Question 1

Which of the following best describes the direction of water movement by osmosis between two solutions separated by a selectively permeable membrane?

Accepted Answer

Water moves from the hypoosmotic solution to the hyperosmotic solution.

Question 2

A marine bony fish constantly loses water to its environment by osmosis. Which adaptation helps it maintain osmotic balance?

Accepted Answer

It drinks large amounts of seawater and excretes excess salts through its gills.

Question 3

Which of the following statements about osmoconformers is correct?

Accepted Answer

Osmoconformers are isoosmotic with their environment and do not experience net water gain or loss.

Question 4

Why do freshwater animals typically produce large amounts of dilute urine?

Accepted Answer

They gain water by osmosis and must excrete the excess to maintain osmotic balance.

Question 5

Which adaptation allows tardigrades to survive extreme dehydration?

Accepted Answer

Entry into a dormant state called anhydrobiosis and accumulation of trehalose.

Question 6

A sandy inland mouse can survive indefinitely on a diet of dried seeds without drinking water. Which physiological adaptation most likely contributes to this ability?

Accepted Answer

Production of highly concentrated urine and metabolic water from cellular respiration.

Question 7

Refer to the table of mean osmolarity and urea concentration in mice. What is the ratio of urine osmolarity to blood osmolarity for mice with unlimited access to water?

Accepted Answer

$$\frac{490}{350} = 1.4$$

Question 8

Which of the following best explains why the movement of salt from the surrounding water to the blood of a freshwater fish requires energy?

Accepted Answer

Salt moves against its concentration gradient, requiring active transport and ATP.

Question 9

Why aren’t any freshwater animals osmoconformers?

Accepted Answer

Freshwater animals would lose too much water by osmosis if they were isoosmotic with their environment.

Question 10

Marine birds can drink seawater and excrete excess salt through their nasal salt glands. What is the primary function of the transport epithelia in these glands?

Accepted Answer

To actively transport salt ions out of the blood, producing a concentrated salt solution.

Question 11

Which of the following would increase the energy cost of osmoregulation for an animal?

Accepted Answer

Living in an environment with a large osmotic gradient compared to body fluids.

Question 12

Which of the following is a real-world consequence for humans who drink seawater?

Accepted Answer

They must use more water to excrete the salt than they gain, leading to dehydration.

Question 13

Which of the following best describes the role of transport epithelia in osmoregulation?

Accepted Answer

They are specialized for moving specific solutes in controlled amounts and directions.

Question 14

A salmon migrates from freshwater to seawater. Which physiological change is most likely to occur?

Accepted Answer

It increases production of cortisol, which enhances salt secretion from gills.

Question 15

Which of the following is an example of a euryhaline osmoregulator?

Accepted Answer

A striped bass that can survive in both fresh and salt water.

Question 16

Which of the following adaptations helps terrestrial animals reduce water loss?

Accepted Answer

Development of waxy body coverings or keratinized skin.

Question 17

If a camel’s fur is shaved off and its body temperature remains the same, but its water requirement increases, what can you conclude?

Accepted Answer

Fur acts as insulation, reducing water loss by minimizing evaporative cooling.

Question 18

Which of the following best explains why the energy cost of osmoregulation is minimized when an animal’s body fluids are adapted to the salinity of its habitat?

Accepted Answer

The osmotic gradient between body fluids and the environment is reduced, requiring less active transport.

Osmoregulation: Balancing Water and Solutes in Animals

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