Which Earth system subsystem is primarily associated with living organisms and nutrient cycling?

• A. Biosphere; The subsystem housing living organisms and nutrient cycling.
• B. Geosphere; The solid Earth including rocks and landforms.
• C. Hydrosphere; The water bodies and groundwater.
• D. Atmosphere; The gases surrounding the planet.

Answer: (A)

Living organisms and nutrient cycling are housed in the biosphere. The biosphere includes all life on Earth and the processes that move nutrients through ecosystems—plants taking up minerals, microbes decomposing matter, and animals transferring energy and matter as they feed and die. These biological activities drive the major nutrient cycles, like carbon and nitrogen, linking living systems with the surrounding environment. The geosphere (rocks and landforms), hydrosphere (water bodies), and atmosphere (air) interact with life and influence nutrient availability, but they are not defined by living systems and their nutrient cycling. So the biosphere best matches the idea of living organisms and nutrient cycling.