All the main molecules that make up our bodies (carbs, proteins, fats and DNA) are based on carbon atoms combined with toher elements.
The amount of carbon on the Earth is fixed. Some of the carbon is "locked up" in fossil fuels like coal, oil and gas. It is only released when we burn them.
Huge amounts of carbon are combined with other elements in carbonate rocks like limestone and chalk. There is a pool of carbon in the form of carbon dioxide in the air. it is also found dissolved in the water of rivers, lakes and oceans. All the time a relatively small amount of available carbon is cycled between living things and the environment. We call this the carbon cycle.
Green plants use carbon…