Which organism are the smallest living cells knonw and can survive without oxygen?

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the smallest living cells known that can survive without oxygen. We need to identify an organism that fits both criteria.

2. **Identifying Characteristics**: We need to look for an organism that is:
- The smallest living cell
- Capable of surviving in anaerobic (without oxygen) conditions

3. **Researching Organisms**: Among various microorganisms, we need to consider prokaryotes, particularly bacteria, as they are known for their small size.

4. **Finding the Right Organism**: Mycoplasma is a genus of bacteria that is known to be the smallest living cells. They are unique because they lack a cell wall, which is a characteristic feature of many other bacteria.

5. **Confirming Anaerobic Capability**: Mycoplasma can survive without oxygen, making them anaerobic organisms. This confirms that they meet the criteria of the question.

6. **Conclusion**: Based on the characteristics and capabilities, the answer to the question is **Mycoplasma**.

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