Test Bank Docx Biogeochemical Cycles Chapter.18

Chapter 18 Biogeochemical Cycles

Multiple Choice

1. In the systems approach to biogeochemical cycles,
2. nutrients are found in sinks.
3. fluxes are the pathways of net gain or loss of nutrients.
4. the cycle must be in equilibrium.
5. the boundaries of the ecosystem are not defined.
6. none of the above
7. In the carbon cycle,
8. photosynthesis always balances respiration.
9. CO₂ enters the ocean primarily by photosynthesis.
10. CO₂ in the ocean forms a weak acid.
11. carbon enters the food chain in the form of CO₃^-2.
12. none of the above
13. Nitrogen fixation
14. is the product of respiration and photosynthesis.
15. can be accomplished by most plants.
16. requires energy to break the triple bond in N₂.
17. occurs when nitrate is converted to nitrite.
18. none of the above
19. Mutualistic bacteria in legumes
20. include the cyanobacteria.
21. provide fixed nitrogen in exchange for carbon.
22. provide carbon in exchange for fixed nitrogen.
23. release nitrogen to the atmosphere.
24. none of the above
25. Eutrophication occurs when
26. trophic levels change.
27. nitrogen is no longer limiting.
28. algal blooms die off.
29. nitrogen fixation releases N₂.
30. none of the above
31. The phosphorus cycle differs from the nitrogen cycle in that
32. the phosphorus cycle has a short residence time.
33. there is no limiting step in the phosphorus cycle.
34. there is a large sedimentary pool of nitrogen.
35. there is a large sedimentary pool of phosphorus.
36. none of the above.
37. The carbon cycle differs from the nitrogen cycle in that
38. there is a large atmospheric pool of carbon.
39. the residence time of carbon is longer.
40. the nitrogen cycle requires specialized organisms.
41. the carbon cycle is in equilibrium.
42. none of the above
43. The increase in oxygen in the atmosphere
44. led to the replacement of eukaryotes by prokaryotes.
45. is associated with changes in the size and diversity of organisms.
46. required new forms of electron donors.
47. was due to the increase in respiration during the Devonian.
48. none of the above
49. Which of the following is not a source of inorganic nutrients in ecosystems?
50. aerosols
51. alluvial deposition
52. weathering
53. loess
54. none of the above
55. Which of the following is not a mechanism of nutrient input to soil?
56. mineralization
57. decomposition
58. photosynthesis
59. humification
60. none of the above
61. Human agriculture is threatened by
62. humus in the A horizon.
63. excess phosphorus and nitrogen in soil.
64. loss of the A horizon.
65. increases in mycorrhizal fungi.
66. none of the above
67. In a nutrient spiral,
68. nutrients are transported downstream.
69. nutrients are transported to deeper waters.
70. salmon move nutrients to terrestrial systems.
71. nutrient cycles occur in discrete segments of the stream.
72. none of the above
73. The two main limiting processes in nutrient cycles are
74. decomposition and nutrient spiraling.
75. decomposition and input of inorganic nutrients.
76. photosynthesis and respiration.
77. deposition of loess and nitrogen fixation.
78. none of the above
79. Studies of nutrient cycles at Hubbard Brook show that
80. nitrogen is continually lost from undisturbed forest.
81. nutrient cycles resist disturbance.
82. disturbance increases stream flow and nutrient loss.
83. disturbance increases the rate of nitrogen cycling.
84. none of the above
85. When organic phosphorus is added to streams
86. the nutrient spiral removes most of it.
87. it is converted into an inorganic form.
88. retention of phosphorus depends on the age of the surrounding forest.
89. retention of phosphorus requires a disturbance.
90. none of the above
91. During the Cambrian explosion,
92. photosynthesis evolved.
93. all organisms were heterotrophs.
94. the atmosphere was anoxic.
95. many novel organisms appeared.
96. none of the above
97. At the Hubbard Brook Experimental Forest stream nitrogen has decreased because of
98. decreased atmospheric nitrogen.
99. disturbance of the vegetation by a hurricane.
100. increased microbial denitrification.
101. increased immobilization of nitrogen in soil.
102. none of the above

True/False

1. The phosphorus cycle is driven by the fundamental processes of photosynthesis and respiration.
2. Photosynthetic plants are not usually limited by CO₂.
3. The variance in the pools and fluxes of the carbon cycle is very small.
4. The movement of nutrients in ecosystems is linear.
5. Nutrient fluxes occur by physical and biological processes.
6. N₂ cannot be absorbed by plants.
7. Algal blooms are indicators of healthy nutrient cycles.
8. Glacial till is a significant threat to agriculture.
9. Humus consists of the stable breakdown products of carbohydrates, lipids, and proteins.
10. Phosphorus has a short residence time in parent material.

Short Answer/Fill in the Blank

1. What is the effect of spatial scale on nutrient budgets?
2. Why is nitrogen fixation the limiting step in the nitrogen cycle?
3. What are the key similarities and differences between the nitrogen and carbon cycles?
4. Why was it important that eukaryotes use oxygen as a final electron receptor in respiration?
5. Why are leaf cutter ants important to the function of tropical rain forests?
6. What factors affect the length of nutrient spirals?