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Teaching Concepts Versus Facts in Developmental Biology

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    Note from the Editor

    Points of View (POV) address issues faced by many people within the life science education community. CBE—Life Sciences Education (CBE-LSE) publishes the POV Feature to present two or more opinions published side-by-side on a common topic. We consider POVs to be “Op-Ed” pieces designed to stimulate thought and dialogue on significant educational issues. They are not meant to be exhaustive treatments of a subject.

    In this issue, we ask the question, “What are key concepts in developmental biology?” We present three POVs. The first is by CBE-LSE Editor-in-Chief, William Wood, and it is in part based on his experience teaching developmental biology to undergraduates at the University of Colorado, Boulder, including his collaborative experiments in the classroom with Jennifer Knight, the first results of which have been published in CBE-LSE (Knight and Wood, 2005). The second, a partially tongue-in-cheek list of key concepts to convey to students about embryonic development, is by Scott Gilbert (Swarthmore College), author of the leading textbook worldwide for teaching developmental biology, Developmental Biology, 8th ed. (Sinauer Associates, Inc.). The third is by Jeff Hardin (University of Wisconsin–Madison), who has produced Web-based educational materials for teaching developmental biology that are used nationally and internationally for conveying dynamic events during early development (see the WWW feature in this issue by Stark for more details), and who deals with the vexing problem of trying to convey the essential four-dimensional nature of embryonic development to introductory students.

    In our teaching of undergraduate life sciences courses, we are admonished to place more emphasis on concepts over facts, conceptual understanding over memorization of details. But understanding the biology of development requires extensive knowledge of facts as well as concepts, and sometimes it seems hard to distinguish which is which. What do we mean by a concept? According to the Concise Oxford English Dictionary, a concept is

    1. an abstract idea. (origin: Latin conceptum, something conceived).

    Merriam-Webster defines a concept as

    1. something conceived in the mind: thought, notion.

    2. an abstract or generic idea generalized from particular instances.

    Over both of these, I prefer a more operational definition from physicist-educator Carl Wieman: A concept is an idea that can be applied in multiple contexts to explain and/or predict outcomes. The conceptual understanding we want to help our students attain then becomes simply the ability to apply an idea in multiple contexts to explain and/or predict outcomes. The kinds of applications we want our students to be capable of can range from lower to higher levels of Bloom's taxonomy (Bloom et al., 1956; Allen and Tanner, 2002), depending on our learning goals.

    But some of the facts we teach in developmental biology (and other life sciences) can also be viewed as concepts. What is the difference? I'll come back to that question at the end of this essay. First, let's look at an example of the perceived concept/fact dichotomy.

    One of our assignments from the editor for this POV was to explain a favorite developmental concept and why we feel it is centrally important. One of mine is the concept of combinatorial control. Probably, I find it so compelling because I encountered it as a revelation of how development, which had earlier seemed largely mysterious, could actually work. I grew up intellectually as a bacterial and bacteriophage molecular geneticist, who turned to developmental biology in mid-career and began teaching it in the late 1970s. It was impossible to understand how development worked with the molecular biology of the day. A turning point for me came when Keith Yamamoto, visiting Boulder in the early 1980s for a departmental seminar, presented us with his evidence that the same transcription factor could repress a reporter gene in one mammalian cell type and activate the same reporter gene in another cell type. This was clearly not simply an elaboration on the lac operon, but something quite different! The action of a transcriptional regulatory component must depend on other factors in its cellular environment, that is, on the past history of the cell. Later, elaboration of signaling pathways and their effects on gene expression told us the nature of some of these factors. Moreover, we learned that signaling works in the same combinatorial way: responses of different cells to a signal depend on the signaling pathway components already present in each cell's plasma membrane, cytoplasm, and nucleus. And to complete the story, signaling controlled many of the transcription factors that regulated transcription!

    The picture of development that emerged from this story was beautiful and understandable. But when we describe in our classes or our textbooks all the possible levels at which development is regulated, via expression of thousands of genes, each controlled by multiple inhibitory and activating cell-type–specific transcription and posttranscription RNA-processing factors, many of which are activated or inactivated by multicomponent signaling pathways, which can in turn be modulated by multiplexing with other signals, and so on, students can be overwhelmed by the seemingly infinite types and variations of developmental regulatory controls. Amid this monstrous complexity, they may miss the simple idea that makes sense of it all: the principle of combinatorial control.

    The concept of combinatorial control may be stated as follows:

    How a cell behaves in response to an autonomous determinant or an external signal depends on the combination of transcriptional and posttranscriptional regulators, signaling pathway components, cytoskeletal elements, and other proteins and RNAs that it has synthesized earlier: i.e., on its developmental history.

    But isn't that a fact? It's a factual statement. But it's also an important concept, an idea that can be applied in multiple contexts to understand and predict outcomes.

    The underlying details are more specific facts, but many of these include important smaller subconcepts:

    There are multiple DNA response elements in the vicinity of each developmentally regulated gene. These interact with multiple protein transcription factors (TFs), which can positively or negatively affect transcription rate. The TFs can also interact with each other, positively or negatively, to control the overall transcriptional effect. The action of the TFs can in turn be regulated positively or negatively by effector proteins activated or inactivated by often multiplexed signaling pathways, and so on, and so on, into the jungle of complexity alluded to above.

    These statements are more factual than conceptual. But without knowledge of some facts, students may find the concept of combinatorial control somewhat meaningless. So which should be learned first, the general concept or the specific underlying facts? Analyses of learning styles (e.g., Felder, 1993) have revealed two distinct groups of learners: those who prefer to learn the facts first and then have the simplifying generalizations emerge as they go along, and those who prefer to begin with an overarching concept on which they can hang specific facts as they are encountered. As a teacher, I believe strongly that the best way to accommodate both groups is to go back and forth between facts and the relevant concept as the course progresses.

    In our development course, we introduce the concept of combinatorial control near the beginning, after reviewing developmentally relevant aspects of gene regulation. We tell our students that we consider it centrally important, and that quite often, when we throw out a question to the class, the answer will be “combinatorial control.” Then, as examples of signaling and gene regulation come up in various contexts during the course, we will ask the class, “What is this an example of?” After a few weeks of this, we start to get choral responses of “combinatorial control!” in unison! It becomes a course joke, but students do incorporate the concept into their thinking and seem to remember it, at least through the final exam!

    So, what's the real distinction between the facts and the concept? Is this just an unimportant semantic question? I don't think so. But the answer cannot be found in the statements themselves. Instead, we have to go back to Wieman's operational definition, and consider how students are being asked to use the information they learn in our courses. If the question on our final exam is “define the term combinatorial control,” we are asking students simply to memorize the statement we gave them. This is the lowest Bloom's level of understanding, and in fact students can get a perfect score on the question without understanding the statement conceptually at all. Conversely, if we ask them to explain at the molecular level how two different cell types in the same tissue can respond differently to the same hormonal signal, or to predict the types of proteins that, for example, a mammary gland cell must have produced during development to increase the steady-state level of casein mRNA in response to prolactin, they will have to apply the principle of combinatorial control to an unfamiliar situation, requiring a deeper understanding of the concept. So whether ideas in developmental biology are learned as factual or conceptual depends partly on how we and our textbooks present them and on how students study them; but most of all, it depends on how we formulate our course learning goals and our homework and exam questions, in terms of factual recall versus application of concepts. Needless to say, I strongly urge less of the former and more of the latter!


    For ideas, clarifying discussions, and collusion in teaching reforms, I thank my colleagues Jennifer Knight, with whom I have taught developmental biology in Boulder for many years; Jo Handelsman, University of Wisconsin–Madison, who has inspired me and many other life sciences faculty to think more deeply about teaching and learning; and Carl Wieman, whose support has enabled dissemination of science teaching reforms more widely at University of Colorado, Boulder, and beyond.


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