Students will be able to:
- recognize that there is a finite amount of carbon on earth.
- model how carbon moves around in the environment, from one place to another.
- identify how humans influence the carbon cycle.
© Kaz Canning
How does the finite amount of carbon on this planet move around in the environment, from one place to another? How do the geosphere, biosphere, hydrosphere, and atmosphere interact? In this active demonstration, students will model the carbon cycle, and consider way in which human actions play a role.
Students will be able to:
Teacher Tip: If you think your students would do better with a lesson where they are able to move around the classroom, see the Extension section for an alternate version of this lesson.
We suggest using the What Contains Carbon? activity as an introduction to carbon and its different forms. If you do not have time for this activity, review with your students that carbon is a common element on earth. Have students recall some of the things in their daily lives that contain carbon. Make a list of these items on the board.
Explain to your students that the carbon contained in any one thing doesn’t stay there forever. The carbon atoms move from one thing to another in what is called the carbon cycle. Parts of the carbon cycle happen very quickly, like when plants take in carbon dioxide from the atmosphere for photosynthesis. But, other parts of the carbon cycle happen very slowly.
Tell students that in this activity, they will learn how carbon moves from one place to another, by performing a carbon cycle role-play.
Explain that they can give their carbon to only one other group, or if they have plenty, they can give the carbon to more than one group.
Explain that carbon exists in all of these things at the same time and only a portion of the carbon in each thing moves. Therefore, when each group moves their carbon, they can’t give away all their carbon: they must keep at least one carbon atom.
As they move their carbon, they must say their script lines to explain the carbon movement that they have chosen.
Humans extract and burn fossil fuels for energy (carbon moves from the sediments and rocks where fossil fuels are buried into the atmosphere).
Humans cut and burn trees to use land for farming, ranching, or building (carbon moves from the land plants into the atmosphere).
Burning fossil fuels takes carbon from sediments and rocks where fossil fuels are buried and puts it into the atmosphere because when fossil fuels are burned they release carbon-containing gases.
Cutting and burning trees takes carbon from the land plants and puts it into the atmosphere because when trees are burned, the carbon that was stored in their structures is released as carbon-containing gases.
Teacher Tip:For older students, you can introduce the specific terms for the earth’s four spheres.
Assessment Boundary: If you are working towards Performance Expectations 5-LS2-1 or MS-LS2-3 or HS-LS2-5 regarding developing a model to describe the movement of matter among living and non-living parts of an ecosystem, remember that students are not expected to demonstrate understanding of molecular movement or describe the process using chemical reactions.
Assessment Boundary: If you are working towards Performance Expectations 5-ESS2-1 or MS-ESS2-1 or HS-ESS2-6 regarding developing a model to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact, remember that 5th graders only need to explain the interactions of two systems at a time. The emphasis for middle school is on the geologic process of the rock cycle, and the emphasis in high school is on how biogeochemical cycles that include the cycling of carbon through the ocean, atmosphere, soil, and biosphere (including humans), provide the foundation for living organisms.
carbon: an element that can be found in all living things
carbon dioxide: a chemical compound composed of two oxygen atoms bonded on either side of a carbon atom (CO2); usually present as a gas
atmosphere: the gases surrounding the Earth
decompose: to be broken down physically and chemically by bacterial or fungal action; to rot
Plants and their processes
algae: plants that mostly grow in water and lacking true roots, stems and leaves.
photosynthesis: the process by which plants use carbon dioxide and energy from the sun to build sugar
respiration: the processes by which plant and animal cells break down sugar, which results in carbon dioxide
erosion: the process by which water, ice, wind, or gravity moves weathered rock or soil
sediment: material, such as stones or sand, deposited by water, wind, or glaciers
weathering: the processes by which rocks exposed to the weather change and break down
Carbon is an important element for life on earth and can be found in all four major spheres of the planet: biosphere, atmosphere, hydrosphere, and lithosphere (the rigid, rocky outer layer of the earth). Carbon is found in both the living and non-living parts of the planet, as a component in organisms, atmospheric gases, water, and rocks. The carbon moves from one sphere to another in an ongoing process known as the carbon cycle. The carbon cycle influences crucial life processes such as photosynthesis and respiration, contributes to fossil fuel formation, and impacts the earth’s climate.
Besides the relatively small additions of carbon from meteorites, the total carbon on Earth is stable. But, the amount of carbon in any given sphere of the planet can increase or decrease depending on the fluctuations of the carbon cycle. The cycle can be thought of in terms of reservoirs (places where carbon is stored) and flows (the movement between reservoirs). The atmosphere (the gases surrounding the Earth), the biosphere (the parts of the land, sea, and atmosphere in which life exists), the hydrosphere (all of Earth’s water), and the lithosphere (rocky outer layer of the Earth) are the reservoirs and the processes by which carbon moves from one reservoir to another are the flows. Although carbon is relatively common on earth, pure carbon is not. Carbon is usually bound to other elements in compounds. Thus, the carbon cycle, includes many carbon-containing compounds, such as carbon dioxide, sugars, and methane.
Carbon cycles both quickly and slowly
The many processes that move carbon from one place to another happen on different time scales. Some of them happen on short time scales, such as photosynthesis, which moves carbon from the atmosphere into the biosphere as plants extract carbon from the atmosphere. Some carbon cycle processes happen over much longer time scales. For example, when marine organisms with calcium carbonate skeletons and shells die, some of their remains sink towards the ocean floor. There, the carbon that was stored in their bodies becomes part of the carbon-rich sediment and is eventually carried along, via plate tectonic movement, to subduction zones where it is converted into metamorphic rock. These two examples show the extreme variety of processes that take place in the carbon cycle.
In general, the short-term carbon cycle encompasses photosynthesis, respiration, and predator-prey transfer of carbon. On land, there is a flow of carbon from the atmosphere to plants with photosynthesis and then a flow back to the atmosphere with plant and animal respiration and decomposition. For aquatic plants, photosynthesis involves taking carbon from carbon dioxide dissolved in the water around them. Carbon dioxide is also constantly moving between the atmosphere and water via diffusion. The long-term carbon cycle involves more of the lithospheric processes. It includes the weathering and erosion of carbon-containing rocks, the accumulation of carbon-rich plant and animal material in sediments, and the slow movement of those sediments through the rock cycle.
Humans affect the carbon cycle
There are natural fluctuations in the carbon cycle, but humans have been changing the carbon flows on earth at an unnatural rate. The major human-induced changes result in increased carbon dioxide in the atmosphere. The largest source of this change is burning fossil fuels, but other actions such as deforestation and cement manufacturing also contribute to this change in the carbon cycle. Because carbon dioxide and methane are greenhouse gases that help to control the temperature of the planet, the human-induced increase in atmospheric carbon levels is resulting in a host of climatic changes on our planet. As discussed above, the natural carbon cycle is important to learn because it is crucial to many of earth’s processes, but an understanding of the carbon cycle is especially important at this time in human history because of the dramatic and consequential alterations we are making to the cycle.
Grades Nine Through Twelve
The items listed below indicate how the Carbon Cycle Unit—composed of the lessons What Contains Carbon?, Carbon Cycle Role-play, and Carbon Cycle Poster—supports the three dimensions of the Next Generation Science Standards.
Developing and using models
3-5: Develop a model using an example to describe a scientific principle.
6-8: Develop and use a model to describe phenomena.
9-12: Develop a model based on evidence to illustrate the relationships between systems or between components of a system.
5-ESS2-A: Earth Materials and Systems Earth’s major systems are the geosphere (solid and molten rock, soil, and sediments), the hydrosphere (water and ice), the atmosphere (air), and the biosphere (living things, including humans). These systems interact in multiple ways to affect Earth’s surface materials and processes.
5-LS2-B: Cycles of Matter and Energy Transfer in Ecosystems Matter cycles between the air and soil and among plants, animals, and microbes as these organisms live and die. Organisms obtain gases, and water, from the environment, and release waste matter (gas, liquid, or solid) back into the environment.
MS-ESS-A: Earth’s Materials and Systems All Earth processes are the result of energy flowing and matter cycling within and among the planet’s systems. The energy that flows and matter that cycles produce chemical and physical changes in Earth’s materials and living organisms.
MS-LS2-B: Cycle of Matter and Energy Transfer in Ecosystems Transfers of matter into and out of the physical environment occur at every level. Decomposers recycle nutrients from dead plant or animal matter back to the soil in terrestrial environments or to the water in aquatic environments. The atoms that make up the organisms in an ecosystem are cycled repeatedly between the living and nonliving parts of the ecosystem.
HS-ESS2-D: Weather and Climate Changes in the atmosphere due to human activity have increased carbon dioxide concentrations and thus affect climate.
HS-LS2.B: Cycles of Matter and Energy Transfer in Ecosystems Photosynthesis and cellular respiration are important components of the carbon cycle, in which carbon is exchanged among the biosphere, atmosphere, oceans, and geosphere through chemical, physical, geological, and biological processes.
Systems and system models
5: A system can be described in terms of its components and their interactions.
6-8: Models can be used to represent systems and their interactions—such as inputs, processes and outputs—and energy, matter, and information flows within systems.
9-12: Models (e.g., physical, mathematical, computer models) can be used to simulate systems and interactions—including energy, matter, and information flows—within and between systems at different scales.
Remember, performance expectations are not a set of instructional or assessment tasks. They are statements of what students should be able to do after instruction. This activity or unit is just one of many that could help prepare your students to perform the following hypothetical tasks that demonstrate their understanding:
5-ESS2-1. Develop a model using an example to describe ways the geosphere, biosphere, hydrosphere, and/or atmosphere interact.
5-LS2-1. Develop a model to describe the movement of matter among plants, animals, decomposers, and the environment.
MS-ESS2-1. Develop a model to describe the cycling of Earth's materials and the flow of energy that drives this process.
MS-LS2-3. Develop a model to describe the cycling of matter and flow of energy among living and nonliving parts of an ecosystem.
HS-ESS2-6. Develop a quantitative model to describe the cycling of carbon among the hydrosphere, atmosphere, geosphere, and biosphere.
HS-LS2-5. Develop a model to illustrate the role of photosynthesis and cellular respiration in the cycling of carbon among the biosphere, atmosphere, hydrosphere, and geosphere.
Mackenzie, F.T. (2003). Our Changing Planet: An Introduction to Earth Science and Global Environmental Change. Upper Saddle River, NJ: Prentice Hall.
Tarbuck, E.J., & Lutgens, F.K. (2002). Earth: An Introduction to Physical Geology. Upper Saddle River, NJ: Prentice Hall.