Chapter 44

Selective secretion of toxins and drugs takes place in the structure labeled ________. (see image)

B

Urea is _____.

the primary nitrogenous waste product of humans

What role do transport epithelia play in osmoregulation of marine fish with bony skeletons?

They are involved in excretion of excess salt.

Terrestrial organisms lose water through evaporation. In what ecosystem might an entomologist find a good study organism to examine the prevention of water loss?

desert

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

proteins and nucleic acids

Increased antidiuretic hormone (ADH) secretion is likely after _____.

sweating-induced dehydration increases plasma osmolarity

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

urea is less toxic than ammonia

Single-celled Paramecium live in pond water (a hypotonic environment relative to the cytosol). They have a structural feature, a contractile vacuole, which enables them to osmoregulate. If sucrose or saline was added to the pond water in different concentrations (in millimolars, mM), under which conditions would you expect the contractile vacuole to be most active?

0.0 mM sucrose

Filtration takes place in the structure labeled ________. (see image)

A

In which of the labeled structures does passive water reabsorption take place? (see image)

in B, C, and E

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

kidneys of vertebrates

Which nitrogenous waste has the greatest number of nitrogen atoms?

uric acid

Antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system (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 the RAAS maintains the osmolarity of the blood by stimulating both Na+ and water reabsorption.

The structure labeled ________ can be influenced by hormones to change the concentration of the urine. (see image)

E

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

increase, and the urine would be isoosmotic compared to plasma

Urea is produced in the _____.

liver from NH3 and carbon dioxide

Within a normally functioning kidney, blood can be found in _____.

the vasa recta

Like other osmoregulatory animals that live in marine environments, sharks maintain tissue concentrations of sodium, potassium, and chloride that are hypoosmotic to the seawater. In contrast to the bony marine fishes, however, sharks do not need to drink seawater. Why?

High urea and trimethylamine oxide concentrations keep shark tissues slightly hyperosmotic relative to seawater, so water is absorbed passively.

Which of the following contribute to maintaining the high osmolarity of the renal medulla? I) active transport of salt from the upper region of the ascending limb II) the spatial arrangement of juxtamedullary nephrons III) diffusion of urea from the collecting duct IV) diffusion of salt from the descending limb of the loop of Henle

I, II, and III

Studies of cricket Malpighian tubules revealed that potassium ions accumulated inside the tubule, moving against the potassium concentration gradient. Based on the information, what can you infer about the mechanism of potassium transport?

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

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.

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

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.

Salmon eggs hatch in fresh water. The fish then migrate to the ocean (a hypertonic solution) and, after several years of feeding and growing, return to fresh water to breed. How can these organisms make the transition from fresh water to ocean water and back to fresh water?

The salt transport mechanisms of the gill epithelia change during migration.

Studies of cricket Malpighian tubules revealed that potassium ions accumulated inside the tubule, moving against the potassium concentration gradient. How would you expect the movement of water to be influenced by the distribution of potassium ions?

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

If you are hiking through the desert for several days, one would pack which of the following to ensure proper hydration?

a drink with a combination of water and electrolytes

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

a mouse species living in a desert

The loop of Henle dips into the renal cortex. This is an important feature of osmoregulation in terrestrial vertebrates because _____.

differential permeabilities of ascending and descending limbs of the loop of Henle are important in establishing an osmotic gradient

Osmoregulatory adjustment via the atrial natriuretic peptide system can be triggered by ________.

drinking several glasses of water

To maintain homeostasis, freshwater fish must ________.

excrete large quantities of water

Which process in the nephron is LEAST selective?

filtration

Low selectivity of solute movement is a characteristic of _____.

filtration from the glomerular capillaries

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

flame bulb: flat worm

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

gout, a painful inflammatory disease that primarily affects the joints

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

have plasma membranes of low permeability to water

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

inhibited secretion of antidiuretic hormone (ADH)

Excretory organs known as Malpighian tubules are present in _____.

insects

The transfer of fluid from the glomerulus to Bowman's capsule ________.

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

Compared to the seawater around them, most marine invertebrates are ________.

isoosmotic

The body fluids of an osmoconformer would be ________ with its ________ environment

isoosmotic; seawater

Developing bird embryos excrete most of their nitrogenous waste as uric acid because ________.

it has a low solubility in water and is less toxic to the embryo than other forms of waste

An examination of a marine sea star that had died after it was mistakenly placed in fresh water would likely show that it died because ________.

it was so hypertonic to the fresh water that it could not osmoregulate

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

juxtamedullary nephrons

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

kangaroo rats

Which of the following is characteristic of juxtamedullary nephrons?

long loop of Henle

An examination 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

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

Processing of filtrate in the proximal and distal tubules _____.

maintains homeostasis of pH in body fluids

Animals have adapted different mechanisms for excreting nitrogenous waste products. Which of the following are selective pressures that likely influence which mechanism an animal uses? I) the amount of water available in the animal's habitat II) the energy needs of the animal III) the temperature of the animal's environment

only I and II

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

passively excrete excess water in order to remove the high concentration of ingested salt

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

protonephridia

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

reabsorption

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

renin

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

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

The fluid with the highest osmolarity is ________.

seawater in a tidal pool

The osmoregulatory process called secretion refers to the _____.

selective elimination of excess ions and toxins from body fluids

The force driving simple diffusion is _____, while the energy source for active transport is _____.

the concentration gradient; ATP

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

they operate an extensive set of active-transport ion pumps

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 are balanced with internal salt concentrations to seawater osmolarity