How is the growth of land plants proof that there is carbon in the atmosphere? how does carbon exist in the atmosphere biosphere and geosphere all at the same time?

The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. They are the four spheres of earth, and when (usually) more than one sphere interacts with another, an event will take place on earth. for example, volcanic eruptions, they are events in the geosphere. volcanoes also release lots of gas and particulate into the atmosphere, and lava flowing down the sides of the volcano, disrupting the biosphere. water will condense around the matter in the atmosphere, so hydrosphere is involved too. the spheres interact.