Evidence-based teaching is a highly complex skill, requiring repeated cycles of deliberate practice and feedback to master. Despite existing well characterized frameworks for practice-based training in K-12 teacher education, the major principles of these frameworks have not yet been transferred to instructor development in higher educational contexts, including training of graduate teaching assistants (GTAs). We sought to determine whether a practice-based training program could help GTAs learn and use evidence-based teaching methods in their classrooms. We implemented a weekly training program for introductory biology GTAs, which included structured drills of techniques selected to enhance student practice, logic-development, and accountability and reduce apprehension. GTAs received regular performance feedback based on classroom observations. To quantify use of target techniques and levels of student participation, we collected and coded 160 hours of video footage. We found that, although GTAs adopted and utilized many of the target techniques with high frequency, techniques which enforced student participation were not stably adopted and their use was unresponsive to formal feedback. We also found that techniques discussed in training, but not practiced, were not used at quantifiable frequencies, further supporting the importance of practice-based training for influencing instructional practices.
Many students use ‘‘mitosis’’ and ‘‘cell division’’ interchangeably, apparently unaware that cell division includes mitosis as well as another, equally important process called cytokinesis. Mitosis separates duplicated chromosomes, whereas cytokinesis divides the parent cell (and duplicated chromosomes) into two daughter cells. Although these phenomena usually are linked temporally as well as spatially, mitosis can and does occur in the absence of cytokinesis (e.g., during the early development of Drosophila and other insects when many mitotic cycles occur before daughter nuclei become compartmentalized into separate cells; Alberts et al., 2002). Moreover, different mechanisms are responsible for each phenomenon. Thus, we give mitosis and cytokinesis different names, and it would be unfortunate (and especially confusing for students) if the definition of the former were expanded to include cytokinesis, as claimed in a recent review (Rieder and Khodjakov, 2003). Thinking about these phenomena, I realized I was much more familiar with mitosis than I was with cytokinesis. Not only had I read contemporary reviews of the subject (Rieder and Khodjakov, 2003 [including 10 videos]; Mitchison and Salmon, 2001) and of mitosis Web sites (Blystone, 2003), I recently had reviewed videos and research articles dealing with the phenomenon in past Video Views and Reviews (Watters, 2003, 2002). My knowledge of cytokinesis, by contrast, was much less current and informed, and I was delighted when I had the opportunity in July 2004 to attend a conference on cytokinesis sponsored by the American Society for Cell Biology. This Feature arises from my experience at the conference and a subsequent search on High Wire Press (http://highwire.stanford.edu) for current research articles and videos on cytokinesis. Interested readers also may want to consult an older, comprehensive review written by a pioneer in the field (Rappaport, 1996) and the collaborative Web site maintained by the ‘‘Cytokinesis Mafia’’: http://www.bio.unc.edu/faculty/salmon/lab/ mafia/index.html. As most students know, mitosis entails the condensation of duplicated chromosomes during prophase; their alignment and separation along the mitotic apparatus (or spindle, as it is sometimes called) during, respectively, metaphase and anaphase; and the chromosomes’ compartmentalization and relaxation during telophase. Once the chromosomes have been separated, cytokinesis begins, typically producing a cleavage furrow oriented at right angles to the axis of the spindle and passing through the plane of the metaphase plate. Anaphase, telophase, and furrow formation in a cultured animal cell are illustrated in Figure 1 (taken from Alsop and Zhang, 2003). Mechanistically, chromosomal movement occurs through the agency of the mitotic spindle, the kinetochores that attach chromosomes to various microtubular fibers of the spindle, the dynamic instability of microtubules themselves, and microtubular ‘‘motor’’ proteins (Rieder and Khodjakov, 2003). In contrast, cytokinesis and the formation of a cleavage furrow depend on the contraction of a cortical ring of actin and myosin filaments located just beneath the plasma membrane (Alberts et al., 2002). Ring constriction during cytokinesis is often referred to as purse-stringing, because the dividing daughter cells often resemble bags with gradually closing necks. The relative organization of the spindle and cortical ring is illustrated in Figure 2 (taken from Alsop and Zhang, 2004). Although mitosis and cytokinesis are different phenomena, it is clear the mitotic apparatus is responsible for the location of the cortical ring midway between the spindle poles (centrosomes) and around the metaphase plate (Alberts et al., 2002). Micromanipulation of the spindle at critical times can cause the relocation of the cleavage furrow (see Rappaport, 1996). In the extreme, cytokinesis can occur in the absence of a spindle, as elegantly shown in an early experiment by Rappaport (1961), in any cytoplasmic region where astral microtubules from two centrosomes contact one another and adjacent regions of the plasma membrane. (This classic experiment is summarized in unattributed Figures 1831 [Alberts et al., 2002] and unattributed Figures 20-41 [Lodish et al., 2003].) It is not well understood how cortical ring contraction causes a furrow to form and to become constricted or how the spindle determines the location of the cortical ring. Here I review recently published videos that depict the roles played by myosin II in contraction of the cortical ring during cellularization and cytokinesis in early development (Royou et al., 2004), by spindle and astral microtubules in regulating the formation of cleavage furrows during the cleavage of primary spermatocytes (Inoue et al., 2004), and DOI: 10.1187/cbe.04-08-0049 Address correspondence to: Christopher Watters (watters@ middlebury.edu). Cell Biology Education Vol. 4, 10–18, Spring 2005
Diffusion and osmosis are central concepts in biology, both at the cellular and organ levels. They are presented several times throughout most introductory biology textbooks (e.g., Freeman, 2002 ), yet both processes are often difficult for students to understand ( Odom, 1995 ; Zuckerman, 1994 ; Sanger et al., 2001 ; and results herein). Students have deep-rooted misconceptions about how diffusion and osmosis work, especially at the molecular level. We hypothesized that this might be in part due to the inability to see and explore these processes at the molecular level. In order to investigate this, we developed new software, OsmoBeaker, which allows students to perform inquiry-based experiments at the molecular level. Here we show that these simulated laboratories do indeed teach diffusion and osmosis and help overcome some, but not all, student misconceptions.
Underpinning science education reform movements in the last 20 years—at all levels and within all disciplines—is an explicit shift in the goals of science teaching from students simply creating a knowledge base of scientific facts to students developing deeper understandings of major concepts within a scientific discipline. For example, what use is a detailed working knowledge of the chemical reactions of the Krebs cycle without a deeper understanding of the relationship between these chemical reactions of cellular respiration and an organism’s need to harvest energy from food? This emphasis on conceptual understanding in science education reform has guided the development of standards and permeates all major science education reform policy docu
Note from the Editors Cell Biology Education (CBE) is pleased to present “Points of View,” a series designed to address issues faced by many people within the life sciences educational realm. We present several differing points of view back-to-back on a given topic to promote discussion of the topic. Readers are encouraged to participate in the online discussion forum hosted by CBE at http://www.cellbioed.org/discussion/public/main.cfm. We hope op-ed pieces on “Points of View” will stimulate thought and dialogue on significant educational issues. In this issue, we address the question “What should a biology student know?” Can biologists agree on a core set of content that all biology students should know? What about biology majors versus nonmajors? Can we create a list of facts or skills that every biology student should master? Or should our goals de-emphasize content and concentrate on ability to think, reason, analyze, and communicate? Are the details unimportant as long as students can ask good questions and figure out ways to answer their questions? We present two different “Points of View” that differ in their preferred educational outcomes. The “Points of View” we present in this issue provide two perspectives that may be familiar ones argued in your department. We invite you to share your ideas, experiences, and insights on the discussion board.
