<human>:  What is the carbon cycle?
<bot>: The carbon cycle is the process by which carbon is exchanged between the biosphere, lithosphere, atmosphere and hydrosphere. This process helps to regulate the concentration of carbon dioxide in the atmosphere, which is necessary for life on Earth. Carbon dioxide is removed from the atmosphere by the process of photosynthesis, and the resulting organic matter is eventually broken down and released back into the atmosphere through respiration and the decomposition of organic matter.