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Biology - Freshwater Organisms

Freshwater Organisms

Body fluids have an osmotic concentration greater than the external
medium, resulting in endosmosis across body surfaces; e.g. gill surfaces.
In freshwater fish, osmoregulation [1] involves:

* removal of excess water in dilute urine

* active uptake of salts across gill surfaces

* avoidance of drinking

In freshwater protozoa [2], excess water is voided by means of contractile
vacuoles.

View the video to see how Paramecium removes excess water using
contractile vacuoles.

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Links:
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[1] http://alison.com/#
[2] http://alison.com/#