For a printable version of the Post-Test, click here.

What did you learn? Select the best response to the questions below.

1. Fish remove dissolved oxygen from water by using their .

A. lungs
B. scales
C. gills
D. fins
E. tails

2. Oxygen is dissolved in water:

A. forming small bubbles.
B. bound to hydrogen to form water itself.
C. bound to carbon in the form of carbon dioxide.
D. as molecules associated with water molecules.
E. only in very warm areas.

3. The amount of dissolved oxygen in water will increase by adding ____________.

A. plants
B. heat
C. fish
D. bacteria
E. dams

4. The maximum percentage of oxygen in water at 4ºC and 1 atom of pressure is ___________.

A. 21%
B. 5%
C. 1%
D. 0.5%
E. 0.001%

5. When do aquatic plants contribute the most dissolved oxygen to water?

A. during the night
B. during the day
C. during periods when plants die
D. production of oxygen by plants is uniform
E. plants do not produce oxygen, they consume oxygen

6. If a pond has an unstable level of dissolved oxygen, the best method of correction would be .

A. to add fertilizer to the pond.
B. to add algae to the pond.
C. to add fish to the pond.
D. to pump air into the pond.
E. to expose the pond to direct sunlight.


7. One liter of water weighs .

A. one pound
B. one kilogram
C. one ounce
D. one milligram
E. one pint

8. You are standing on the banks of a large lake where dozens of different kinds of fish are floating dead on the surface. Which of the following things is most likely to have occurred?

A. Bacteria in the water infected the fish causing them to die.
B. Nitrates in the water poisoned the fish.
C. The dissolved oxygen levels dropped below 2 mg/L and the fish suffocated.
D. The fish ate algae and died from toxins produced by the algae.
E. The temperature of the lake was too low for reproduction, so the fish could not breed and died of advanced age.

9. When water is rapidly moving, like in white water rapids, the turbulence the surface area and the amount of oxygen dissolved in the water.

A. decreases; decreases
B. does not effect; increases
C. increases; increases
D. decreases; does not effect
E. decreases; increases

10. In general, which of the following best describes the effects that dams have on dissolved oxygen and water quality?

A. Dams increase dissolved oxygen by slowing the flow of rivers and warming the water.
B. Dams have little or no impact on dissolved oxygen in water.
C. Dams decrease dissolved oxygen by decreasing aeration and slowing flow.
D. Dams have devastating effects on the aquatic life behind the dams.
E. Dams are beneficial to the aquatic life behind them.

11. Addition of fertilizer to rivers and streams often results in:

A. an increase in the amount of dissolved oxygen in the water.
B. an overgrowth of aquatic plants and algae.
C. an overgrowth of fish and other aquatic organisms.
D. a complete depletion of oxygen due to binding of oxygen by fertilizer.
E. an increase in mutations in fish.

12. You are serving as a research scientist with the Environmental Protection Agency. You are monitoring the health of rivers in an area by examining the amount of oxygen dissolved in the water. In an effort to work with the local industries, you ask companies along these rivers to collect samples and determine the amount of oxygen dissolved in the samples. You receive the following results.

River
Company
Dissolved oxygen
Apple River Apple Sewage Treatment Plant 6 mg/dL
Big River Big River Golf Course 9 mg/dL
Chattanooga River Chattanooga Dam and Electric Plant 14 mg/dL
Durham River Durham Fertilizer Plant 10 mg/dL
East River East River Sawmill 4 mg/dL

You note one value that causes you some alarm, and you immediately alert your boss and tell her that you suspect one company is causing problems. Who do you suspect and why?

A. Apple Sewage Treatment; the levels of dissolved oxygen are too low considering the sewage that is probably getting in the water.
B. Big River Golf Course; the levels of dissolved oxygen are too high for the amount fertilizer that is probably entering the water.
C. Chattanooga Dam and Electric Plant; the levels of dissolved oxygen are impossible to obtain under normal circumstances.
D. Durham Fertilizer Plant; the levels of dissolved oxygen are too high for the amount of waste that is probably entering the water.
E. East River Sawmill; the levels of dissolved oxygen are impossible to obtain under normal circumstances.

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