律的监控和综合评价显示,深度学习的学生在各种评价指标中都显著表现优秀。因此,在混合式教学模式下,如何引导学生进行真实有效的深度学习是教师在新教学模式下的重任。     

任务驱动法在“微生物学实验”混合式教学中的实践

通过“微生物学实验”课程多年来的混合式教学实践发现,学生的主动性是学习效果的核心要素。鉴于在以往的教学实践中,无论采用何种教学手段,总有部分学生的学习主动性不能得到体现。我们近年来采用轮流组长责任制下的任务驱动教学法,极大地调动了所有学生的学习动力。每位学生在担任组长工作时从课前任务、课堂执行、课后总结等方面都发挥了重要作用,而不担任组长时也会积极主动地配合组长工作。最终,实验课程学习成绩优秀率占比、体现素质能力培养的成绩分项都显著提升。同时,课程教学也收获了良好的学生认可和反馈。