Question

Two species of Amoeba X and Y were Kept in fresh water and got adapted. Species X developed contractile vacuole. When both were transferred to sea water and got adapted, both X and Y lost their contractile vacuole. From these observation we conclude that __________________.

• A. Both X and Y are marine species
• B. Species Y is marine and X is fresh water
• C. Species X is marine and Y is fresh water
• D. Both X and Y are fresh water

Answer 1

The correct option is A Both X and Y are marine species

• The contractile vacuole eliminates excess water which enters the cell by osmosis.
• Because of the hypotonic nature, freshwater continuously transfers into amoeba by osmosis. To avoid this, they develop contractile vacuoles.
• Marine amoeba is isotonic in water and they do not have contractile vacuoles.
• Both X and Y species are marine species. That’s why they developed contractile vacuoles when they kept in freshwater.
• But they lost their contractile vacuoles when transferred to seawater. There is already a hypertonic environment in seawater to control water loss by themselves.

Hence, the correct answer is option A.