To determine which option is not an abiotic factor, let’s first clarify what abiotic factors are. Abiotic factors are the non-living parts of an ecosystem that influence living organisms. These include elements like temperature, sunlight, water, and minerals.
Now let’s analyze each option provided:
- A: Proportion of oxygen in the atmosphere – This is an abiotic factor as it is a non-living chemical component of the environment that affects respiration in living organisms.
- B: Winter to summer temperature fluctuations – This is also an abiotic factor because it refers to the changes in temperature, which is a physical environmental condition.
- C: How many microbes are in the soil – This is not an abiotic factor. Instead, microbes are living organisms, and their abundance is a biotic factor that influences soil health and fertility.
- D: How many – This option appears incomplete and does not specify what it is referring to.
Considering the explanations above, the correct answer is C: How many microbes are in the soil, as it involves living organisms which categorize it as a biotic factor.