In an ecosystem, there is a flow of energy at different trophic levels. This is as follows

Options

A. Primary consumers — Tertiary consumers — Secondary consumers — Decomposers — Producers
B. Producers — Primary consumers — Secondary consumers — Tertiary consumers — Decomposers
C. Producers — Decomposers — Primary consumers — Tertiary consumers — Secondary consumers
D. Producers — Primary consumers — Tertiary consumers — Secondary consumers — Decomposers

Explanation

### Step-by-Step Solution:

1. **Understanding Trophic Levels**:
- In an ecosystem, organisms are arranged in a hierarchy known as trophic levels. The primary levels are:
- Producers (autotrophs)
- Primary consumers (herbivores)
- Secondary consumers (carnivores that eat herbivores)
- Tertiary consumers (carnivores that eat other carnivores)
- Decomposers (organisms that break down dead organic matter)

2. **Flow of Energy**:
- Energy flow in an ecosystem begins with producers, which convert solar energy into chemical energy through photosynthesis.
- Primary consumers eat the producers, transferring energy from plants to herbivores.
- Secondary consumers consume primary consumers, transferring energy from herbivores to carnivores.
- Tertiary consumers eat secondary consumers, continuing the energy transfer up the food chain.
- Decomposers break down dead organisms and organic waste, returning nutrients to the soil and allowing producers to utilize them again.

3. **Chart of Energy Flow**:
- The flow of energy can be represented as follows:
- **Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers → Decomposers**

4. **Unidirectional Flow**:
- It is important to note that the flow of energy in an ecosystem is unidirectional. Energy moves from one trophic level to the next in a one-way direction and is not recycled back to the previous levels.

5. **Identifying the Correct Option**:
- Based on the flow of energy described, the correct order of trophic levels is:
- Producers → Primary Consumers → Secondary Consumers → Tertiary Consumers → Decomposers
- Therefore, the correct option is the one that reflects this order.