Still a Private Universe? Community College Students’ Understanding of Evolution

Background Measuring what students know and retain about evolution is essential to improving our understanding of how students learn evolution. The literature shows that college students appear to have a poor understanding of evolution, answering questions on various instruments correctly only about half of the time. There is little research regarding evolution understanding among community college students and so this study examines if those students who are enrolled in life science classes, who are assessed using questions based on grade eight standards, show a better understanding of evolutionary principles than younger students and if there are differences in knowledge based on course enrollment. The authors utilized a survey of 41 items of the Life Sciences Concept Inventory that were specifically designed to measure knowledge about various aspects of evolution that relate to the 5–8 grade science standards on evolution. They administered it to 191 adult students who were enrolled in nine sections across five life sciences courses at one community college in Southern California. Results Results indicated that the students in this study possessed a fair understanding of evolution, averaging scores of nearly 70%, higher than what other researchers have found (using different instruments). Students enrolled in biology major classes scored significantly higher than those enrolled in non/mixed-major courses. There was a strong relationship between item difficulty and discrimination as well as difficulty and misconception strength. When compared with the 5–8 grade student data, the community college students showed a lower level of difficulty and higher levels of item discrimination, but the proportion choosing the most popular wrong answer (the dominant misconception), was comparable. College students showed similar patterns to the grade 5–8 students in terms of which questions and which material were the most challenging, despite performing better overall. Conclusions In this study, students possessed fair understanding of evolution. However, they were assessed with an instrument designed for 5th through 8th grade students. The results of this study support the need for more research into how community college students understand evolution and which factors impact that understanding

Defining Evolution: Exploring Students’ Conceptions of Evolution in Introductory Biology Courses

Background Understanding evolution is an important part of undergraduate biology education. Despite its importance, however, students often struggle to understand evolution, often holding preconceived notions of what evolution is. Here, we investigate how students in both majors and non-majors introductory biology define and conceive of evolution at the start of the semester for a two-year college and a four-year university near each other. We analyze open-ended responses to an in-class activity on the first day of the semester that asked students to define evolution, generating insight into how students are thinking of evolution prior to any formal instruction on evolution in college. Results Our analysis of over 300 student responses reveals that students hold diverse conceptions about evolution, with some students perceiving evolution in the context of evolutionary processes while other students define evolution by referring to perceived evolutionary consequences. In addition, we identify multiple non-normative conceptions about evolution, including students viewing evolution and natural selection as synonymous and not recognizing other evolutionary forces, and find that very few students likely have developed mental models linking evolution and genetics. In addition, we find few differences between how students at the two- and four-year institutions perceive evolution, and similarly few differences between students in a majors and non-majors introductory biology, suggesting that these conceptions of evolution are widespread at the beginning of introductory biology, regardless of major or institution. Conclusions We situate our results in the existing literature examining student conceptions of evolution, with our results extending past work that has primarily relied on more closed-ended questions or focused on specific evolutionary concepts (e.g., natural selection). Our results largely align with past work on student thinking of evolution but provide a broader, more holistic perspective at the ideas and framework that students are drawing upon when introductory biology instructors first introduce the term ‘evolution’. We conclude our paper by discussing implications for the biology education research community as well as instructors

System Dynamics as a Structural Theory in Operations Management

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Inflammatory Flt3l is essential to mobilize dendritic cells and for T cell responses during Plasmodium infection

Innate sensing mechanisms trigger a variety of humoral and cellular events that are essential to adaptive immune responses. Here we describe an innate sensing pathway triggered by Plasmodium infection that regulates dendritic cell homeostasis and adaptive immunity through Flt3 ligand (Flt3l) release. Plasmodium-induced Flt3l release in mice requires Toll-like receptor (TLR) activation and type I interferon (IFN) production. We found that type I IFN supports the upregulation of xanthine dehydrogenase, which metabolizes the xanthine accumulating in infected erythrocytes to uric acid. Uric acid crystals trigger mast cells to release soluble Flt3l from a pre-synthesized membrane-associated precursor. During infection, Flt3l preferentially stimulates expansion of the CD8-α+ dendritic cell subset or its BDCA3+ human dendritic cell equivalent and has a substantial impact on the magnitude of T cell activation, mostly in the CD8+ compartment. Our findings highlight a new mechanism that regulates dendritic cell homeostasis and T cell responses to infection

Deciphering the transcriptional network of the dendritic cell lineage

Although much progress has been made in the understanding of the ontogeny and function of dendritic cells (DCs), the transcriptional regulation of the lineage commitment and functional specialization of DCs in vivo remains poorly understood. We made a comprehensive comparative analysis of CD8(+), CD103(+), CD11b(+) and plasmacytoid DC subsets, as well as macrophage DC precursors and common DC precursors, across the entire immune system. Here we characterized candidate transcriptional activators involved in the commitment of myeloid progenitor cells to the DC lineage and predicted regulators of DC functional diversity in tissues. We identified a molecular signature that distinguished tissue DCs from macrophages. We also identified a transcriptional program expressed specifically during the steady-state migration of tissue DCs to the draining lymph nodes that may control tolerance to self tissue antigens