Figure 4. Students’ participation in modeling activity during the seed claim-making phase
cycle). Students were able to apply measures of success to compare the growth of plants in Petri dishes to those in the light box, concluding that plants can germinate without soil but will not be successful. However, because the plants in the Petri dishes were less successful on all measures than those in the pots, there was no need to privilege any particular measure.
Students next returned to the backyard to think about whether conditions across the backyard varied in any way that might matter for the success of seeds that landed there. After considering several possibilities, they decided to investigate amount of moisture, crowding, and nutrients. With assistance, they designed analog systems (flats of soil, nutrient pellets, water, a light box, and Wisconsin Fast Plant™ seeds) to test their ideas. During these investigations, seedpods emerged as one of the two most useful indicators of comparative success (the other being whether plants in one condition died, as occurred in some of the crowding conditions).
Unfortunately, a major weather event that closed the school limited students’
opportunities to share and defend their claims about their systems when the plants had completed their life cycles. However, of the eleven students who participated in the post-interview, eight privileged seedpods as a primary source of evidence about which condition was more successful, explaining that seedpods meant that the plant made more of its kind. Of the three who did not, two students had crowding conditions in which all the plants in one condition had died and the other was studying moss, which did not produce seedpods. Over the course of this work,
students’ ideas of reproduction shifted substantially. Reproduction came to be seen and used as a measure in a new scientific enterprise. Moreover, it was a measure that could be theoretically justified and privileged over others.
Example episode: Julie and Kelly’s system. The episode that follows took place on students’ first day back at school after ten days out due to the weather event. During this time,
the plants had flowered and grown seedpods. Mrs. W. began by asking students what they noticed changing. Julie and Kelly mentioned that they had seedpods, and that there were more in their “spaced out” condition as opposed to their “crowded” condition.
1. Mrs. W: So you see more seedpods in the one that is spaced out. Would you consider that evidence [… about] which one you think is being more successful?
2. J&K: [Yes] (nodding) 3. Kelly: Yes Ma'am.
4. Mrs. W: Ok. Uh…Would anybody else see that as evidence? Do you think? In... that Julie and Kelly are saying that they think because the one where their
condition is more spaced out that it is being more successful than the one where it's crowded because it's producing more seedpods. Raise your hand if you think that would be a kind of [evidence.]
5. Kelly: [I only] have a little one (undertone, referring to the crowded condition).
6. Mrs. W: I'm seeing William, Shanequa, Chris's, OK. (about half to two-thirds of hands are up).
7. Mrs. W: And why… why, Julie, would you consider that to be evidence?
8. Julie: (Pointing to spaced out condition) Because I see, like, first the seedpods was like tiny, tiny like this, and now you see them, they're just growing so big and it seems like it's a lot. (Reaches over to crowded condition.) But when you look at the uh crowded one, it's it barely-well it has some seedpods, but it's still small.
9. Mrs. W: Why is that evidence? [...Why does] that matter?
10. Kelly: (undertone) [There's a big one] (points to crowded condition) 11. Julie: Because, uh, this one's (points to spaced out condition) growing seedpods
first, before that one.
Mrs. W. shifts the conversation from noticing changes to using seedpods as evidence of success, explicitly asking students not only whether they would consider seedpods to be evidence (many of the students in the class concur, Lines 1-4), but why they should be considered as evidence. Thus, she repositions students from noticers of change to makers of claims within the model system who need to justify the use of measures. Julie does not initially participate in this justification; instead, she demonstrates a common form of practice in the classroom,
differentiating an attribute to define it as a measure. She first mentions that one condition has more seedpods and bigger seedpods (Line 8), then, when pushed again by Mrs. W., differentiates
the timing of seedpod growth across the two conditions (Line 11). Mrs. W. next rephrases and clarifies her question several times (Lines 12, 14, and 21):
12. Mrs. W: Does that make any difference?
13. Kelly: No because that one (points to spaced out) might die before this one (points to crowded).
14. Mrs. W: Huh. Umm…but whenever we're thinking about it as evidence about whether or not the plants in one condition are more successful than the plants in another condition. (2 sec) Do you think seedpods matter?
15. J. & K.: Yes.
16. Mrs. W: Growth of seedpods.
17. J. & K.: Yes.
18. Mrs. W: And why would you think that?
19. Kelly: Because if you have seedpods, then that's how you know that they’re more successful, and if it you don’t have any seedpods then [your…] plant wasn’t that successful.
20. Mrs. W: [Why, though?]
21. Mrs. W: Why would having more seedpods make it more successful?
22. Kelly: Well, then because you'll have more seeds to grow umm more plants.
23. Mrs. W: Oh...because then you have more seeds to grow more plants... I see.
Mrs. W helps her students not only consider evidence as something that can be measured or compared across the two systems, but as something that can be theoretically justified, given what they know about plants and their prior scientific work. She stops probing only when Kelly explicitly states that success means making more plants and that seedpods help you “know they’re more successful” (Lines 19 and 22). She then restates the justification, emphasizing the outcome of more plants. However, once reproduction as a proxy for making more plants is theoretically justified, another student challenges the way that the comparison is being made.
24. Tyree: Umm... I really had something to kind of m-to add because umm, Kelly said that if it has seedpods, it's more successful, and if it doesn't have seedpods, it's not successful, but so you're just… you’re just saying that if it like, it just has flowers it's not being really successful, but it could be on its way to growing the seedpods.
25. Mrs. W: Ohh… OK. So you see the flowers as on their way to growing seedpods, so you think they could be just as successful, OK.
Tyree is concerned that one set of plants might be slightly ahead of another in timing, but could
the design study. Measures simplify the system at hand, but they need unpacking and carefully justified operationalization to serve their purpose.
Summary: relation of modeling and concept. Here, the development of meanings of reproduction occurred as students applied and discussed it as a measure that enabled claim making in a new model system (Figure 5). Ideas from previous modeling activity were imported into this system as students called on their understanding of the role of reproduction in plant dispersal and multiplication to theoretically justify measures. During this activity, the idea of reproduction shifted in its use and meaning within the community toward disciplinary notions of reproductive success. Though students did not have access to genetic mechanisms, they
considered it important that plants “make more of their own kind.” This explicit connection across multiple generations of plants has the potential to serve as a link between the effects on an individual and predictions about future groups. In addition, students could challenge each other to justify the operationalization of the measure, providing an opportunity to deepen the ideas that substantiated it. For instance, reproduction could be considered not just as an endpoint in a plant’s life, but as a stage linked by mechanisms (i.e., pollination) to other stages (i.e., flowering).
These are initial forms of engagement in sophisticated scientific practices and aspects of scientific argumentation. They are also highly conceptual. The positioning of reproductive success in relation to the activity described above underscores the inseparability of concept and practice. For students, the idea of reproductive success would have had little meaning outside their practice of investigating how the plants got to the backyard. Likewise, the practice of creating and understanding model investigations, then privileging reproductive success as a
measure, relied on shared conceptions of seeds as agents responsible for plants being where they were.
Figure 5. Students’ participation in modeling activity during the soil flats phase
Summary of the Four Phases of Activity
A summary of the development of meanings for reproduction across the four phases of activity is presented in Table 2. Analysis of conceptual meanings suggests that students brought to instruction a varied set of productive ideas about seeds, which were eventually used to explain how plants got into the backyard, deepened as students developed differentiated ideas of seed structures and backyard conditions related to seed travel, and recruited for an approximation of the disciplinary concept of reproductive success. These meanings became increasingly powerful in community activity, as evident in the focus of talk around ideas of reproduction later in the
Model Making
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Claims in Model System
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Little time to understand entailments in backyard due to weather event
Magnification and Testing of Seeds
rainsun
soil success
seeds, seed travel, growth of new plants
?
instructional phases. As students worked around shared representations, seeds were made visible and useful to backyard explanations, then functioned as the subject of model- and claim-making activity, and, finally, were recruited as a measure in a new enterprise.
Table 2. Summary of the conceptual, social, and epistemic aspects of students’ work with ideas of reproduction over the four instructional phases.
Instructional Phase
Conceptual Social Epistemic: Position in Modeling Activity
Posing
questions •Plants make seeds
•Seeds can travel
•Seeds grow into new plants
•Talk wide •No shared representations
•Students do not seek to
question or explain processes in BY
Reading
books •BY as wild
•Plants populate the backyard through seed travel
•Talk focused
•Spontaneous argument
•Seeds and seed travel made visible in representations
•Concepts useful as they are applied to backyard
Seed travel
claims •Differentiation of seed structures and BY conditions
•Talk focused
•Students respond to and question each other’s ideas
•Seed travel as subject of model and claim-making
•Concepts differentiated as students arrange and question models and model entailments Soil models •Notions of
reproductive success
•Talk focused
•Students respond to and question each others’ ideas
•Seeds as a measure in a new enterprise
•Differentiation/development occurs as measures are justified and defined
Discussion
In this paper, I described the co-development of ecological understanding and modeling practice in one third grade classroom in an effort to analytically integrate the conceptual, epistemic, and social strands of students’ scientific activity (Duschl, 2008). To do so, I outlined
representations to explain the distribution of plants in a wild backyard area. Analysis compared the visibility and use of concepts of reproduction at four time periods in the year. This analysis suggests the utility of attending to student knowledge as it is used in practice and provides images of knowledge-practice relations that support productive scientific activity.
This perspective involves moving beyond determining whether students “have” or “do not have” ideas to focus on how ideas are used and refined in students’ scientific activity (Duschl et al., 2007). Pre-instruction interviews and early classroom discussions demonstrated that
students initially “had” an idea of reproduction; they knew that plants made seeds that, in turn, grew new plants. What changed over the course of the year was when and how they sought to use these ideas to pose questions and to make and defend new claims. In pre-interviews and early instruction, students generally mentioned seeds and reproduction only when asked explicitly about them. In later instruction and post-interviews, they recruited these ideas for a much wider set of questions and purposes, several of which exhibited nascent resemblances to sophisticated scientific practices. These results affirm that expertise resides not in the recitation of principles, but rather, in imposing conceptual structure to navigate complexity and opacity (Hmelo-Silver et al., 2007; Magntorn & Hellden, 2007). They also add to a growing body of work suggesting that elementary school students should be supported to participate in relatively complex scientific practices to develop conceptual understanding, rather than first being taught the concepts in isolation of practice or being initiated only into simple forms of practice such as observation or categorization (Lehrer, Schauble, Carpenter, & Penner, 2000; Louca, Elby, Hammer, & Kagey, 2004; Metz, 1995, 2011).
This study’s treatment of the development of concepts in socially situated modeling practice builds from and extends recent perspectives on engaging students in disciplinary
practice. The results demonstrate a case of the development of productive disciplinary engagement (PDE) (Engle & Conant, 2002) in the sense that over the course of the year, reproduction (a) increasingly sparked explosion in participation, argument, questioning, and elaboration by students and (b) facilitated activity that approximated important disciplinary practices, in this case material and representational aspects of modeling (Engle, 2011; Ford &
Forman, 2006). Here, the focus on tracing one disciplinary concept, following methods for understanding PDE, made visible useful analytic distinctions in the relations of knowledge and practice in community activity. In the classroom described here, the concept of reproduction was used in a variety of ways: it was named and connected to experience; it became a constituent in argument and explanation; it was deepened and expanded by students through experimentation;
and it was recruited to make sense of new systems and investigations.
In the context of recommendations to organize science instruction around fewer big ideas that are generative for practice (NRC, 2011), this study provides some evidence that
reproduction is one such fruitful big idea. Within our larger project, the complexity and utility of concepts of reproduction for early elementary school students was something of a surprise.
Reproduction is often mentioned in standards documents, but there is little specification of how it might be uncovered and explored, or what purposes it might serve for students’ larger
scientific activity. We have now come to see it as a critical idea that links young students’
evolving conceptions of relations between organisms and populations and enables their practice of ecology. As we begin to follow the development of conceptual meanings in practice and to better understand the challenges of organizing shared scientific practice in relation to disciplinary concepts, we will be in a better position to determine which concepts to focus on and what trajectory to envision for them.
A second goal of this study was to explore implications for the design of learning environments that support the co-development of knowledge and scientific practice. The nature of modeling provides a venue where knowledge and practice can bootstrap, or iteratively push on and expand each other (Lehrer et al., 2008; Metz, 2011; Nersessian, 2008). Three forms of modeling and knowledge relations that appear to be productive for the design of instruction were evident in the analysis of student activity.