What is the primary excretory and osmoregulatory organelle found in freshwater unicellular protozoans like Amoeba proteus?
Answer and explanation
Correct answer: D. contractile vacuole
- Step 1: Amoeba lives in hypotonic freshwater, so water constantly enters its cytoplasm by endosmosis. Step 2. The contractile vacuole collects excess intracellular water, moves to the cell boundary, and contracts to expel water outward, preventing lysis. Answer: contractile vacuole. Why not the others: Food vacuoles digest ingested food; pseudopodia are for locomotion and engulfing; pellicle is a cell covering.
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