Question

Marine protozoans lack contractile vacuole because ________________.

• A. Their body cannot accommodate it
• B. They are hypotonic to their environment
• C. They are isotonic with their environment
• D. Osmoregulation is done by cell membrane

Answer 1

Answer: (B)

They are hypotonic to their environment

• Marine protozoa live in a hypertonic environment, unlike freshwater protozoa.
• The contractile vacuole is used to store and remove excess water which is due to endosmosis.
• Marine protozoa do not have contractile vacuole because they need to conserve water content from getting lost in the hyperosmotic environment.

So, the correct answer is 'They are hypoosmotic to their environment'