Question 1

Which of the following best explains why marine bony fish produce small amounts of highly concentrated urine?

Accepted Answer

They lose water by osmosis to the surrounding seawater and must conserve as much water as possible.

Question 2

Which structure in the mammalian nephron is primarily responsible for creating the osmotic gradient necessary for water reabsorption?

Accepted Answer

Loop of Henle

Question 3

A mutation that prevents the insertion of aquaporin proteins into the collecting duct membrane would most likely result in which of the following conditions?

Accepted Answer

Production of large volumes of dilute urine

Question 4

Which of the following equations correctly represents the conversion of ammonia to urea in the urea cycle?

Accepted Answer

$$2 \mathrm{NH}_3 + \mathrm{CO}_2 \rightarrow \mathrm{CO}((\mathrm{NH}_2)_2)$$

Question 5

Which adaptation allows the albatross to drink seawater without becoming dehydrated?

Accepted Answer

Specialized nasal glands that excrete excess salt

Question 6

Which of the following best describes the function of the flame bulb in protonephridia?

Accepted Answer

It draws interstitial fluid into the tubule system for filtration.

Question 7

Why do desert mammals, such as the kangaroo rat, have longer loops of Henle compared to mammals living in moist environments?

Accepted Answer

Longer loops of Henle allow for greater water reabsorption, producing highly concentrated urine.

Question 8

Which of the following is a key difference between the excretory systems of insects and annelids?

Accepted Answer

Insects use Malpighian tubules that empty into the digestive tract, while annelids use metanephridia that empty to the outside.

Question 9

Which hormone is released in response to increased blood osmolarity and acts to increase water reabsorption in the kidney?

Accepted Answer

Antidiuretic hormone (ADH)

Question 10

A patient with a mutation that prevents the production of ADH would most likely present with which of the following symptoms?

Accepted Answer

Severe dehydration and production of large volumes of dilute urine

Question 11

Which of the following best explains why sharks (chondrichthyans) are able to maintain osmotic balance in seawater?

Accepted Answer

They retain high concentrations of urea and TMAO, making their body fluids slightly hyperosmotic to seawater.

Question 12

Which of the following is the correct sequence of processes in the formation of urine in the mammalian nephron?

Accepted Answer

Filtration → Reabsorption → Secretion → Excretion

Question 13

Which of the following would most likely occur if the ascending limb of the loop of Henle lost its ability to actively transport NaCl?

Accepted Answer

The osmotic gradient in the medulla would decrease, reducing water reabsorption in the collecting duct.

Question 14

Which of the following best describes the role of aldosterone in kidney function?

Accepted Answer

It increases reabsorption of Na+ and water in the distal tubule, raising blood volume and pressure.

Question 15

Which of the following is a major advantage of excreting uric acid rather than urea or ammonia?

Accepted Answer

Uric acid is poorly soluble and can be excreted as a semi-solid paste, conserving water.

Question 16

A person is lost in the desert and becomes severely dehydrated. Which hormone would you expect to be elevated in their blood?

Accepted Answer

Antidiuretic hormone (ADH)

Question 17

Which of the following best explains why the juxtamedullary nephrons are essential for mammals living in arid environments?

Accepted Answer

They allow for the production of highly concentrated urine, minimizing water loss.

Question 18

Which of the following would be a likely consequence of a defect in the countercurrent multiplier system of the loop of Henle?

Accepted Answer

Inability to concentrate urine, leading to excessive water loss

Question 19

Which of the following is a function of the nasal salt glands in marine birds?

Accepted Answer

They excrete excess sodium chloride from the blood, allowing the bird to drink seawater.

lecture 5 Osmoregulation and Excretion: Mechanisms and Adaptations in Animals

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