The diagram illustrates the carbon cycle, demonstrating how carbon dioxide circulates between plants, animals and atmosphere, as well as how human contributes to this process.
Overall, the natural process is continuous, and includes absorbtion of carbon dioxide through respiration, and then releasing it through photosynthesis. During this cycle, the carbon is absorbed from factory emissions, vehicle exhausts and animal wastes.
Initially, the carbon dioxide in the atmosphere absorbed by respiration by plants during photosynthesis, which requires sunlight. Thereafter, the plants release the carbon to atmosphere causing rain. Similarly, animals release the carbon dioxide through respiration, whereas humans contribute to it by vehicle exhausts and factory wastes.
During the cycle, the plants absorbs the carbon dioxide not only from atmosphere, but also from water and underground levels. As water absorbs the factory wastes, dead organisms and fossils and fossil fuels, it travels down to underground levels, allowing the respiration through roots.