Consider the following statements regarding abiotic and biotic components of the environment:

Question

Consider the following statements regarding abiotic and biotic components of the environment:

I. Abiotic components are governed primarily by physical and chemical laws and do not reproduce.

II. Biotic components include only plants and animals, excluding microorganisms.

III. Interaction between abiotic and biotic components determines productivity and carrying capacity of an ecosystem.

Which of the statements given above is/are correct?

1. A. I and II only
2. B. I and III only (Correct answer)
3. C. II and III only
4. D. I, II and III

Correct Answer

Option B — I and III only

Detailed Solution & Explanation

The correct answer is I and III only.

Key Points

• Statement I is correct. Abiotic components — light, temperature, water, air, minerals — behave according to physical and chemical laws and have no capacity to reproduce or evolve.
• Statement II is incorrect, and this is what the question turns on. The biotic component includes microorganisms alongside plants and animals. Bacteria and fungi are the decomposers that return nutrients to the soil, so excluding them removes an entire functional group.
• Statement III is correct. It is the interaction between the two that fixes an ecosystem's primary productivity and its carrying capacity — sunlight, water and nutrients set the ceiling on how much biomass the producers can build, and that in turn limits every level above them.

Additional Information

• Carrying capacity (K) is the maximum population an environment can sustain indefinitely given its resources, and it is the parameter that turns exponential growth into the logistic (S-shaped) curve.
• Net Primary Productivity (NPP) is gross photosynthesis minus plant respiration and is the energy actually available to consumers. It peaks in tropical rainforests and coral reefs, and is lowest in deserts and open ocean.
• Only about 10% of energy passes from one trophic level to the next — Lindeman's ten per cent law — which is why food chains rarely exceed four or five links.
• A quick way to sit statement-based ecology questions is to distrust absolutes: words like only, never and all usually mark the false statement, as "only plants and animals" does here.