Final answer:
The atmosphere and the biosphere interact when plants take carbon dioxide from the air during photosynthesis, highlighting their roles in the biological carbon cycle.
Step-by-step explanation:
When a plant takes carbon dioxide from the air, the two spheres that are interacting are the atmosphere and the biosphere. This process is a central part of the biological carbon cycle, where plants (autotrophs) use carbon dioxide to perform photosynthesis, creating oxygen and organic compounds like glucose.
Consequently, this interaction allows the exchange of carbon between different systems, impacting factors such as the oxygen content of the atmosphere and the carbon reservoir in oceans.