Ans:Carbon cycle is a perfect cycle in the sense that carbon is returned to atmosphere as soon as it is removed.
Carbon atom is the principal building block of many kinds of bimolecular. Source of Carbon: Carbon is found as graphite and diamond in nature. It also occurs as carbon dioxide in atmosphere.
Major source of carbon for the living world is carbon dioxide present in atmosphere and water. Fossil fuels like peat, coal, natural gas and petroleum also contain carbon. Carbonates of Earth's crust also give rise to carbon dioxide
Figure 16.7 Carbon cycle
Cycle of Carbon: The major process that brings carbon from atmosphere or water into living world is photosynthesis. Producers take in carbon dioxide from atmosphere and convert it into organic compounds. In this way, carbon becomes a part of the body of producers. This carbon enters food chains and to herbivores, carnivores and decomposers.
Carbon dioxide is released back to environment by respiration of producers and consumers. It is also released by the decomposers. Burning of wood and fossil fuels also adds large amount of carbon dioxide atmosphere. Figure 16.7
Impact of human activities on carbon cycle: The balance of carbon cycle has been upset by human activities such as deforestation and excessive burning of fossil fuels. As a result, the amount of carbon dioxide in atmosphere is increasing, causing the green house effect and global warming.