Which of the following is not a producer?

Options

A. Spirogyra
B. Agaricus
C. Volvox
D. Nostoc

Answer

To solve the question "Which of the following is not a producer?", we need to understand the concept of producers in an ecosystem.

### Step-by-step Solution:

1. **Define Producers**: Producers are organisms that can convert light energy into chemical energy through the process of photosynthesis. They are also known as autotrophs because they can synthesize their own food.

2. **Identify Examples**:
- **Spirogyra**: This is a type of algae that belongs to the group Thallophyta. Algae are photosynthetic organisms and thus are considered producers.
- **Agaricus**: Commonly known as mushrooms, Agaricus belongs to the kingdom Fungi. Fungi are not capable of photosynthesis; they are saprophytic, meaning they obtain their nutrients from decaying organic matter.
- **Nostoc**: This is a cyanobacterium that is capable of photosynthesis and is also a nitrogen-fixing organism, making it a producer.
- **Other examples of producers**: Any green plants or algae that perform photosynthesis.

3. **Determine the Non-Producer**: From the examples given:
- Spirogyra and Nostoc are producers because they can perform photosynthesis.
- Agaricus (mushroom) is not a producer because it does not perform photosynthesis and instead derives its nutrients from dead organic matter.

4. **Conclusion**: The organism that is not a producer among the given options is **Agaricus**.

### Final Answer:
**Agaricus** is not a producer.