Choose the odd one out with respect to the functional aspects of ecosystem.
(a) Energy flow
(b) Decomposition
(c) Species composition
(d) Nutrient cycling

Options

A. Energy flow
B. Decomposition
C. Species composition
D. Nutrient cycling

Answer

To solve the question of identifying the odd one out with respect to the functional aspects of an ecosystem, let's analyze each option step by step.

### Step 1: Understanding the Options
1. **Energy Flow**: This refers to the transfer of energy from one trophic level to another within an ecosystem. It is a crucial process that sustains life but does not constitute a functional unit on its own.

2. **Decomposition**: This is the process by which organic substances are broken down into simpler organic or inorganic matter. It involves various organisms and is vital for nutrient recycling in ecosystems, making it a functional aspect.

3. **Species Composition**: This refers to the variety and abundance of different species within an ecosystem. It plays a significant role in ecosystem stability and functioning, thus qualifying as a functional aspect.

4. **Nutrient Cycling**: This involves the movement and exchange of organic and inorganic matter back into the production of living matter. It is a crucial process that ensures the sustainability of ecosystems and is considered a functional aspect.

### Step 2: Identifying the Odd One Out
Now, we need to determine which of these options does not fit with the others in terms of being a functional aspect of an ecosystem.

- **Energy Flow** is primarily about the movement of energy and does not represent a functional unit or process that contributes to the ecosystem's stability or sustainability.
- **Decomposition**, **Species Composition**, and **Nutrient Cycling** all involve processes that are essential for the functioning and health of an ecosystem.

### Conclusion
The odd one out is **(a) Energy Flow**, as it does not represent a functional aspect of the ecosystem in the same way that the other options do.

### Final Answer
**(a) Energy Flow** is the odd one out.

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