Concept covered in activity: Students will learn how photosynthesis and cellular respiration work and how they work together in the carbon cycle. Students will take part in a whole-class activity, using props to visualize molecules of carbon through photosynthesis and cellular respiration
Grade level or other prerequisites for activity: 7th grade life sciences. The students should have covered cell structure and function as well as the differences between animal and plant cells.
Standards: national AND state standards:
A: Science as inquiry - Abilities necessary to do scientific inquiry
C: Life Science – Structure and function in living systems
CO Science Standards:
CO Science Standard 2.7.3 (Cells are the smallest unit of life that can function independently and perform all the necessary functions of life)
CO Science Standard 2.7.4 (Photosynthesis and cellular respiration are important processes by which energy is acquired and utilized by organisms)
Learning objectives: Students will be able to (SWBAT)
Describe why plants require carbon dioxide, water, and sunlight to carry out photosynthesis and store sugar molecules
Describe how plants and animals break apart sugar molecules to use stored energy through cellular respiration
Describe how plants exchange gas through stomata
Describe how land vertebrates exchange gas through lungs
36 Ping-Pong balls (per group of 4-6) labeled with the appropriate molecules (see instructions attached)
24 “energy tokens” (per group of 4-6)
6 egg cartons (per group of 4-6) labeled with the appropriate molecules (see instructions attached)
3 signs, one reads “stomata”, one reads “stem”, and one reads “lungs”
Edible plant leaf, such as a lettuce leaf
The teacher should have all the materials set up and ready for the students to use when they come in. Egg cartons can be collected year round (have your students bring in empty egg cartons from home). Detailed instructions for setting up the materials see attached.
Respond to notebook prompt: “Describe 2 possible causes of the increase of CO2 levels here on earth”
Arrange in groups of 4-6
Write the prompt on the board ahead of time, so students begin when they enter class (notebook prompt at the beginning of class should be routine)
Group students into groups (4 to 6 students per group)
Explain that the classroom will represent a leaf. Hold up a leaf as an example. (If you can, use an edible leaf for this, such as lettuce or spinach.)
Tell students that each table within the classroom will represent a cell within the leaf.
Explain that the students will be working in groups to build a sugar molecule in their cell.
Have students use their science notebooks to write down the procedures they use to make the sugar molecules
Answer the guided questions with previous knowledge
Write down the steps your group took to make the sugar molecules in science notebooks
From knowledge gained during the activity formulate a chemical formula for photosynthesis (copy down formula in science notebooks)
Explain the Materials to the students (see attached)
As you explain the materials ask guiding questions about how cells receive the materials. (i.e. “What is necessary for photosynthesis to occur?”, “How does the CO2 get into the leaf?”, “How does the water get into the leaf?”) as these questions are answered show the materials that represent (ping-pong balls represent individual atoms etc.)
Explain the roles and rules (see attached)
As you explain ask the students more guiding questions (“CO2 enters the leaf through the?) After the students answer place the “Stomata” sign over the door and explain the CO2 will be located outside the door. Do this for the water as well by placing the sign over a sink.
Explain the “energy tokens” and how they can be converted (see attached) and explain that you are the “sun” and will be sprinkling the “energy tokens” throughout the room.
After all the students are clear on where to find the materials have them try and make a sugar molecule in their “sugar frame”
*The students should have many questions about the process, but let them work for a little while on their own to try and figure it out in their groups.
After all the groups have attempted to make their sugar molecules hold a discussion with the students. Ask the students what was needed to successfully make the sugar molecule
*at this point start to formulate the photosynthesis formula on the board.
Run through the procedure again to limit the number of leftover atoms
Record the steps your group took to limit the number of leftover atoms in science notebook, also record how many materials you used to do so
Share with the class the procedure you used to limit the leftover atoms and how many materials you used in the process
Write down the procedure that yielded the least amount of atoms in science notebooks as well noting how many materials were used in the process
Run through procedures with one of the materials missing, explain why photosynthesis needs to be successful to the class and record in science notebook
Explain to the students the photosynthesis formula is not complete because it needs quantities.
Have the students run the procedure again, but to limit the amount of unused atoms, this will limit the materials the students can grab.
Have the students record how many water molecules, CO2 molecules they use.
Hold a class discussion on how many materials were necessary to make a sugar molecule with the least amount unused atoms. This will allow you to add the quantities to the photosynthesis formula.
Run the Procedure a few more times, but now take out one of the materials (i.e. shut the door so the “stomata” is closed and no CO2 can get into the cell, or take away the water or tell them it is night time and there is no sunlight)
Hold a class discussion and ask students “What do plants need in order to photosynthesize? They should now be able to answer that air (specifically CO2), water, and sunlight are all required for photosynthesis.
Work through the next procedure to try and use some of the energy in the sugar molecule. Record what is needed for this process in science notebook (record procedure in notebook)
Participate in class discussion on what is needed to break down the plant sugar (oxygen) and where it comes from
Work through animal cell respiration (record procedure in notebook)
Discuss the similarities and differences between respiration in a plant cell and respiration in an animal cell (Record answers in science notebooks)
Tell students that they now need to use some of the energy that they stored in their plant sugar molecules.
This is a problem-solving task. Tell students that when cells break down sugar to access energy, they release CO2 and water. (Give them empty CO2 and H2O frames.) However, there is a piece missing—they need to get something in addition to sugar to make this happen. Their task is to discover what that is and how to get it.
Give them time to break apart the sugar molecule, remove the energy tokens, and try to make the CO2 and H2O molecules. Leave the door (stomata) open and the oxygen atoms from earlier outside.
Students should find that they need oxygen in order to complete the molecules, and should go get it from the “air” outside the leaf.
The CO2 and H2O molecules should then be taken out the stomata (released into the air)
Show the class the photosynthesis formula again and have them explain the process (The process is the reverse as the time before)
Hold a class discussion and ask the students “How do animal cells get there energy?”
Explain that animals cannot make their own sugars like plants can. Pose the same question to the students “How do animal cells get there energy?” The students should come to the realization that animals eat plants to get their sugars.
Tell students that the leaf they are a part of is about to be swallowed by a hungry herbivore. (If you used an edible leaf as a model earlier, pick up the leaf and eat it!) Explain that the leaf is getting chewed up and digested. Then the sugar molecules that were contained within the leaf are passed to cells in the body.
Take down the “stomata” sign and the “stem” sign. Tell students that the classroom now represents the teacher’s body. Each table is a cell within the teacher. The cells need to break apart the sugars to release energy so the teacher will have the energy to keep teaching. Just like in plants, the process will release CO2 and H2O.
Ask the class what is missing (oxygen) and where will the teacher get the oxygen? (the lungs)
Replace the stomata sign with a sign that reads “lungs”
Tell the students to get the energy from the sugar molecules. (This will be the very same process
as it was for plants—the only difference is that oxygen enters through the lungs instead of the stomata. Students should bring oxygen in through the lungs (door)
and release the CO2 and H2O produced in the process through the lungs
Hold a class discussion the similarities between respiration in a plant cell and an animal cell.
Show the class the photosynthesis formula again and have them explain the process, point out it that it is the same formula for the plant cell.
Students will fill out the ticket out the door at the end of the lesson
Hand in science notebooks
Hand out the ticket out the door (see attached)
Review science notebooks
Formative (informal and/or formal)
The teacher should informally listen/observe group discussions to see if the students seem to be finding the key to building/breaking apart sugar molecules to make needed products.
The teacher should informally listen/observe class discussions
The teacher should also periodically check in with individual groups to check for understanding, to check for group achievement and to guide the group in the right direction if need be.
The teacher should observe the individual groups to see how they work together and to make changes to students in groups if need be.
Summative (usually formal)
The teacher will grade the journal prompt on two things that might be possible to cause the increase in CO2 in the atmosphere.
The teacher will also grade the ticket-out-the-door activity on the chemical formula for photosynthesis and cellular respiration, and the differences between them.
Students may think that water or sunlight is the most important factor for photosynthesis instead of CO2
Students may confuse cellular respiration with respiration of lungs
Only animals utilize cellular respiration
Specifically group with students who are advanced, or group together so they can all work with one para-professional, provide an agenda for the day ahead of time, possibly let them have a special job, possibly provide skeleton notes, completed notes, or word banks ahead of class, provide outlined timelines for students to keep track of information from lesson
Provide a translated definition sheet or notes, provide full notes ahead of time or word banks, provide translated agenda and instructions ahead of class, provide translated instructions for activity.
Ask the students to write a short essay on the differences between respiration and cellular respiration. What is happening in these processes and explain why most people get these two terms confused with one another.
Instructions for activity:
Explain the materials
First, review the difference between atoms and molecules. An atom is the smallest possible piece of a pure substance, like carbon or hydrogen. A molecule is made of two or more atoms bonded together. (If your students are not already familiar with this concept, spend a little time on it before starting the activity.)
Give each group an empty sugar frame.
Look at labels in the frame. Review what atom each letter represents. (C = carbon.
H = hydrogen. O = oxygen.)
Tell students the carbon atoms will be coming from carbon dioxide molecules (CO2).
CO2 is a molecule found in the air. Ask students how CO2 gets into the leaf. (CO2 in the air enters the leaf through the stomata.)
The hydrogen atoms will be coming from water molecules (H2O). Ask students how water gets into the leaf. (It is drawn from the soil into the roots, up the stem, and into the leaf.)
Some of the oxygen atoms will come from the CO2 molecules and some from the H2O molecules.
Show students the energy tokens. Explain that sugar molecules store energy. To represent this, students will have to pack an energy token under each atom in the sugar frame. Ask students where the leaves get this energy. (From sunlight.) However, the energy in light is not in a form that can be used by a plant. Show students how to unfold the token from “light energy” (L.E.) and re-fold it as “chemical energy” (C.E.). Explain that plants convert energy from one form to another so that it can be stored in sugar molecules.
Explain roles and rules:
Students will have to work together within their groups to gather the things they need and put the sugar molecule together. You may decide whether to assign a role to each student or to let the groups work out the process on their own.
Air must be carried to and from the cell. Ask students again how the air gets into the leaf. (Through the stomata.) Post a sign on the classroom door that says “stomata.” Tell students that the classroom represents the leaf and the area outside the room represents the air surrounding the leaf. Open the door and place filled CO2 molecules and empty O2 frames just outside. Students will bring the CO2 molecules from the outside area to their table, and will take any leftover atoms or molecules from the table to the outside area.
Water must also be carried to the cell. Ask students again how water gets into the leaf. (Through stems from roots, drawn from soil.) Post a sign next to the classroom sink (if there is one; otherwise choose any location) that says “stem.” Place the H2O molecules under the sign. Students will bring these molecules from the sink to the table.
Energy must be collected and converted into a usable form. Ask students again where the cell will be getting energy. (From sunlight.) The teacher will act as the sun and will sprinkle the energy tokens around the room. Students will gather energy tokens to the table and convert them from “light energy” into “chemical energy.” To convert the energy from “light energy” to “chemical energy” simply unfold the piece of paper and refold it so it reads “C.E.”
As the materials are gathered, students must take atoms from the CO2 and H2O molecules and place them in the appropriate places in the sugar frame.
They must pack an energy token under each atom in the sugar molecule. This represents the energy stored in the bonds within a sugar molecule.
Point out that when students take apart a molecule, they need to take all the atoms out of the frame. For example, you can’t take the hydrogen out of the water frame and leave the oxygens in. Without the hydrogen, it’s not a water molecule anymore.
Tell students that at the end of the activity, the only thing they should have on their table is the completed sugar molecules. Any leftover materials need to be taken out of the leaf and expelled into the air.
* Note that gathering and preparing these materials will be time-consuming the first time you do the activity, BUT all the materials can easily be stored and reused year after year.
1. Determine how many groups you will have. Each group will need 4 – 6 students. (If you are short on supplies, groups as large as 8 students could work.) You will need 36 ping-pong balls, 24 energy tokens, and 6 egg cartons for each group.
2. Prepare “energy tokens.” These should be small pieces of paper or cardstock (about 2 inches by 2 inches) with “L.E.” written on one side and the “C.E.” on the other side, as shown below:
Each group of students will need at least 24 energy tokens.