Q22 - Nephron Structure and Urine Concentrating Ability Across Habitats

Theoretical 1 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license

Human Excretory System Comparative Osmoregulation & Excretion

Animals living in deserts like kangaroo rats achieve the ability to sustain themselves on a limited supply of water through incredibly well adapted kidney. To remove waste without losing water, species have developed mechanisms to concentrate their urine. There are two types of nephrons that concentrate urine, a type with a short Henle loop located in the renal cortex (cortex: C) and a type with a long Henle loop located near the renal medulla (juxtamedullary: JM). The ratio of these two types of nephrons differs depending on the animal. The table shows the habitat of each animal species and the urea concentration in urine. The graph plots the juxtamedullary-cortex ratio (the number of JM type loop/the number of C type loop) in each animal species.

Figure 1. Figure 1.

Using the information and data, determine which of the statements are true or which are false.

A. Beavers seem not to possess the cortex type nephron.

B. The JM/C ratio of the kangaroo rat is estimated at 1.5 or more.

C. Longer Henle loops can efficiently reabsorb salts, resulting in urine concentration.

D. Animals living in dry regions have a higher proportion of cortex type nephrons than those living in freshwater.

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Question reproduced from IBO 2020, Theoretical Exam 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)