How are fish in fresh water affected by osmosis?

Answer 1

swallow plenty of sea water to increase amount of water in the body

have chloride secretory cells in their gills to remove excess salts

few glomeruli thus slow filtration rate in the kidneys

eliminate nitrogenous wastes in form of trimethylamine oxide which requires little water for elimination.

Answer 2

Osmosis is the reason that a fresh water fish placed in the ocean desiccates and dies. Osmosis is the reason that blisters form on fiberglass boat hulls. Osmosis is how waste products of metabolism enter and leave the blood stream. Osmosis determines how you, me and every living thing lives and dies. One would think that a civilization that spends billions of dollars every year on medical research would understand something as basic as osmosis. Wrong, wrong, wrong.

Osmosis is the tendency of water in salt water to flow from an area of low salt concentration to an area of high salt concentration across a semi permeable membrane. Of course, osmosis applies to all solvents, not just water, and to all solutes, not just salt. I will discuss only water and salt for simplicity. Salt in solution comprises ions of chlorine and sodium, but I will refer to 'dissolved salt' for simplicity. A semi permeable membrane is a barrier that has holes large enough to allow molecules of water to pass but small enough to block the passage of the dissolved salt. In the example of the fresh water fish placed in the ocean, the water in the fish has a lower salt concentration than the

surrounding ocean. The water in the fish moves through the semi permeable membrane (the cells of the gills of the living fish) from the area of low salt concentration (the fish) to the area of high salt concentration (the ocean). As a result, the fish dies of dehydration while surrounded by water.

But how does this process actually work? The ions making up the dissolved salt in the salt water jiggle at random due to Brownian motion. The ions bounce against all of the boundaries of the salt water, including a free surface. The free surface is where the salt water meets the air. When the ions making up the salt bounce against the free surface, the jiggling ions press against the liquid water molecules at the free surface. The liquid water molecules at the free surface are bonded to all of the other liquid water molecules and pull on all of the liquid water molecules, including the pure water on the other side of the semi permeable membrane. The pressure exerted by the ions making up the salt bouncing against the free surface pulls water through the semi permeable membrane.

In the case of the unfortunate fish, the free surface is the surface of the ocean. The effect is the same for any boundary that can move in response to pressure, such as, for example, a cell wall.

Answer 3

Unless I have it backwards (which is possible) Freshwater Fish in saltwater die from being internally crushed. Saltwater Fish die from internal expansion.