These global cycles involve the circulation of elements and nutrients that sustain both the biological and physical aspects of the environment. For example, all known organisms on this planet depend on water to sustain them. They are constantly cycling water, consuming it on a regular basis either by itself or with nutrients, while expelling water (with waste products) at the same time. Besides being critical for the biosphere, water is also an extremely important part of the physical environment. When water vapor condenses to form clouds, more of the Suns rays are reflected back into the atmosphere, usually cooling the climate. Conversely, water vapor is also an important greenhouse gas in the atmosphere, trapping heat in the infrared part of the spectrum in the lower atmosphere. Water is also involved in other biogeochemical cycles. The hydrologic cycle intersects with almost every other element cycles, as well as some of the geological cycles such as the sedimentary cycle.
In this and other activities, we are going to study how carbon cycles through our ecosystem and how mankind affects this cycle. It is important that we understand how carbon cycles through the ecosystem for two reasons. The first of these reasons is that all organic material contains carbon. From the smallest vitamin molecule all the way up to the long polymer chains of proteins and DNA, carbon provides the basis of all organic compounds.
The second reason why we need to understand the carbon cycle is because of its effect on the physical environment. Carbon, in the form of carbon dioxide, is released as a waste product of oxidation. This means that it is released during the combustion of fossil fuels, as well as the respiration of organisms. As we will see later, this can have a tremendous effect on our climate, since carbon dioxide is a greenhouse gas.
Carbon has two phases in the carbon cycle: gaseous and solid. Its gaseous phase is mostly in the