In the red underlined portions the authors of this paper lay

In the red underlined portions, the authors of this paper lay out a physiological dilemma for the hummingbird kidney. In one sentence, state this dilemma.

Using what you know about kidney structure (especially the amount of cortex vs. medulla) and the ability of the mammalian and bird kidney to concentrate urine, make a prediction for how the structure of the hummingbird kidney may differ from other birds that don’t face the dilemma that you stated above.

Solution

Answer:

The kidney of Humming bird differs from the other aves. The cortical region of the humming bird kidney occupies nearly 90% area and medullary region (2%) occupies is very less area. The loop of Henle is absent in the most nephrons (99%) of Humming Birds kidney,which is similar to reptiles. Few nephrons have loops but that loop lack descending limb. Due to this observed differences in kidneys of Humming birds compared to other aves, these excrete dilute urine and lose more water.