Playing this game should help you to

• trace the transfer of energy and carbon through living organisms and non-living systems (like power plants)
• identify energy conversions in the carbon cycle; and
• describe how energy is used and "lost" during transfers in the carbon cycle.

Background
Look at your arm; what do you see? Would you believe that you see sunlight? Yes! Millions of molecules make up your muscles, skin, and bones, and the energy holding these molecules together can be traced back through the food chain to the sun.

One of the key elements in the molecules in your arm, as well as all organic material, is carbon. Carbon and other elements of matter cycle within ecosystems, being used again and again as they travel through food chains, the atmosphere, soil, and water. What enables carbon to move through these different components of an ecosystem is energy. However, while carbon cycles within a system, energy flows through an ecosystem.

The diagram illustrates the primary places carbon visits as it cycles within an ecosystem, and indicates where energy enters and leaves the carbon cycle. Carbon and energy enter living organisms through the process of photosynthesis. In photosynthesis, plants and other producers use solar energy to combine carbon dioxide and water molecules into a new molecule-glucose. The energy used in photosynthesis is converted to the energy stored in the chemical bonds of the glucose molecule. When an animal or other consumer eats the producer, the carbon and stored energy become a part of the consumer. The result is a food chain with carbon and stored energy traveling from one organism to the next.

Carbon and energy leave living organisms through processes such as combustion, respiration, excretion, and death. Combustion of organic matter, such as burning wood, breaks chemical bonds converting chemical energy to heat energy. Carbon dioxide is a by-product of combustion. Respiration (which takes place in living cells and is a process similar to combustion but is more controlled) converts the energy stored in chemical bonds to a form the organism can use. The converted energy is used by organisms to move, grow, and function. Food materials that cannot be digested are excreted. Decomposers, such as certain bacteria and insects, are an important part of the carbon cycle. They consume waste materials and dead organic matter.

Since no energy conversion is 100 percent efficient, some energy is lost as heat during respiration. Carbon dioxide produced during respiration is eventually released into the atmosphere. While carbon from carbon dioxide can be reintroduced into the food chain, heat energy cannot. Because organisms convert stored energy to kinetic and heat energy, only about ten percent of the energy received by one organism is available to the next organism in the food chain.

In some cases, organisms die in locations where decomposition occurs very slowly or not at all. These locations include swamps, marshes, and shallow coastal basins where, buried deep in the mud, the environmental conditions needed for decomposers to survive (such as oxygen) may not exist. Partially or undecomposed organisms that are buried in these locations for millions of years can be subjected to heat and pressure from geologic processes (for example, plate tectonics). As a result, the carbon and stored energy that originally made up these prehistoric organisms can be converted to coal, oil, and natural gas-the fossil fuels.

The energy that was stored long ago in the chemical bonds of these fossil fuels can be converted to heat energy through combustion. Modern societies have learned to harness the energy released from fossil fuel combustion to do work. For example, heat released from burning coal is used to turn water into steam that spins a turbine connected to an electric generator. The turbine�s kinetic energy is then used by the generator to produce electrical energy. This electrical energy can be converted into kinetic energy, then used to operate an appliance. Eventually, all these forms of energy are unintentionally converted to heat that is dissipated into the environment.

Therefore, there is evidence of the sun�s energy all around you. Consider the microwave you use to heat a piece of pizza. The energy stored in the molecules that make up dough and cheese can be traced back to the sun. If the power plant that fuels your home uses coal, then the electricity you use can be traced back to the sun. And finally, the molecules in your arm that you use to operate the oven contains stored solar energy as well.

Vocabulary: Biosphere, Carbonate, Carbon cycle, Carbon dioxide, Carnivore, Combustion, Decomposer, Excretion, Glucose, Herbivore, Inorganic, Kinetic energy, Omnivore, Organic, Photosynthesis, Plate tectonics, Primary consumer, Producer, Respiration, Secondary consumer.