Question

Assertion (A): Ecosystems require a constant supply of energy to synthesize the molecules they require.
Reason (R): This is to counteract the universal tendency towards increasing disorderliness as per Second Law of Thermodynamics.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

To test if a Reason correctly explains an Assertion, read them together using the word "because": "Ecosystems require a constant supply of energy... because this counteracts the universal tendency towards increasing disorderliness." Since this combined statement makes complete physical and ecological sense, option (A) is the correct choice.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The problem presents an assertion regarding the metabolic energy requirements of an ecosystem and a reason rooted in thermodynamic laws. We must assess their individual accuracy and determine if the physical law provides the correct underlying mechanism.

Step 2: Key Formula or Approach:
* The Second Law of Thermodynamics: States that any isolated physical system naturally progresses toward maximum thermodynamic entropy (disorder) unless work or energy is actively put into the system.
* Living organisms and ecological trophic networks are open systems that maintain internal molecular structural order by capturing, processing, and dissipating dynamic energy currents.

Step 3: Detailed Explanation:
Evaluating Assertion (A): An ecosystem is a complex network of living components that constantly carry out endergonic biochemical processes, such as biosynthesis, cellular active transport, growth, and cellular repair. These processes require a steady, continuous input of energy (mostly starting as solar radiation captured via photosynthesis) because energy cannot be recycled within an ecosystem. Therefore, Assertion (A) is true.
Evaluating Reason (R): According to the Second Law of Thermodynamics, all closed or undriven systems naturally drift toward a state of maximum entropy or global disorderliness. To maintain highly organized, complex macromolecular structures (like proteins, nucleic acids, and cellular membranes) and prevent metabolic decay, organisms must continuously perform thermodynamic work. This metabolic work requires a continuous flow of energy to push back against this spontaneous tendency toward increasing disorder. Thus, Reason (R) is true.
Evaluating the Link: Why do ecosystems require this constant stream of incoming energy? They require it specifically because it is the only physical mechanism that counteracts the natural increase in entropy dictated by the Second Law of Thermodynamics. Thus, the reason provides the direct physical explanation for the assertion.

Step 4: Final Answer:
Both Assertion (A) and Reason (R) are true, and Reason (R) is the correct explanation of Assertion (A), matching option (A).