[Campbell Biology P.1046] A newly discovered mammal species lives in an extremely arid desert... | Practice Question

A newly discovered mammal species lives in an extremely arid desert environment. Based on the principles of osmoregulation discussed, which adaptation would you expect to find in its nephrons to maximize water reabsorption?

  • A: Shorter loops of Henle extending shallowly into the renal medulla.
  • B: Longer loops of Henle extending deep into the renal medulla.
  • C: Increased permeability of the ascending limb of the loop of Henle to water.
  • D: Reduced activity of the countercurrent multiplier system.

Explanation

The text states, "Natural selection has shaped the form and function of nephrons in various vertebrates to the osmoregulatory challenges of the animals' habitats. For example, desert mammals, which excrete the most hyperosmotic urine, have loops of Henle that extend deep into the renal medulla, whereas mammals in moist habitats have shorter loops and excrete more dilute urine." Longer loops of Henle are crucial for establishing a stronger osmotic gradient in the renal medulla, allowing for greater water reabsorption and the production of highly concentrated urine, which is essential for survival in arid environments.