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12 Developing Understanding Through Model-Based Inquiry
Pages 515-566

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From page 515...
... But major progress in understanding these phenomena has come only relatively recently through scientific inquiry. At the heart of that inquiry is the careful collection of data, the observation of patterns in the data, and the generation of causal models to construct and test explanations for those
From page 516...
... While causal models are central in both disciplines, different reasoning patterns are involved in the use or con struction of such models. The major difference is that the reconstruction of past events, a primary activity in the practice of evolutionary biology, is not common in the practice of genetics.
From page 517...
... The genetics course is centered around a set of scientific models. However, in our study of student learning we have found, as have others,3 that students have misunderstandings about the origin, the function, and the very nature of causal models (see Box 12-1)
From page 518...
... . Throughout the genetics unit, students were prompted to use these criteria to evaluate their own inheritance models.
From page 519...
... A subsequent study has shown that these instructional modifications (along with other curricular changes in the genetics unit) help students understand the conceptual nature of scientific models and learn how to evaluate them for consistency with other ideas.6 We now provide an example of an initial instructional activity -- the black box -- designed to focus students' attention on scientific modeling.
From page 520...
... 400 0 400 400 400 600 400 400 400 0 400 1000 400 0 400 400 and so forth. FIGURE 12-1 One black box used in the MUSE science curriculum and typical data patterns associated with the box.
From page 521...
... " Over the next two class periods, the students work in animated groups to develop models that can be used to explain their observations. They describe, draw, and create three-dimensional representations of what they think is in the carton.
From page 522...
... As the class shares early ideas, the teacher leads discussion about the criteria they are using to decide whether and how to modify these initial explanations. Together, the class establishes that causal models must be able to explain the data at hand, accurately predict the results of future experiments, and be consistent with prior knowl edge (or be "realistic")
From page 523...
... However, such a model fails to hold up when evaluated according to the criteria established during the black box activity because it is in consistent with the students' prior knowledge about meiosis and equal segrega tion of parental information during gamete formation: Teacher I'm confused. I'm just curious.
From page 524...
... While the core set of causal models, assumptions, and argument structures generated the content and learning outcomes for our genetics unit, our study of student understanding and reasoning influenced both the design and the sequencing of instruc tional activities. For example, many high school students do not understand
From page 525...
... By providing tasks that require students to attend to knowledge across domains and by structuring classrooms so that students must make their thinking about such integration public, we have seen improvements in their understanding of genetics.12 We then focus on inheritance models, beginning with Mendel's model of simple dominance. Mendel, a nineteenth-century monk, grew generation after generation of pea plants in an attempt to understand how traits were passed from parent plants to their offspring.
From page 526...
... Students propose alternatives, such as the codominance model, to explain these more complex patterns. Once students have come to understand that there are multiple models of allele interaction, they are primed for an explanation of why we observe these different inheritance patterns.
From page 527...
... aides in the identification of important inheritance models and strategies used by scientists to judge those models, it is the work of Kitcher15 that places the simple dominance model developed by students into context with comparable models of geneticists. According to Kitcher,16 genetic models provide the following information: (a)
From page 528...
... (a) Students' representation of Mendel's simple dominance model.
From page 529...
... During the previous few days, the students in this class have studied the work of Mendel. Years of work resulted in his publication of Experiments on Plant Hybridization,18 a paper in which he presented his model explaining the inheritance of discontinuous traits in plants.19 The students have read an edited version of this paper and refer to Mendel's idea as the "simple dominance model" because it explains the inheritance of traits derived from two alleles (or pieces of genetic information)
From page 530...
... . Teacher Kelly thinks that the allele that causes Marfan syndrome is dominant and she's put some genotypes up there to help us see her idea.
From page 531...
... (a) The original pedigree, representing the inheritance pattern within the Summers family without specifying individual genotypes.
From page 532...
... 532 HOW STUDENTS LEARN: SCIENCE IN THE CLASSROOM 2,2 1,2 1,2 1,2 2,2 2,2 1,2 1,2 2,2 FIGURE 12-3 (c) Curtis' genotype assignments, assuming that Marfan syndrome is inherited as a recessive trait.
From page 533...
... DEVELOPING UNDERSTANDING THROUGH MODEL-BASED INQUIRY 533 BOX 12-3 Sarah's Thought Experiment In Sarah's thought experiment, two individuals with Marfan's syndrome would pro duce sex cells, and those sex cells would recombine during fertilization (see Figure 12-3)
From page 534...
... Our course is designed to provide those opportunities. Once the students have represented and used the simple dominance model to explain phe nomena such as the inheritance of characteristics in peas and disease traits in humans, they use the model to explain data they generate using the software program Genetics Construction Kit or GCK.20 This program enables students to manipulate populations of virtual organisms (usually fruit flies)
From page 535...
... FIGURE 12-4 Example of student work on a GCK homework assignment. Students were asked to infer as much as possible from each successive cross within this population.
From page 536...
... "21 However, this conclusion is inconsistent with the students' prior concept of recessiveness as it was developed under the simple dominance model. Thus, it is at this point in the unit that we emphasize the need for models to be consistent with other knowledge in a scientific discipline.
From page 537...
... After about a week of data collection, model testing, and team meetings, each small research group is usually able to describe a model of inheritance for at least one of the traits in its population, and most groups can describe inheritance models for both of the traits on which they chose to focus. The entire class then gathers for a final conference during which students create posters that summarize their research findings, take turns
From page 538...
... As a primary goal of practicing scientists is to construct causal models to explain natural phenom ena, involving students in the construction of their own models is given major emphasis in the classroom. The students work in groups structured like scientific communities to develop, revise, and defend models for inher itance phenomena.
From page 539...
... Inheritance of PKU in the Samsom Family Kate Joe Curtis Anne Max Natalie Devon Ken Kimberly Ryan Donna 1. Use Mendel's simple dominance model to assign genotypes to the individu als in this pedigree.
From page 540...
... First, they will need to use their knowledge of the natural selection model to develop an explanation for the bright coloration of the male ring-necked pheasant. Second, they will have to write a research proposal that will then be considered by the rest of the students in a research grant competition.
From page 541...
... Grace It is similar to the last case. We need to come up with a Darwinian explanation for why the males look brighter than the females.
From page 542...
... In doing so, they attend to and discuss such ideas as selective advantage and reproductive success that are core components of the Darwinian model. Early in the course, students have opportunities to learn about natural selection, but as the course progresses, they are re quired to use their understanding to develop explanations (as illustrated in the vignette)
From page 543...
... Kitcher27 describes a Darwinian history as a "narrative which traces the successive modifications of a lineage of organisms from generation to generation in terms of various factors, most notably that of natural selection." The use of narrative explanation is a key means of distinguishing evolutionary biology from other scientific disciplines. "Narratives fix events along a temporal dimension, so that prior events are understood to have given rise to subsequent events and thereby explain them."28 Thus, our concept of a Darwinian explanation draws together the components of the natural selection model and a narrative structure that demands attention to historical contingency.
From page 544...
... Providing opportunities for students to use the natural selection model to develop narrative explanations that are consistent with the view described above is a central goal of the course. Attending to Student Knowledge Anyone who has ever taught evolution can attest to the fact that stu dents bring a wide range of conceptions and attitudes to the classroom.
From page 545...
... All three principles are tightly woven in the instruction described below. Laying the Groundwork Constructing and defending Darwinian explanations involves drawing inferences and developing arguments from observed patterns in data.
From page 546...
... The 13 images are given to the students in random order, and the students are asked to create narrative stories. GroupOne 1 2 3 ÒWe think that in this first frame little red riding hood is telling the pigs that she is going to visit her sick grandmother.
From page 547...
... DEVELOPING UNDERSTANDING THROUGH MODEL-BASED INQUIRY 547 GroupTwo 1 2 3 "The pigs have discovered grandma tied up in the woods and they try to throw the wolf off the track by telling him that he must get away before the hunter comes. In the last frame, little red riding hood is thanking the pigs for saving the grandmother and they feel bashful ."
From page 548...
... This occurs as students create Darwinian explanations. Such expla
From page 549...
... This activity takes place before students need to draw on their understanding of variation to construct explanations using the natural selection model.
From page 550...
... Darwin's model of natural selection. The models of Paley and Lamarck were chosen because each represents some of the common ideas students bring with them to the class room.
From page 551...
... Comparing the assumptions of the three models enables students to distinguish between those beliefs that underlie the model of natural selection and those that do not. Unlike some classroom contexts, however, in which it is the students' ideas that are laid bare and examined for inconsistencies, here we have developed a situation in which students' ideas are represented by the models of Paley and Lamarck.
From page 552...
... Using the Darwinian Model During the final weeks of the course, students are engaged in creating Darwinian explanations using the components of the natural selection model to make sense of realistic data they have been given. Each scenario is pre sented to the students as a case study, and they are given materials that describe the natural history of the organism.
From page 553...
... As within all species, there exists natural variation among the popula tions of monarchs and viceroys, including variations of color. In the past popula tions, some butterflies were brightly colored and others were dull.
From page 554...
... As they examine competing Darwinian explanations for the same phenomena, they invoke an evolution-specific argument-analysis norm -- that the explanation of the history of a trait has to be consistent with the natural selection model. For example, the second case requires students to provide a Darwinian explanation for the similarity in color between the monarch and viceroy butterflies.
From page 555...
... Assessment of student understanding needs to be undertaken with an eye to the various types of prior knowledge described above (misconceptions of science concepts, ideas about what science is,
From page 556...
... In the evolution course, students are required during instruction to use the natural selection model to develop Darwinian explanations that account for rich data sets. To then ask them about data or the components of natural selection in a multiple-choice format that would require them to draw on only bits and pieces of knowledge for any one question appears incomplete at best.
From page 557...
... Justify your placement of that line. data 1 scientific models is 2 a meiosis is a model is a atomic 3 model 4 pedigree Mendel model day of class (see Box 12-8)
From page 558...
... In my original explanation I also touched on ideas of use and disuse to explain how the saddleback carapace came to be, this is a Lamarkian model of evolution which is incorrect. I did explain how the saddleback carapace was an advantage because it allowed the tortoise to eat higher vegetation.
From page 559...
... It involves norms for making and justifying claims. At the source of the productivity of such a community is an understanding of central causal models, the ability to use such models to conduct inquiry, and the ability to engage in the assessment of causal models and related explanations.
From page 560...
... Thus, we explicitly discuss with our students the expectations for their participa tion in the course. Teachers state that the students' task is not simply to produce an "answer" (a model in genetics or a Darwinian explanation in evolutionary biology)
From page 561...
... That MUSE combined this collaboration with a research program on student learning and reasoning was essential. With the knowledge thus gained, we believe it is possible to help others realize the expectations for improving science education that are set forth in reform documents such as the National Science Education Standards.38 In particular, there has been a call for curricular reforms that allow students to be "engaged in inquiry" that involves "combin[ing]
From page 562...
... . The site includes discussions of student knowledge and reasoning, intended learning outcomes, instructional activities, instructional notes, assessments, examples of student work, teachers' reflections, and connections to the Na tional Science Education Standards and Benchmarks for Science Literacy.
From page 563...
... . Student conceptions of natural selection and its role in evolution.
From page 564...
... Research report 98-1 for the National Center for Improving Student Learning and Achievement in Mathematics and Science. Available: http://www.wcer.wisc.edu/ncisla/publications/main.
From page 565...
... . National science education standards.


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