The biosphere is super important for the carbon cycle. It helps move carbon around between living things through things like photosynthesis and breathing. If we didn't have the biosphere, the carbon cycle would get really messed up. Carbon would just stay mostly in the air, oceans, and rocks, and it wouldn’t be available for plants and animals.
Even though the Earth would still have some carbon because of natural processes in the ground and oceans, we wouldn't have the important recycling that happens with living things. This would make everything slow down and hurt how ecosystems grow and stay healthy. So, the biosphere is really necessary for keeping the carbon cycle working well, showing how important living things are in making sure carbon moves around and is available in nature!