The Carbon Cycle: What Goes Around, Comes Around.

Introduction

Imagine that you live in a large, complex city like New York with lots of different neighborhoods and with people, cars, and trains moving at different speeds between those neighborhoods. Like New York city, carbon moves at different speeds into and out of the "neighborhoods" of the Earth System, changing as it moves.

In Lab 2, you will investigate how carbon moves (cycles) through the "neighborhoods" of the Earth System - the atmosphere, the hydrosphere (Earth's oceans), the geosphere (Earth's soils and rock layers) and the biosphere (all the living organisms that exist on Earth). As you can see in the carbon cycle diagram below, carbon moves around quite a bit - just like New York taxi cabs! As you investigate the carbon cycle, you will find answers to the following essential questions:

• How does carbon move from one Earth System sphere (neighborhood) to another
• How does carbon change as it moves from one part of the carbon cycle to another?
• Where is carbon stored? For how long?



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The Global Carbon Cycle. Source: University of Waikato, NZ

You already know a lot about how carbon can change from one carbon compound into another from your investigations of carbon in Lab 1. You determined that carbon can easily recombine with oxygen and hydrogen atoms to form an almost endless variety of carbon compounds. For example, you demonstrated that the atoms in glucose could be rearranged to form other molecules made by plants, such as chlorophyll and cellulose molecules. You also learned that hydrocarbons, such as oil and natural gas, are carbon-compounds originally formed from different carbon compounds in dead and decaying marine plankton. When hydrocarbons are burned, they release carbon dioxide into the atmosphere. Understanding that carbon behaves this way is critical to understanding the carbon cycle.

By the end of Lab 2, you will be able to:

• Describe how the the three primary biosphere processes of photosynthesis, cell respiration, and decomposition
  
• Identify the major carbon reservoirs and describe how carbon is stored in these reservoirs.
  
• Describe the effects of negative feedback or positive feedback on a complex system - the carbon cycle.
  
• Provide examples of the various time scales at which carbon moves through Earth's spheres.
  

In Part A, you will take a carbon journey through a forest carbon cycle. In this activity, you will expore the importance of biosphere processes in moving carbon through a forest ecosystem.

In Part B, you will use a carbon cycle interactive to determine how carbon moves through the global carbon cycle.

In Part C, you will use systems thinking strategies to identify causal connections and feedbacks in a complex system - the Carbon Cycle.

Keeping Track of What You Learn

Throughout these labs, you will find two kinds of questions.

• Checking In questions are intended to keep you engaged and focused on key concepts and to allow you to periodically check if the material is making sense. These questions are often accompanied by hints or answers to let you know if you are on the right track.
• Stop and Think questions are intended to help your teacher assess your understanding of the key concepts and skills you should be learning from the lab activities and readings.

Your teacher will let you know which answers you should record and turn in.