Which one of these is not a eukaryote ?

Options

A. Euglena
B. Anabena
C. Spirogyra
D. Agaricus

Answer

To determine which of the given options is not a eukaryote, we will analyze each option based on the definition of eukaryotes and prokaryotes.

### Step-by-Step Solution:

1. **Understanding Eukaryotes and Prokaryotes**:
- Eukaryotes are organisms whose cells have a well-defined nucleus enclosed by a nuclear membrane. They also possess membrane-bound organelles.
- Prokaryotes, on the other hand, lack a nuclear membrane and have an undeveloped nucleus. Their genetic material is not enclosed within a membrane.

2. **Analyzing the Options**:
- **Option 1: Euglena**:
- Euglena is a unicellular organism that has a well-defined nucleus and is classified as a eukaryote.
- **Option 2: Anabina**:
- Anabina (or Anabaena) is a genus of cyanobacteria, which are prokaryotic organisms. They do not have a nuclear membrane.
- **Option 3: Spirogyra**:
- Spirogyra is a type of green algae that has a well-defined nucleus and is classified as a eukaryote.
- **Option 4: Agaricus**:
- Agaricus is a genus of fungi, which are also eukaryotic organisms.

3. **Identifying the Non-Eukaryote**:
- From the analysis, we see that:
- Euglena, Spirogyra, and Agaricus are all eukaryotes.
- Anabina is the only organism that is not a eukaryote as it is a prokaryote.

4. **Conclusion**:
- Therefore, the answer to the question "Which one of these is not a eukaryote?" is **Anabina**.

### Final Answer:
**Anabina** is not a eukaryote.