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Specific to the topic of oxidation–reduction (redox), teachers are obligated by the discipline to prioritise symbolic traditions such as writing equations, documenting oxidation states, and describing changes ( e.g. , what undergoes oxidation/reduction). Although the chemistry education research community endorses connecting the vertices of Johnstone's triangle, how symbolic traditions undermine chemistry concept development, especially during lesson planning and teaching, is underexplored. To clarify this gap, we use the Mangle of Practice framework to unpack the clash between symbolic vs. particulate-focused instruction. We investigate teachers’ ( n = 3) co-planning and micro-teaching of a redox learning design at the VisChem Institute-2 using a narrative approach and video research methods. Our results show that the traditions of redox instruction are problematically entrenched in chemistry symbols. Mnemonics, the single replacement reaction scheme, and the written net ionic equation all constrain instruction focused on chemical mechanism and causality in various ways. We assert that the nature of redox knowledge in terms of what is worth teaching and learning must first be re-evaluated for reform-based efforts to succeed. Implications and suggestions for chemistry teaching and research at both secondary and tertiary levels are discussed. 

Despite years of research and practice inspired by chemistry education research, a recent report shows that US secondary instruction is not aligned with current national reform-based efforts. One means to mitigate this discrepancy is focusing on pedagogical conceptual change, its precursors (higher self-efficacy and pedagogical discontentment), and the subtleties of its mechanisms (assimilation and accommodation). In this study, we investigate the final reflections of participants ( N = 35) who completed our professional development program known as the VisChem Institute (VCI). Our results show that Johnstone's triangle as well as evidence, explanations, and models can be conducive for stimulating pedagogical discontentment among VCI teachers who exhibit higher self-efficacy. In addition, how VCI teachers assimilate and/or accommodate reform-based chemistry teaching ideas problematizes conventional assumptions, broadens application of novel theories, and is germane to introductory chemistry learning environments across the world. Implications and recommendations for chemistry instruction and research at both secondary and tertiary levels are discussed. 

Researchers have typically identified and characterized teachers’ knowledge bases ( e.g. , pedagogical content knowledge and subject matter knowledge) in an effort to improve enacted instructional strategies. As shown by the Refined Consensus Model (RCM), understanding teacher learning, beliefs, and practices is predicated on the interconnections of such knowledge bases. However, lesson planning (defined as the transformation of subject matter knowledge to enacted pedagogical content knowledge) remains underexplored despite its central position in the RCM. We aim to address this gap by developing a conceptual framework known as Pedagogical Chemistry Sensemaking (PedChemSense). PedChemSense theoretically expands upon the RCM that generates actionable guidelines to support chemsistry teachers’ lesson planning. We incorporate the constructs of sensemaking, Johnstone's triangle, and the models for perspective to provide a lesson-planning mechanism that is specific, accessible, and practical, respectively. Lesson examples from our own professional development contexts, the VisChem Institute, demonstrate the efficacy of PedChemSense. By leveraging teachers’ sensemaking of the limitations and utility of models, PedChemSense facilitates teachers’ designing for opportunities to advance their students’ chemistry conceptual understanding. Implications and recommendations for chemistry instruction and research at secondary and undergraduate levels are discussed. 

Elevated rates of evolution in reproductive proteins are commonly observed in animal species, and are thought to be driven by the action of sexual selection and sexual conflict acting specifically on reproductive traits. Whether similar patterns are broadly observed in other biological groups is equivocal. Here, we examine patterns of protein divergence among wild tomato species ( Solanum section Lycopersicon ), to understand forces shaping the evolution of reproductive genes in this diverse, rapidly evolving plant clade. By comparing rates of molecular evolution among loci expressed in reproductive and non-reproductive tissues, our aims were to test if: (a) reproductive-specific loci evolve more rapidly, on average, than non-reproductive loci; (b) ‘male’-specific loci evolve at different rates than ‘female’-specific loci; (c) genes expressed exclusively in gametophytic (haploid) tissue evolve differently from genes expressed in sporophytic (diploid) tissue or in both tissue types; and (d) mating system variation (a potential proxy for the expected strength of sexual selection and/or sexual conflict) affects patterns of protein evolution. We observed elevated evolutionary rates in reproductive proteins. However, this pattern was most evident for female- rather than male-specific loci, both broadly and for individual loci inferred to be positively selected. These elevated rates might be facilitated by greater tissue-specificity of reproductive proteins, as faster rates were also associated with more narrow expression domains. In contrast, we found little evidence that evolutionary rates are consistently different in loci experiencing haploid selection (gametophytic-exclusive loci), or in lineages with quantitatively different mating systems. Overall while reproductive protein evolution is generally elevated in this diverse plant group, some specific patterns of evolution are more complex than those reported in other (largely animal) systems, and include a more prominent role for female-specific loci among adaptively evolving genes.