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The main cause of the increase in the amount of CO 2 in Earthʹs atmosphere over the past 150 years is
- A. increased worldwide primary production.
- B. increased worldwide standing crop.
- C. an increase in the amount of infrared radiation absorbed by the atmosphere.
- D. the burning of larger amounts of wood and fossil fuels.
- Correct Answer: Option D
Which of the following is a consequence of biological magnification?
- A. Toxic chemicals in the environment pose greater risk to top-level predators than to primary consumers.
- B. Populations of top-level predators are generally smaller than populations of primary consumers.
- C. The biomass of producers in an ecosystem is generally higher than the biomass of primary consumers.
- D. Only a small portion of the energy captured by producers is transferred to consumers
- Correct Answer: Option A
The Hubbard Brook watershed deforestation experiment yielded all of the following results except that
- A. the flow of minerals out of a natural watershed was offset by minerals flowing in.
- B. deforestation increased water runoff.
- C. the nitrate concentration in waters draining the deforested area became dangerously high.
- D. calcium levels remained high in the soil of deforested areas.
- Correct Answer: Option D
Which of the following has the greatest effect on the rate of chemical cycling in an ecosystem?
- A. the ecosystemʹs rate of primary production
- B. the production efficiency of the ecosystemʹs consumers
- C. the rate of decomposition in the ecosystem
- D. the trophic efficiency of the ecosystem
- Correct Answer: Option C
Nitrifying bacteria participate in the nitrogen cycle mainly by
- A. converting nitrogen gas to ammonia.
- B. releasing ammonium from organic compounds, thus returning it to the soil.
- C. converting ammonia to nitrogen gas, which returns to the atmosphere.
- D. converting ammonium to nitrate, which plants absorb.
- Correct Answer: Option D
Which of these ecosystems has the lowest net primary production per square meter?
- A. a salt marsh
- B. an open ocean
- C. a coral reef
- D. a grassland
- Correct Answer: Option B
Which of the following organisms is incorrectly paired with its trophic level?
- A. cyanobacterium--primary producer
- B. grasshopper--primary consumer
- C. zooplankton--primary producer
- D. eagle--tertiary consumer
- Correct Answer: Option C
Why are ecologists concerned about the shift in date from May 28 in 1980 to May 15 in 2000 of the caterpillar peak mass?
- A. The caterpillars will eat much of the foliage of the trees where flycatchers nest, and their nests will be more open to predation.
- B. The earlier hatching of caterpillars will compete with other insect larval forms on which the flycatchers also feed their young.
- C. The flycatcher nestlings in 2000 will miss the peak mass of caterpillars and may not be as well fed.
- D. The flycatchers will have to migrate sooner to match their brood-rearing season with the time of caterpillar peak mass.
- Correct Answer: Option C
The most likely cause for the shift in caterpillar peak mass is
- A. pesticide use.
- B. earlier migration returns of flycatchers.
- C. an innate change of biological clock by caterpillars.
- D. global warming.
- Correct Answer: Option D
Which of the following statements best describes why biologists are currently concerned with global warming and the thawing of permafrost in many areas of the tundra biome?
- A. The thawing process will likely decrease the abundance and diversity of soil-dwelling organisms in tundra habitats.
- B. The bacterial decomposition of the thawed organic materials on the widespread areas of the tundra will produce large quantities of CO2, which will add to greenhouse gases and exacerbate global warming.
- C. Oil and coal deposits will thaw and rise to the surface (because of their lower density) of the tundra, destroying millions of acres of arctic habitat.
- D. Populations of humans inhabiting the arctic will have to move to more southern latitudes, resulting in increased competition for resources in already densely populated areas.
- Correct Answer: Option B