Match each of the following components of blood (on the left) with what happens to it as the blood is processed by the kidney (on the right). Note that each lettered choice may be used more than once.


8. Water
9. Glucose
10. Plasma protein
11. Toxins or drugs
12. Red blood cell
13. Urea


a. passes into filtrate; almost all excreted in urine
b. remains in blood
c. passes into filtrate; mostly reabsorbed
d. secreted and excreted

Birds and insects excrete uric acid, whereas mammals and most amphibians excrete mainly urea. What is the chief advantage of uric acid over urea as a waste product?

a. Uric acid is a much simpler molecule.

b. It takes less energy to make uric acid.

c. Less water is required to excrete uric acid.

d. More solutes are removed excreting uric acid.

The chloride cells of fish gills have a high density of mitochondria. How does this characteristic relate to the functional role of chloride cells?

Would you expect other epithelial cells involved in ion transport to contain large numbers of mitochondria? Explain.

A freshwater fish would be expected to

a. Pump salt out through its gills.

b. Produce copious quantities of dilute urine.

c. Have scales and a covering of mucus that reduce water loss to the environment.

d. Do all of the above.

Explain why mammals would not be able to produce concentrated urine if their nephrons lacked loops of Henle.

Scientists have noted that marine invertebrates tend to be osmoconformers, while freshwater invertebrates tend to be osmoregulators. Suggest an explanation for this phenomenon.

Biologists have been able to produce mice that lack functioning genes for aquaporins. How would the urine of these mice compare to that of mice with normal aquaporins?

a. Lower volume and lower osmolarity

b. Lower volume and higher osmolarity

c. Higher volume and lower osmolarity

d. Higher volume and higher osmolarity

To test the hypothesis that mussels are osmoconformers, researchers exposed mussels to water of varying osmolarities and then drew hemolymph samples from the mussels. Graph the data provided here. Put the independent variable on the x-axis and the dependent variable on the y-axis.

Is the researchers' hypothesis supported by the data? Explain.

Fish and other aquatic organisms are exposed to many types of water pollutants, including metals such as aluminum. Although a low level of aluminum is found in unpolluted water, many lakes and streams have an increased level because of mining, sewage treatment, and accidental spills of toxic materials. Aluminum pollution can result in mass fish die-offs such as the one pictured here. How does this occur? Which of the following is an osmoregulatory challenge that freshwater fishes need to overcome?

a. Diffusion of sodium ions out of the body

b. Diffusion of water out of the body

c. Active transport of sodium ions out of the body

d. Active transport of water out of the body