Question

Multiple Choice

1.Salmon spend most of their lives in the ocean, but swim up freshwater rivers to spawn.  Which of the following physiological adaptations must occur for this transition to take place.

A.Their gills must begin to excrete salt and the salmon start drinking water.

B.Their kidneys must produce more concentrated urine and the gills absorb salt from the water.

C.Their gills must absorb salt from the water and the kidneys produce copious dilute urine.

D.The salmon stop drinking water and the kidneys produce more concentrated urine.

E. The salmon are osmoconformers like most fish and do not regulate water and salt balance.

2.If the ascending limb of the Loop of Henle were to stop moving sodium (Na+), potassium (K+) and chloride (Cl−) ions into the interstitial fluid of the renal medulla, what would be the effect on the urine the kidneys produced?

A.Your urine would have less salt and less water

B.Your urine would have more salt and more water.

C.Your urine would have less salt and more water

D. Your urine would have more salt and less water.

Answer 1

Answer 1: Correct option is (C)

When salmon swim up from ocean to freshwater rivers to spawn, the physiological adaptation that must occur for this transition to take place is :their gills must absorb salt from the water and the kidneys produce dilute urine.

Because in freshwater medium that is nearly devoid of ions, especially NaCl, and much more dilute than its body fluids ,the water will diffuse into the salmon body .Salmon don't drink water in freshwater medium. In fresh water, the salmon's kidneys produce large volumes of dilute urine (to cope with all of the water that's diffusing into the salmon's body fluids).

In the gill epithelial cells, salmon have a special enzyme that hydrolyzes ATP and uses the released energy to actively transport both Na+ and Cl- against their concentration gradients.

In fresh water, these same Na+-Cl- ATPase molecules 'pump' Na+ and Cl- from water into the salmon's blood, thereby compensating the continuous diffusion-driven loss of NaCl in freshwater.

Option (A) is wrong because this is the adaptation for marine environment. Option (B),(D) and (E) are also wrong according to the above explanation.

Answer 2: correct option (B)

If the ascending limb of the Loop of Henle were to stop moving sodium (Na+), potassium (K+) and chloride (Cl−) ions into the interstitial fluid of the renal medulla the urine have more water and more salt.because reabsorption of Sodium (Na+), potassium (K+) and chloride (Cl−) ions will not occur. Failing which the medullary interstitial hypertonicity will be decreased and water reabsorption from renal tubule will also decrease which leads to dilute urine.