Final answer:
The biosphere is the interface between the lithosphere, hydrosphere, and atmosphere, encompassing all areas where life exists and interacts with these physical spheres.
Step-by-step explanation:
The system that serves as the interface between the other spheres is the biosphere. The biosphere is the highest level of ecological organization, encompassing areas from the deep sea to high in the atmosphere, where life is found. It includes parts of the lithosphere (land), the hydrosphere (water), and the atmosphere (air). The biosphere is where life, in all its forms, exists and interacts with the physical environments of the other spheres. This interaction is vital, as the hydrosphere plays a key role within the biosphere by participating in the water cycle, hosting aquatic life, and interacting with the atmosphere and lithosphere. Similarly, the biosphere can significantly alter the composition of the atmosphere and the reflection spectrum of Earth. A disturbance in the balance of these interactions can have profound consequences for life on our planet.