College-level Biology Research Articles

How should we teach tree-thinking? An experimental test of two hypotheses

Phylogenies are ubiquitous in college-level biology textbooks, yet many college students continue to struggle to interpret them correctly. Multiple activities and frameworks for teaching phylogenies have been proposed to address this problem. In an introductory biology course for majors, we tested two contrasting hypotheses about the best way for students to learn the basic principles of ‘tree-thinking’. We constructed two 30-minute, pencil-and-paper-based guided group activities: one focused on using a character matrix to build a tree and one focused on analyzing an existing tree. Groups of three students completed one of these activities during one class session of a large lecture course. All students completed an identical assessment the night of the activity. We confirmed that students in the two groups were of equal academic ability, and found that students in the ‘build your own tree’ treatment performed significantly better on the assessment than students in the ‘analyze an existing tree’ treatment. We also had first-year graduate students in a Biology PhD program complete the assessment, without doing the activity beforehand. The scores of undergraduates who had done a modified version of the tree building activity were indistinguishable from those of the graduate students. We recommend simple tree-building activities be a standard part of training for tree-thinking in introductory biology.

Epigenetics

Research Article| January 01 2013 Epigenetics The Epigenetics Revolution. By Nessa Carey. 2012. Columbia University Press. (ISBN 9781848312920). 339 pp. Hardcover. $26.95. Paula Petterson Paula Petterson 1Science Teacher and Head of College Advising, Ridgeview Classical Schools, Fort Collins, CO 80525 ppetterson@ridgeviewclassical.com Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (2013) 75 (1): 64. https://doi.org/10.1525/abt.2013.75.1.14 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Paula Petterson; Epigenetics. The American Biology Teacher 1 January 2013; 75 (1): 64. doi: https://doi.org/10.1525/abt.2013.75.1.14 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search The PBS Nova episode “Ghost in Your Genes” has served as an introduction to epigenetics for some members of the general public, biology teachers, and their students. However, this exciting and important field of study is discussed in three pages or less in some of the most recent college-level biology textbooks (e.g., Reese et al., 9th ed.; Starr & Taggart, 13th ed.; Freeman, 4th ed.; Hillis, et al.). With welcome expanded coverage, Carey, an epigenetics researcher, provides details about her field with a clear and captivating narrative that employs analogies, diagrams, a broad array of examples, and an accurate portrayal of the nature of science. For the novice, Carey uses the analogy of a script and film to explain the difference and interactions between genetics and epigenetics. Shakespeare’s script of Romeo and Juliet has resulted in countless different films and stage productions; it is compared to an individual’s genes. During... You do not currently have access to this content.

Issue-Oriented Science: Using Socioscientific Issues to Engage Biology Students

In today’s global society, with science and technology advancing at a rapid pace, issues about biological topics are common. A typical standards-based high school or general college-level biology classroom naturally lends itself to teaching issue-oriented science. In an issue-oriented classroom, students analyze and discuss personal, societal, and global issues that require an application of relevant scientific evidence. Learning in the context of issues can help engage students in higher-order thinking skills that will help them to become the scientifically literate citizens needed in the current global community.

Students in Differential Equations and Epidemiology Model a Campus Outbreak of pH1N1

We describe a semester-long collaboration between a mathematics class and a biology class. Students worked together to understand and model the trajectory of the pandemic H1N1, pH1N1, outbreak across campus in fall 2009. Each course had about 30 students and was an upper-level elective for majors. Some mathematics students had taken no college-level biology, and some biology students had taken no college-level mathematics. All students had taken at least three quantitative courses, so they had some experience working with data. Our goals were to allow students to work with and model a real data set that affected them personally, to explore how the outbreak spread within our small campus, and for students to share their areas of expertise. This project created opportunities for synthesis and evaluation.

Opening Pathways for Underrepresented High School Students to Biomedical Research Careers: The Emory University RISE Program

Increasing the college graduation rates of underrepresented minority students in science disciplines is essential to attain a diverse workforce for the 21st century. The Research Internship and Science Education (RISE) program attempts to motivate and prepare students from the Atlanta Public School system, where underrepresented minority (URM) students comprise a majority of the population, for biomedical science careers by offering the opportunity to participate in an original research project. Students work in a research laboratory from the summer of their sophomore year until graduation, mentored by undergraduate and graduate students and postdoctoral fellows (postdocs). In addition, they receive instruction in college-level biology, scholastic assessment test (SAT) preparation classes, and help with the college application process. During the last 4 yr, RISE students have succeeded in the identification and characterization of a series of proteins involved in the regulation of nuclear organization and transcription. All but 1 of 39 RISE students have continued on to 4-year college undergraduate studies and 61% of those students are currently enrolled in science-related majors. These results suggest that the use of research-based experiences at the high school level may contribute to the increased recruitment of underrepresented students into science-related careers.

From Cambridge to the Amazon in a Few Simple Steps

Immersive experiences contribute to and enhance diverse curricula. Although more commonly applied to language curricula, student travel has much to offer science courses as well. Here, several options are described for secondary and college-level biology courses to participate in field-based study. The experience of one high school with one Amazonian field station is considered in detail, and several alternative opportunities for science-based student travel are provided as well. Traveling to the Amazon as an extension of classroom-based hypothesis generation and experimental design contextualized content for one high school biology course in a way that is powerful and repeatable.

Integrating Applied Ethics into a College-Level Non-Majors Biology Course

Integrating Applied Ethics into a College-Level Non-Majors Biology Course

Examining the Interaction of Acceptance and Understanding: How Does the Relationship Change with a Focus on Macroevolution?

The goal of this research was to illuminate the relationship between students’ acceptance and understanding of macroevolution. Our research questions were: (1) Is there a relationship between knowledge of macroevolution and acceptance of the theory of evolution?; (2) Is there a relationship between the amount of college level biology course work and acceptance of evolutionary theory and knowledge of macroevolution?; and (3) Can college student acceptance of the theory of evolution and knowledge of macroevolution change over the course of a semester? The research participants included 667 students from a first-semester biology course and 74 students from the evolutionary biology course. Data were collected using both the MATE (a measure of the acceptance of evolutionary theory) and the MUM (a measure of understanding of macroevolution). Pre-instruction data were obtained for the introductory biology course, and pre- and post-data were obtained for the evolutionary biology course. Analysis revealed acceptance of evolution (as measured by the MATE) was correlated to understanding of macroevolution, and the number of biology courses was significantly correlated to acceptance and knowledge of macroevolution. Finally, there was a statistically significant change in students’ understanding of macroevolution and acceptance of evolution after the one-semester evolutionary biology course. Significance of these findings is discussed.

Evaluating Two Approaches to Helping College Students Understand Evolutionary Trees through Diagramming Tasks

To understand evolutionary theory, students must be able to understand and use evolutionary trees and their underlying concepts. Active, hands-on curricula relevant to macroevolution can be challenging to implement across large college-level classes where textbook learning is the norm. We evaluated two approaches to helping students learn macroevolutionary topics. Treatment 1 is a laboratory for the software program EvoBeaker designed to teach students about evolutionary trees. We tested Treatment 1 among nine college-level biology classes and administered pre/posttests to assess learning gains. We then sought to determine whether the learning gains from Treatment 1 were comparable to those derived from an alternate hands-on treatment, specifically the combination of a prerecorded lecture on DVD and paper-based activity based on Goldsmith's Great Clade Race (Treatment 2). Comparisons of pre- and posttests among participants using either Treatment 1 or 2 show large learning gains on some misconceptions and skills beyond knowledge gained from reading standard textbook entries. Both treatments performed equivalently in overall learning gains, though both had areas where they performed better or worse. Furthermore, gains among students who used Treatment 1 representing a wide range of universities suggest that outcomes are potentially applicable to a variety of "real-world" biology classes.

Cultural Competence in the College Biology Classroom

Your words and actions can make a difference. (Center for the Integration of Research, Teaching, and Learning, University of Wisconsin) We would, of course, all like to think of ourselves as being “culturally competent.” Any biologist looking at these two words themselves would rightly presume that they understand the phrase. General definitions of the two words are as follows: Cultural: of or relating to the arts and manners that a group favors; denoting or deriving from or distinctive of the ways of living built up by a group of people; of or relating to the shared knowledge and values of a society (www.dictionary.com) Competence: adequacy; possession of required skill, knowledge, qualification, or capacity (www.dictionary.com) As a general phrase, “cultural competence” can often conjure for the unfamiliar reader a vision of a person who is fair, just, and open, a person who is nice, someone who is a good person at heart. Cultural competence, however, goes far beyond the everyday meanings that its component words invoke, and it is an active area of scholarship and professional development, especially in the training of K–12 education and health care professionals (Diller and Moule, 2005 ; Klump and Nelson, 2005 ; National Center for Cultural Competence [NCCC{, 2007 ). In fact, one would be hard pressed to find a medical, pharmacy, or nursing school or a precollege teacher preparation program that does not devote significant curricular time to developing cultural competence among their trainees. Yet, the term cultural competence is rarely found within the vocabulary of most practicing biologists and university-level biology teachers, and its relevance to biology may seem questionable. However, given the limited progress that has been made in diversifying the sciences as a discipline, the time has come for us to consider the implications and importance of cultural competence within the biological sciences, especially in the context of our teaching in classrooms and laboratories. So, what is cultural competence? Why should biologists care about it? What are common pitfalls that reveal our lack of cultural competence? And what are some teaching strategies that we can all use to continue to increase our cultural competence? Here, we attempt to address these questions and to connect readers in the biological sciences with insights from other disciplines that may aid them in striving for cultural competence in their own college or university classrooms and laboratories.

MENDEL MEETS CSI: Forensic Genotyping as a Method To Teach Genetics & DNA Science

The popularity of crime scene dramas provides an opportunity for educators to engage students in science. Solving mock crimes helps students develop critical thinking skills and reinforces the importance of the scientific method. The expertise required in forensic science is extremely broad and includes mathematics and statistics, physics, chemistry, earth science, and biology (Funkhouser & Deslich, 2000). Numerous excellent reports for mock crime scene investigations integrated into general science units are available (Johnson, 1997; Hurley, 1995; Hein, 2003). Projects specific to biology include a forensic entomology simulation (Carloye, 2003) and several that outline methods for Restriction Fragment Length Polymorphism (RFLP) as the basis for genetic identification (Guilfoile & Plum, 1998; Pallandino & Cosentino, 2001; Reed, 2001). Since the O.J. Simpson trial, the techniques for DNA fingerprinting no longer rely on RFLP analysis, which requires a relatively large amount of non-degraded DNA for success. The standard developed by the FBI is now a PCR-based, fluorescently-labeled amplification of microsatellite markers, followed by capillary electrophoresis. Although this technique requires specialized instrumentation and expensive reagents, it is an excellent method to teach students Mendelian genetics and genome organization. We describe a method to introduce students to the state-of-the art genetic profiling technique by forming partnerships with high school teachers, forensic science centers, and universities. Many biology instructors include biotechnology principles and applications within the greater topic of molecular genetics. However, the sophistication of biotechnology education programs varies, as do the objectives, resources, and opportunities of instructors and institutions. Secondary biology courses introduce students to the concepts of restriction enzyme digestion, gel electrophoresis, DNA fingerprinting, and genetic engineering. The activities at this level are primarily designed for exposure and can take the form of either simulation-based dry labs or actual wet labs. Advanced Placement biology and college level biology courses emphasize gel electrophoresis, recombinant DNA technology, the gene libraries, PCR (polymerase chain reaction), determination of Alu insertions (Bloom et al., 1996b), and sometimes mitochondrial gene sequencing in expanded coverage of genetics and biotechnology. Students learn the science behind the concepts through the use of specialized kits designed for educators. The latest method of DNA profiling relies on a form of microsatellite DNA called small tandem repeats (STRs). The technology is appropriate for biology students at the advanced secondary or introductory college level, and for teachers having prior experience with biotechnology. We have conducted a DNA profiling unit as a one-week summer mini-course, however the activities can be arranged to complement a genetics or biotechnology unit within a regular semester. Students genotype themselves first to learn the technique, then recover DNA from saliva left at a fictitious crime scene and from suspects for comparison. After a simple DNA isolation technique, they use PCR to amplify target DNA fragments, followed by capillary electrophoretic separation of the fragments and their identification with specific fluorescently-labeled probes. This lab is novel in that students work with the analytical reagents and instruments themselves made possible by partnerships with local college research labs, forensic science labs, biotechnology companies, and granting agencies. In New Mexico, we have established this lab through collaborative efforts between secondary schools, the New Mexico Institute of Mining and Technology in Socorro, and the Metropolitan Forensic Science Center in Albuquerque. The purpose of this article is to share our experiences in developing a forensic genotyping lab. We will review information on DNA profiling and the related biotechnology; explain how to obtain the necessary reagents and equipment; offer suggestions for establishing partnerships with local universities, crime labs, or biotechnology firms; and discuss appropriate forensic scenarios and course content. …

Assessing Students' Ability to Trace Matter in Dynamic Systems in Cell Biology

College-level biology courses contain many complex processes that are often taught and learned as detailed narratives. These processes can be better understood by perceiving them as dynamic systems that are governed by common fundamental principles. Conservation of matter is such a principle, and thus tracing matter is an essential step in learning to reason about biological processes. We present here multiple-choice questions that measure students' ability and inclination to trace matter through photosynthesis and cellular respiration. Data associated with each question come from students in a large undergraduate biology course that was undergoing a shift in instructional strategy toward making fundamental principles (such as tracing matter) a central theme. We also present findings from interviews with students in the course. Our data indicate that 1) many students are not using tracing matter as a tool to reason about biological processes, 2) students have particular difficulties tracing matter between systems and have a persistent tendency to interconvert matter and energy, and 3) instructional changes seem to be effective in promoting application of the tracing matter principle. Using these items as diagnostic tools allows instructors to be proactive in addressing students' misconceptions and ineffective reasoning.

Does Herbicide Resistance Have a Cost in Brassica rapa?

The evolution of resistance to pesticides has become a classic example of natural selection at work (Palumbi, 2001). As humans chemically modify their environment, organisms with short generation times respond. Examples include resistance of bacteria to antibiotics, of insects to insecticides, and of weeds to herbicides. Here the focus is on resistance to herbicides in weedy plants. In particular, genetic strains of rapid-cycling Brassica rapa offer opportunities to study resistance to the herbicide atrazine, a triazine herbicide. In the presence of the herbicide, individuals of the resistant strain survive whereas individuals of the susceptible strain die. This experiment has been used in a college-level biology class but may, also be applicable to an Advanced Placement Biology class in high school. In addition to the biological content, students gain experience in hypothesis formation and testing, experimental design, and statistical analysis. Herbicide resistance may come with a cost to the organism. Resistance to triazine herbicides is often dependent on a mutation that also inhibits photosynthesis (Warwick, 1991; Holt et al., 1993). For atrazine to kill a plant, it first binds to the polypeptide psbA, located in the thylacoid membrane of chloroplasts. In resistant plants of Amaranthus hybridus, the herbicide fails to bind to psbA. One mutation, in the chloroplast DNA coding for psbA, accounts for the difference between susceptible and resistant plants (Hirschberg & McIntosh, 1983). The mutation that confers resistance also inhibits electron transfer in Photosystem II and under certain environmental conditions will inhibit the rate of photosynthesis (Dekker & Sharkey, 1992). Photosystem II is part of the energy-capturing apparatus of chloroplasts. When chlorophyll in Photosystem II absorbs a photon of light, it initiates a complex cascade of electron transport that eventually captures the energy in chemical form in the chloroplast. If electron transport is inhibited, less energy, can be captured (see Campbell & Reece, 2002, for a lucid and detailed explanation). In the absence of the herbicide, resistant organisms may be disadvantaged. Reduction of photosynthesis will lead to reduced biomass accumulation and may negatively affect competitive ability and fitness (Warwick, 1991; Warwick & Black, 1994). Williams et al. (1995) worked with two strains of jimsonweed (Datura stramonium) that were either susceptible or resistant to the triazine herbicides. They found that resistant jimsonweeds, when grown alone, had lower total biomass and lower reproductive biomass than susceptible jimsonweeds. When jimsonweed was grown in competition with maize, its total biomass and reproductive biomass were still lower than without competition. Resistant jimsonweeds were more negatively affected by competition than susceptible jimsonweeds. Cost of resistance is defined as the reduction in fitness of resistant plants grown in the absence of herbicide. Brassica rapa, in the form of Wisconsin Fast Plants[TM] (Hafner, 1990), is ideal for studying the cost of herbicide resistance. An atrazine-resistant strain (Aaa, Rci, zr, atrazine resistant) can be grown alone and in combination with an atrazine-susceptible strain without the use of herbicide. Cost of resistance can be measured as the reduction in growth and/or reproduction of the resistant strain relative to the susceptible strain. Competitive ability can be measured by comparing plants of one strain grown alone with plants of the same strain grown in combination with the second strain. When two plants of the same strain are grown together they experience intrastrain competition, whereas a resistant plant and a susceptible plant growing together experience inter-strain competition. Based on the experiment described below, students should be able to answer the questions: * Does herbicide resistance have a cost in terms of growth and reproduction in rapid-cycling Brassica rapa? …

An evaluation of web enhanced instruction in college level biology courses

<span>Websites that accompany science courses typically aim to provide easy access to learning materials, and to facilitate student-instructor communication. We tested whether these aims were achieved in two web enhanced, lower division undergraduate biology courses in an Israeli college. We collected data on the students' attitudes through pre- and post-course questionnaires, monitored their usage of the course websites, and related these data to the students' final course grades.</span><p>The students (n=96) accessed the websites frequently and regularly, and regarded them as important sources of information. About 47% of the students reported an increased level of general interest in the courses due to the websites. Students mainly downloaded lecture slides and exercise forms from the websites, but did not use the sites to communicate among themselves, or with the instructor. Final course grades were not correlated with the frequency of usage of the website. Female students had a more positive pre-course attitude towards the websites as compared with male students. However, there was no difference between men and women in usage of the course websites, and in achievement levels.</p><p>We conclude that the website component of the courses in our study facilitated delivery of learning materials and individual study, but not the social aspects of learning. We suggest that effective design of web enhanced courses can overcome this limitation by stressing social interactions and group learning during face to face sessions.</p>

Review of Introduction to Psychoneuroimmunology.

JORGE H. DARUNA Introduction to Psychoneuroimmunology Boston, MA: Elsevier Academic Press, 2004, 304 pages (ISBN 0-12-203456-2, US$69.95 Hardcover) Reviewed by LINDA E. CARLSON Dr. Daruna tackles a large and daunting area of research in psychoneuroimmunology (PNI). PNI is not defined, except to say, It seeks to shed light on how mental events and processes modulate the function of the immune system, and how, in turn, immunological activity is capable of altering the function of the mind (p. 7). Throughout, the fundamental unity and interconnectedness of bodily systems is emphasized, a cornerstone of PNI first articulated by Robert Ader in 1980. The first two chapters discuss the aim and organization of the book and historical antecedents. Insight from ancient medical wisdom is summarized with the recognition that these philosophies had essentially understood the principal dynamics of balancing bodily systems centuries ago. In this context, PNI uses scientific method to show the long-recognized unity of the organism. The book is well organized with each chapter suitably divided into sections and subsections; necessary as the text itself is physically small. The intended audience are students in medicine, nursing, psychology, public health or social work. However, those without a university-level biology education may find the chapters on the immune, endocrine, and nervous systems difficult, as the language assumes an understanding of cell biology, neurochemistry, and neuroanatomy. The glossary of terms is helpful but not inclusive and there are a very large number of abbreviations introduced in the first few chapters. Medical students and basic scientists will be most at home in these first chapters, which cover immune system basics (Chapter 3), endocrineimmune modulation (Chapter 4), and neuroimmune modulation (Chapter 5). Much more detail is given here than other sources aimed at students, perhaps too in-depth for some, but valuable for graduate researchers who require a better understanding of the complexities of these systems. A section in Chapter 3 on commonly used measures of immune function is most welcome. The next section deals with stress, contextual change, and disease (Chapter 6), and psychosocial stress: neuroendocrine and immune effects (Chapter 7). The basic understanding of systemic functioning is applied to the stress paradigm with a repeated emphasis on the importance of context. Stress is viewed as contextual change, with context broken down into the social environment, other life forms, nonliving environment and within the individual organism. Change in any of these spheres constitutes stress. Disease is also framed as a contextual change and therefore, stress. The individual shapes the context in which the immune system operates through thoughts, feelings, and behaviour. This view of the organism existing in several different contexts simultaneously is fitting and recognizes the complexity of layered influences on health and illness. Chapter 7 moves from theoretical to empirical, summarizing research on neuroendocrine and immune effects of psychosocial stress. As is the case throughout the book, the focus is on the human literature, and research is summarized without reference to studies or authors. Sources are listed at the end of each chapter but without reference in the text to specific findings. Most sources are review articles, books or book chapters, so determining original studies is difficult. This is appropriate for some textbooks but is frustrating to those who wish to investigate specific findings further. Psychosocial effects of stress are organized by the type of outcomes assessed: endocrine activity, autonomie and peripheral neural activity, central nervous system activity, immune system activity (further broken down into nonspecific, humoral, and cell-mediated immunity), and neuroendocrine-immune pathways. This specificity allows the reader easily to focus on areas of interest. …

How Good Are Students at Testing Alternative Explanations of Unseen Entities?

THE purpose of the present study is to test the hypothesis that a fifth stage of intellectual development characterized by the ability to test alternative explanations involving unseen theoretical entities exists. This fifth-stage hypothesis will be tested in the context of a nonmajors, college-level biology course in which the assumption is made that some, but by no means all, students have acquired stage-five reasoning skills. Jean Piaget’s well-known developmental theory proposes that the development of thinking skills, which most would characterize as ‘‘scientific,’’ takes place in a stage-like fashion. Stage one, the sensorymotor stage, lasts from birth to about 18 months. As the name suggests, the stage involves the development of sensory-motor knowledge and acquisition of practical knowledge such as the fact that objects continue to exist even when out of sight. Stage two, the pre-operational stage, lasts until seven years of age. This stage primarily involves development of the ability to speak and understand the spoken word. Stage three, concrete operations, which begins at age seven, involves the development of descriptive thinking skills in which the child acquires an understanding of class subclass relationships and begins to understand the world in terms of specific variables such as weight, length, area and volume (e.g. Flavell 1963; Inhelder & Piaget 1958; Lawson & Renner 1975; Piaget & Inhelder 1969; Trifone 1991). Potential for moving into Piaget’s fourth and highest stage of thinking, called formal operational, generally occurs between 11 and 12 years of age. Inhelder and Piaget (1958) invented several widely used tasks to find out whether or not students have developed formal thinking patterns. A prototype task is the pendulum task. The pendulum task asks students to identify variables that may cause differences in the rate at which pendulums swing. If a student conducts controlled experiments to test the possible effects of

Restructuring knowledge in Biology: cognitive processes and metacognitive reflections

This follow-up study explored successive and progressive changes in the structural complexity and propositional validity of knowledge held by students enrolled in an advanced, undergraduate, university-level biology course. To examine the way learners restructure their knowledge during the semester, subjects constructed concept maps at intervals of four-six weeks. The concept maps were scored for structural complexity and propositional validity based on a modified version of Novak and Gowin's methods, and for structural change based on the work of Rumelhart and Norman. Results support previous findings that a significant amount of 'weak' knowledge restructuring occurs, resulting in an incremental, cumulative and limited form of conceptual change. However, the most 'radical' type of 'strong' restructuring (involving wholesale, abrupt and extensive change) is concentrated during the first six weeks of the course. The findings also suggest that gender plays a significant mediating effect in knowledge restructuring. Significant differences favouring females were found in the number of crosslinks depicted and a significant interaction, also favouring females, was found in the amount of branching. Finally, clinical interviews with rote and meaningful learners suggest that the latter group displays an enhanced level of awareness, and a stronger ability to monitor, regulate and control their own learning. The significance of these findings for research and practice are discussed.

The Photosynthetic Dark Reactions Do Not Operate in the Dark

Acommon misconception that has stubbornly persisted in high school and college-level introductory biology texts is that the ‘‘dark reactions’’ of the Calvin cycle actually occur in the dark. The reality of the situation is that several enzymes in the so-called ‘‘dark reactions’’ are, in fact, indirectly dependent on the presence of light for their activity. Evidence was available in the literature throughout the mid-to-late 70s that is irreconcilable with the commonly held view of the dark reactions (Buchanan 1980). Yet, despite these reports, most introductory texts and most high school teachers and college professors still hold to the position that the carbon fixation enzymes can and do operate in the dark, even though most college-level botany and plant physiology texts correctly present the story (Salisbury & Ross 1992; Taiz & Zeiger 1991). There are three pathways by which plants can fix atmospheric CO2 into carbohydrate. When discussing photosynthesis, we normally refer to plants that use the Calvin cycle enzymes to create two molecules of 3-phospho-glyceric acid, a three-carbon compound. Plants that begin photosynthesis in this manner are called C3 plants, and the pathway is referred to as the C3 pathway. Another group of plants have, in addition to the C3 pathway, a second pathway in which CO2 is fixed by the enzyme phosphoenolpyruvate carboxylase (PEP carboxylase) to form malic acid. Throughout the day, the malate is metabolized and CO2 is regenerated and supplements CO2 entering the leaves through the stomatal pores. Plants having this additional CO2 fixing pathway are called C4 plants (malate is a four-carbon compound). The CO2 generated by the C4 pathway, as well as the atmospheric CO2, is fixed by the C3 pathway in the light and dramatically stimulates growth, making C4 plants greater producers as compared to C3 plants. A third group of plants, the Crassulacean Acid Metabolism (CAM) plants, survive living in arid environments by opening their stomata in the dark instead of the light, as do C3 and C4 plants. CAM

Impacts of instructor and student loci of commitment on biology learning for prospective elementary school teachers

This study explored the dynamic in the loci of commitment of several participants in a university-level biology course developed for elementary school teachers. The analysis concentrated on two instructors with almost opposing loci of commitment. Through both instructors were committed to teaching, one showed commitment to the subject matter (accuracy, quantity, depth) while the other was more concerned with having the students get involved in the topic development. When the instructor focused on the coverage of content, the students and the instructor felt disappointment— each ending the unit expressing reciprocal discontent with the outcome of the unit. This situation eventually proved detrimental to the students' learning and application of biology. Situations where the instructor proved to be more student-oriented resulted in students making sense of relevant ideas, understanding concepts, and incorporating those ideas and concepts into their knowledge web and teaching practice.

Knowledge restructuring in the life sciences: A longitudinal study of conceptual change in biology

This study examined successive and progressive changes in the structural complexity of knowledge held by introductory, college-level biology students and how those changes are affected by the students' primary learning mode and gender. To examine the way learners restructure knowledge over the course of a semester, subjects constructed concept maps at 4-week intervals throughout the term. The maps were then evaluated for structural complexity and change based on the works of other investigators. Results suggest that a substantial amount of knowledge restructuring takes place and that much of it is incremental in nature; “accretion” and “tuning” accounting for 75% of the observed structural changes. Of potential importance, however, is that “radical” changes involving higher order, superordinate concepts are concentrated in the first 4 weeks of the semester. The observed relationships between knowledge restructuring and predominant learning mode and gender of students are potentially significant. The evidence suggests that students who use “active,” “deep” information processing strategies construct more elaborate, well-differentiated knowledge structures. Furthermore, it appears that gender may be an important mediator of meaningful learning. It is particularly notable that where gender differences were found, they tended to favor females. © 1997 John Wiley & Sons, Inc. Sci Ed 81:193–215, 1997.