Which of the following is not an abiotic component of biosphere?

Concept: An ecosystem/biosphere has two component types — abiotic (non-living physical and chemical factors: soil, water, air, temperature, and mineral/organic nutrients such as phosphorus and proteins present in dead organic matter) and biotic (all living organisms: producers, consumers, and decomposers such as bacteria and fungi).

Application: Checking each option against this definition — soil is the physical substrate, phosphorus is a mineral nutrient, and protein is an organic chemical compound present in the ecosystem's dead organic matter, so all three sit in the abiotic (non-living) category. Fungi, however, are living heterotrophic organisms that actively decompose organic matter, which places them in the biotic category, not the abiotic one.

• Protein: an organic compound present in the ecosystem's dead organic matter — a chemical/abiotic constituent, not a living organism.

• Soil: the non-living mineral and organic substrate of the ecosystem — an abiotic (edaphic) factor.

• Phosphorus: an inorganic mineral nutrient cycled via the phosphorus cycle — an abiotic (chemical) factor.

• Fungi: living, heterotrophic decomposer organisms — a biotic component.

Cross-check: Standard ecology classification groups all living organisms — producers, consumers, and decomposers (bacteria, fungi) — as biotic, while every non-living physical/chemical factor (soil, water, minerals, and organic compounds like proteins) is abiotic. Since fungi alone are living organisms among the four options, Fungi is the component that is not abiotic.