The theory given by Schleiden and Schwann and modified by Virchow is not applicable to :

Options

A. Bacteria
B. Fungus
C. Algae
D. Viruses

Answer

To solve the question regarding the applicability of the theory given by Schleiden and Schwann, modified by Virchow, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Cell Theory**:
- The cell theory proposed by Schleiden and Schwann states that all living organisms are composed of cells, and Virchow later added that all cells arise from pre-existing cells.

2. **Identifying the Organisms in Question**:
- The question lists four types of organisms: bacteria, fungi, algae, and viruses.

3. **Analyzing Each Organism**:
- **Bacteria**: These are prokaryotic cells and do follow the cell theory as they are made up of cells and can reproduce by cell division.
- **Fungi**: These are eukaryotic organisms that are also composed of cells and reproduce through cell division.
- **Algae**: Similar to fungi, algae are also eukaryotic and consist of cells, adhering to the cell theory.
- **Viruses**: Viruses are unique in that they are acellular and do not possess a cellular structure. They cannot reproduce independently and require a host cell to replicate.

4. **Conclusion**:
- Since the cell theory states that all living organisms are made of cells and that new cells arise from pre-existing cells, it is not applicable to viruses because they are not made of cells and do not divide independently.

5. **Final Answer**:
- The theory given by Schleiden and Schwann and modified by Virchow is not applicable to **viruses**.