Elements of Ecology, 8e (Smith/Smith) Test Bank Chapter 23

Elements of Ecology, 8e (Smith/Smith) Chapter 23 Biogeochemical Cycles 23.1 Short Answer Questions 1) The two basic types of biogeochemical cycles are gaseous and ________. Answer: sedimentary Topic: Section 23.1 2) Precipitation brings appreciable quantities of nutrients into ecosystems that are collectively called ________. Answer: wetfall Topic: Section 23.2 3) Large quantities of nutrients are bound tightly in ________ structure; they are not readily available until released by the activities of decomposers. Answer: organic matter Topic: Section 23.3 4) Some nutrients are ________ from the soil and carried out of ecosystems by underground water flow to streams. Answer: leached Topic: Section 23.3 5) The element ________ is a basic constituent of all organic compounds and is involved in the fixation of energy by photosynthesis. Answer: carbon Topic: Section 23.5 6) The difference between the rate of carbon uptake in photosynthesis and the rate of carbon loss due to autotrophic and heterotrophic respiration is the net ________ productivity. Answer: ecosystem Topic: Section 23.5 7) The ability of the surface waters of the ocean to take up carbon dioxide is governed by the reaction of carbon dioxide with the ________ ion to form bicarbonates. Answer: carbonate Topic: Section 23.7 8) Nitrogen is generally available to plants in only two forms: ammonium and ________. Answer: nitrate Topic: Section 23.8 9) Biological nitrogen fixation is accomplished by symbiotic ________ living in mutualistic association with plants. Answer: bacteria Topic: Section 23.8 1 Copyright © 2012 Pearson Education, Inc.

10) Nitrogen can be returned to the atmosphere when certain bacteria convert it from nitrate into nitrogen gas, which is a process called ________. Answer: denitrification Topic: Section 23.8 11) Microbial decomposition of organic matter results in NH4+ production through a process called ________. Answer: ammonification Topic: Section 23.8 12) ________ is the most common form of nitrogen exported from terrestrial ecosystems in stream water. Answer: Nitrate Topic: Section 23.8 13) Nearly all of the phosphorus in terrestrial ecosystems comes from the ________ of calcium phosphate minerals. Answer: weathering Topic: Section 23.9 14) In aquatic ecosystems, the phosphorous cycle moves through three states: particulate organic phosphorous, dissolved organic phosphates, and ________ phosphates. Answer: inorganic Topic: Section 23.9 15) The major source of free oxygen that supports life on Earth is the ________. Answer: atmosphere Topic: Section 23.12 16) The main reservoirs of oxygen are water and ________. Answer: carbon dioxide Topic: Section 23.12 17) The branch of chemistry dealing with the quantitative relationships of elements in combination is called ________. Answer: stoichiometry Topic: Section 23.13

2 Copyright © 2012 Pearson Education, Inc.

23.2 Multiple-Choice Questions 1) In ecosystems, internal cycling is dominated by A) global nutrient turnover. B) wet and dry deposition. C) decomposition and biological uptake. D) photosynthesis and weathering. Answer: C Topic: Introduction to Chapter 23 2) In ________ biogeochemical cycles, the main reservoirs of nutrients are the atmosphere and the oceans. A) sedimentary B) gaseous C) aquatic D) terrestrial Answer: B Topic: Section 23.1 3) Nutrients deposited on leaves as dust and materials leached from leaves through insect action are most often transported to the forest floor by A) animal activity. B) throughfall. C) wind action. D) sap flow. Answer: B Topic: Section 23.2 4) Fire results in the production of ash from vegetation and soil organic matter. This ash contains nutrients that are most often A) lost from ecosystems almost immediately following the fire. B) devoid of elements required for plant growth. C) unavailable for mineralization causing nutrient retention in the system. D) available for plant uptake and vulnerable to loss if not taken up by recovering vegetation. Answer: D Topic: Section 23.3 5) Which of the two basic types of biogeochemical cycles is most likely to have global cycle patterns? A) atmospheric B) aquatic C) gaseous D) sedimentary Answer: C Topic: Section 23.4

3 Copyright © 2012 Pearson Education, Inc.

6) Which of the following nutrients is most closely linked to the energy cycle in ecosystems? A) carbon B) nitrogen C) lead D) sulfur Answer: A Topic: Section 23.5 7) The source of all carbon in living organisms is A) simple sugars. B) carbon dioxide from atmosphere and water. C) carbon-fixing bacteria. D) sedimentary rocks. Answer: B Topic: Section 23.5 8) Carbon is released into the atmosphere as carbon dioxide through the process of A) photosynthesis. B) primary production. C) respiration. D) fixation. Answer: C Topic: Section 23.5 9) Carbon dioxide concentrations fluctuate in predictable seasonal patterns on the surface of the planet largely as a result of A) the influence of vegetation patterns in tropical systems. B) weathering of rock surfaces following seasonal rain events. C) vegetation growth and flux patterns in aquatic systems. D) large-scale patterns of terrestrial plant uptake and dormancy. Answer: D Topic: Section 23.6 10) The largest active carbon pool is A) the atmosphere. B) the oceans. C) living organisms. D) dead organisms. Answer: B Topic: Section 23.7

4 Copyright © 2012 Pearson Education, Inc.

11) Consider the following: on an annual basis, C exchange from photosynthesis is 120 Gt, decomposition is 60 Gt, respiration is 60 Gt, ocean uptake of CO2 is 92 Gt of C, ocean release is 91 Gt C, release of C to the atmosphere from anthropogenic sources (fossil fuel use and land use change) is 6 Gt, and the atmosphere is increasing by 3.2 Gt of C. If terrestrial processes are responsible for the remaining C for net balance of the C cycle, then which of the following is likely? A) The terrestrial surface is a net sink of 1.8 Gt of C. B) The terrestrial surface is a net source of 1.8 Gt of C. C) The terrestrial surface is a net sink of 2.8 Gt of C. D) The terrestrial surface is a net source of 2.8 Gt of C. Answer: A Topic: Section 23.7 12) Biological nitrogen fixation is accomplished by A) protozoans. B) bacteria. C) fungi. D) plants. Answer: B Topic: Section 23.8 13) The largest pool of nitrogen is A) the atmosphere. B) the oceans. C) living organisms. D) dead organisms. Answer: A Topic: Section 23.8 14) Plant roots compete with Nitrosomonas and Nitrobacter for ammonium in soil. When these bacterial groups acquire the ammonium, they turn it into A) N2 gas through nitrification. B) N2 gas through denitrification. C) NO3- through nitrification. D) NO3- through denitrification. Answer: C Topic: Section 23.8

5 Copyright © 2012 Pearson Education, Inc.

15) Global estimates of denitrification in terrestrial ecosystems vary widely but are of the order 200*1012 g/yr, and more than half of that total occurs in wetland ecosystems. If restoration results in an increase in wetland area by approximately 25%, it would be expected that losses of nitrogen through denitrification would be closer to A) 175*1012 g/yr. B) 225*1012 g/yr. C) 275*1012 g/yr. D) 325*1012 g/yr. Answer: B Topic: Section 23.8 16) Which of the following nutrients has a cycle that does not contain an appreciable atmospheric phase? A) carbon B) nitrogen C) phosphorus D) sulfur Answer: C Topic: Section 23.9 17) The major process regulating phosphorus availability for net primary production is the internal cycling of phosphorus from A) organic to inorganic forms. B) inorganic to organic forms. C) atmospheric fixation. D) rock weathering. Answer: A Topic: Section 23.9 18) Hydrogen sulfide is transformed into sulfate or elemental sulfur by A) protozoans. B) bacteria. C) fungi. D) algae. Answer: B Topic: Section 23.10 19) Which of the following represents the largest anthropogenic source of sulfur released to the atmosphere? A) fixation for agricultural fertilizer B) burning of fossil fuels C) trash-burning incinerators D) biomass burning Answer: B Topic: Section 23.10 6 Copyright © 2012 Pearson Education, Inc.

20) Which of the following cycles is thought to be most under biological control? A) oxygen B) phosphorus C) sulfur D) lead Answer: A Topic: Section 23.12 23.3 True/False Questions 1) Without the cycling of water, biogeochemical cycles would cease. Answer: TRUE Topic: Section 23.1 2) Soil formation and soil characteristics have major influence on the processes of nutrient retention and release. Answer: TRUE Topic: Section 23.2 3) Flowing water aquatic systems (streams and rivers) contain high levels of organic matter so are rarely dependent on inputs from terrestrial system. Answer: FALSE Topic: Section 23.2 4) Precipitation can be a significant input of nutrients in ecosystems. Answer: TRUE Topic: Section 23.2 5) The biogeochemical cycles of one ecosystem are typically independent from those of other ecosystems. Answer: FALSE Topic: Sections 23.4 and 23.13 6) Carbon cycles more quickly through cold and dry ecosystems than it does through warm and wet ecosystems. Answer: FALSE Topic: Section 23.5 7) Fossil fuels develop as a result of complete decomposition of organic matter in swamps and marshes. Answer: FALSE Topic: Section 23.5 8) Atmospheric carbon dioxide concentrations in a forest are greater during the day than during the night. Answer: FALSE Topic: Section 23.6 7 Copyright © 2012 Pearson Education, Inc.

9) Seasonal fluctuations in atmospheric carbon dioxide concentrations are greater in the Northern Hemisphere than in the Southern Hemisphere. Answer: TRUE Topic: Section 23.6 10) Most carbon is buried in sedimentary rocks. Answer: TRUE Topic: Section 23.7 11) There is more carbon per unit of soil in cold polar regions than in the warm tropics. Answer: TRUE Topic: Section 23.7 12) The nitrogen cycle is a series of chemical transformations, which makes it relatively insensitive to environmental conditions such as temperature and moisture. Answer: FALSE Topic: Section 23.8 13) Lightening converts N2 to a nitrogen form that enters soil and can be readily assimilated by plants. Answer: TRUE Topic: Section 23.8 14) The process of nitrification produces a form of nitrogen that is easily lost from soil through leaching. Answer: TRUE Topic: Section 23.8 15) Humans have altered the nitrogen cycle by burning fossil fuels. Answer: TRUE Topic: Section 23.8 16) The phosphorus cycle is a sedimentary cycle with essentially no gaseous cycle. Answer: TRUE Topic: Section 23.9 17) The main reservoir of plant-available phosphorus is organic matter in the soil. Answer: FALSE Topic: Section 23.9 18) Phosphorus is typically in short supply in aquatic and terrestrial ecosystems. Answer: TRUE Topic: Section 23.9 19) The sulfur biogeochemical cycle is a sedimentary cycle with essentially no gaseous cycle. Answer: FALSE Topic: Section 23.10 8 Copyright © 2012 Pearson Education, Inc.

20) One way that sulfur enters the atmosphere is through volcanic activity. Answer: TRUE Topic: Section 23.10 21) Atmospheric sulfur dioxide returns to Earth in rain as weak sulfuric acid. Answer: TRUE Topic: Section 23.10 22) Oceans represent the largest natural source of sulfur gases released to the atmosphere. Answer: TRUE Topic: Section 23.11 23) Oxygen is taken up by plants during photosynthesis. Answer: FALSE Topic: Section 23.12 24) Most aerobic autotrophs produce and consume oxygen in order to live. Answer: TRUE Topic: Section 23.12 25) Undecomposed organic matter in the form of fossil fuels and carbon in sedimentary rocks represents a net positive flux of oxygen to the atmosphere. Answer: TRUE Topic: Section 23.12 26) Stratospheric ozone shields the planet from biologically harmful ultraviolet radiation. Answer: TRUE Topic: Section 23.12 27) Although nitrogen can act as a fertilizer initially, too much nitrogen added to a forest system can cause forest decline. Answer: TRUE Topic: Ecological Issues: Nitrogen Saturation 28) In the later stages of nitrogen saturation, soils tend to become more acidic, which increases the concentration of aluminum ions in the soil solution. Answer: TRUE Topic: Ecological Issues: Nitrogen Saturation

9 Copyright © 2012 Pearson Education, Inc.

23.4 Essay Questions 1) Explain the difference between the two basic types of biogeochemical cycles, using specific examples of each. Topic: Section 23.1 2) First describe three ways that nutrients can be lost from an ecosystem; then describe how nutrients are replaced in those systems. Topic: Section 23.3 3) Describe how atmospheric carbon dioxide levels fluctuate daily, seasonally, and geographically. Explain why such fluctuation occurs. Topic: Sections 23.5—23.7 4) Describe a pathway of nitrogen from the atmosphere into the body tissue of an herbivore. Topic: Section 23.8 5) Describe how an atom of phosphorus might move from the crystal lattice of a mineral in a rock through a plant and into the ocean. Topic: Section 23.9 6) List and describe three inputs of sulfur into the atmosphere. Be sure to describe the mechanism by which sulfur is liberated to move into the atmosphere. Topic: Sections 23.10 and 23.11 7) Bacteria are major players in biogeochemical cycles. Describe the way in which the environment will determine the rate at which nutrients become available through impacts on bacteria. Provide explicit examples for the N, P, and S cycles. Topic: Sections 23.8—23.10 8) Describe how ozone is formed at different levels of the atmosphere and how biological organisms are affected by ozone. Topic: Section 23.12

10 Copyright © 2012 Pearson Education, Inc.