1. Ecosystems Unit Activity 4.1 Farms are Ecosystems, Too
Carbon: Transformations in Matter and Energy
Environmental Literacy Project Michigan State University
Ecosystems Unit Activity 4.1 Farms are Ecosystems, Too

2. Humans and Ecosystems
From previous Lessons, you’ve learned that ecosystems are comprised of different carbon pools (e.g., producers, herbivores, carnivores) and that matter and energy move among these pools through carbon-transforming processes.
Are humans part of ecosystems? How?
Introduce a farm as an ecosystem.
Ask students to share ideas about how people are a part of ecosystems and how people use ecosystems. Point out that humans get all of our food and oxygen from ecosystems.
Point out that farms are ecosystems, too, and that these are the focus of the Activity today.
Pass out Lesson 4.1 Farm Ecosystems Worksheet to each student. Use Slides 2-5 of Lesson 4.1 Farm Ecosystem Presentation to talk about how farms are ecosystems too, and humans are part of those ecosystems.
Image Credit: Hannah Miller, Michigan State University

3. Humans and Ecosystems
Of course humans are part of ecosystems! All of the matter and energy that we need to survive come from ecosystems, as well as the oxygen we breathe.
One key type of ecosystem that we greatly depend on are farms.
Introduce a farm as an ecosystem.
Ask students to share ideas about how people are a part of ecosystems and how people use ecosystems. Point out that humans get all of our food and oxygen from ecosystems.
Point out that farms are ecosystems, too, and that these are the focus of the Activity today.
Pass out Lesson 4.1 Farm Ecosystems Worksheet to each student. Use Slides 2-5 of Lesson 4.1 Farm Ecosystem Presentation to talk about how farms are ecosystems too, and humans are part of those ecosystems.
Image Credit: Hannah Miller, Michigan State University

4. Farms are Ecosystems?
Yes! But they operate a bit differently than natural ecosystems.
How are farms and natural ecosystems alike?
How are farms and natural ecosystems different?
Use Slides 4-5 to collect student ideas about how farm ecosystems are different from natural ecosystems, and to compare the student ideas to some other ideas (in blue).
Image Credit: Hannah Miller, Michigan State University

5. Farms are Ecosystems?
Yes! But they operate a bit differently than natural ecosystems.
How are farms and natural ecosystems alike?
Have similar carbon pools (e.g., producers, herbivores)
Experience the same carbon-transforming processes (photosynthesis, cellular respiration)
How are farms and natural ecosystems different?
Humans help regulate carbon and energy movement through pools (e.g., planting crops, harvesting, animal slaughtering)
Use Slides 4-5 to collect student ideas about how farm ecosystems are different from natural ecosystems, and to compare the student ideas to some other ideas (in blue).
Image Credit: Hannah Miller, Michigan State University

6. Farms are Ecosystems?
We’ve seen this box and arrow diagram before when talking about carbon pools and movement in ecosystems.
Carnivores
Atmosphere
How do farm organisms fit in the boxes?
Where are humans located?
Herbivores
Use Slide 6 to point out the different pools of carbon: This ecosystem has carbon pools just like the others we have studied: atmosphere, producers, herbivores, and carnivores, and soil carbon.
Ask students to locate humans in the food chain.
Use Slides 6-9 to discuss where humans can be placed in the diagram. Ask: Are we herbivores or carnivores? In the ecosystem model in the presentation, humans can be placed either in the herbivore pool (if they eat a plant-based diet) or in the carnivore pool (if they eat a meat-based diet). Tell students that since humans eat both plants and animals, we can choose where we go on the food pyramid.
Use Slide 6 to ask students where humans belong in this ecosystem. IN which box do humans belong?
Image Credit: Craig Douglas, Michigan State University
Soil Carbon
Producers

7. Farms are Ecosystems?
In farm ecosystems, humans are the primary carnivores (we eat hamburgers, pork chops, fried chicken). But humans also eat a lot of plant products that are grown on farms (wheat, oats, corn, lettuce, other vegetables).
Therefore, humans are both carnivores and herbivores. They don’t fit neatly into just one box, but sometimes it’s simpler to think that way.
Herbivores
Soil Carbon
Atmosphere
Carnivores
Producers
Use Slide 7 to explain that humans do not neatly fit into one box, but that we will place them in one box for the purpose of this Activity.
Image Credit: Craig Douglas, Michigan State University

8. Does it matter if humans are primarily carnivores or herbivores?
There are 7 billion people on the earth. It takes A LOT of food to feed that many people, and food production takes a lot of resources.
Does it matter if humans are in the carnivore or the herbivore box when it comes to feeding all those people? Let’s find out…
Use Slide 8 to set up the question for this activity: which diet produces the greatest amount of food for people, a plant-based diet or a meat-based diet?
Image Credit: Hannah Miller, Michigan State University

9. Let’s compare: Which ecosystem below produces the most food for people?
Meat-based diet (humans are carnivores)
Plant-based diet (humans are herbivores)
Herbivores
Soil Carbon
Atmosphere
Carnivores
Producers
Herbivores
Soil Carbon
Atmosphere
Producers
Use Slide 9 to introduce the two model ecosystems for this Activity: in the ecosystem on the left, humans are herbivores (plant-based diet), and on the ecosystems on the right, humans are carnivores (meat-based diet).
Image Credit: Craig Douglas, Michigan State University

10. In this ecosystem, humans are the herbivores.
Round 1: Plant-based diet PREDICTION
Corn plant photosynthesis occurs, so let’s start with 500 carbon atom units in the producer pool.
Herbivores
Soil Carbon
Atmosphere
Producers
Make a prediction: if we start with 500 atoms in the producer pool, how many atoms are available for human growth?
Hint: use what you know about the organic matter pyramid to make your prediction.
Have students make a prediction about the plant-based ecosystem.
Tell students that in round 1, we will look at how carbon moves from pool to pool in an ecosystem where humans are herbivores. When we say “plant-based diet,” we mean a diet in which a person eats meat about 1-2 times a week.
Display Slide 10 of the presentation. 500 atom units will begin in the producer pool as a result of plant photosynthesis.
Have students make a prediction: if 500 atoms begin in the producer pool, how many carbon atoms will make it to the herbivore pool (thereby feeding the person)?
Encourage students to use what they know about the organic matter pyramid from previous Lessons to make their prediction. What causes atoms to move from the producer to the herbivore pool?
Image Credit: Craig Douglas, Michigan State University

11. Corn plant cellular respiration occurs.
In this ecosystem, humans are the herbivores.
Round 1: Plant-based diet
Corn does photosynthesis, so let’s start with 500 carbon atom units in the producer pool.
Corn plant cellular respiration occurs.
200 carbon atom units move from the producers to the atmosphere.
Corn ears are harvested while the rest of the corn plant dies.
100 carbon atom units move from the producers to the soil.
Corn ears are harvested.
100 carbon atom units move from the producers to the herbivore pool.
200 carbon atoms go back to the atmosphere when plants use the sugar for cellular respiration.
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500 carbon atoms become part of sugar molecules through photosynthesis.
Herbivores
100 carbon atoms go to herbivores when they eat plants.
300 carbon atoms become part of the plant through biosynthesis.
Have students record their prediction on their worksheet and continue with Slides to complete round 1.
100 carbon atoms go to the soil when plants or leaves die.
100 carbon atoms stay in the living plants.
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12. 3) People digest & biosynthesize 2) People digest food & respire.
In this ecosystem, humans are the herbivores.
In this ecosystem, humans are the herbivores.
One of three things can happen to food (corn) in a person’s stomach:
3) People digest & biosynthesize
Large molecules in corn are broken down into small molecules.
Small molecules are made into a person’s organic matter.
2) People digest food & respire.
50 carbon atom units move from the herbivores to the atmosphere.
1) People defecate indigestible food.
25 carbon atom units move from the herbivores to soil.
25 carbon atoms stay in the living people.
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Atmosphere
50 carbon atoms go back to the atmosphere when people use the food for cellular respiration.
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Herbivores
25 carbon atoms go to the soil when people defecate.
Have students record their prediction on their worksheet and continue with Slides to complete round 1.
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13. In this ecosystem, humans are the herbivores.
Add it up!
How much carbon is available to humans when they are herbivores?
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Atmosphere 25
Out of 500 carbon atoms that originally went through photosynthesis, 25 carbon atoms are used for human growth.
Herbivores
On Slide 13, have students compare their predictions with the results.
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14. If people eat a plant-based diet, where are they in the organic matter pyramid?
Plant-based diet (humans are herbivores)
Organic Matter Pyramid
Herbivores
Soil Carbon
Atmosphere
Producers ?
Use Slide 14 to have students compare the farm ecosystem they just observed and the organic matter pyramid. Where are humans located in the organic matter pyramid when humans are herbivores?
Image Credit: Craig Douglas, Michigan State University

15. Think Pair Share
Question 1: Answer the carbon pools question. How are carbon pools changing size?
Question 2: Answer the carbon fluxes question. How are carbon atoms moving among pools?
Question 3: Answer the energy question. How is energy moving through this farm ecosystem?
Use Slide 15 to have students practices answering the Three Questions about the farm ecosystem they just observed.

16. Let’s compare: In round 2, we will look at an ecosystem in which people are the carnivores.
Round 1: Plant-based diet (people are herbivores)
Round 2: Meat-based diet (people are carnivores)
Herbivores
Soil Carbon
Atmosphere
Carnivores
Producers
Herbivores
Soil Carbon
Atmosphere
Producers
Have students make a prediction about the meat-based diet ecosystem.
Tell students that in round 2, we will look at how carbon moves from pool to pool in an ecosystem where cows are herbivores and humans are carnivores. In this scenario, the cows eat the corn and the humans eat the cows. When we say “meat-based diet,” we mean a diet in which a person eats meat 5 or more times a week.
Use Slides to walk students through Round 2.
Have students predict: if 500 atoms begin in the producer pool, how many carbon atoms will make it to the carnivore pool (to feed the people)?
Encourage students to use what they know about the food pyramid from previous Lessons to make their prediction.
Have students record their prediction on their worksheet and continue with Slides to complete Round 2.

17. Round 2: Meat-based diet predictions
Corn plant photosynthesis occurs, so let’s start with 500 carbon atom units in the producer pool.
Carnivores
Carnivores
Atmosphere
Make a prediction: if we start with 500 atoms in the producer pool, how many atoms are available for human growth?
Hint: use what you know about the organic matter pyramid to make your prediction.
Herbivores
Have students make a prediction about the meat-based diet ecosystem.
Tell students that in round 2, we will look at how carbon moves from pool to pool in an ecosystem where cows are herbivores and humans are carnivores. In this scenario, the cows eat the corn and the humans eat the cows. When we say “meat-based diet,” we mean a diet in which a person eats meat 5 or more times a week.
Use Slides to walk students through Round 2.
Have students predict: if 500 atoms begin in the producer pool, how many carbon atoms will make it to the carnivore pool (to feed the people)?
Encourage students to use what they know about the food pyramid from previous Lessons to make their prediction.
Have students record their prediction on their worksheet and continue with Slides to complete Round 2.
Soil Carbon
Producers

18. Corn plant cellular respiration occurs.
Round 2: meat-based diet
In this ecosystem, humans are the carnivores.
Corn plant cellular respiration occurs.
200 carbon atom units move from the producers to the atmosphere.
Corn ears are harvested while the rest of the corn plant dies.
100 carbon atom units move from the producers to the soil.
Corn does photosynthesis, so let’s start with 500 carbon atom units in the producer pool.
Corn ears are harvested.
100 carbon atom units move from the producers to the herbivore pool.
Carnivores
200 carbon atoms go back to the atmosphere when plants use the sugar for cellular respiration.
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Atmosphere
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500 carbon atoms become part of sugar molecules through photosynthesis.
Herbivores
100 carbon atoms go to herbivores when they eat plants.
300 carbon atoms become part of the plant through biosynthesis.
Have students make a prediction about the meat-based diet ecosystem.
Tell students that in round 2, we will look at how carbon moves from pool to pool in an ecosystem where cows are herbivores and humans are carnivores. In this scenario, the cows eat the corn and the humans eat the cows. When we say “meat-based diet,” we mean a diet in which a person eats meat 5 or more times a week.
Use Slides to walk students through Round 2.
Have students predict: if 500 atoms begin in the producer pool, how many carbon atoms will make it to the carnivore pool (to feed the people)?
Encourage students to use what they know about the food pyramid from previous Lessons to make their prediction.
Have students record their prediction on their worksheet and continue with Slides to complete Round 2.
100 carbon atoms go to the soil when plants or leaves die.
100 carbon atoms stay in the living plants.
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19. 1) Cows defecate indigestible food. (ew!)
One of three things can happen to food (corn) in a cow’s stomach:
In this ecosystem, humans are the carnivores. 13 14 12 10 11 15 7 5 2 1 3 4 8 6 9
1) Cows defecate indigestible food. (ew!)
25 carbon atom units move from the herbivores to soil.
Cows got eaten by people! (Burgers anyone?)
15 carbon atom units move from the herbivores to carnivores.
2) Cows digest food & respire.
50 carbon atom units move from the herbivores to the atmosphere.
3) Cows digest & biosynthesize
Large molecules in corn are broken down into small molecules.
Small molecules are made into a cow’s organic matter.
Carnivores
15 carbon atoms go to carnivores when they eat herbivores.
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Atmosphere
50 carbon atoms go back to the atmosphere when herbivores use the food for cellular respiration.
10 carbon atoms stay in the living herbivores.
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Herbivores
25 carbon atoms go to the soil when herbivores defecate.
Have students make a prediction about the meat-based diet ecosystem.
Tell students that in round 2, we will look at how carbon moves from pool to pool in an ecosystem where cows are herbivores and humans are carnivores. In this scenario, the cows eat the corn and the humans eat the cows. When we say “meat-based diet,” we mean a diet in which a person eats meat 5 or more times a week.
Use Slides to walk students through Round 2.
Have students predict: if 500 atoms begin in the producer pool, how many carbon atoms will make it to the carnivore pool (to feed the people)?
Encourage students to use what they know about the food pyramid from previous Lessons to make their prediction.
Have students record their prediction on their worksheet and continue with Slides to complete Round 2.
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20. 3) People digest & biosynthesize 2) People digest food & respire.
One of three things can happen to food (cows) in a person’s stomach:
In this ecosystem, humans are the carnivores.
6 carbon atoms go back to the atmosphere when carnivores use the food for cellular respiration. 11 12 10 13 14 15 3 5 7 9 8 6 4
3 carbon atoms stay in the living carnivores.
3) People digest & biosynthesize
Large molecules in cows are broken down into small molecules.
Small molecules are made into a person’s organic matter.
2) People digest food & respire.
6 carbon atom units move from the carnivores to the atmosphere.
1) People defecate indigestible food. (ew!)
6 carbon atom units move from the carnivores to soil.
Carnivores
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6 carbon atoms go to the soil when carnivores defecate or die.
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Herbivores
Have students make a prediction about the meat-based diet ecosystem.
Tell students that in round 2, we will look at how carbon moves from pool to pool in an ecosystem where cows are herbivores and humans are carnivores. In this scenario, the cows eat the corn and the humans eat the cows. When we say “meat-based diet,” we mean a diet in which a person eats meat 5 or more times a week.
Use Slides to walk students through Round 2.
Have students predict: if 500 atoms begin in the producer pool, how many carbon atoms will make it to the carnivore pool (to feed the people)?
Encourage students to use what they know about the food pyramid from previous Lessons to make their prediction.
Have students record their prediction on their worksheet and continue with Slides to complete Round 2.
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21. In this ecosystem, humans are the carnivores.
Add it up!
In this ecosystem, humans are the carnivores. 3
How much carbon is available to humans when they are carnivores?
Carnivores
Carnivores
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Atmosphere 10
When we started with 500 atoms, 3 atoms were left for human growth with a meat-based diet.
Herbivores
On Slide 21, have students compare their predictions with the results.
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22. If people eat a meat-based diet, where are they in the organic matter pyramid?
Meat-based diet (humans are carnivores)
Herbivores
Soil Carbon
Atmosphere
Carnivores
Producers
Organic Matter Pyramid ?
Image Credit: Craig Douglas, Michigan State University
 Use Slide 22 to help students make connections to the farm ecosystem they just observed and the organic matter pyramid.
Have students complete the other questions for Round 2 on their worksheet. Have them share their answers about what is happening to carbon atoms and energy in this ecosystem with the class.

23. Compare the difference between ecosystems where humans eat a plant-based diet (left) and humans eat a meat-based diet (right).
Round 1:
Plant-based
diet
Round 2: Meat-
based
diet
Herbivores
Soil Carbon
Atmosphere
Carnivores
Producers
Herbivores
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Atmosphere
Producers 3 10
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Image Credit: Craig Douglas, Michigan State University
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24. Let’s think about the farm ecosystem in two new ways.
Help students think about carbon and energy in the farm ecosystem using a new tool.
Display Slide 24 of the presentation. Tell students they will use these posters (they discussed these briefly in Lesson 3) to discuss how matter and energy move through pools in farm ecosystems.

25. Matter and energy are being transformed differently in the two farm ecosystems.
Using this graph, describe how matter cycles and energy flows through a farm ecosystems where humans are herbivores.
Using this graph, describe how matter cycles and energy flows through a farm ecosystems where humans are carnivores.
What are the major differences?
Use the questions and graphic on Slide 25 to hear students’ ideas about how matter cycles and energy flows in the two different farm ecosystems.

26. Carbon pools and fluxes are different in the two farm ecosystems.
Using this graph as a tool, describe how carbon moves from the top grey box (CO2) to the bottom grey box (CO2) in farm ecosystems where humans are herbivores.
Using this graph as a tool, describe how carbon moves from the top grey box (CO2) to the bottom grey box (CO2) in farm ecosystems where humans are carnivores.
What are the major differences?
Use the questions and graphic on Slide 26 to hear students’ ideas about carbon pools and fluxes in the two different farm ecosystems.

27. Think Pair Share
Question 1: How many atoms are available for humans if humans eat a plant-based diet?
Question 2: How many atoms are available for humans if humans eat a meat-based diet?
Use the questions on Slides to hear students’ ideas about how their food choices impact carbon cycling and energy flow.
After they answer the questions, have students complete the final question on their worksheet.

28. How might these graphs affect our decisions about what food to eat?
Use the questions on Slides to hear students’ ideas about how their food choices impact carbon cycling and energy flow.
After they answer the questions, have students complete the final question on their worksheet.
Image Credit: Craig Douglas, Michigan State University