Question

8. Describe what will happen to an exclusively saltwater fish (meaning it only lives in saltwater) if it is placed in a freshwater environment. Be sure to describe what will happen to the cells of the saltwater fish when put in this environment.
9. Why is osmoregulation an important process for animal cells?
10. If the concentration of water molecules is greater outside a cell, then the solution is ______ to the cell

Answer 1

Some important terms before understanding the concept:-

1. Osmosis: It is the process in which there is spontaneous movement of solvent molecules from a region of higher concentration to a region of lower concentration across a selectively permeable membrane.
2. Hypertonic solution: This solution contains higher concentration of solutes than the surrounding medium.
3. Hypotonic solution: This solution contains lower concentration of solutes than the surrounding medium.

Consider the following conditions:-

• When a cell is placed in a hypertonic solution- due to osmosis water flows out of the cell so as to acieve a balance in the concentration of solutes on the either side of the cell membrane. This results in shrinking of the cell.
• When a cell is placed in a hypotonic solution- due to osmosis water enters the cell so as to achieve a balance in the concentration of solutes on the either side of the cell membrane. This results in bloating of the cell.

How does a saltwater fish survive in its saltwater environment?

• Seawater- becomes hypertonic for the fishes.
• Body of the fishes- becomes hypotonic(due to higher salt content in the surounding)
• Therefore, as explained above water loss from the cells of the fishes will take place and the fish would start to dehydrate.
• Hence, to stay alive they need to compensate the water loss which takes place due to osmosis.
• Thus, they drink a lot of water and then filter out the excess of salts from their bloodstream through their gills and kidneys by urinating.

Now, if an exclusively saltwater fish is placed in a freshwater environment(opposite to its normal environment) the following happens:

• Freshwater- becomes hypotonic for the fishes
• Body of the fishes- becomes hypertonic( due to the salt content)
• Therefore, as explained above in such a condition the fishes would take up water from the surrounding to maintain the balance in concentration.The water quantity in the body of fishes would increase resulting in bloating.
• Slowly cytolysis(breakdown of cells beacause of the increased pressure inside them due to the water content) would take place and the fish dies.

Hence, a saltwater fish cannot survive if kept in freshwater.

EURYHALINE FISHES- These kind of fishes can survuve in both saltwater as well as freshwater medium.

Importance of osmoregulation:

• To maintain homeostasis in the body of an organism
• To maintain the fluid balance and the electrolyte concentration
• To maintain the osmotic pressure of the cell.

If the concentration of water molecules is greater outside a cell, then the solution is HYPOTONIC to the cell.