A contractile mid body forms during cytokinesis in :-

Options

A. Animals
B. Higher plants
C. Fungi
D. Algae

Answer

### Step-by-Step Solution:

1. **Understanding Cytokinesis**:
- Cytokinesis is the process where the cytoplasm of a parental cell divides into two daughter cells after mitosis or meiosis.
- It is crucial for the final separation of the two new cells.

2. **Formation of the Contractile Midbody**:
- During cytokinesis, a structure known as the contractile midbody forms.
- This structure is primarily involved in the physical separation of the two daughter cells.

3. **Components of the Contractile Midbody**:
- The contractile midbody is composed of non-muscle myosin II and actin filaments.
- These proteins play a significant role in the contraction mechanism that leads to cell division.

4. **Assembly at the Cell Cortex**:
- The actin filaments and non-muscle myosin II assemble at the equatorial region of the cell cortex.
- This assembly is crucial for the formation of the cleavage furrow.

5. **Mechanism of Contraction**:
- The myosin II uses energy derived from ATP hydrolysis to move along the actin filaments.
- This movement pulls the plasma membrane inward, forming the cleavage furrow.

6. **Ingression of the Cleavage Furrow**:
- Continued hydrolysis of ATP causes the cleavage furrow to deepen, leading to the eventual separation of the two daughter cells.
- This process is vital for successful cytokinesis in animal cells.

7. **Conclusion**:
- Therefore, the contractile midbody forms during cytokinesis specifically in animal cells.

### Final Answer:
A contractile midbody forms during cytokinesis in **animal cells**.

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