Deck 22: Biogeochemical Cycles

Question 1

The major source of free oxygen that supports life on Earth is the ________.

Answer 1

atmosphere

Question 2

Nitrogen can be returned to the atmosphere when certain bacteria convert it from nitrate into nitrogen gas,which is a process called ________.

Answer 2

denitrification

Question 3

Nitrogen is generally available to plants in only two forms: ammonium and ________.

Answer 3

nitrate

Question 4

Some nutrients are ________ from the soil and carried out of ecosystems by underground water flow to streams.

Question 5

Nearly all of the phosphorus in terrestrial ecosystems comes from the ________ of calcium phosphate minerals.

Question 6

Which of the following cycles have particles deposit from the atmosphere in both a dryfall and a wetfall?

A)nitrogen
B)oxygen
C)carbon dioxide
D)sulfur

Question 7

Large quantities of nutrients are bound tightly in ________ structure; they are not readily available until released by the activities of decomposers.

Question 8

In aquatic ecosystems,the phosphorous cycle moves through three states: particulate organic phosphorous,dissolved organic phosphates,and ________ phosphates.

Question 9

Biological nitrogen fixation is accomplished by symbiotic ________ living in mutualistic association with plants.

Question 10

Precipitation brings appreciable quantities of nutrients into ecosystems that are collectively called ________.

Question 11

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.

Question 12

The two basic types of biogeochemical cycles are gaseous and ________.

Question 13

The branch of chemistry dealing with the quantitative relationships of elements in combination is called ________.

Question 14

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.

Question 15

Microbial decomposition of organic matter results in NH4+ production through a process called ________.

Question 16

The main reservoirs of oxygen are water and ________.

Question 17

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.

Question 18

________ is the most common form of nitrogen exported from terrestrial ecosystems in stream water.

Question 19

The element ________ is a basic constituent of all organic compounds and is involved in the fixation of energy by photosynthesis.

Question 20

In ________ biogeochemical cycles,the main reservoirs of nutrients are the atmosphere and the oceans.

A)sedimentary
B)gaseous
C)aquatic
D)terrestrial

Question 21

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.

Question 22

Which region contains the largest amount of the global nitrogen pool?

A)fossil fuels
B)aboveground terrestrial systems
C)ocean
D)atmosphere

Question 23

Which of the following represents a loss of nutrients from an aquatic ecosystem?

A)leaves falling into a stream
B)fish feeding on surface insects
C)tadpoles metamorphosing out of the water
D)shredding insects breaking down leaf litter

Question 24

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.

Question 25

The largest active carbon pool is

A)the atmosphere.
B)the oceans.
C)living organisms.
D)dead organisms.

Question 26

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 of 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.

Question 27

Carbon is released into the atmosphere as carbon dioxide through the process of

A)photosynthesis.
B)primary production.
C)respiration.
D)fixation.

Question 28

Biogeochemical cycles should be regarded

A)primarily within a terrestrial ecosystem.
B)primarily within an oceanic ecosystem.
C)primarily linking terrestrial and oceanic ecosystems.
D)with a global perspective.

Question 29

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.

Question 30

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

Question 31

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.

Question 32

The waste product of microbial decomposition is converted to what in acidic soils?

A)NH4+
B)NH₃
C)NO42-
D)NO3-

Question 33

A primary measure of productivity is linked to

A)carbon.
B)nitrogen.
C)oxygen.
D)water.

Question 34

Which of the following nutrients is most closely linked to the energy cycle in ecosystems?

A)carbon
B)nitrogen
C)lead
D)sulfur

Question 35

Which of the following contains the most nutrients?

A)dryfall
B)wetfall in an open prairie
C)wetfall on a forest floor
D)wetfall in the ocean

Question 36

Which region contains the largest amount of the global carbon pool?

A)fossil fuels
B)aboveground terrestrial systems
C)ocean
D)atmosphere

Question 37

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.

Question 38

According to the figure,when is atmospheric CO₂ the highest?

A)at night
B)during the day
C)when trees are present
D)at high altitudes

Question 39

Why are carbon dioxide fluctuations more pronounced in the Northern Hemisphere?

A)larger CO₂ emissions
B)more terrestrial habitat
C)more humans
D)more solar energy absorbed

Question 40

Biological nitrogen fixation is accomplished by

A)protozoans.
B)bacteria.
C)fungi.
D)plants.

Question 41

Which area has the highest nitrogen deposition?

A)East Coast
B)West Coast
C)South
D)Midwest

Question 42

Soil formation and soil characteristics have major influence on the processes of nutrient retention and release.

Question 43

Which of the following cycles is thought to be most under biological control?

A)oxygen
B)phosphorus
C)sulfur
D)lead

Question 44

The biogeochemical cycles of one ecosystem are typically independent from those of other ecosystems.

Question 45

A danger of nitrogen saturation is

A)increased productivity.
B)basic soils.
C)acidic soils.
D)lack of carbon.

Question 46

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.

Question 47

Which region contains the largest amount of the global phosphorus pool?

A)fossil fuels
B)aboveground terrestrial systems
C)ocean
D)atmosphere

Question 48

Carbon cycles more quickly through cold and dry ecosystems than it does through warm and wet ecosystems.

Question 49

Without the cycling of water,biogeochemical cycles would cease.

Question 50

Hydrogen sulfide is transformed into sulfate or elemental sulfur by

A)protozoans.
B)bacteria.
C)fungi.
D)algae.

Question 51

Fossil fuels develop as a result of complete decomposition of organic matter in swamps and marshes.

Question 52

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

Question 53

Which of the following nutrients has a cycle that does not contain an appreciable atmospheric phase?

A)carbon
B)nitrogen
C)phosphorus
D)sulfur

Question 54

Which group is responsible for converting H2S into sulfates?

A)purple bacteria
B)cyanobacteria
C)soil fungi
D)plants

Question 55

Which chemical is responsible for breaking down ozone in the atmosphere?

A)CO₂
B)CH₃
C)CFC
D)CO₄

Question 56

Precipitation can be a significant input of nutrients in ecosystems.

Question 57

Which of the following elements is a limiting reagent in forming rubisco?

A)O
B)C
C)Ca
D)N

Question 58

Flowing-water aquatic systems (streams and rivers)contain high levels of organic matter so are rarely dependent on inputs from terrestrial systems.

Question 59

What is the dominant sulfur gas emitted from freshwater wetlands?

A)dimethylsulfide
B)S2
C)SO4
D)H2S

Question 60

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 percent,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.

Question 61

Phosphorus is typically in short supply in aquatic and terrestrial ecosystems.

Question 62

Atmospheric carbon dioxide concentrations in a forest are greater during the day than during the night.

Question 63

Although nitrogen can act as a fertilizer initially,too much nitrogen added to a forest system can cause forest decline.

Question 64

Most carbon is buried in sedimentary rocks.

Question 65

There is more carbon per unit of soil in cold polar regions than in the warm tropics.

Question 66

Oxygen is taken up by plants during photosynthesis.

Question 67

Stratospheric ozone shields the planet from biologically harmful ultraviolet radiation.

Question 68

One way that sulfur enters the atmosphere is through volcanic activity.

Question 69

The sulfur biogeochemical cycle is a sedimentary cycle with essentially no gaseous cycle.

Question 70

Undecomposed organic matter in the form of fossil fuels and carbon in sedimentary rocks represents a net positive flux of oxygen to the atmosphere.

Question 71

Most aerobic autotrophs produce and consume oxygen in order to live.

Question 72

The phosphorus cycle is a sedimentary cycle with essentially no gaseous cycle.

Question 73

Humans have altered the nitrogen cycle by burning fossil fuels.

Question 74

Lightning converts N₂ to a nitrogen form that enters soil and can be readily assimilated by plants.

Question 75

Oceans represent the largest natural source of sulfur gases released to the atmosphere.

Question 76

Atmospheric sulfur dioxide returns to Earth in rain as weak sulfuric acid.

Question 77

The process of nitrification produces a form of nitrogen that is easily lost from soil through leaching.

Question 78

The nitrogen cycle is a series of chemical transformations,which makes it relatively insensitive to environmental conditions such as temperature and moisture.

Question 79

Seasonal fluctuations in atmospheric carbon dioxide concentrations are greater in the Northern Hemisphere than in the Southern Hemisphere.

Question 80

The main reservoir of plant-available phosphorus is organic matter in the soil.