Giant Sequoia Tree – Assessment Probe from Uncovering Student Ideas in Science, Vol. 2

Page Keeley, Francis Eberle, and Joy Tugel
Type Category
Assessment Materials
Assessment Item
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This is one of 25 assessment probes from the book, “Uncovering Student Ideas in Science, Volume 2: 25 More Formative Assessment Probes”, by Page Keeley, Francis Eberle, and Joy Tugel. All assessment probes in this collection are aligned to a particular science concept and field-tested by several teachers in classes of diverse student backgrounds.  The “Giant Sequoia Tree” formative assessment probe elicits student ideas about the transformation of matter through photosynthesis in plants.  The probe presents a multiple choice question asking where most of the matter in a giant sequoia tree comes from, and then asks students to explain their thinking.  The probe could be used to present the phenomena of plant growth and photosynthesis and to reveal students’ initial ideas about this concept.  The probe could then be revisited at the end of a unit in which students investigate plant growth and carbon cycling.


An assessment probe is a purposefully designed question that asks students to provide a two-part response. Part one consists of a selected response, and part two asks students to provide an explanation. The probe is designed for students at elementary, middle, or high school grade levels. This format helps teachers identify students’ existing ideas about phenomena or concepts, which can help inform further instruction.  Assessment probes can also be used to engage students, encourage thinking, and promote sharing of ideas. When implementing probes in the classroom, the authors suggest using the probe to encourage teacher-student, student-teacher, and student-student feedback on learning. Each probe is accompanied by teacher notes that include information on the purpose of the probe, related science concepts, an explanation of all answer choices, curricular and instructional considerations, suggestions for administering the probe, related standards (National Science Education Standards, 1996), related ideas in Benchmarks for Science Literacy (AAAS, 1993),  related research, description of common student misconceptions, suggestions for instruction and assessment, and related NSTA science store publications and journal articles.

Intended Audience

Educator and learner
Educational Level
  • High School
Access Restrictions

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Performance Expectations

HS-LS1-6 Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon-based molecules.

Clarification Statement: Emphasis is on using evidence from models and simulations to support explanations.

Assessment Boundary: Assessment does not include the details of the specific chemical reactions or identification of macromolecules.

This resource was not designed to build towards this performance expectation, but can be used to build towards it using the suggestions provided below.

Comments about Including the Performance Expectation
This assessment probe could help introduce the phenomenon of plant growth to spark student learning leading up to this performance expectation. To guide students toward this performance expectation, teachers might present a guiding question, like: How is the sugar made during photosynthesis used to make the parts of the plant? The probe elicits students’ ideas on some of the basic concepts that would serve as the basis for such an explanation.

HS-LS1-5 Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy.

Clarification Statement: Emphasis is on illustrating inputs and outputs of matter and the transfer and transformation of energy in photosynthesis by plants and other photosynthesizing organisms. Examples of models could include diagrams, chemical equations, and conceptual models

Assessment Boundary: Assessment does not include specific biochemical steps.

This resource was not designed to build towards this performance expectation, but can be used to build towards it using the suggestions provided below.

Comments about Including the Performance Expectation
The probe provides a phenomenon and context for building toward this performance expectation. In order to make sense of the growth of the giant sequoia tree, students will need to analyze the inputs, outputs, and transformations of matter and energy during photosynthesis. The probe does not directly involve modeling, but the teacher notes suggest that using models, including molecular models, will help students make sense of how matter is rearranged during photosynthesis. High level lines of inquiry that could lead students toward the performance expectation are: How do plants take in the matter they need to grow? and How is that matter transformed into the “stuff” that makes up the plant?

Science and Engineering Practices

This resource was not designed to build towards this science and engineering practice, but can be used to build towards it using the suggestions provided below.

Comments about Including the Science and Engineering Practice
The assessment probe presents seven potential claims to answer the question of where most of the mass of plants comes from. After sharing their initial ideas, students can explore and evaluate these claims through investigations and simulations. An example of a full unit that thoroughly addresses the PEs cited here is Plant Growth and Gas Exchange Unit also reviewed on the NGSS@NSTA Hub ( Students should use evidence they gather through these learning experiences to assess the original claims and develop an explanation of how carbon dioxide is transformed into larger molecules that make up plant tissue. The element of the explanations practice cited here is more directly addressed by the probe. However to fully meet the practice as indicated in HS-LS1-6, students will use evidence from multiple sources to support an explanation. This would be accomplished in a full learning sequence, anchored by this probe.

Disciplinary Core Ideas

This resource appears to be designed to build towards this disciplinary core idea, though the resource developer has not explicitly stated so.

Comments about Including the Disciplinary Core Idea
The main focus of this assessment probe is the transformation of carbon dioxide into sugars, and then into the larger molecules that make up the cell and tissues of plants. As the teachers notes suggest, it can be beneficial to call on high school students’ knowledge of chemistry to help them make sense of these transformations. One example is using knowledge of molecular masses to reason that carbon dioxide contributes more mass than water. The probe is designed to elicit student ideas on photosynthesis and plant growth, but students will likely need to be prompted to make their thinking more explicit. As the teacher notes indicate, students who know the chemical equation for photosynthesis may have difficulty moving beyond that basic model. The teacher will need to probe for deeper thinking.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
In order to understand where the mass of plants comes from, students will need to analyze how matter and energy flow and are transformed within the plant. Students’ understanding can be enhanced by using models and simulations, such as the Leaf Photosynthesis Netlogo Model ( The teacher can also facilitate student thinking by asking generative questions, like the following. - What are the inputs and outputs of matter and energy? - How are matter and energy changed during the process? - How do these changes serve the needs of the plant?

Resource Quality

  • Alignment to the Dimensions of the NGSS: This assessment probe can provide a meaningful context for a three-dimensional instructional sequence. The probe presents the phenomenon of plant growth through the example of a sequoia tree, and the teacher notes provide suggestions for making the example more relevant to students. Teachers will need to design the subsequent learning activities to address the three dimensions, but the probe will focus student thinking on developing an explanation for an authentic phenomenon.

  • Instructional Supports: The probe presents a phenomenon that will be familiar to some students, and the teacher notes provide suggestions for making the phenomenon relevant to other students. The probe directly elicits student ideas, and can provide a good context for further exploration. The accompanying teacher notes provide good content background, a progression of student understanding from elementary to middle school to high school, common misconceptions, and suggestions for implementation. The probe is actually based on a similar question in the Private Universe series, which explored science misconceptions among graduates of elite colleges. As you can see in this video (, even MIT graduates hold misconceptions related to this phenomenon. The teacher notes also provide general background information that will help the teacher respond to various student ideas. The resource does not address differentiation.

  • Monitoring Student Progress: The teacher notes discuss expected student understanding at different grade bands but not at different levels of understanding within those grade bands, and a rubric is not provided. This probe should provide information that will be useful in the teacher’s efforts to plan and adjust instruction. However, the teacher notes do not give specific guidance on this.

  • Quality of Technological Interactivity: This is not a technology-based resource. However, the probe could be administered through online technologies (e.g. Google Forms), which would facilitate the teacher’s ability to analyze and respond to class-level data generated through this assessment.