Find the incorrect statement .

Options

A. In a terrestrial ecosystem , a larger fraction of energy flow occurs through detritus food chain.
B. In the aquatic ecosystem , a major conduit for energy flow is grazing food chain.
C. Detritus food chain is not at all connected with grazing food chain at any level.
D. Natural interconnection of food chain makes it a food web.

Answer

To solve the question of identifying the incorrect statement from the given options, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Analyze Statement 1**:
- Statement: "In a terrestrial ecosystem, a larger fraction of energy flows occurs through the detritus food chain."
- Evaluation: This statement is **correct**. In terrestrial ecosystems, a significant amount of energy is indeed transferred through the detritus food chain, which involves decomposers breaking down organic matter.

**Hint**: Remember that in terrestrial ecosystems, decomposers play a crucial role in recycling nutrients.

2. **Analyze Statement 2**:
- Statement: "In the aquatic ecosystem, a major conduit for energy flow is the grazing food chain."
- Evaluation: This statement is also **correct**. In aquatic ecosystems, the grazing food chain, which starts with phytoplankton and moves up to herbivores and then carnivores, is a primary pathway for energy flow.

**Hint**: Consider how energy moves from producers (like phytoplankton) to consumers in aquatic environments.

3. **Analyze Statement 3**:
- Statement: "The detritus food chain is not all connected with the grazing food chain at any level."
- Evaluation: This statement is **incorrect**. The detritus food chain and the grazing food chain are interconnected. Decomposed organic matter from the detritus food chain can provide nutrients for primary producers, which are part of the grazing food chain.

**Hint**: Think about how nutrients cycle through ecosystems and how different food chains interact.

4. **Analyze Statement 4**:
- Statement: "The natural interconnection of the food chain makes it a food web."
- Evaluation: This statement is **correct**. A food web is indeed formed by the interconnections of various food chains within an ecosystem.

**Hint**: Recall that a food web represents the complex feeding relationships in an ecosystem.

### Conclusion:
Based on the evaluations, the incorrect statement is **Option 3**: "The detritus food chain is not all connected with the grazing food chain at any level."

### Final Answer:
**Option 3** is the incorrect statement.