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

Which of the following most accurately describes selective permeability?

A) An input of energy is required for transport.

B) Lipid-soluble molecules pass through a membrane.

C) There must be a concentration gradient for molecules to pass through a membrane.

D) Only certain molecules can cross a cell membrane.

Answer: D

Through studies of insect Malpighian tubules, researchers found that K+ accumulated on the inner face of the tubule, against its concentration gradient. What can you infer about the mechanism of transport?

A) Potassium transport is a passive process.

B) Movement of potassium into the lumen of the Malpighian tubules is an energy-requiring process.

C) Potassium moves out of the tubules at a faster rate than it moves into the lumen of the tubules.

D) Sodium ions will follow potassium ions.

Answer: B

The advantage of excreting nitrogenous wastes as urea rather than as ammonia is that _____.

A) urea can be exchanged for Na+

B) urea is less toxic than ammonia

C) urea does not affect the osmolar gradient

D) less nitrogen is removed from the body

Answer: B

In animals, nitrogenous wastes are produced mostly from the catabolism of _____.

A) starch and cellulose

B) triglycerides and steroids

C) proteins and nucleic acids

D) phospholipids and glycolipids

Answer: C

Birds secrete uric acid as their nitrogenous waste because uric acid _____.

A) is readily soluble in water

B) is metabolically less expensive to synthesize than other excretory products

C) requires little water for nitrogenous waste disposal, thus reducing body mass

D) can be reused by birds as a protein source

Answer: C

Among the following choices, the most concentrated urine is excreted by _____.

A) frogs

B) kangaroo rats

C) humans

D) freshwater bass

Answer: B

Urea is produced in the _____.

A) liver from NH3 and carbon dioxide

B) liver from glycogen

C) kidneys from glycerol and fatty acids

D) bladder from uric acid and water

Answer: A

Urea is _____.

A) insoluble in water

B) the primary nitrogenous waste product of humans

C) the primary nitrogenous waste product of most birds

D) the primary nitrogenous waste product of most aquatic invertebrates

Answer: B

Which nitrogenous waste has the greatest number of nitrogen atoms?

A) ammonia

B) ammonium ions

C) urea

D) uric acid

Answer: D

Ammonia is likely to be the primary nitrogenous waste in living conditions that include _____.

A) lots of fresh water flowing across the gills of a fish

B) lots of seawater, such as a bird living in a marine environment

C) a terrestrial environment, such as that supporting crickets

D) a moist system of burrows, such as those of naked mole rats

Answer: A

Excessive formation of uric acid crystals in humans leads to _____.

A) a condition called diabetes, where excessive urine formation occurs

B) a condition of insatiable thirst and excessive urine formation

C) gout, a painful inflammatory disease that primarily affects the joints

D) osteoarthritis, an inevitable consequence of aging

Answer: C

One of the waste products that accumulates during cellular functions is carbon dioxide. It is removed via the respiratory system. What is another waste product that accumulates during normal physiological functions in vertebrates?

I) ammonia

II) uric acid

III) urea

A) only I and III

B) only II and III

C) only I and II

D) I, II, and III

Answer: D

The fluid with the highest osmolarity is _____.

A) distilled water

B) plasma in birds

C) plasma in mammals

D) seawater in a tidal pool

Answer: D

A human who has no access to fresh water but is forced to drink seawater instead will _____.

A) thrive under such conditions, as long as he has lived at the ocean most of his life

B) excrete more water molecules than taken in, because of the high load of ion ingestion

C) develop structural changes in the kidneys to accommodate the salt overload

D) risk becoming overhydrated within twelve hours

Answer: B

Unlike most bony fishes, sharks maintain body fluids that are isoosmotic to seawater, so they are considered by many to be osmoconformers. Nonetheless, these sharks osmoregulate at least partially by _____.

A) using their gills and kidneys to rid themselves of sea salts

B) monitoring dehydration at the cellular level with special gated aquaporins

C) tolerating high urea concentrations that are balanced with internal salt concentrations to seawater osmolarity

D) synthesizing trimethylamine oxide, a chemical that binds and precipitates salts inside cells

Answer: C

The necropsy (postmortem analysis) of a freshwater fish that died after being placed accidentally in saltwater would likely show that _____.

A) loss of water by osmosis from cells in vital organs resulted in cell death and organ failure

B) high amounts of salt had diffused into the fish's cells, causing them to swell and lyse

C) the kidneys were not able to keep up with the water removal necessary in this hyperosmotic environment, creating an irrevocable loss of homeostasis

D) the gills became encrusted with salt, resulting in inadequate gas exchange and a resulting asphyxiation

Answer: A