AP BIOLOGY

Detailed explanation-1: -Controlling Osmosis Organisms that live in a hypotonic environment such as freshwater, need a way to prevent their cells from taking in too much water by osmosis. Freshwater and saltwater fish have the ability to adjust to the osmotic pressure in the water around them.

Detailed explanation-2: -Contractile vacuoles have been shown to contain osmotically active substances; they shrink in hypertonic and swell in hypotonic solutions regardless of whether remain in the cell or have been removed from the cell.

Detailed explanation-3: -Hypertonic solution In biology, the tonicity of a solution usually refers to its solute concentration relative to that of another solution on the opposite side of a cell membrane; a solution outside of a cell is called hypertonic if it has a greater concentration of solutes than the cytosol inside the cell.

Detailed explanation-4: -Because the cell is filled with salts, sugars, proteins, and other molecules, it is almost always hypertonic to fresh water. So if a cell is in fresh water, water tends to move quickly into the cell, causing it to swell or even burst.