Compare and contrast osmolality among vertebrate groups that live in marine, fre

Question

 Compare and contrast osmolality among vertebrate groups that live in marine, freshwater, and terrestrial environments. What are the major threats to survival related to osmolality, and what are the organs and mechanisms that are involved in osmoregulation (give examples of organisms with each type). b. Describe the concept of the tripartite kidney and relate this concept to the development of urogenital ducts (i.e., both urinary and reproductive ducts) in relation to the organs they drain (be sure to contrast these ducts in males and females); what specializations have developed in amniotes vs. fish.  

Explanation / Answer

Marine vertebrates are osmoregulators. The ocean water is much saltier than the internal fluids of these animals. Hence, water is lost from their bodies through osmosis. Marine bony fishes such as as cod have body fluids that are hypotonic to sea water. They lose water by osmosis and gain salt through diffusion and from the food that they eat.

Freshwater animals gain water by osmosis and lose salts through diffusion. The reason being that the osmolarity of their internal body fluids is much higher as compare to those of the surroundings.However, since fresh water has low salinity level, the body fluids of freshwater animals mostly have lower solute concentrations than marine animals.

fish such as perch, excrete large amounts of dilute urine to maintain water balance. They regain lost salts through the food they eat and through active uptake of salts from their surroundings.

The key to survival in terrestrial habitats is prevention of water loss. Coverings of dead keratinized skin prevents water loss. These animals balance water loss by drinking and eating foods with water content. Desert animals like kangaroo rats lose very little water and compensate 90% of water loss through metabolic water. Their diet comprising of seeds compensates for the remaining water.

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