What is the role of contractile vacuole in protozoans ?

Explanation

### Step-by-Step Solution:

1. **Definition of Contractile Vacuole**:
- A contractile vacuole is a fluid-filled organelle found in protozoans. It plays a crucial role in maintaining the internal environment of the cell.

2. **Function of Osmoregulation**:
- One of the primary functions of the contractile vacuole is osmoregulation. This process involves regulating the concentration of solutes and water within the protozoan.
- The contractile vacuole helps to expel excess water that enters the cell due to osmotic pressure, thus maintaining the balance of water and solutes in the cell.
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