An exception to cell theory is

Options

A. Mycoplasma
B. Pneumococcus
C. Bacteriophage
D. Amoeba

Answer

**Step-by-Step Solution:**

1. **Understanding Cell Theory**: The cell theory states that all living organisms are made up of cells, and that new cells arise from pre-existing cells. This theory was proposed by scientists Schleiden and Schwann and later expanded by Virchow.

2. **Identifying Living Organisms**: Living organisms are classified into five kingdoms: Monera, Protista, Fungi, Plantae, and Animalia. All these organisms are composed of cells, which possess cell machinery and genetic material.

3. **Considering Exceptions**: While the cell theory applies to most living organisms, there are exceptions. One notable exception is viruses, which do not fit neatly into the definition of living organisms because they cannot replicate independently and are considered obligate parasites.

4. **Analyzing the Options**:
- **Mycoplasma**: This is a type of bacteria that lacks a defined cell wall and is part of the Monera kingdom. It follows the cell theory.
- **Pneumococcus**: Another type of bacteria found in the Monera kingdom, which also adheres to the cell theory.
- **Bacteriophage**: This is a virus that infects bacteria. Since viruses are considered non-living when not inside a host, they do not conform to the cell theory.
- **Amoeba**: A unicellular organism in the Protista kingdom that is eukaryotic and follows the cell theory.

5. **Conclusion**: The exception to the cell theory among the provided options is **Bacteriophage**, as it is a virus and does not conform to the characteristics of living cells when outside a host.

**Final Answer**: Bacteriophage

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