Which of the following points were not explained by Schleiden and Schwann when they formulated their original cell theory ?

Options

A. All plants are composed of different kinds of cells which form the tissues of the plant
B. Animal cells had a thin outer layer which is today known as the ‘plasma membrane’
C. Cells divide and new cells are formed from pre-existing cells
D. The presence of cell wall is a unique character of the plant cells

Answer

To determine which points were not explained by Schleiden and Schwann in their original cell theory, we need to analyze the statements provided in the question:

1. **Statement 1**: All plants are composed of different types of cells from the tissue of the plant.
2. **Statement 2**: Animal cells have a thin layer which is called a plasma membrane.
3. **Statement 3**: Cells divide into new cells that are formed from pre-existing cells.
4. **Statement 4**: The presence of a cell wall is a unique character of the plant cell.

Now, let's evaluate each statement in relation to Schleiden and Schwann's original cell theory:

### Step 1: Evaluate Statement 1
- **Analysis**: Schleiden stated that all plants are made up of cells, and these cells can be of different types forming various tissues.
- **Conclusion**: This statement is consistent with their theory.

### Step 2: Evaluate Statement 2
- **Analysis**: Schwann proposed that animal cells have a plasma membrane, which is indeed a thin outer layer.
- **Conclusion**: This statement is also consistent with their theory.

### Step 3: Evaluate Statement 3
- **Analysis**: The idea that cells divide and new cells arise from pre-existing cells is a fundamental concept in cell theory, but it was more explicitly articulated in later developments of cell theory (not originally by Schleiden and Schwann).
- **Conclusion**: This statement is not part of the original cell theory by Schleiden and Schwann.

### Step 4: Evaluate Statement 4
- **Analysis**: The presence of a cell wall as a unique characteristic of plant cells is acknowledged in their theory.
- **Conclusion**: This statement is consistent with their theory.

### Final Conclusion
The statement that was not explained by Schleiden and Schwann when they formulated their original cell theory is **Statement 3**: "Cells divide into new cells that are formed from pre-existing cells."

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