Question

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Why do all the fresh water organisms have contractile vacuoles whereas

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majority of marine organisms lack them?

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Answer 1

• The major function of contractile vacuole is Osmotic & Volume regulation.
• The contractile vacuoles expel the excess water from the fresh water organisms to save them from swell up and burst.
• Because, the fresh water has fewer ions in it. If water keeps on coming into their body the osmolarity would become high. Hence they need to send water, out of their body.
• Salt water itself has high osmolarity and hence the organisms keep the water inside their body and that is why, they are lack of contractile vacuoles.