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12 Developing Understanding Through Model-Based Inquiry
Pages 147-198

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From page 147...
... 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 148...
... While causal models are central in both disciplines, different reasoning patterns are involved in the use or construction of such models. The major difference is that the reconstruction of past events, a pnrnarv activity in the practice of evolutionary biology, is not common in the practice of genetics.
From page 149...
... . They view models in a "naive realistic" manner rather than as conceptual structures that scientists use to explain data and ask questions about the natural world 4 Following our study of student thinking about models, we altered the instruction in the genetics unit to take into consideration students' prior knowledge about models and particular vocabulary for describing model attnbutes.
From page 150...
... Similarly, when attempting to apply model assessment criteria to their explanations for data patterns in liquid poured from a box, several students treated "internal consistency" and "external consistency" literally: they evaluated the box's proposed internal components and the external phenomena (observations) separately Th is conf usion stemmed f rom students' prior understanding of concepts associated with the vocabulary we provided: clearly "internal" and "external" were already meaningful to the students, and their prior knowledge took precedence over the new meanings with which we attempted to imbue these terms.
From page 151...
... A subsequent study has shown dhat 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 o her ideas 6 We now provide an example of an initial instructional activity—The black box—designed to focus students' attention on scientific modeling, As Chapter 1 suggests, children begin at a very young age to develop informal models of how things work in the world around them.
From page 152...
... Classmates offer cnticism and seek clarification during these presentations As the dialogue below suggests, the exercise begins with students engaged in a central activity of scientists making observations. Teacher Making observations is important in science.
From page 153...
... And, one last thing, I want each group to develop at least one test of you r model. Ask you rself, "If the wo rid inside the carton is as I imagine it and I do X to the carton, what result would I expects" Over the next two class periods, the students work in animated groups to develop models that can be used to explain their observations.
From page 154...
... 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 explanati ons. Together, the class establishes that causal models must be able to explain the data at hand, accurately predict the results of future expenments, and be consistent with prior knowledge (or be "realistic")
From page 155...
... However, such a model fails to hold up when evaluated according to the criteria established during the black box activity because it is inconsistent with the students' prior knowledge about meiosis and equal segregation of parental information during gamete formation: Teacher David Michelle David Michelle Chee David Chee I'm confused. I'm just curious.
From page 156...
... 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 instructional activities. For example, many high school students do not understand
From page 157...
... when conducting their genetic investigations and when presenting model-based explanations to account for patterns in their data. 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.' We then focus on inheritance models, beginning with Mendel's model of simple dominance.
From page 158...
... arden's work and our own experiences as teachers and researchers, we made a primary feature of the course engaging students in building and revising Mendel's simple dominance model. Students thereby have rich opportunities to learn important genetics concepts, as well as key ideas about the practice of genetics.
From page 159...
... aides in The identification of Important inheritance models and strategies used by scientists to judge those models, it is the work of Kitcher's That places The simple dominance model developed by students into context with comparable models of geneticists. According to Kitcher,'6 genetic models provide the following information: (a)
From page 160...
... 2 V.rhibn A RGURE 12 2 Mendels model of simple dominonce to] Siudenis ' represenpGhon of Mendels simple dominonce model This model occounis for ibe inherinonce of discreie hoiis for which ibere ore wo vorionis (designoP d A ond B]
From page 161...
... Years of work resulted in his publication of Experiments on Plant Hybndtzafton a a paper in which he presented his model explaining the inheritance of discontinuous traits in planTs.'9 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) when one of the alleles is completely dominant over the other (see Figures 12-2a and 12-2b)
From page 162...
... . Teacher David Teacher Lucy Sarah Sam Sarah Well, that's very interesting.
From page 163...
... The original pedigree, representing ibe inherifonoe posers within ibe Summers fomiy without speci King individual geno ypes. T~ ,~, FIGURE 12 3 Ebb Kellys genorrpe ossignmenis, assuming ihoiMorfon syndrome is inhen Ados o dominant iroit Cu rtis Teacher Sarah .
From page 164...
... Teacher Sam Teacher Kelly Teacher Teacher Chee Ch ris Chee Teacher Sarah David Ta nya Teacher Ta nya Chee Tanya Lee Do you all see that7 Sarah is saying that if the parents had what genotypes They'd have to be a 1,2, right?
From page 165...
... Through meiosis and hnnilization photo Hera no onto r Id Parental genotype produce Spring with genotypes (1,1)
From page 166...
... The next step for the class is to study these "anomalous" inheritance patterns using GCK. They begin with achondroplasia, a trait for which there are three variations rather than two students revise the simple dominance model to account for the codominant
From page 167...
... BE [] Ears coat Length _ I Flared Short _ w Flared Long ~ 1 1 ~ Field Population So we can only tell that these is one wer/atbn Or ears but two ten coat length Another wlriation ten ears mkabt show up F1: Cn f35 n frtmnle Flared Short with a male Flanad Lon g imm the Field Population E E Ears coat Length _ e Flared Short _ Narrow Narrow F1 T1 I T I d Flared Long w Flared Short Long Short Long F2: Cross two Narnow Short individuals from F1 ~ ....
From page 168...
... and (1,2) genotypes are both "recessive."' However, this conclusion is inconsistent with the students prior concept of recessiveness as it was developed under The simple dominance model.
From page 169...
... x-linkage. 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.
From page 170...
... Metacognition: Engaging Students in Reflective Scientific Practice Ultimately, students need to learn to redect on and judge dheir own work radher Than relying solely on assessments from odhers Several early studies of students' GCK work in our genetics unit revealed that students assessed dheir tentative models primarily on The basis of empirical radher than conceptual critena.23 Even when conceptual inconsistencies occurred between the students' proposed models and o he- models or biological knowledge, dheir primary focus was usually on how well a given model could explain the data at hand. They frequendy had diff culty recognizing specific inconsistencies between their models and meiosis or odher biological knowledge, such as The medhod of sex detemmination in humans In some instances, students recognized that dheir models were inconsistent with o her knowledge but were willing to overlook such inconsistencies when They judged their models to have adequate explanatory power (For example, students sometimes proposed models to account for x-linkage inheritance patterns wherein a male organism simply could never be heterozygous.
From page 171...
... Use Mendel's simple dominance model to assign genotypes to the individu als in this pedigree.
From page 172...
... She tells the students that there are two parts to this third case. First, they will need to use their knowledge of the natural selection model to develop an explanation for the bright coloration of the male nng-necked pheasant.
From page 173...
... We need to come up with a Darwinian explanation for why the males look brighter than the females. How can this bet it seems like being bright would be a problem for the males, so how can it fit with Darwin's ideas7 Well, I guess we need to look at the rest of the stuff in the folder The three students spend the remainder of the penod looking over and discussing vanous aspects of the case.
From page 174...
... arwin's model of natural selection and realistic data to create arguments about evolution in a population of organisms. In doing so, they attend to and discuss such ideas as selective advantage and reproductive success that are core components of the L)
From page 175...
... arwinian explanation draws together the components of the natural selection model and a narrative structure that demands attention to historical contingency. Textbook examples of explanations for particular traits frequently take the
From page 176...
... In other words, he constructs a historical narrative. 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.
From page 177...
... Our course has since been modified to provide opportunities for students to develop a common framework for making and critiquing arguments. As with The black box activity at the beginning of the genetics course, we use a cartoon sequencing activity dhat does not introduce course content, thus allowing students to focus more fully on drawing inferences and developing arguments.
From page 178...
... In the second scene, the pigs are telling the wolf ESbU U t little red riding hood and her sick grandmother and showing hnn which way she went. In the next frame, the pigs see that the grandmother is tied up in the woods and they feel had that they gave the wolf the information earner."
From page 179...
... In the last frame, little red riding hood is thanking the pigs for saving the gramdmother and they feel bashful:'
From page 180...
... In this capacity, the emphasis is on the importance of being explicit about how prior knowledge and beliefs influence the inferences drawn from particular data. At this general level, the activity is linked to the common MUSE framework of models and modeling as the teacher coronas the ideas concerning inferences to those concerning models.
From page 181...
... This activity takes place before students need to draw on their understanding of variation to construct explanations using the natural selection model.
From page 182...
... t) arwin's model of natural selection.
From page 183...
... arwin's model. Companng 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.
From page 184...
... arwinian explanations using the components of the natural selection model to make sense of realistic data they have been given Each scenario is presented to the students as a case study, and they are given materials that describe the natural history of the organism Photographs, habitat and predator information, mating behavior and success, and phylogenetic data are examples of the types of information that may be included in a given case. Students then weave the information into a narrative that must take into account all of the components of a natural selection model and describe the change over time that may have occurred (see Box 12-6 for one group's t)
From page 185...
... These include ensunng that there is consistency among the data, the natural selection model, and claims; that the history of the shift in a trait is feasible (i.e., consistent with genetics) ; and that the proposed selection agent could have brought about the change in the trait between times 1 and 2.
From page 186...
... As they examine competing t) arwinian explanations for The same phenomena, dhey invoke an evolution-specific argument-analysis norm That The explanation of The history of a trait has to be consistent widh The natural selection model.
From page 187...
... Assessment-Centered We have attempted to embed formative and authentic assessments throughout our courses. 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 188...
... In The evolution course, students are required during instruction to use The natural selection model to develop t) arwinian explanations that account for mich data sets.
From page 189...
... Many students are critical of the need-based language that was present in their original explanation, or they find that they described evolutionary change as having happened at the individual rather than the population level.
From page 190...
... Below are the original explanation and critique offered by one student. Original Answer The saddleback carapace came into being due to the need of migrating tortoises to adjust to a new environment.
From page 191...
... 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 192...
... If the idea had explanatory or predictive power, The solver remained satisfied widh it; if not, The solver would quickly test another idea. The positive test strategy was frequendy applied by students in early versions of our genetics course.37 This medhod of problem solving does not map well to scientific practice in most cases, however: it is The absence of disproving evidence, and not the presence of confirming evidence that is more commonly persuasive to scientists.
From page 193...
... 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 39 In particular, there has been a call for curricular refomms that allow students to be "engaged in inquiry" that involves "combin[ing]
From page 194...
... . The site includes discussions of student knowledge and reasoning, intended learning outcomes, irst uctional activities, inst uctional notes, assessments, examples of student work, teachers' ref ections, and connections to the NatSonal Science Education Standards and Benclhmarksfor Science Literacy 2.
From page 195...
... . Student conceptions of natural selection and its role in evolution.
From page 196...
... . Assessment of explanatory models in genetics Insights into students, conceptions of scientific models Research report 98-1 for the National Center for Impmving Student Leaming and Achievement in Mathematics and S cience.
From page 197...
... National Committee on Science Education Standards and Assessment, Center for Science, Mathematics, and Engineering Education. Washington, DC: National Academy Pass.


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