Which sphere contains all life on Earth and interacts with all other spheres?

• A. Atmosphere
• B. Biosphere
• C. Geosphere
• D. Hydrosphere

Answer: (B)

Life exists in the biosphere, the part of Earth that contains all living organisms and their ecosystems. This sphere is where life interacts with every other sphere—air, water, and rocks—driving and responding to exchanges and cycles that connect the whole system. For instance, plants in the biosphere take carbon dioxide from the atmosphere to fuel photosynthesis and release oxygen, linking life to the air. Aquatic life connects with the hydrosphere through nutrient and energy transfer in oceans and rivers. Soil organisms and plant roots interact with the geosphere by weathering rocks and cycling minerals that support ecosystems. In short, the biosphere both houses life and continually exchanges matter and energy with the atmosphere, hydrosphere, and geosphere, making it the sphere that contains life and ties all the others together.