Chapter 19
1. Phosphorus is an important constituent of
a) DNA.
b) bone tissue.
c) RNA.
d) ATP.
e) all of the above
Answer: E
2. The largest reservoir of phosphorus in most ecosystems is phosphorus
a) in the atmosphere.
b) dissolved in water.
c) in rocks and sediments.
d) bound in animal tissues.
e) bound in plant tissues.
Answer: C
3. The major pool of nitrogen in the atmosphere is the direct source of nitrogen for most
organisms.
Answer: F
4. “Nitrogen fixation” refers to the conversion of
a) carbon compounds to nitrogen compounds.
b) nitrogen gas (N2) to ammonia (NH2).
c) ammonia (NH3) to nitrogen gas (N2).
d) ammonium (NH4+) to nitrate (NO3-).
e) ammonium (NH4+) to nitrite (NO2-).
Answer: B
5. Which of the following is NOT an agent of nitrogen fixation?
a) mycorrhizal fungi
b) cyanobacteria (blue-green algae)
c) bacteria associated with legume roots
d) lightning
e) actinomycete bacteria associated with alder roots
Answer: A
6. “Nitrification” is the conversion of
a) carbon compounds to nitrogen compounds.
b) nitrogen gas (N2) to ammonia (NH2).
c) ammonia (NH3) to nitrogen gas (N2).
d) ammonium (NH4+) to nitrate (NO3-).
e) ammonium (NH4+) to nitrite (NO2-).
Answer: D
7. The “denitrification” reaction converts nitrate (NO3-) to nitrogen gas (N2) under
aerobic conditions.
Answer: F
8. The release of ammonium (NH4+) from decaying organic material is called
____________.
Answer: ammonification
9. A major perturbation of the carbon cycle by human activity is associated with
a) release of carbon from carbonate rocks.
b) release of carbon from fossil fuel deposits.
c) removal of carbon from the atmosphere in the industrial production of fertilizers.
d) accelerated removal of carbon from the atmosphere by forests.
e) respiratory production of CO2 by the large human population.
Answer: B
10. The release of nutrients from organic material in inorganic form is called
_____________.
Answer: mineralization
11. The rate of decomposition of leaf litter in woodlands can be strongly influenced by
a) moisture.
b) nitrogen content.
c) leaf toughness.
d) all of the above
e) none of the above
Answer: D
12. High soil nutrient content usually leads to slower decomposition, because soil
organisms have less need for nutrients of organic origin.
Answer: F
13. In aquatic ecosystems, leaves with high lignin content decompose
a) rapidly because lignin is a nutrient-rich compound.
b) rapidly because lignin enhances colonization by decomposing fungi.
c) slowly because lignin reduces colonization by decomposing fungi.
d) slowly because lignin is a carbon-poor compound.
e) slowly because lignin-containing leaves sink rapidly.
Answer: C
14. In aquatic ecosystems, the major agents of decomposition are
a) aquatic fungi.
b) bacteria.
c) algae.
d) detritivorous fish.
e) piscivorous fish.
Answer: A
15. Which of the following is NOT an assumption of the t-test?
a) Each sample is drawn from a population with a normal distribution.
b) The two populations being compared have equal variances.
c) The two populations being compared have equal means.
d) All of each sample is drawn from a population with a normal distribution, the two
populations being compared have equal variances, and the two populations being
compared have equal means are assumptions.
e) None of each sample is drawn from a population with a normal distribution, the two
populations being compared have equal variances, or the two populations being
compared have equal means are assumptions.
Answer: C
16. The combination of nutrient cycling and downstream movement of nutrients in
streams is called ____________.
Answer: nutrient spiralling
17. Spiralling length of nutrients in streams can be calculated as S = VT. In this
equation,
a) V represents nutrient concentration, and T represents water temperature.
b) V represents the speed of water flow, and T represents water temperature.
c) V represents the speed of water flow, and T represents the time required for nutrients
to cycle.
d) V represents nutrient retentiveness, and T represents the time required for nutrients to
cycle.
e) V represents nutrient retentiveness, and T represents species diversity.
Answer: C
18. Streams with higher densities of stream invertebrates would be expected to have
shorter spiralling lengths.
Answer: T
19. In stream ecosystems, rates of leaf breakdown
a) increase with shredder species diversity.
b) decrease with shredder species diversity.
c) peak at intermediate shredder diversity.
d) are lowest at intermediate shredder species diversity.
e) are unrelated to shredder species diversity.
Answer: A
20. Pocket gophers change the nitrogen cycle in prairies because they
a) bring nitrogen-rich subsoil to the surface.
b) bring nitrogen-poor subsoil to the surface.
c) bury nitrogen-rich organic material in their burrows.
d) cultivate nitrogen-fixing bacteria in burrow chambers.
e) selectively remove nitrogen-fixing legumes from plant communities.
Answer: B
21. Invasive Acacia species in the South African fynbos were introduced
a) accidentally in contaminated agricultural seed.
b) accidentally in ships ballast.
c) deliberately to provide cattle forage.
d) deliberately to stabilize sand dunes.
e) deliberately by ecosaboteurs.
Answer: D
22. Effects of introduced Acacia in the South African fynbos include
a) reduced rates of decomposition.
b) reduced rates of plant litter production.
c) increased soil nitrogen content.
d) increasing soil erosion.
e) all of the above
Answer: C
23. Clearcutting at Hubbard Brook Experimental Forest sharply
a) increased export of nitrate (NO3-) in stream water.
b) decreased export of nitrate (NO3-) in stream water.
c) increased rates of denitrification in soils.
d) decreased deposition of ammonia (NH3) from the atmosphere.
e) increased deposition of ammonia (NH3) from the atmosphere.
Answer: A
24. In Judy Meyer and Gene Likens’ study of phosphorus in Bear Brook,
a) most phosphorus inputs occurred during spring snowmelt.
b) phosphorus inputs were nearly constant over the year.
c) most phosphorus losses occurred during autumn leaf fall.
d) most phosphorus losses occurred during storms and snowmelt.
e) phosphorus losses were nearly constant over the year.
Answer: D
25. Nitrogen enrichment of ecosystems by human activity is largely driven by
a) addition of nitrogen fertilizers.
b) nitrogen pollution from burning of fossil fuels.
c) nitrogen fixation by bacteria in landfills.
d) Both addition of nitrogen fertilizers and nitrogen pollution from burning of fossil fuels.
e) Both addition of nitrogen fertilizers and nitrogen fixation by bacteria in landfills.
Answer: D