Coal deposits were made from plant remains that over millions of years changed, due to heat and pressure. However, when these plants were alive, they absorbed carbon dioxide to use in the process of photosynthesis. The carbon that was in these ancient plants eventually became part of the coal that is mined today. When it is burned in powerplants to obtain energy to produce electricity, it re-enters the atmosphere as carbon dioxide, due to oxidation. This carbon dioxide can then be utilized in photosynthesis by producers. Oil and gas are used to power vehicles, heat homes, cook, etc. These were formed under the sea from microscopic organisms that were buried under layers of sediment. Due to heat and pressure, oil and gas eventually formed. The carbon trapped in these organisms became hydrocarbon fossil fuels. When combustion of these fuels occurs in car engines, home heating systems, etc. carbon dioxide re-enters the atmosphere and the carbon cycle once again, when producers use the carbon dioxide to manufacture glucose during photosynthesis. When plant eaters consume these producers, the carbon(which is part of the glucose molecule) enters the body of the plant eater. As this organism is eaten by a secondary consumer, the carbon is incorporated into that organism's body. Finally, through the process of decomposition, carbon dioxide is released once again to the environment. Of course living things carry out respiration and one of the waste products that is released to the environment is carbon dioxide.Therefore, carbon can be found in our bodies, the food we eat, the fossil fuels we burn and is even incorporated into the shells of marine organisms. It is found in the atmosphere as carbon dioxide gas and is released by the process of respiration and decomposition.