The Carbon Cycle

Carbon is a very important element for life. It is the base building block for many of the most important organic compounds such as carbohydrates, fats, and proteins, DNA, along with others. Carbon cycles through the earth and the biosphere like water and many other elements. The cycle of carbon is based on carbon dioxide (CO2) gas that composes on average .038% of the troposphere and can also be dissolved in water. There are many processes, both organic and inorganic, that add carbon dioxide to the atmosphere. Some of them include volcanic eruptions and cellular respiration of organisms.
Let's trace carbon around the biosphere. Starting in the atmosphere, carbon dioxide will diffuse between the atmosphere and the ocean (also other bodies of water). The carbon dioxide dissolved in ocean water will either be used up in photosynthesis of marine producers or be incorporated into sediments and form Marine sediments, along with fossil fuels. The carbon dioxide that goes into Marine producers becomes part of the food web and the organisms that live in the ocean which by respiration, return the carbon dioxide back to the ocean. By death and sedimentation, the organisms in the ocean will become fossil fuels over time. These marine sediments will be uplifted over geological time and become terrestrial rocks. By weathering, it will move into soil water in the form of dissolved carbon. When it rains, leaching and runoff will cause the carbon to go back into the ocean.
Let's look at the carbon cycle on land now. Starting with the atmosphere again, photosynthesis will move carbon dioxide into land food webs and through aerobic respiration will return the carbon back to the atmosphere. When wood is burned, the combustion will send carbon dioxide into the air. Also, when biotic matter dies it is compacted over geological time and becomes peat or fossil fuels. Finally, the combustion of fossil fuels will allow carbon to go back into the atmosphere.
As you can clearly see, carbon moves throughout the environment just like water and other matter. It is easier to visualize the cycles if you draw pictures and follow along with the descriptions. Carbon is important to every form of life on this planet for various purposes.