Deck 20: Nutrient Cycles

Question 1

Which of the following is a sulfide?

A)H₂S
B)HS⁻
C)S²⁻
D)H₂S,HS⁻,and S²⁻ are all sulfides.

Answer 1

D

Question 2

The burning of fossil fuels produces significant amounts of

A)sulfate.
B)sulfite.
C)sulfonate.
D)sulfur dioxide.

Answer 2

D

Question 3

The metabolic process of ammonification ________ ammonia.

A)oxidizes
B)produces
C)reduces
D)transforms

Answer 3

B

Question 4

Which of the following is/are NOT a degradation product of organic material?

A)carbon dioxide
B)methane
C)oxygen
D)carbon dioxide,methane,and oxygen

Question 5

What would the result be when a soil is supplemented with S⁰?

A)dimethyl sulfide production due to mixotrophs
B)organic carbon production due to anaerobes
C)soil acidification due to chemolithotrophs
D)syntrophic utilization of sulfite

Question 6

Bacterial oxidation of Fe²⁺ occurs BEST under which environmental condition?

A)cold temperature
B)high sunlight
C)low (acidic)pH
D)nutrient-replete

Question 7

Diatoms require silicon due to their

A)Ca²⁺/Si⁴⁺ symporters.
B)DNA replication mechanism.
C)ornate frustules.
D)unique phototrophic physiology.

Question 8

________ is a term used to describe dead organic matter.

A)Humus
B)Loam
C)Pyrite
D)Xenocompost

Question 9

The Ca cycle is tightly coupled to the

A)carbon cycle through calcium carbonate formation in ocean waters.
B)phosphorus cycle through calcium phosphate formation in sediments and rocks.
C)silica cycle through calcium silicate formation in coastal ocean sediments.
D)nitrogen cycle because nitrogenase requires calcium ions.

Question 10

Which iron species is produced primarily from iron smelting and rarely is produced by microbial-mediated processes?

A)ferric iron (Fe³⁺)
B)ferrous iron (Fe²⁺)
C)ferrulic iron (Fe¹⁺)
D)iron (Fe⁰)

Question 11

Nitrate (NO₃⁻)reduced into ammonia (NH₃)to produce energy for the cell is called

A)ammonification.
B)dissimilative reduction of nitrate to ammonia (DRNA).
C)nitrification.
D)redox.

Question 12

The metabolic process of denitrification

A)oxidizes N₂.
B)oxidizes NO₃⁻.
C)reduces N₂.
D)reduces NO₃⁻.

Question 13

Which organisms form the foundation of the carbon cycle?

A)anaerobic chemolithotrophs
B)chemoheterotrophs
C)chemoorganotrophs
D)phototrophs

Question 14

Frozen methane molecules are called

A)anhydrous methane.
B)anoxic methane.
C)methane anhydrates.
D)methane hydrates.

Question 15

The primary energy source for termites comes from

A)acetogenic Archaea.
B)acetogenic Bacteria.
C)methanogenic Archaea.
D)methanogenic Bacteria.

Question 16

When dimethylsulfoniopropionate (DMSP)is aerobically degraded in a marine environment,which product is most often used to support growth?

A)acrylate
B)dimethyl disulfide
C)dimethyl sulfoxide
D)methanethiol

Question 17

Which compound in fertilizer do farmers use to inhibit the production of easily leached nitrogen compounds?

A)anhydrous ammonia
B)carbonate
C)nitrapyrin
D)nitrate

Question 18

A process where different microbial taxa work in cooperation to degrade a compound that neither can perform entirely on their own is called

A)allotrophy.
B)ammensalism.
C)commensalism.
D)syntrophy.

Question 19

What is a characteristic of a deep sea marine cold seep/vent?

A)acidic
B)luminous
C)low pressure
D)rich in methane

Question 20

One important difference between the C,N,and S cycles and the P,Ca,and Si cycles is that

A)P,Ca,and Si are NOT cycled in terrestrial environments.
B)the P,Ca,and Si cycles do NOT involve redox changes or gaseous forms that can alter Earth's atmospheric chemistry.
C)the P,Ca,and Si cycles do NOT involve microbial activity.
D)the P,Ca,and Si cycles are NOT affected by global warming or other human activity.

Question 21

The ocean has mitigated the impact of anthropogenic carbon dioxide production by

A)absorbing 500 billion tons of atmospheric carbon dioxide.
B)absorbing over 80% of the trapped heat energy.
C)storing 600 billion tons of organic carbon.
D)absorbing 500 billion tons of atmospheric carbon dioxide and over 80% of the trapped heat energy.

Question 22

The largest reservoir of methane is found

A)trapped under permafrost and marine sediments.
B)in the rumen of cows and other ruminant animals.
C)in the atmosphere.
D)trapped in volcanic rocks.

Question 23

In the oceans,sulfur exists primarily as ________,and in rocks and sediments sulfur occurs mostly as ________ and ________.

A)hydrogen sulfide (H₂S)/ gypsum (CaSO₄)/ elemental sulfur (Sᵒ)
B)hydrogen sulfide (H₂S)/ sulfate (SO₄²⁻)/ elemental sulfur (Sᵒ)
C)sulfate (SO₄²⁻)/ gypsum (CaSO₄)/ pyrite (FeS₂)
D)sulfate (SO₄²⁻)/ sulfide (H₂S)/ elemental sulfur (Sᵒ)

Question 24

Sulfide is toxic to respiring organisms,because it can combine with metals present in ________ that serve a critical function in respiration.

A)glycolysis enzymes
B)oxidases
C)NADH
D)cytochromes

Question 25

Which of the following processes does denitrification contribute to?

A)acid rain
B)ozone depletion
C)global warming
D)acid rain,ozone depletion,and global warming

Question 26

Lignin is a complex polymer of methoxylated ________ compounds and is present in ________.

A)silica / aquatic environments
B)mineral / rocks
C)oil / fossil fuels
D)aromatic / vascular plant material

Question 27

What reaction is catalyzed by mercuric reductase?

A)CH₃HgCH₃ to Hg²⁺
B)CH₃Hg⁺ to Hg²⁺
C)Hg⁴⁺ to Hg²⁺
D)Hg²⁺ to Hg⁰

Question 28

The two major forms of carbon that remain following microbial degradation are

A)methane,organic matter,and fossil fuels.
B)methane and carbon dioxide.
C)lignin and fossil fuels.
D)organic matter and hydrocarbons.

Question 29

Phosphorus reservoirs include

A)phosphate minerals in rocks,dissolved phosphates in aquatic environments,and the nucleic acids and phospholipids of living organisms.
B)mineral phosphonates and the nucleic acids and phospholipids of living organisms.
C)elemental phosphorus minerals and phosphonates.
D)elemental phosphorous,polyphosphate,and phosphonates.

Question 30

Which is the MOST toxic form of mercury?

A)CH₃Hg⁺
B)Hg⁰
C)Hg²⁺
D)Hg⁴⁺

Question 31

What is the largest carbon sink on Earth?

A)terrestrial biosphere
B)rocks and sediments
C)aquatic biosphere
D)fossil fuels

Question 32

Lysis of marine algae and cyanobacteria releases the major osmoregulatory solute,dimethylsulfoniopropionate (DMSP),which is degraded into the most abundant organic S compound in nature,________.

A)dimethyl sulfide (CH₃-S-CH₃)
B)hydrogen sulfide (H₂S)
C)gypsum (CaSO₄)
D)elemental sulfur (Sᵒ)

Question 33

Which statement exemplifies the biological pump concept?

A)Autotrophs bring in light photons to synthesize ATP.
B)Bacteria oxidize Fe²⁺ into Fe³⁺,and Archaea reduce Fe³⁺ back into Fe²⁺.
C)Calcium ions are brought into cells while toxic physiological byproducts are released.
D)Primary producers sink to the deep ocean,which provides deep ocean organisms with nutrients when the primary producers die.

Question 34

Agricultural application of nitrogen fertilizer

A)reduces global warming by increasing the storage of carbon dioxide in plant biomass.
B)increases global warming by increasing microbial respiration in agricultural soils.
C)increases global warming by increasing the production of nitrous oxide (N₂O)by denitrification in agricultural soils.
D)has little to no effect on the carbon cycle.

Question 35

What is the main form of nitrogen found on Earth?

A)N₂
B)NO
C)NO₃⁻
D)NH₄

Question 36

Phosphonate comprises 25% of the ________ phosphorous pool in marine environments.

A)inorganic
B)organic
C)insoluble
D)biologically unavailable

Question 37

The Fe and Mn cycles include

A)reduced and oxidized forms that are very chemically reactive.
B)large reservoirs of solid mineral forms that are chemically inert.
C)incorporation of Fe and Mn into the exoskeletons of diatoms and other alga.
D)toxic forms that can poison aquatic ecosystems if the cycles are imbalanced.

Question 38

Greenhouse gases

A)such as CO₂,CH₄,and N₂O trap infrared radiation and heat the Earth.
B)such as CO₂ increase plant and animal growth,resulting in more heat production on Earth.
C)such as CO₂ and O₃ (ozone)interact with UV light and heat the Earth.
D)such as CO₂,CH₄,and N₂O destroy O₃ (ozone)and allow more UV light to enter the atmosphere,thus increasing the temperature of the Earth's surface.

Question 39

Coccolithophores and foraminiferans both use ________ to form their exoskeletons.

A)Si⁴⁺
B)Fe³⁺
C)Ca²⁺
D)HPO₄⁻

Question 40

Mercury is NOT used in

A)electronics.
B)neurotoxins.
C)pesticides.
D)paper pulping.

Question 41

The disposal of garbage or sewage in the ocean is known to cause the sudden growth of sulfate reducers.

Question 42

In the natural carbon cycle,carbon dioxide is returned to the atmosphere by the respiration of animals and chemoorganotrophic microorganisms.

Question 43

When carbon is limiting in a system,sulfate reducers often predominate the system when sufficient sulfate ions are present for reduction.

Question 44

More carbon is present in dead organic material on Earth than in living organisms.

Question 45

Increasing atmospheric carbon dioxide is

A)increasing sedimentation of C,Ca,and Si.
B)increasing the effect of the biological pump.
C)fueling increased primary production in ocean waters.
D)acidifying the ocean and decreasing the rate of formation of calcareous shells.

Question 46

Acetogens can ferment glucose into acetate,but methanogens cannot.

Question 47

Most chemolithotrophic bacteria that oxidize sulfur are aerobes.

Question 48

Nitrogen fixation results in the

A)loss of biologically available N from an ecosystem.
B)formation of nitrogen gas.
C)direct formation of nitrate.
D)addition of biologically available N to an ecosystem.

Question 49

Climate scientists are developing methane hydrates to decrease the effects of global warming.

Question 50

In a global sense,ALL nutrient cycles are coupled together.

Question 51

Nitrification and anammox both

A)create nitrogen gas,but nitrification is aerobic while anammox is anaerobic.
B)oxidize ammonia,but nitrification uses O₂ and anammox uses NO₂- for electron acceptors.
C)are aerobic processes,but nitrification produces NO₃- and annamox produces N₂ gas.
D)occur in soils at neutral pH.

Question 52

Nitrous oxide (N₂O)is a

A)product of denitrification.
B)product of nitrification.
C)potent greenhouse gas.
D)potent greenhouse gas that is a product of denitrification.

Question 53

The precipitation of soluble iron ions into solid iron occurs spontaneously in the presence of organic carbon compounds.

Question 54

Humic acids are difficult to degrade,and therefore they usually remain in a system for several decades.

Question 55

The oxidation of ________ occurs both biotically and abiotically; however,at ________ pH values biotic oxidation is more common.

A)Si / low
B)ammonia / high
C)Fe²⁺ / low
D)Hgᵒ / low

Question 56

Studying the redox cycling of Fe in the environment has led to the discovery

A)of bacteria that transfer electrons long distances and generate electric currents.
B)of bacteria that destroy toxic metal ions.
C)of archaea that have Fe in their cell walls.
D)that Fe limits primary production in terrestrial ecosystems.

Question 57

Syntrophic organisms cannot grow fermentatively without a hydrogen-consuming partner organism.

Question 58

Methanogens,among other compounds,use alcohols and fatty acids to synthesize methane gas in anoxic environments.

Question 59

Human activities have disrupted the carbon cycle by

A)burning carbon stored as fossil fuels or biomass,thus increasing the amount of carbon dioxide in the atmosphere.
B)decreasing the primary productivity of the oceans,resulting in increased atmospheric carbon dioxide.
C)burning methane hydrates to produce electricity.
D)acidifying the ocean,resulting in the release of large amounts of dissolved carbon dioxide into the atmosphere.

Question 60

Abiotic oxidation of Fe²⁺ requires oxygen; no other chemicals can directly oxidize Fe²⁺.

Question 61

Silicoflagellates use silicon compounds in substrate-level phosphorylation.

Question 62

Denitrification of fertilizer can result in harmful algal blooms.

Question 63

Calcium is cycled most rapidly in terrestrial environments.

Question 64

Coal contains substantial amounts of mercury.When coal is burned to generate heat or electricity,the mercury is released into the atmosphere.Most of this mercury is eventually deposited in the ocean or other aquatic environments.What happens to the mercury once it is deposited in the ocean?

Question 65

Mercury-resistant bacteria detoxify mercury by producing Hg⁰.

Question 66

The mercury in fish is normally in the form of elemental mercury (Hg⁰).

Question 67

Why is the water solubility of different nitrogen species of importance to agriculturalists? What processes in the nitrogen cycle are LEAST beneficial to agricultural production of crops?

Question 68

Carbon dioxide is the only greenhouse gas produced by anthropogenic activities.

Question 69

Mercury can serve as a transcriptional activator in the regulation of certain genes.

Question 70

Marine wetlands (salt marshes)are highly productive coastal ecosystems that produce a lot of organic carbon,similar to freshwater wetlands; however,salt marshes smell very different than freshwater wetlands.What nutrient cycle is different between the two ecosystems that causes this difference in smell?

Question 71

Mercury has both organic and inorganic forms that are neurotoxic.

Question 72

Microbial activity generates methylmercury,which is much less toxic than the mercuric ion.

Question 73

Most phosphorous,such as that found in inorganic phosphate (HPO₄⁻),exist in the +5 oxidation state in nature.

Question 74

Some bacteria have genes that confer resistance to mercury.

Question 75

The two main biological activities in the Ca and Si cycles are the biosynthesis of shells and exoskeletal material as well as the mineralization of these materials in sediments.

Question 76

Ocean acidification decreases the precipitation of calcium carbonate and thus will probably affect the cycling of Ca and other nutrients in the ocean.

Question 77

Energy yields are high enough for Fe²⁺ oxidation that the bacteria that perform this reaction require only small quantities of Fe²⁺ to be available.

Question 78

How would Si depletion in the photic zone of the open ocean affect the biological pump and the C cycle?

Question 79

Using the sudden bloom of cyanobacteria in a lake due to anthropogenic fertilizer inputs as an example,explain the coupling of carbon,nitrogen,and oxygen cycling.Exclude discussion of all organisms other than microorganisms.

Question 80

What are the similarities and differences between the Fe cycle and Ca cycle?