Exercises: The Carbon Cycle

Plants take carbon dioxide from the air and use it to make sugars. Name this process, and name the process that organisms use to release carbon dioxide back into the air when they break down sugars for energy.

Name two greenhouse gases that contain carbon or are involved in the carbon cycle. Then state one natural process and one human activity that release carbon dioxide into the atmosphere.

Coal, oil, and natural gas are called fossil fuels. Explain in one or two sentences what they are made from and what happens to the stored carbon when they are burned.

Aaliyah draws a diagram of the carbon cycle with these parts: atmosphere, ocean, forest, and fossil fuels. Describe the path of a carbon atom that starts as carbon dioxide in the air, is taken in by a tree, and later is released again. Name each process and each reservoir it passes through.

A table shows carbon moving each year between reservoirs, in billions of metric tons of carbon.

1. a) Find the total carbon added to the atmosphere and the total removed in one year, using only the rows in the table.
2. b) Does the atmosphere gain or lose carbon? By how much?
3. c) Explain how this result relates to the greenhouse effect.

A volcano erupts and releases carbon dioxide. At the same time, a large forest in the western United States is cut down and not replanted. Explain how each event affects the amount of carbon dioxide in the atmosphere, and classify each event as a natural or human-caused change in the carbon cycle.

Jayden measures the atmospheric carbon dioxide at a research station over one year. He finds that the concentration falls from April to September and rises from October to March.

1. a) Use the carbon cycle to explain this seasonal pattern in the Northern Hemisphere.
2. b) Over many years, the yearly peaks keep getting higher. Explain what this long-term trend suggests about the balance of carbon sources and sinks.
3. c) Name two actions that could slow the increase, and explain how each affects the carbon cycle.

Compare two scenarios for the same region. In Scenario 1, a wetland stores dead plant material under water for thousands of years. In Scenario 2, a power plant burns coal that formed from ancient plants.

1. a) Describe the carbon pathway in each scenario, including whether carbon is stored or released.
2. b) Compare how fast carbon moves in each case.
3. c) Explain why burning fossil fuels can increase the greenhouse effect even though the carbon came from natural sources.