Question

17) Fresh water fish usually live in hypotonic environments. Marine fish usually live in hypertonic environments. Describe the different challenges they each face during osmoregulation (regulating water balance). 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

Osmoregulation :-
• Maintaining water and salt balance in body.

• *water moves from low salt concentration to high salt concentration/ water moves from low osmotic pressure to high osmotic pressure.

Question 17.
Osmoregulation in fresh water fishes :-
• Fresh water fish lives in a hypotonic environment, so water is naturally being drawn into them and there is a tendency to lose salt.
• Freshwater fish have very efficient kidneys that excrete water quickly and reabsorb salt from urine. Hence, these fishes excrete very dilute urine.
• Using special cells in the gills these fishes actively take salt from their environment.

Osmoregulation in marine water fishes :-
• In marine water, there is relatively more salt and less water outside their bodies, so there is a tendency to absorb the salt and lose water.
• To eliminate this problem, marine fishes drink large amounts of water and urinate little. These fishes do not absorb any salt from the water they drink.
• Special cells in the gills eliminate salt by active transport.

Question 18.
• Osmoconformer - are organisms that remain isotonic with seawater.
• Hagfish and many marine invertebrates are osmoconformers.
• Their body fluids are almost the same concentration of ions as seawater, but they use different ions.
• Osmoconformers decrease the net flux of water into or out of their bodies and maintain internal solute concentrations within their bodies at a level equal to the osmolarity of the surrounding medium.
• These organisms have permeable bodies which allow the in and out movement of water and, therefore, no need to ingest surrounding water.
• Some organisms like sharks hold high concentrations of waste chemicals like urea and TMAO (trimethylamine N-oxide) in their bodies to create the diffusion gradient necessary to absorb water.