Arguing from evidence is one of eight key science practices in which students should engage. It is an essential component of science, yet students have difficulties with this practice. We describe a scaffolded claims-evidence-reasoning (CER) argumentation framework that is embedded within a new eight-week, freely available curriculum unit developed by the Genetic Science Learning Center – Evolution: DNA and the Unity of Life. The scaffold provides high school students with practice in both developing and evaluating written arguments. It is designed to incrementally build student skill week-by-week, starting with an introduction to the CER components of an argument, and ending with students evaluating data and constructing a supported written argument. We also present evaluation findings from field testing the argumentation scaffold in the context of the complete Evolution unit in dozens of classrooms. And we discuss how this integrated, scaffolded approach to argumentation influenced both student and teacher learning.
Building arguments from evidence is a central component of science. The authors of the Next Generation Science Standards (NGSS; NGSS Lead States, 2013) agree: they included it as one of eight key science practices in which students should engage. Further, research has shown that when argumentation is an explicit part of instruction, students better understand science concepts (Osborne, 2010).
The benefits of including argumentation are evident in evolution (Catley et al., 2005) and genetics (Zohar & Nemet, 2002) instruction. For example, students who engaged explicitly in argumentation showed significantly improved learning gains and retention of evolution concepts (Asterhan & Schwarz, 2007). In a genetics unit that included argumentation, students scored significantly higher than the comparison group in both genetics and argumentation (Zohar & Nemet, 2002). Yet, despite its importance, this practice is difficult for students (McNeill et al., 2006).
To meet the call for instruction that includes argumentation, we have developed an embedded argumentation scaffold within our newly developed, free, integrated evolution and heredity curriculum unit for ninth- and 10th-grade biology. Titled Evolution: DNA and the Unity of Life, the unit incorporates a claims-evidence-reasoning (CER) argumentation framework (Berland & McNeill, 2010) that incrementally builds students’ skill in both developing and evaluating written arguments (Osborne et al., 2016). Here, we focus on describing this argumentation scaffold, how teachers have used it in classrooms, results from classroom testing, and how this practice helps students make sense of the phenomena in the unit. For details on the whole unit’s theoretical framework, curriculum descriptions, and pilot testing, see Homburger et al. (2019).
Evolution Unit & Argumentation Scaffold Overview
Developed by the Genetic Science Learning Center at the University of Utah, Evolution: DNA and the Unity of Life is freely available on our teacher website (https://teach.genetics.utah.edu/content/evolution/) and student website (https://learn.genetics.utah.edu/content/evolution/). The eight-week, five-module, comprehensive curriculum unit illuminates the underlying role of genetics in evolution by maintaining a conceptual connection to DNA and heredity throughout. The unit’s paper-based and interactive multimedia lessons were designed for the NGSS. They engage students in high-interest phenomena, and they incorporate relevant science practices (arguing from evidence, and analyzing and interpreting data) and crosscutting concepts (patterns, systems and system models, and cause and effect).
We developed, classroom tested, and revised the argumentation scaffold over several cycles, as we developed the entire unit. During each testing phase, we gathered written and verbal feedback from teachers to inform the unit’s content and flow.
The topic of evolution lends itself well to argumentation from evidence. In an early draft of the unit, we asked students to carry out this practice. However, testing revealed that although students had some familiarity with the components of an argument, they did not have the skills to effectively develop their own. In response, we added a claims-evidence-reasoning (CER) framework.
The CER lessons built into each of the unit’s five modules incrementally build students’ capacity to develop an argument from evidence. Students begin with simple identification of each CER component, progress through practice using each one, and finally put them all together to write an argument. The argumentation activities are framed around the same science ideas and phenomena that students are studying in each module. This structure serves to simultaneously reinforce content knowledge and contextualize the CER process. The unit also includes explicit teacher instructions, which support teachers in building comfort and skill in incorporating this science practice into the classroom, and full materials lists. The argumentation lessons embedded within each module are briefly described below.
Module 1: Shared Biochemistry
Students are introduced to argumentation from evidence as a method for combating cognitive bias. A video highlights how bias might distort perceptions of reality and introduces the CER components of an argument. Students learn that scientific argument should include a clear claim, supporting evidence, and reasoning that connects claim and evidence. Next, students receive examples of properly and poorly constructed arguments about bioengineering examples that align with the module’s learning objectives. Students identify each CER component in the arguments, then evaluate their merit using a checklist (see Figure 1). Figure 2 shows the online teacher instructions.
Module 2: Common Ancestry
Much of this module is framed around a case study of cetacean ancestry, in which students work with data from anatomy, fossils, embryology, and DNA. Now familiar with the components of an argument, students begin exploring each one in more detail. As they progress through the case study, prompts on an “evidence organizer” guide them in making data-based evidence statements. Next, students are given claim and reasoning statements about cetacean ancestry. They must identify the pieces of evidence from their organizer that both support the claim and are consistent with the reasoning provided. Figure 3 shows the key for the evidence organizer.
Module 3: Heredity
During an early pilot test of the unit, students tended to include all accurate evidence in their written arguments, even if the evidence was not relevant to the claim. Therefore, we added more practice with reasoning – the justification for why the evidence supports the claim. Students are given a set of claims and supporting evidence, and they must choose the reasoning statement that best connects the two. This exercise also serves as a review of the concepts explored in the module, including the role of mutation and sexual reproduction in generating genetic variation (Figure 4).
Module 4: Natural Selection
This module is centered around a real-world case study of stickleback fish, where a body armor trait changes over time in a population. Figure 5 shows a teacher working with students on gathering evidence for stickleback evolution. One exercise reviews how the CER components work together in an argument. Here, students match “evidence cards” to reasoning statements, and use their matches to identify correct and plausible claims about body armor and reproductive advantage (Figure 6). Then, for the first time, students write their own supported arguments. They gather evidence from a suite of data analysis activities and summarize them onto an organizer. Next they use this evidence to write an argument about whether the change over time in stickleback body armor is a result of natural selection. Students peer review the arguments with the aid of the “evaluating arguments” checklist from module 1. The checklist helps students assess whether each component of CER is present and is used appropriately. Students use feedback from peer review to revise their arguments (Figure 7). Teacher instructions detail common student misconceptions to look out for in the written arguments.
Module 5: Speciation
In the final module, students engage in an authentic science investigation to decide whether hawthorn flies living on hawthorn and apple fruit are becoming two species – a question that scientists are still studying. A “speciation organizer” aids students in collecting and sharing several lines of evidence. They evaluate the evidence to decide whether the two fly populations are reproductively isolated and whether different heritable characteristics are being selected for in each population (Figure 8). Students then place the populations on a “same species to different species” continuum and write a supported CER argument that justifies their placement. Teacher materials provide implementation details and answer keys.
Using the Language of CER
To help students incorporate the language of CER into their vocabulary, we used this terminology throughout the unit – not just in the argumentation lessons. This consistency helps students identify CER in each activity, reinforces their understanding, and builds their confidence in using the terms. The benefit of this repetition is particularly evident in the final two modules, at which point students are very familiar with the CER language.
The language of CER spans content areas, including the Common Core State Standards (NGA/CCSSO, 2010). Many teachers use CER or similar processes to teach argumentation in other subjects, such as language arts. Applying the same process and language across subjects reinforces interdisciplinary connections and facilitates curriculum integration.
To improve alignment, biology teachers can easily modify our CER terminology to match the terms used in other subjects. For example, one pilot test teacher changed the unit’s CER language to “if…and…then…because” deduction statements to better leverage what students were learning from the school’s language arts teachers.
Each module provides opportunities for teachers to monitor students’ progress in developing argumentation skill. The following formative assessment tasks explicitly illuminate student thinking:
Student-generated written arguments demonstrate individual students’ progress.
Several opportunities to engage in verbal argumentation allow students and teachers to critique and consider others’ arguments.
Students’ peer review checklists reveal the understanding of both the reviewer and reviewee.
Evaluating the Argumentation Framework
We conducted a national pilot test of the entire Evolution: DNA and the Unity of Life unit in the classrooms of 20 teachers. Here, we present the results on the topic of argumentation.
Student Pilot Test Results
We measured students’ argumentation knowledge through eleven multiple-choice items on pre/posttests. Test items used different phenomena than were in the unit. They evaluated students’ knowledge of CER, their ability to justify why data support a claim, and their ability to select data that support a particular claim. Scores from the 944 students who completed both the pretest and posttest increased significantly from pretest to posttest, t(943) = 5.0, p < .001, with an average score gain of 14.5%. These findings indicate that students increased in their argumentation skills over the course of the unit.
Teacher Pilot Test Feedback
We collected teacher feedback from the 20 pilot test teachers during an in-person, 3.5-day summer institute, as well as during and after curriculum classroom pilot testing through interviews, daily teaching logs, and classroom observations. Our findings showed the following.
(1) The argumentation framework and scaffolding built students’ skills in arguing from evidence. Many teachers indicated that the framework was their favorite part of the unit because it provided an accessible formula for a process that would otherwise be very complicated. As one teacher explained: “I want curricula to continue this kind of approach to the rest of biology…. I’ll definitely be doing more student writing, defending using evidence, the CER, for argumentation…. It’s a scientific approach.” Another teacher described how “students learn about claim, evidence, and reasoning. They construct arguments from real data. This unit does more than just give students information about evolution. Through an eight-week scientific experiment, students prove it to themselves.”
(2) Teachers are applying the unit’s argumentation scaffold to their other classes, and 36% indicated that they shared it with colleagues. For example: “I was able to use what I learned about claim, evidence, reasoning activities for my freshman physics class as well.” And: “I led a professional development for my colleagues…. I showed them how each module advanced a set of skills from NGSS…. I used argumentation as an example and how the practice is methodically developed…. I emphasized the student struggle and how well they understood the content after the struggle.”
(3) The unit educates teachers about integrating NGSS science practices. For example: “The argumentation [lessons] give a great way to provide student feedback…. The better I’ve gotten at giving students feedback, the better their arguments get.” And: “The evolution curriculum is now our go-to model for how to design an NGSS-aligned lesson.”
Data from teachers and students show that the argumentation scaffold built into the Evolution: DNA and the Unity of Life unit supports students’ capacity to identify elements of CER and to create written arguments from scientific evidence. Further, the scaffold has educative value for teachers in incorporating this NGSS science practice into their classroom teaching, particularly as they are learning the science practices themselves. The unit provides a model that teachers can use in other lessons. As one teacher explained following the pilot test: “My favorite part of the unit was the argumentation. Simply because I didn’t have to convince students about the scientific principles, they found the proof themselves. Watching them defend their positions, I could see how much they had learned from the unit’s activities.”
The curriculum unit and research reported here are based on work supported by the National Science Foundation under grant nos. DRL-141418136 and DRL-1222869. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors or teachers who tested the curriculum unit and do not necessarily reflect the views of the National Science Foundation. We would like to extend special thanks to Nicola C. Barber for her early work on the argumentation scaffold and to Ryan D. Perkins for preparing the figures for this article. We are grateful to the many teachers, scientists, and the Genetic Science Learning Center staff who contributed to this project throughout its development. For a full list of acknowledgments, schools, and locations, see https://learn.genetics.utah.edu/content/evolution/credits/.