Question 31
ExcretionA marine protozoan is likely to have no contractile vacuole mainly because the cytoplasm is
- A.isotonic to sea water
- B.hypotonic to sea water
- C.hypertonic to sea water
- D.impervious to sea water
Show the answer and explanation
Answer: A (isotonic to sea water)
Explanation
When the cytoplasm and sea water have the same concentration (isotonic), no extra water flows in by osmosis, so the protozoan needs no contractile vacuole to pump it out.