Ch. 44 Osmoregulation and Excretion

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Campbell & Reece 8th edition test questions

A marine sea star was mistakenly placed in freshwater and it died. What is the most likely explanation for its
death?

The sea star is hyperosmotic to the freshwater, and it could not osmoregulate.

Organisms categorized as osmoconformers are most likely

marine.

The body fluids of an osmoconformer would be __________ with its __________ environment.

isoosmotic; saltwater

Compared to the seawater around them, most marine invertebrates are

isoosmotic.

Which feature of osmoregulation is found in both marine and freshwater bony fish?

gain of water through food

Unlike most bony fishes, sharks maintain body fluids that are isoosmotic to sea water. They are therefore considered by many to be osmoconformers because of the unusual way they maintain homeostasis. They osmoregulate by

tolerating high urea concentrations that balance internal salt concentrations to sea water osmolarity.

A freshwater fish was accidentally placed in salt water. After several minutes in this saline water, it died. What is the most logical explanation for its death?

Loss of water by osmosis in cells in vital organs resulting in cell death and eventually organ failure.

Where and from what compound(s) is urea produced?

liver from NH3 and CO2

Which of the following is true of urea? It is

the primary nitrogenous waste product of humans.

Which of the following is true of ammonia?

It is soluble in water.

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

urea is less toxic than ammonia.

What is the main nitrogenous waste excreted by birds?

uric acid

Which of the following nitrogenous wastes requires hardly any water for its excretion?

uric acid

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

proteins and nucleic acids.

Birds secrete uric acid as their nitrogenous waste because uric acid

requires little water for nitrogenous waste disposal which is conducive to the function of flight in terms of
weight.

The most concentrated urine is excreted by

kangaroo rats.

Materials are returned to the blood from the filtrate by which of the following processes?

selective reabsorption

Which group possess excretory structures known as protonephridia?

flatworms

Which group possess excretory organs known as Malpighian tubules?

insects

Which of the following mechanisms for osmoregulation or nitrogen removal is correctly paired with its corresponding animal?

direct cellular exchange-marine invertebrate

Which of the following excretory systems is partly based on the filtration of fluid under high hydrostatic pressure?

kidneys of vertebrates

The transfer of fluid from the glomerulus to Bowmanʹs capsule

is mainly a consequence of blood pressure in the capillaries of the glomerulus

Which of the following would contain blood in a normally functioning nephron?

vasa recta

What substance is secreted by the proximal-tubule cells and prevents the pH of urine from becoming too acidic?

ammonia

Which structure passes urine to the renal pelvis?

collecting duct

Which structure descends deep into the renal medulla only in juxtamedullary nephrons?

loop of Henle

Which of the following processes of osmoregulation by the kidney is the least selective?

filtration

Proper functioning of the human kidney requires considerable active transport of sodium in the kidney tubules. If these active transport mechanisms were to stop completely, how would urine production be affected?

A greater-than-normal volume of isoosmotic urine would be produced.

Which one of the following is extremely important for water conservation in mammals?

juxtamedullary nephrons

Processing of filtrate in the proximal and distal tubules accomplishes what important function?

maintaining a constant pH in body fluids

What is unique about transport epithelial cells in the ascending loop of Henle in humans?

Their membranes are impermeable to water.

What is the typical osmolarity of human blood?

300 mosm/L

Which one of the following, if present in a urine sample, would likely be caused by trauma?

erythrocytes

Which structure increases the reabsorption of Na+ when stimulated by aldosterone?

distal tubules

What would account for increased urine production as a result of drinking alcoholic beverages?

inhibition of antidiuretic hormone secretion (ADH)

In a laboratory experiment with three groups, one group of people drinks pure water, a second group drinks an equal amount of beer, and a third group drinks an equal amount of concentrated salt solution all during the same time period. Their urine production is monitored for several hours. At the end of the measurement period, which group will have produced the greatest volume of urine and which group the least?

beer the most, salt solution the least

Which of the following activities would initiate an osmoregulatory adjustment brought about primarily through the renin-angiotensin-aldosterone system?

spending several hours mowing the lawn on a hot day

How does ADH function at the cellular level?

It causes an increase in the number of aquaporin molecules of collecting duct cells.

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