The following are abiotic components of an ecosystem except

Step 1: Analyze the question The question asks which item is NOT an abiotic component of an ecosystem. "Except" means we are looking for the odd one out, the one that is biotic.

Step 2: Explain the concept An ecosystem has two kinds of components:

• Abiotic components are the non-living physical and chemical factors, such as temperature, light, water, air and gases, soil, pH, and humidity.
• Biotic components are the living things: plants, animals, fungi, bacteria and other microorganisms.

Step 3: Go through the options

• A. Temperature: a physical, non-living factor, so it is abiotic.
• B. Oxygen: a gas in the air and water, non-living, so it is abiotic.
• C. Bacteria: living microorganisms that act as decomposers, so they are biotic.
• D. Soil: made of rock particles, minerals, air and water, a non-living part of the environment, so it is abiotic. (Soil contains living organisms, but the soil itself is classed as abiotic.)

Step 4: Answer Bacteria are the only living component in the list, so they are the exception.

Exam tip: For "abiotic vs biotic" questions, ask yourself, "Is it alive or was it ever a living organism?" If yes, it is biotic. Remember: a-biotic = no life (like the prefix in "amoral" or "atypical").