What is Carbon Cycle explain briefly?

Life on earth is mainly carbon-based. Most of the material substances that make up living organisms consist of organic compounds of carbon. In contrast, carbon is relatively scarce in substances that are non-living. Carbon exists in the non-living environment as carbon dioxide in the atmosphere, dissolved carbon dioxide in the ocean, and as carbonates in the Earth's crust.

Carbon is said to "cycle" between the biosphere (all of the living organisms on Earth) and the non-living forms of carbon in the environment. Carbon is "fixed," or converted from atmospheric carbon dioxide by photosynthetic plants into organic compounds. Plants and algae in the oceans also carry on photosynthesis that fixes carbon derived from dissolved carbon dioxide. Carbon in this way is converted into carbon compounds that form the cells and bodies of plants. When these plants die, they decompose, releasing carbon dioxide into the atmosphere.

Plant material containing the carbon compounds can also be eaten by other heterotrophic organisms, such as fungi, bacteria, or animals. In this way, the carbon that originally came from the atmosphere or oceans can be passed through the food web, and eventually back into the atmosphere or oceans through cellular respiration, or when they die and decompose.

Carbon that is "fixed" can also return to the atmosphere if the plant material is burned, either naturally, or through human activities. Even ancient plant and animal material that contains carbon that was fixed millions of years ago can be returned to the atmosphere by burning fossil fuels. Carbon can also be recycled back into the atmosphere through volcanic activity.