A potassium ion gradient is set up in insect Malpighian tubules through an active transport process. As a result, potassium concentration is higher in the lumen of the tubules than in hemolymph. How would the potassium gradient affect water movement?

A) Water would be forced out of the lumen of the Malpighian tubules through an osmotic gradient.

B) The potassium gradient would have no effect on water movement.

C) There would be a net movement of water into the lumen of the tubules.

D) Water would be conserved, forming a hypertonic solution in the Malpighian tubules.

Answer: C

Why are the renal artery and vein critical to the process of osmoregulation in vertebrates?

A) The kidneys require constant and abnormally high oxygen supply to function.

B) The renal artery delivers blood with nitrogenous waste to the kidney and the renal vein brings blood with less nitrogenous wastes away from the kidneys.

C) The kidneys require higher than normal levels of hormones.

D) The renal artery and vein are the main pathways regulating how much is produced by the kidneys.

Answer: B

The figure above shows a nephron. Filtration takes place in the structure labeled _____.

A) a

B) b

C) c

D) d

Answer: A

African lungfish, which are often found in small, stagnant pools of fresh water, produce urea as a nitrogenous waste. What is the advantage of this adaptation?

A) Urea takes less energy to synthesize than ammonia.

B) Small, stagnant pools do not provide enough water to dilute the toxic ammonia.

C) The highly toxic urea makes the pool uninhabitable to potential competitors.

D) Urea makes lungfish tissue hypoosmotic to the pool.

Answer: B