Which of the following animals is having longitudinal binary fission

Options

A. Euglena
B. Plasmodium
C. Planaria
D. Paramecium

Answer

### Step-by-Step Solution

1. **Understanding Binary Fission**: Binary fission is a type of asexual reproduction where an organism divides into two parts, each becoming a new organism. It can occur in different planes, namely longitudinal and transverse.

2. **Defining Longitudinal Binary Fission**: In longitudinal binary fission, the division occurs along the longitudinal axis of the organism. This means that the organism splits lengthwise, resulting in two new organisms that are similar in shape to the original.

3. **Analyzing the Options**: The question provides four options. We need to identify which of these organisms undergoes longitudinal binary fission:
- **Euglena**: A protist that can reproduce by longitudinal binary fission.
- **Plasmodium**: Undergoes multiple fission, not binary fission.
- **Planaria**: Reproduces by transverse fission.
- **Paramecium**: Also reproduces by transverse fission.

4. **Identifying the Correct Answer**: Among the options, Euglena is the only organism that undergoes longitudinal binary fission. The other organisms either undergo multiple fission or transverse fission.

5. **Conclusion**: Therefore, the correct answer to the question is **Euglena** (Option 1).