Tiny seedlings grow and transform into trees with a great quantity of matter.
Plan an investigation that would provide evidence to explain where all the matter in a tree comes from when it begins as a small seedling.
Continuation of the anchoring phenomenon: Tiny seedlings grow and transform into trees with a great quantity of matter.
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This lesson follows Lesson 7.1: Tree Matter where students modeled their thinking of where the matter comes from that makes up a tree. The students build on their thinking by planning an investigation to test where the matter of a tree comes from. The students will not carry out the investigation but will use this planning to further understand the elements of a scientific investigation. The use of the crosscutting concept Systems and System Models is used to discuss the possible components that are involved in the phenomenon of a tree gaining mass. In the next lesson, they will obtain information from a resource that describes the historical investigations that eventually led to the understanding of photosynthesis. Pre-read the historical investigations in order to help guide your students to create investigations that mimic the actual investigations. Do not tell the students about the investigations. Students’ understanding and use of the practice Planning and Conducting Investigations is limited to designing a plan. This will be their initial opportunity in the unit to consider independent and dependent variables and controls, tools that they need to gather data, how measurements will be recorded, and how many data are needed to support a claim. In 7.4: Investigating Gases they will have another opportunity to develop an investigation and carry it through to data collection.
Throughout the lesson, a flag () denotes formative assessment opportunities where you may change instruction in response to students’ level of understanding and making sense of phenomena.
One 60-minute session
Plan an investigation that would provide evidence to explain where all the matter in a tree comes from when it begins as a small seedling.
During Lesson 1: Tree Matter, students modeled their initial thinking of where the matter comes from that makes up a tree.
Ask students to review their models from Lesson 7.1: Tree Matter. Ask students to consider whether they are satisfied with their model’s ability to explain the phenomenon. Where is the model limited? What additional information would strengthen their model? Students should also consider the system described in the model. Ask students to consider which components of the system are uncertain and in need of further investigation.
The student suggestions might vary depending on whether you provided choices for the students in Lesson 7.1: Tree Matter or if you made the initial question open-ended. If you use an open-ended question, students often suggest that the tree gets its mass from the soil, water, or nutrients but rarely mention air or carbon dioxide. The students may have had lessons in fifth grade around the DCI LS1.C: Organization for Matter and Energy Flow in Organisms: Plants acquire their material for growth chiefly from air and water. (5-LS1-1) If they have, they may have suggested air as the source for the matter that makes up a tree. The idea of this lesson is that students plan an investigation to test their ideas. In Lesson 7.3: Historical Investigations, the students will obtain information about the historical investigations that led to the understanding of photosynthesis.
If students are struggling to share their models, you may need to do a think-aloud in front of the class first. Verbally describe, as if you were thinking aloud, the components seen in the model (I have included a tree, because that is the thing that is growing) and ideas they were not sure how to include (I wanted to show the tree GROWING but was unsure how to do that so I just made a small tree and then a bigger tree). Some students may need more processing time or opportunities to practice communicating their ideas. You may want to have students discuss their models in small groups before going to a whole-class discussion. This will give English Learners a different linguistic register in which to communicate. It will also allow students more processing time with peers and an opportunity for you to interact with students and to assess their ideas about the phenomenon and their model.
This is the first point in the unit that students are engaging in the practice of planning and conducting an investigation. In Lesson 7.3: Historical Investigations, students will focus on planning an investigation that will then be extended through comparisons of historical investigations. In Lesson 7.4: Investigating Gases, students plan and conduct an investigation about gases that are exchanged within a plant. Students may need support in identifying independent and dependent variables in their designs rather than simply considering which variables will be controlled (grade 3–5 band). In the grade 3–5 band, students are asked to consider what data is needed to serve as the basis for evidence. In this lesson, students may also need support in identifying what they will measure and what tools are needed to gather the data. If students are struggling to identify variables, they can brainstorm the possible things they could change in the experiment (independent variable) by writing each on a different sticky note. They can also identify all the possible things they could measure on different sticky notes. With the sticky notes in two clumps (things we could change and things we could measure), instruct students to identify ONE sticky note in the “things we could change ‘’ clump. Explain that this is their independent variable. All the other sticky notes in that clump are controls, or things that they should make sure do not change. Do the same with the “things we could measure” clump and explain that these are dependent variables. However, you may decide to allow students to measure more than one dependent variable. This sticky note strategy could be modified for English Learners by adding symbols or drawings to the text on the sticky note. For students above the target level, measuring multiple dependent variables in the lesson is an option as well.
During the discussion, probe students to find out what they would measure and what different results would mean depending upon where the matter came from. For example, if the students suggest that soil makes up the matter of the tree, the students could think about how they would measure soil before and after a seedling grows into a tree and compare the mass of the leftover soil with the mass of the tree. If the students suggest water makes up the matter of a tree, they could plan an investigation where they keep track of the water they add to the tree. The idea of this lesson is to have the students think through the investigations that actually occurred in history. They don’t know about these investigations yet but will read about them in Lesson 7.3: Historical Investigations. Because they are encouraged to wonder how someone might go about finding out if the matter of the tree came from soil, water, nutrients, air, etc., they will be very interested in reading about the historical investigation in Lesson 7.3: Historical Investigations.
Plan an investigation that would provide evidence to explain where all the matter in a tree comes from when it begins as a small seedling.
This step of the lesson is about having the students be sure they have included the elements of a scientific investigation for the grade 6–8 band. Two different ways of achieving this are suggested here.