Chapter 44 Bio

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

Where and when does osmolarity of the filtrate increase?

As the filtrate moves down the descending limb of the loop of Henle

Select the correct statement about osmolarity.

Osmolarity measures the moles of solute per liter of solution.

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

They are involved in excretion of excess salt.

Osmoregulation and excretion are _____.

mechanisms that maintain volume and composition of body fluids

Urea is _____.

the primary nitrogenous waste product of humans

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

urea is less toxic than ammonia

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.

Select the correct statement about osmoregulation.

All osmoconformers are marine animals.

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.

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.

You just received a freshwater aquarium as a gift and decide to add more fish. When you get to the pet store, you find that the most beautiful fish are saltwater animals, but you decide to buy them anyway. What will happen when you put your expensive saltwater fish in your freshwater aquarium?

The cells of the fish will take up too much water, and the fish will die.

Select the correct statement describing the osmolarity of mammalian urine.

The osmolarity of mammalian urine may vary over time.

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.

Which of the following is a general property of epithelial cells?

They display an apical and a basal surface that define cell polarity.

What is the difference between a countercurrent multiplier system, such as the one involving the loop of Henle, and the countercurrent systems that maximize oxygen absorption by fish gills or reduce heat loss in endotherms?

Unlike the other countercurrent systems, a countercurrent multiplier system, such as the one involving the loop of Henle, expends energy in active transport.

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

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

a marine bony fish

In which of the following species should natural selection favor the highest proportion of juxtamedullary nephrons?

a mouse species living in a desert

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

a mouse species living in a desert

Aldosterone is _____.

a steroid hormone that reduces the amount of fluid excreted in the urine

Freshwater fish excrete nitrogenous wastes as _____.

ammonia

The structural component(s) of the mammalian nephron where the transcytosis of water increases due to the action of anti-diuretic hormone is/are the _____.

collecting duct

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

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

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.

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

Nitrogen is absent from

fatty acids

Which process in the nephron is LEAST selective?

filtration

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

In osmosis, water undergoes net diffusion to an area of lower

free water concentration.

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

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

increase, and the urine would be isoosmotic compared to plasma

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

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

kidneys of vertebrates

Urea is produced in the _____.

liver from NH3 and carbon dioxide

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

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

Terrestrial animals are _____.

osmoregulators that must obtain water from the environment.

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

Which of the following is the least likely substance to be found in the glomerular filtrate?

plasma proteins

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

proteins and nucleic acids

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

Unlike an earthworm's metanephridia, a mammalian nephron

receives filtrate from blood instead of coelomic fluid.

Birds, insects, and many reptiles excrete nitrogenous waste in the form of uric acid, which _____.

reduces water loss compared to other nitrogenous wastes, but requires more metabolic energy to produce

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

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

sweating-induced dehydration increases plasma osmolarity

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

the concentration gradient; ATP

An appropriate group of animals to examine to observe a Malpighian tubule would be _____.

the insects

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

the vasa recta

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

Which nitrogenous waste has the greatest number of nitrogen atoms?

uric acid

As a result of the non-selectivity of the kidney's filtration of small molecules, _____.

useful substances must be selectively reabsorbed