Here's why:
* Osmosis: The movement of water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.
* Protozoans: Single-celled organisms that live in aquatic environments.
* Contractile Vacuole: A specialized organelle found in many protozoans.
How it works:
1. Water uptake: Protozoans living in freshwater environments constantly take in water due to the osmotic gradient (higher water concentration outside the cell than inside).
2. Contractile vacuole fills: The contractile vacuole collects excess water from the cytoplasm.
3. Contraction: The vacuole contracts, expelling the water out of the cell, preventing the cell from bursting.
Essentially, the contractile vacuole acts like a pump, removing excess water and maintaining the cell's osmotic balance.
