What is the source of carbon in BGC cycle​

Plants absorb CO2 and water, and through the process of photosynthesis produce large carbon molecules (sugar, wood, plants). Animals, including humans, eat plants and use the stored solar energy releasing heat through the process of respiration.

Explanation:

Carbon (C) is the basis of life on Earth. Scientists consider 99.9% of all organisms on the planet to be carbon based life. Those organisms need carbon to survive. Whether the carbon is in the form of a sugar or carbon dioxide gas, we all need it. Unlike energy, carbon is continuously cycled and reused. The Earth only has a fixed amount of carbon. The carbon cycle is the ultimate form of recycling.