Assertion: The loss of biologically useful energy as heat with every energy transfer in a food chain is a consequence of the second law of thermodynamics.
Reason: Energy does not remain trapped permanetly in any organism. It is either passed on to higher trophic level or becomes available to detritivores and decomposers after the organism dies.

Explanation

To solve the assertion-reason question, we need to analyze both statements and determine their validity and relationship.

### Step 1: Analyze the Assertion
The assertion states that "The loss of biologically useful energy as heat with every energy transfer in a food chain is a consequence of the second law of thermodynamics."

- According to the second law of thermodynamics, energy transformations are not 100% efficient. When energy is transferred from one trophic level to another in a food chain, some energy is lost as heat. This aligns with the principle that energy tends to disperse and increase in entropy. Therefore, the assertion is **true**.

### Step 2: Analyze the Reason
The reason states that "Energy does not remain trapped permanently in any organism. It is either passed on to a higher trophic level or becomes available to detritivores and decomposers after the organism dies."

- This statement is also accurate. Energy is transferred through various trophic levels in an ecosystem. When an organism dies, its energy becomes available to decomposers and detritivores, contributing to nutrient cycling. Thus, the reason is also **true**.

### Step 3: Determine the Relationship
Now, we need to assess whether the reason correctly explains the assertion.

- While both statements are true, the reason does not directly explain why energy loss occurs as heat during energy transfer. The assertion focuses on the thermodynamic principle, while the reason discusses energy transfer and decomposition processes. Therefore, they are not causally related.

### Conclusion
Both the assertion and reason are true, but the reason is not the correct explanation for the assertion.

Thus, the correct answer is: **Both assertion and reason are true, but reason is not the correct explanation of assertion.**

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