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When a marine fish was taken from the ocean and put in a tank of freshwater, it died after a short period because
A. the tank was too small compared to the large-ocean
B. the body cells of the fish swelled and burst as a result of the hypotonic fresh water
C. the body cells of the fish shrank as their sap was hypertonic to the freshwater
D. there was no food in the tank, so the fish starved
When a marine fish was taken from the ocean and put in a tank of freshwater, it died after a short period because the body cells of the fish swelled and burst as a result of the hypotonic fresh water.
Osmosis involves the movement of water molecules from a less concentrated solution to a more concentrated solution across a membrane, this is because the more concentrated solution will always be water-craving to reduce its concentration.
Ocean water is salty, fishes here will have a more salt-concentrated internal solution.
When transferred to freshwater, the internal solution of the fish will attract water from the environment, causing the fish to swell and burst.
Now for the right answer to the above question:
- Option A is incorrect. the size difference here isn’t a valid reason.
- Option B is correct. water will naturally move from the freshwater to the internal salty solution of the fish, causing it to swell and eventually burst.
- C is incorrect. water will not move outward from the fish; therefore, it will not shrink.
- D is not the correct answer. starvation is not a valid reason.
You may please note these/this:
- Osmosis ensures water moves from a less concentrated solution (freshwater) to a saltier solution (fish internal solution).
- When water moves in, swelling is expected, and an eventual burst is also expected.
/ culled from 2021 JAMB-UTME BIOLOGY question 24 /