If there would be no biosphere on earth the atmosphere would be quite different. There would be no oxygen to support because oxygen is liberated by plants in photosynthesis so no plants means no oxygen. The earth would be a planet without life just like Venus and Mars. Therefore, no organism would be surviving in the world.
There would be no negligible green house effect and global warming since it is all created due to activities of men.The earth's atmosphere would be much cleaner and with lesser amount of CO2 and O2 but no organism would be there to use them.
Answer: The atmosphere would be impacted in the absence of the biosphere because without any living organism in the planet, there would be no oxygen. Also, there would be no need to have the atmosphere because there would be nothing to protect because there are no living organisms.
