Paramecium and other unicellular eukaryotes that live in hypotonic environments have cell membranes that limit water uptake, while those living in isotonic environments have membranes that are more permeable to water. Describe what water regulation adaptations might have evolved in unicellular eukaryotes in hypertonic habitats such as the Great Salt Lake and in habitats with changing salt concentration.

The movement water or a solvent through a semipermeable membrane like the cell membrane into a solution of higher solute concentration is known as osmosis. An easy way to learn the net movement of water is that water tends to move to the hypertonic solution. In this question water will have a tendency to move out of the cell (plasmolysis).

Cells could have a higher concentration of salt inside the cell, this would require a mechanism like membrane channels that could facilitate the entrance of salts. This could be complemented with having membranes that are more permeable allowing more water to enter the cell to avoid plasmolisis.

Answer: Protists have more permeable membranes than those that are in hypotonic or isotonic environments, they allow more water to enter the cell. They could also possibly develop a higher salt concentration within the cell, they retain the water within it and don't diffuse quickly. The cell will become plasmolyzed without these adaptations. Protists in an unstable salt concentration will have a semi-permeable membrane in order to keep up with the changes in concentration and take in water along with a contractile vacuole in order to pump out any unnecessary water it takes in.