Question

op. sur - no less than Cobserung hy po Tonic equal. cell membrare con is what anor.n gaining Marine fish w ally live in hyp 177 Freshwater fish usually live in hypotonic environments. differe e ha s ally live in hypertonic environments. Describe the erent challenges they each face during osmoregulation (regulating water balancel. Use the specific vocabulary. 18) Some marine animals (including seastars and hagfish) have no ability to osmoregulate. What kind of solute environment do these animals live in? Explain your answer using specific vocabulary.

Answer 1

Answer 17:

Water moves from a medium of low solute concentration to a medium of high solute concentration via osmosis. (Stated in other terms, water moves from a region of high water concentration to a region of low water concentration).

Freshwater fishes live in a hypotonic environment, which means the medium surrounding them has lesser solute concentration. Thus, water tends to enter the body of freshwater fishes by osmosis. This creates a high internal osmotic pressure in freshwater fishes.

On the other hand, marine fishes live in a hypertonic medium, which has more solute concentration (due to salts) than cells of fishes. Thus, water tends to move out from body of fishes into the external environment by osmosis. This creates a low internal osmotic pressure in marine fishes.

​​The various challenges faced and adaptation strategies for freshwater and marine fishes can be compared as follows:

Freshwater fishes	Marine fishes
Live in a hypotonic environment, thus water tends to enter body of fishes by osmosis. This may cause cells to swell up and burst. Higher internal osmotic pressure. To cope with the situation, they ingest minimum water and excrete maximum fluids in urine (dilute urine). Uptakes salts through gills.	Live in hypertonic environment, and water tends to move out of body of marine fishes into the external environment by osmosis. This may lead to serioius dehydration of cells. Lower internal smotic pressure. They ingest large amounts of water and excrete large amounts of salt in urine (concentrated urine). Excretes salts through gills.

Answer 18:

Marine fishes which do not need to perform osmoregualtion are those which maintain an internal ionic concentration similar to that of the environment. Thus, their internal body osmotic pressure equals the external osmotic pressure and such organisms, like hagfish, are called isoconformers.

Since, the concentration of solute in internal body of such fishes is equal to that of the external environment, the external solute environment would be called an isotonic one.