Unit 8 Practice Question

Significant increases in water temperature can drastically change dissolved oxygen (DO) levels in a lake. Why does the combined effect of these two environmental changes result in an algal bloom?

A Low dissolved oxygen leads to death for aerobic organisms, like fish, whose decomposition provides an overabundance of nutrients for the algae, resulting in the large blooms.

The graph below depicts the dose response curves for 3 common bacteria and a newly discovered bacterium found in streams near certain AG properties A individual is exposed to water which of the following bacteria would have the lowest probability of causing illness if ingested?

A. C. jejuni

alligators in a Florida lake polluted by high levels of dioxins had low testosterone levels and failed to reproduce. scientists came to the conclusion that the dioxins were acting as

A. Endocrine disruptors

Chemical compound that can cause algal blooms and cultural eutrophication in streams

A. Nitrates (NO3-)

A sanitary landfill with a surface area of 6000m2 receives a yearly rainfall amount of 300 mm. About 20% of the precipitation is runoff and does not infiltrate the surface. A leachate collection system, which is installed underneath the landfill, is 90% effective at collecting and treating any water that infiltrates the surface of the landfill.

B. 1,296 m3

Which of the following best describes the action of the endocrine disruptor?

B. An endocrine disruptor blocks the receptor protein binding site of a hormone so that the cell cannot receive a signal.

Which of the following is the most likely route for mercury to enter the food web.?

B. Coal-burning emissions-> deposition->ocean->plankton and vegetation

Which of the following is the best description of bioaccumulation?

B. The absorption of a substance by an organism at a rate greater than the rate of elimination.

A massive bluegill fish kill was observed in a lake near a power plant during the winter months. It was determined that the plant was releasing large amounts of hot water into the lake. Which of the following explains what likely caused the death of so many bluegill in the lake?

B. The influx of warmer water caused an unexpected increase in the metabolic rate of the bluegills, which led to increased physiological stress from limited resource availability.

Based on the LD50 values, which of the following best describes the toxicity level of the household substances shown in the table?

C. Antifreeze is more toxic than aspirin.

The graph above shows the effect of sewage on biological oxygen demand (BOD) and dissolved oxygen (DO) in a flowing stream. The smallest fish populations will most likely be found at point?

C. C

The dangers of disposing of toxic chemicals underground came to public attention in which of the following locations?

C. Love Canal, NY

Although the use of DDT was banned in the US in 1972, a test of the body tissue of an average US resident today would most likely reveal the presence of DDT because...

C. Other countries that export produce to the US still use DDT

The LD50 for arsenic in humans in 13 mg/kg. Which of the following approaches should be used to calculate the number of grams of arsenic it would take to reach the LD50 in a 140 lb person?

D. 13mg/1kg X 1kg/2.2lb X140lb/1

The risk that many cancer-causing chemicals pose to humans can be estimated using laboratory tests on rats. A significant scientific limitation of such tests is that...

D. Animal models may not reflect human responses