Which Earth sphere is not involved in biogeochemical cycling?

• A. Exosphere
• B. Atmosphere
• C. Lithosphere
• D. Hydrosphere

Answer: (A)

Verified step by step guidance

1. Understand the concept of biogeochemical cycles: These are pathways by which chemical elements and compounds move through Earth's spheres, including the atmosphere, lithosphere, hydrosphere, and biosphere.
2. Identify the Earth spheres involved in biogeochemical cycles: The atmosphere (air), lithosphere (land), hydrosphere (water), and biosphere (living organisms) are all involved in these cycles.
3. Recognize the role of each sphere: The atmosphere is involved in cycles like the carbon and nitrogen cycles. The lithosphere is involved in the phosphorus cycle. The hydrosphere is involved in the water cycle. The biosphere interacts with all these cycles.
4. Consider the exosphere: The exosphere is the outermost layer of Earth's atmosphere, where the atmosphere thins out into space. It is not directly involved in biogeochemical cycles because it is too far removed from Earth's surface processes.
5. Conclude which sphere is not involved: Based on the understanding of biogeochemical cycles and the roles of different spheres, the exosphere is not involved in biogeochemical cycling.