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Daily Do

What Do Plants Do in the Dark?

Biology Crosscutting Concepts Disciplinary Core Ideas Is Lesson Plan Life Science NGSS Phenomena Science and Engineering Practices Three-Dimensional Learning High School Grades 9-12

Sensemaking Checklist

Welcome to NSTA's Daily Do

Teachers and families across the country are facing a new reality of providing opportunities for students to do science through distance and home learning. The Daily Do is one of the ways NSTA is supporting teachers and families with this endeavor. Each weekday, NSTA will share a sensemaking task teachers and families can use to engage their students in authentic, relevant science learning. We encourage families to make time for family science learning (science is a social process!) and are dedicated to helping students and their families find balance between learning science and the day-to-day responsibilities they have to stay healthy and safe.

Interested in learning about other ways NSTA is supporting teachers and families? Visit the NSTA homepage.

What is sensemaking?

Sensemaking is actively trying to figure out how the world works (science) or how to design solutions to problems (engineering). Students do science and engineering through the science and engineering practices. Engaging in these practices necessitates students be part of a learning community to be able to share ideas, evaluate competing ideas, give and receive critique, and reach consensus. Whether this community of learners is made up of classmates or family members, students and adults build and refine science and engineering knowledge together.

Introduction

Have you ever wondered what plants do all night long? Are they sleeping? Do they do anything at all? Students likely understand that plants capture light energy through photosynthesis. However, they may not understand that plants also must perform cellular respiration to release usable energy from the organic molecules produced as a result of photosynthesis. Some students may think that plants only carry out photosynthesis, while others may think plants carry out photosynthesis during the day and respiration during the night.

Today’s task, What Do Plants Do in the Dark?, builds on students’ understanding of the processes of photosynthesis and respiration and will begin to help them clarify ideas about the relationship between these two processes. Students download and analyze data from an investigation that has already been completed and use the thinking tool of patterns to construct an explanation of what plants do all night long. While students need opportunities to develop and use the knowledge and skills of Planning and Conducting Investigations, today’s Daily Do is an example of how students-as-scientists can engage in sensemaking without physically conducting the investigation themselves. 

Watch from start to 0:36

Engaging with the Phenomenon

Tell students you have an interesting phenomenon to share. Play the Photosynthesis with bubbling pondweed (elodea bubbling in front of a spotlight) with no sound from the start to 0:36. Ask students to make and record observations while you play the video segment a second time. (Replay as many times as needed.)

Next, present students the following scenario (formative assessment probe). Five friends were discussing what would happen if the spotlight was turned off. This is what they thought:

Marice: I think the bubbles in the video are oxygen produced during photosynthesis. The bubbles would stop when the spotlight is turned off because photosynthesis stops in the dark.

Sally: I think the bubbles are carbon dioxide produced during cellular respiration. The bubbles would stop when the spotlight is turned off because cellular respiration stops in the dark.

Cameron: I think the bubbles are oxygen and carbon dioxide. Plants need light for photosynthesis and cellular respiration so the bubbles would stop when the spotlight is turned off.

Arya: I think the bubbles are oxygen and carbon dioxide. When the spotlight is turned off, the number of bubbles would be less because photosynthesis stops but cellular respiration is still happening in the dark.

Ask students, “Who do you most agree with? Explain your thinking.” Provide students independent thinking time to complete the formative assessment probe. Ask them to record their thinking in their science notebook; encourage students to use words, pictures, and/or symbols to communicate their thinking. You might ask students to put the probe away (assure students you’ll come back to their probes later) and then poll them on which friend’s claim they selected. If you have a large group of students, you can have students write their claims on sticky notes and create a sticky note bar chart on a wall or whiteboard or use a free digital tool like Mentimeter or Socrative.

Ask students, “How could we figure out which friend has the best claim?” Provide the equation for each process and ask students, “What could we measure to determine if photosynthesis and/or cellular respiration are happening?”

  • Photosynthesis: 6H2O + 6CO2 + light energy → C6H12O6 + 6O2
  • Cellular Respiration: C6H12O6 + 6O2 → 6H2O + 6CO2 + energy

Students might share many different ideas about measuring the inputs or outputs of each process. Practically, the gases (O2 or CO2) that are consumed or released are easiest to measure. In this task, we are leading up to analyzing data from an investigation in which sensors were used to measure changes in the amounts of these gases.

Say to students, “We may not be in a situation where we can carry out this investigation, but we can analyze data from an investigation that was already conducted.”

Exploring the Phenomenon

Teacher Guidance: Students will analyze data from Vernier’s Experiment and Sample Data Library,using Vernier’s free software Graphical Analysis 4. The data was collected using probeware in the same way that students would if they were in a classroom with access to the required equipment.

Provide students with the Photosynthesis and Respiration investigation handout and have them read through the procedure. You can use slides 1 and 2 in the How Do Plants Get Energy in the Dark? presentation to walk through the investigation setup. Use the following questions to guide a discussion to clarify students’ understanding of the procedure.

  • Why is the chamber wrapped in foil to collect Data Set 1?
  • Why is the light needed to collect Data Set 2?
  • Why is the heat sink needed to collect Data Set 2?
  • Why is it important to have fresh, turgid spinach leaves?
  • How will we know whether photosynthesis is happening?
  • How will we know whether cellular respiration is happening?

Have students complete the hypotheses graphic organizer (Slide 3) based on the claim with which they agreed. If you have a large group of students, you could partner them based on their selected claim. This graphic organizer is adapted from Argument-Driven Inquiry’s instructional resources. Have students share their predictions and reasoning first in small groups and then with the class. 

Teacher guidance: This table summarizes the expected results based on each claim in the prompt.

Analyzing the Data

Tell students to download the data from the experiment and Graphical Analysis 4 software. Have students refer to steps 8, 13, and 14 to analyze data for the datasets and determine the rates of photosynthesis and/or respiration. Have students use the curve fitting tool as directed in the Photosynthesis and Respiration investigation handout and record the rates in the data table on the handout.

In addition to the steps listed in the investigation handout, performing the following steps will make the graphs easier to read and interpret.

  1. Click the “View Options” button at the top right. The button looks like a small table.
  2. Click “Table.”
  3. Click the three dots next to each data set title.
  4. Click “Rename Data Set.”
  5. Rename Data Set 1 “Dark” and Data Set 2 “Light.”
  6. Click the “View Options” button and click “2 Graphs.”
  7. For each graph, click the Graph Tools button and toggle on “Graph Legend.”

The final graphs should look like the ones in the screenshot below:

O2 and CO2 vs Time (graphs)

Ask students to work with a partner to answer the following questions and record their thinking in their science notebooks:

  • What patterns do you observe in the data presented in the graphs?
  • How does the amount of O2 change with time? 
  • How does the amount of CO2 change with time?
  • How is the rate of change changing over time? How might you represent that rate of change mathematically?

Revising Claims

Use questions 1-4 from the Photosynthesis and Respiration investigation handout to guide a discussion to help students make sense of the phenomenon.

  1. Was either of the rate values for CO2 a positive number? If so, what is the biological significance of this?
  2. Was either of the rate values for O2 a negative number? If so, what is the biological significance of this?
  3. Do you have evidence that cellular respiration occurred in the leaves? What is the evidence?
  4. Do you have evidence that photosynthesis occurred in the leaves? What is the evidence?

Note: Question 5 and the extensions are not needed to answer “What do plants do in the dark?”, but they can lead to further sensemaking opportunities.

Have students return to their hypothesis graphic organizers and answer these questions, first as individuals or pairs. Then, have students share with the whole group.

  • Do the results support or refute your selected claim?
  • Are the results consistent with any other claim(s)?

Say to students, “Let’s revisit the claims we are evaluating. Based on our data analysis, can we determine which claim is the most accurate? How do we know?” Facilitate a discussion to build consensus around the claim that plants carry out respiration but not photosynthesis in the dark.

Students might still be wondering why plants carry out respiration at all. Ask them, "Should we investigate his question next?" (This question will be investigated in a forthcoming Daily Do.)

NSTA Collection of Resources for Today's Daily Do

NSTA has created a What do plants do in the dark? collection of resources to support teachers and families using this task. If you're an NSTA member, you can add this collection to your library by clicking Add to my library located near the top of the page.

Check Out Previous Daily Dos from NSTA

The NSTA Daily Do is an open educational resource (OER) and can be used by educators and families providing students distance and home science learning. Access the entire collection of NSTA Daily Dos.

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