Exchange Cycles Image Map
Whether you are sleeping or running in a race, you constantly use energy stored in your body. You may already be aware that you get this energy by consuming foods like the nutritious banana you may have had at lunch time. Review our lesson on Cells Are Us that deals with energy transformations in the cell. In this lesson we are going to be concerned about the environmental cycles of energy and chemical elements.

  • Do you know where that banana got its energy? 

  • How is that banana’s energy used in your body? 

  • Where does the energy go once you use it up?

  • What happens to an animal when it dies? 

  • Do its contents just disappear? 

Well, forests aren’t full of dead animals lying around everywhere, so something has to happen to them when they die. 

  • What happens to the contents of a log when it is burned in a fireplace? 

  • Are the log’s ashes made up of the same stuff as the log?

All of these questions can be answered by knowing how materials are exchanged in cycles within the environment. Not even a magician can make matter disappear – it always has to go somewhere. Matter simply gets exchanged to allow reuse in many ways. The cyclical exchange of certain biological chemicals allow ecosystems to sustain life without the risk of running out of resources.

If matter were not recycled, where would it go once it was used? Think about carbon. All living matter is made with carbon. The amount of carbon present on earth right now is essentially the amount that was present a million years ago and it will be the amount present a million years from now. If organisms just disappeared when they died, they would take their carbon with them. Eventually, all the carbon they contained would be gone, and nothing would be able to grow or develop.

  • Are the exchange cycles perfect? 

  • Do all materials get perfectly passed around without being wasted or hurting the environment?

Unfortunately, certain human actions create environmental hazards that tend to disrupt different phases of the cycles and cause harmful effects to all parts of the ecosystem involved with the cycle. Explanations of these different types of hazards can be found in the Properties of Hazards module. 

  • What are the general effects of these common hazards? 

  • Are some cycles affected more than others? 

  • How can we limit the effects of these hazards?

Understanding the effects of disturbing the cycles will make it easier to understand the importance of the cycles. But even at this point, you must realize that the natural exchange cycles are necessary for sustaining ecosystems.




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