What is the primary function of contractile vacuoles in aquatic protists?

• A. To facilitate movement through the environment
• B. To store nutrients for cellular metabolism
• C. To expel excess water and maintain osmotic balance
• D. To digest food particles within the cell

Answer: (C)

Verified step by step guidance

1. Understand that contractile vacuoles are specialized organelles found in many aquatic protists, which live in hypotonic environments where water tends to enter the cell by osmosis.
2. Recognize that the primary challenge for these protists is to prevent the cell from swelling and bursting due to excess water intake.
3. Know that contractile vacuoles collect excess water that diffuses into the cell and periodically expel it out of the cell to maintain osmotic balance.
4. Eliminate other options by understanding their functions: movement is typically facilitated by cilia or flagella, nutrient storage is done by other organelles like food vacuoles or cytoplasm, and digestion occurs in lysosomes or food vacuoles.
5. Conclude that the primary function of contractile vacuoles is to expel excess water and maintain osmotic balance, ensuring the cell's survival in its aquatic environment.