Chapter 44

A necropsy (postmortem analysis) of a marine sea star that died after it was mistakenly placed in fresh water would likely show that it died because

it was so hyperosmotic to the fresh water that 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.

The fluid with the highest osmolarity is

seawater in a tidal pool.

Birds that live in marine environments and thus lack access to fresh drinking water

drink seawater and secrete excess ions mainly through their nasal salt glands.

Osmoconforming sharks take in water, as needed,

via osmosis, as their body cells are slightly hyperosmotic to seawater.

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

will excrete more water molecules than taken in, because of the high load of ion ingestion.

Many marine and freshwater bony fish achieve osmoregulation via

gain of water through food.

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

tolerating high urea concentrations that balance internal salt concentrations to seawater osmolarity.

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

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

Urea is produced in the

liver from NH3 and CO2.

Urea is

the primary nitrogenous waste product of humans.

Which nitrogenous waste has the greatest number of nitrogen atoms?

uric acid

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

lots of fresh water flowing across the gills of a fish.

Among vertebrate animals, urea

is made in the liver by combining two ammonia molecules with one carbon dioxide.

The nitrogenous waste that requires the most energy to produce is

uric acid.

Excessive formation of uric acid crystals in humans leads to

gout, a painful inflammatory disease that primarily affects the joints.

Ammonia

is soluble in water.

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

urea is less toxic than ammonia.

The primary nitrogenous waste excreted by birds is

uric acid.

Which nitrogenous waste requires hardly any water for its excretion?
A) amino acids

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, thus reducing body mass.

Among the following choices, 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

Excretory structures known as protonephridia are present in

flatworms.

Excretory organs known as Malpighian tubules are present in

insects.

The osmoregulatory/excretory system of a freshwater flatworm is based on the operation of

protonephridia.

Freshwater flatworms form a urine that is typically

of low solute concentration and of high volume, matching their normal fluid uptake.

The osmoregulatory process called secretion refers to the

selective elimination of excess ions and toxins from body fluids

The osmoregulatory/excretory system of an earthworm is based on the operation of

metanephridia.

The osmoregulatory/excretory system of an insect is based on the operation of

Malpighian tubules.

Which of the following pairs of organisms excrete nitrogenous wastes in the form of uric acid?

insects and birds

Choose a pair that correctly associates the mechanism for osmoregulation or nitrogen removal with the appropriate animal.

direct cellular exchangemarine invertebrate

An excretory system that is partly based on the filtration of fluid under high hydrostatic pressure is the

kidneys of vertebrates.

The transfer of fluid from the glomerulus to Bowman’s capsule

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

Within a normally functioning kidney, blood can be found in

the vasa recta.

A person with alkalosis will likely excrete urine that has abnormally high levels of

sodium ions.

The filtrate in the renal pelvis enters directly from

the collecting duct.

Juxtamedullary nephrons can concentrate salt effectively in the renal medulla because of their long

) loops of Henle.

The filtrate in the proximal convoluted tubule of the human does not normally include

plasma proteins.

Human urine is usually more acidic than most other body fluids because

hydrogen ions are actively moved into the filtrate.

The osmolarity of human urine

can be four times as great as normal osmolarity of human plasma.

A primary reason that the kidneys have one of the highest metabolic rates of all body organs is that

it operates an extensive set of active-transport ion pumps.

Low selectivity of solute movement is a characteristic of

filtration from the glomerular capillaries.

If ATP production in a human kidney was suddenly halted, urine production would

increase, and the urine would be isoosmotic compared to plasma.

Compared to wetland mammals, water conservation in mammals of arid regions is enhanced by having more

juxtamedullary nephrons.

Processing of filtrate in the proximal and distal tubules

maintains homeostasis of pH in body fluids.

In humans, the transport epithelial cells in the ascending loop of Henle

have plasma membranes of low permeability to water.

The typical osmolarity of human blood is

300 mosm/L.

Trauma to the human kidney could result in a urinary filtrate containing an abnormally high level of

erythrocytes.

When stimulated by aldosterone, the reabsorption of Na+ is increased along

the distal tubule.

Increased ADH secretion is likely after

sweating-induced dehydration increases plasma osmolarity.

After blood flow is artificially reduced at one kidney, you would expect that kidney to secrete more of the hormone known as

renin.

After drinking alcoholic beverages, increased urine excretion is the result of

inhibited secretion of antidiuretic hormone (ADH).

Osmoregulatory adjustment via the renin-angiotensin-aldosterone system can be triggered by

severe sweating on a hot day.

Antidiuretic hormone (ADH) functions at the cellular level by

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

ADH and RAAS work together in maintaining osmoregulatory homeostasis through which of the following ways?

ADH regulates the osmolarity of the blood by altering renal reabsorption of water, and RAAS maintains the osmolarity of the blood by stimulating Na+ reabsorption.

(Picture 8) Which of the following is excreted readily by aquatic animals because of its high solubility in the respiratory medium?

A

(Picture 8)Which of the following is synthesized by mammals, most amphibians, sharks, and some bony fishes, and has lower toxicity than its nitrogenous substrate?

B

(Picture 8) Which of the following is excreted as a paste by land snails, insects, birds, and many reptiles, because of its solubility and toxicity properties?

C

In a laboratory experiment with three groups of students, one group 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. Which groups are expected to have the greatest and least amounts of urine, respectively?

Beer drinkers have the most; salt solution drinkers have the least.

Unlike an earthworm’s metanephridia, a mammalian nephron

receives filtrate from blood instead of coelomic fluid.

Which process in the nephron is least selective?

filtration

Which of the following animals generally has the lowest volume of urine production?

a marine bony fish

The high osmolarity of the renal medulla is maintained by all of the following except

diffusion of salt from the descending limb of the loop of Henle.

Natural selection should favor the highest proportion of juxtamedullary nephrons in which of the following species?

a mouse species living in a desert

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?

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