The scope of cell theory was extended by

Options

A. Schleiden & Schwann
B. R. Virchow
C. Robert Hooke
D. Corti

Answer

To answer the question, "The scope of cell theory was extended by," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Cell Theory**:
- The original cell theory was formulated in the 19th century and includes three main statements:
1. All living organisms are composed of one or more cells.
2. The cell is the basic unit of life.
3. All cells arise from pre-existing cells.

2. **Identifying Key Contributors**:
- The initial formulation of the cell theory was credited to scientists such as Schleiden and Schwann in 1839, who proposed that cells are the fundamental units of life.
- Robert Hooke is known for discovering cells in 1665, but he did not contribute to the extension of the cell theory.

3. **Recognizing the Extension of Cell Theory**:
- The extension of cell theory came from Robert Virchow in 1855. He introduced the idea that all cells arise from pre-existing cells, encapsulated in the phrase "Omnis cellula e cellula."

4. **Conclusion**:
- Therefore, the correct answer to the question is Robert Virchow, as he was the one who extended the scope of cell theory by stating that new cells come from existing cells.

### Final Answer:
The scope of cell theory was extended by Robert Virchow.

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