The Global Carbon Cycle

Duration: One class period.

Category:Inquiry

Materials, equipment and/or facilities:
butcher paper, colored markers, white 5 x 7 index cards (3 per group).

Background Information:
General, 'everyday' knowledge of carbon-based substances in the environment is assumed. Since students work in small groups, the collective, shared prior knowledge of group members is adequate to complete the activity.

This activity can be adjusted to meet the capabilities of students across a relatively wide range of abilities. To make the activity easier, you could print a copy of table 1 with the information deleted. This gives the students a starting point.

However, for all classes, it is encouraged that the student generate and develop their own unique carbon cycle, including major carbon reservoirs and fluxes.

Teaching and Learning Strategies:
Ensure inquiry: Students will develop independent group charts illustrating the global carbon cycle. Teachers should not feel the need to answer all their questions, let the students discover their own answers. When helping students, teachers can stimulate the thought process by answering student questions with questions.

Prerequisite Instruction:
Before this activity, introduce the concepts of flux and reservoir.
Reservoir- global location
Flux- a change

Invitation to Learn:
Problem: Speculate on the "fate" of carbon atoms contained in carbon dioxide molecules found in a breath of air. Trace possible pathways of the carbon atom over a short and long time and possible reservoirs of the carbon atom in the past.

• Divide students into groups of 3, and provide them with a set of the materials listed.
• After index cards are labeled and filled in, have students decide which of the reservoirs respresents the largest and smallest reservoir of carbon atoms on a global scale. Write the phrase 'most carbon', and 'least carbon' on that card.
• Attach your three cards to a large piece of butcher paper. Arrange the cards so they are roughly equally spaced from the sides of the paper. Students should realize that a carbon atom can move from one reservoir to another. A carbon flux can be indicated by drawing an arrow from one reservoir to another and writing down the process that moved the carbon atom.

Summary of Learning:
Assessment of Learning: Have students share their observations by taping their group chart on the board. Compare the different charts. Emphasize the similarities among the charts rather than just differences. Answers to include are as follows:

Table 1: Some carbon-containing substances and their global locations

Common carbon-containing substances	Major Global Locations
carbon dioxide	atmostphere
carbon dioxide (dissovled), hydrogencarbonate ions, carbonate ions, some biomolecules	ocean water
biomolecules	aquatic life
biomolecules, hydrogencarbonate ions, carbonate ions	land-based life
biomolecules, hydrogencarbonate ions	land (soil)
carbon, methane, other hydrocarbons	fossil fuels

a. If an oil spill occurs, hydrocarbons will also be present, particularly at the surface

b. 'Biomolecules' are any molecules of biological origin.

Next have the class identify different carbon fluxes and write those on them on the board. Some likely examples include:

fossil fuels- (burning)- atmosphere
atmosphere- (dissolving)- ocean
atmosphere - (photosynthesis)- land-based life
land-based life - (respiration)- atmosphere
aquatic life- (respiration)- atmosphere
land- (acid rain attack on carbonates)- atmosphere

Next have students identify the reservoir with the most and least amount of carbon. The actual ranking is:

1. oceans (including mid and deep waters)
2. land (soil)
3. atmosphere