Notes

4) Compared to the seawater around them, most marine invertebrates are
A) hyperosmotic.
B) hypoosmotic.
C) isoosmotic.
D) hyperosmotic and isoosmotic.
E) hypoosmotic and isoosmotic.

Answer: C

8) A human who has no access to fresh water but is forced to drink seawater instead
A) will thrive under such conditions, as long as he has lived at the ocean most of his life.
B) will excrete more water molecules than taken in, because of the high load of ion ingestion.
C) will develop structural changes in the kidneys to accommodate the salt overload.
D) will find that drinking saltwater satiates his thirst.
E) will risk becoming overhydrated within 12 hours.

Answer: B

10) 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 balance internal salt concentrations to seawater osmolarity.
D) synthesizing trimethylamine oxide, a chemical that binds and precipitates salts inside cells.
E) possessing a special adaptation that allows their cells to operate at an extraordinarily high salt concentration.

c

X22) Which nitrogenous waste requires hardly any water for its excretion?
A) amino acids
B) urea
C) uric acid
D) ammonia
E) nitrogen gas

C

X25) Among the following choices, the most concentrated urine is excreted by
A) frogs.
B) kangaroo rats.
C) humans.
D) desert tortoises.
E) birds.

B

X29) The osmoregulatory/excretory system of a freshwater flatworm is based on the operation of
A) protonephridia.
B) metanephridia.
C) Malpighian tubules.
D) nephrons.
E) ananephredia.

A

X5) The lymphatic fluid
A) is a filtrate of the blood, as is urine.
B) is completely separate from the circulatory system for blood.
C) carries both red and white blood cells.
D) functions in adaptive immunity but not in innate immunity.
E) carries a toxic gas that kills cancerous cells.

A

2) In a positive-feedback system where hormone A alters the amount of protein X
A) an increase in A always produces an increase in X.
B) an increase in X always produces a decrease in A.
C) a decrease in A always produces an increase in X.
D) a decrease in X always causes a decrease in A.
E) it is impossible to predict how A and X affect each other.

A

10) The reason that the steroid hormone aldosterone affects only a small number of cells in the body is that
A) only its target cells get exposed to aldosterone.
B) only its target cells contain aldosterone receptors.
C) it is unable to enter nontarget cells.
D) nontarget cells destroy aldosterone before it can produce any effect.
E) nontarget cells convert aldosterone to a hormone to which they do respond.

B