The force driving simple diffusion is ________, while the energy source for active transport is ________.
A) the concentration gradient; ADP
B) the concentration gradient; ATP
C) transmembrane pumps; electron transport
D) phosphorylated protein carriers; ATP
To maintain homeostasis, freshwater fish must ________.
A) excrete large quantities of electrolytes
B) consume large quantities of water
C) excrete large quantities of water
D) take in electrolytes through simple diffusion
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?
A) 0.0 mM sucrose
B) 0.05 mM saline
C) 0.08 mM sucrose
D) 1.0 mM saline
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?
A) High urea and trimethylamine oxide concentrations keep shark tissues slightly hyperosmotic relative to seawater, so water is absorbed passively.
B) Sodium, chloride, and potassium do not influence water balance in shark tissues.
C) Shark blood is hypotonic to the surrounding tissues, so water always moves passively into the tissue from the blood.
D) Sharks excrete large quantities of salt through their gills in exchange for water
What role do transport epithelia play in osmoregulation of marine fish with bony skeletons?
A) They actively transport salt into the animal through the gills.
B) They mediate the movement of water from seawater through the gills.
C) They are involved in excretion of excess salt.
D) They allow the fish to produce dilute urine.
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?
A) The rectal gland functions in the ocean water, and chloride cells function in fresh water.
B) The salt transport mechanisms of the gill epithelia change during migration.
C) Salmon in fresh water excrete concentrated urine, and salmon in salt water secrete dilute urine.
D) Their metabolism changes in salt water to degrade electrolytes.
Terrestrial organisms lose water through evaporation. In what ecosystem might an entomologist find a good study organism to examine the prevention of water loss?
A) wet rain forest
B) desert
C) prairie
D) chaparral
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 ________.
A) it was stressed and needed more time to acclimate to the new conditions
B) it was so hypertonic to the fresh water that it could not osmoregulate
C) its kidney had ruptured
D) its cells dehydrated and lost the ability to metabolize
The body fluids of an osmoconformer would be ________ with its ________ environment
A) hyperosmotic; freshwater
B) hyperosmotic; seawater
C) isoosmotic; seawater
D) hypoosmotic; seawater
Compared to the seawater around them, most marine invertebrates are ________.
A) hyperosmotic
B) hypoosmotic
C) isoosmotic
D) both hyperosmotic and isoosmotic
The fluid with the highest osmolarity is ________.
A) distilled water
B) blood in birds
C) blood in mammals
D) seawater in a tidal pool
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
An examination 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
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
A) only I and III
B) only II and III
C) only I and II
D) I, II, and III
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
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
Which nitrogenous waste has the greatest number of nitrogen atoms?
A) ammonia
B) ammonium ions
C) urea
D) uric acid
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
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
Developing bird embryos excrete most of their nitrogenous waste as uric acid because ________.
A) it is less metabolically expensive to produce compared to other waste products
B) it has a low solubility in water and is less toxic to the embryo than other forms of waste
C) it requires less energy to transport across the egg shell
D) it can be recycled by the embryo to make new protein
The advantage of excreting nitrogenous wastes as urea rather than as ammonia is that ________.
A) urea can be removed as a semi-solid paste
B) urea is less toxic than ammonia
C) urea does not affect the osmotic gradient
D) less nitrogen is removed from the body
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
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
Among the following choices, the most concentrated urine is excreted by ________.
A) frogs
B) kangaroo rats
C) humans
D) freshwater bass
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.
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?
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.
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?
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.
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.
The osmoregulatory/excretory system of a freshwater flatworm is based on the operation of ________.
A) protonephridia
B) metanephridia
C) Malpighian tubules
D) nephrons
Materials are returned to the blood from the filtrate by which of the following processes?
A) filtration
B) reabsorption
C) secretion
D) excretion
Excretory organs known as Malpighian tubules are present in ________.
A) flatworms
B) insects
C) jellyfish
D) sea stars
The osmoregulatory process called secretion refers to the ________.
A) reabsorption of nutrients from a filtrate
B) selective elimination of excess ions and toxins from body fluids
C) formation of an osmotic gradient along an excretory structure
D) expulsion of urine from the body
Which of the following is characteristic of juxtamedullary nephrons?
A) large Bowman's capsule
B) absence of proximal tubule
C) limited branching of vasa recta
D) long loop of Henle
Choose a pair that correctly associates the mechanism for osmoregulation or nitrogen removal with the appropriate animal.
A) protonephridium—earthworm
B) Malpighian tubule—frog
C) flame bulb—flat worm
D) exchange across the body surface—snake
An excretory system that is partly based on the filtration of fluid under high hydrostatic pressure is the ________.
A) flame-bulb system of flatworms
B) protonephridia of rotifers
C) Malpighian tubules of insects
D) kidneys of vertebrates
The transfer of fluid from the glomerulus to Bowman's capsule ________.
A) results from active transport
B) transfers large molecules as easily as small ones
C) is very selective as to which sub-protein-sized molecules are transferred
D) is mainly a consequence of blood pressure in the capillaries of the glomerulus
Within a normally functioning kidney, red blood cells can be found in ________.
A) the vasa recta
B) Bowman's capsule
C) the proximal tubule
D) the collecting duct
A primary reason that the kidneys have one of the highest metabolic rates of all body organs is that ________.
A) they have membranes of varying permeability to water
B) they operate an extensive set of active-transport ion pumps
C) they are the body's only means of shedding excess nutrients
D) they have an abundance of myogenic smooth muscle
Which process in the nephron is least selective?
C) active transport
D) secretion
The loop of Henle dips into the renal cortex. This is an important feature of osmoregulation in terrestrial vertebrates because ________.
A) absorptive processes taking place in the loop of Henle are hormonally regulated
B) differential permeabilities of ascending and descending limbs of the loop of Henle are important in establishing an osmotic gradient
C) the loop of Henle plays an important role in detoxification
D) additional filtration takes place along the loop of Henle
Low selectivity of solute movement is a characteristic of ________.
A) H+ pumping to control pH
B) reabsorption mechanisms along the proximal tubule
C) filtration from the glomerular capillaries
D) secretion along the distal tubule
If ATP production in a human kidney was suddenly halted, urine production would ________.
A) decrease, and the urine would be hypoosmotic compared to plasma
B) increase, and the urine would be isoosmotic compared to plasma
C) increase, and the urine would be hyperosmotic compared to plasma
D) decrease, 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 ________.
A) juxtamedullary nephrons
B) urinary bladders
C) ureters
D) podocytes
Processing of filtrate in the proximal and distal tubules ________.
A) achieves the conversion of toxic ammonia to less toxic urea
B) maintains homeostasis of pH in body fluids
C) regulates the speed of blood flow through the nephrons
D) reabsorbs urea to maintain osmotic balance
In humans, the transport epithelial cells in the ascending loop of Henle ________.
A) are the largest epithelial cells in the body
B) are not in contact with interstitial fluid
C) have plasma membranes of low permeability to water
D) are not affected by high levels of nitrogenous wastes
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
A) All of these conditions contribute to the osmolarity of the medulla.
B) I, II, and III
C) I and IV
D) I, II, and IV
Natural selection should favor the highest proportion of juxtamedullary nephrons in which of the following species?
A) a river otter
B) a mouse species living in a tropical rain forest
C) a mouse species living in a temperate broadleaf forest
D) a mouse species living in a desert
If you are hiking through the desert for several days, one would pack which of the following to ensure proper hydration?
A) a drink with a combination of water and electrolytes
B) caffeinated beverages
C) bottled water kept at room temperature
D) bottled water that had been frozen to ensure that it would be as cold as possible
Increased antidiuretic hormone (ADH) secretion is likely after ________.
A) drinking lots of pure water
B) sweating-induced dehydration increases plasma osmolarity
C) eating a small sugary snack
D) blood pressure becomes abnormally high
After blood flow is artificially reduced at one kidney, you would expect that kidney to secrete more of the hormone known as ________.
A) angiotensinogen
B) renin
C) antidiuretic hormone
D) atrial natriuretic peptide
After drinking alcoholic beverages, increased urine excretion is the result of ________.
A) increased aldosterone production
B) increased blood pressure
C) inhibited secretion of antidiuretic hormone (ADH)
D) increased reabsorption of water in the proximal tubule
Osmoregulatory adjustment via the atrial natriuretic peptide system can be triggered by ________.
A) sleeping for one hour
B) severe sweating on a hot day
C) eating a pizza with olives and pepperoni
D) drinking several glasses of water
Antidiuretic hormone (ADH) and the renin-angiotensin-aldosterone system (RAAS) work together in maintaining osmoregulatory homeostasis through which of the following ways?
A) 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.
B) ADH and the RAAS work antagonistically; ADH stimulates water reabsorption during dehydration, and the RAAS causes increased excretion of water when it is in excess in body fluids.
C) Both stimulate the adrenal gland to secrete aldosterone, which increases both blood volume and pressure via its receptors in the urinary bladder.
D) ADH and the RAAS combine at the receptor sites of proximal tubule cells, where reabsorption of essential nutrients takes place.
A human who has no access to fresh water but is forced to drink seawater instead will ________.
A) produce excessive antidiuretic hormone to remove more water but hold back salts
B) passively excrete excess water in order to remove the high concentration of ingested salt
C) release atrial natriuretic peptide to decrease blood pressure
D) risk becoming overhydrated within twelve hours
Unlike an earthworm's metanephridia, a mammalian nephron
A) is intimately associated with a capillary network.
B) functions in both osmoregulation and excretion.
C) receives filtrate from blood instead of coelomic fluid.
D) has a transport epithelium.
Which of the following animals generally has the lowest volume of urine production?
A) vampire bat
B) salmon in fresh water
C) marine bony fish
D) freshwater flatworm
The high osmolarity of the renal medulla is maintained by all of the following except
A) active transport of salt from the upper region of the ascending limb.
B) the spatial arrangement of juxtamedullary nephrons.
C) diffusion of urea from the collecting duct.
D) diffusion of salt from the descending limb of the loop of Henle.
In which of the following species should natural selection favor the highest proportion of juxtamedullary nephrons?
B) a mouse species living in a temperate broadleaf forest
C) a mouse species living in a desert
D) a beaver
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?
B) Small stagnant pools do not provide enough water to dilute ammonia, which is toxic.
C) Urea forms an insoluble precipitate.
