Deck 22: Microbes in Global Elemental Cycles

Question 1

Which of the following techniques is used to quantify carbon influx and efflux of CO₂ in small, controlled model ecosystems?

A) gas chromatography
B) mass spectroscopy
C) radioisotope incorporation
D) stable isotope ratios
E) atomic force microscopy

Answer 1

C

Question 2

Which of the following is NOT an example of a reduced form of carbon in the carbon cycle?

A) methane
B) biomass
C) hydrocarbons
D) carbon dioxide
E) methanol

Answer 2

D

Question 3

The NASA FLUXNET tower is used for sampling and monitoring

A) atmospheric CO₂ and carbon flux.
B) dinitrogen gas and denitrification.
C) biomass carbon and dissolved CO₂ oceans.
D) hydrogen cycle and carbon flux.
E) atmospheric nitrogen and carbon.

Answer 3

A

Question 4

Corrosion of cement in the sewer pipe shown below is caused by

A) H₂S.
B) H₂S + O₂.
C) H₂ + SO₄^2-.
D) Ca(OH)₂ + H₂SO₄.
E) sewage liquid.

Question 5

The upper region indicated in the figure below is called

A) deep oxycline.
B) upwelling zone.
C) benthos.
D) oxygen minimum zone.
E) upper oxycline.

Question 6

Marine dead zones are characterized as being

A) hypoxic.
B) aerated.
C) devoid of nitrogen fixation.
D) dangerous for ship sail.
E) usually naturally occurring.

Question 7

The elemental proportions in microbes are

A) constant.
B) variable.
C) not measurable.
D) independent of abiotic factors.
E) called their "reservoirs."

Question 8

What is the cause of the highlighted zone with dissolved oxygen less than 2.0 mg/l?

A) high carbon and nitrogen concentrations
B) high iron concentrations
C) low oxygen concentrations
D) high phosphorus concentrations
E) the Deepwater Horizon oil spill

Question 9

What is one of the main challenges of treating industrial runoff versus municipal wastewaters?

A) more solid waste
B) higher oxygen concentrations
C) toxic chemicals
D) higher organic loads
E) lower oxygen concentrations

Question 10

Aeration of an environment containing microbes actively producing methane will

A) increase methane release.
B) decrease methane release.
C) not affect methane release.
D) increase nitrous oxide release.
E) increase dinitrogen release.

Question 11

Which of the following is an anaerobic respiration reaction?

A) conversion of phosphine to phosphate
B) methanogenesis
C) photolysis of hydrogen sulfide to sulfur
D) precipitation of ferric iron with hydroxide
E) nitrogen fixation

Question 12

The release of CO₂ by human industry has/is ________ the rate of CO₂ fixation globally.

A) equal to
B) tripled
C) outpaced
D) far less than
E) decreased

Question 13

Which of the following would decrease the amount of carbon dioxide in the atmosphere?

A) burning of logs
B) microbial decomposition of logs
C) increase in photosynthesis by plants
D) anaerobic fermentation
E) increase in respiration by microbes

Question 14

The largest reservoir for carbon is

A) the atmosphere.
B) ocean biomass.
C) carbonate rocks and subsurface carbon.
D) wetlands.
E) fossil fuels.

Question 15

Which of the following reservoirs contains the most rapidly cycled carbon?

A) the atmosphere
B) ocean biomass
C) ocean inorganic molecules
D) land biomass
E) crust below land and ocean

Question 16

The element with the highest percentage of dry weight in bacteria is

A) calcium.
B) carbon.
C) hydrogen.
D) nitrogen.
E) phosphorus.

Question 17

In the marine photic zone, the rate of photosynthesis

A) is equal to the amount of CO₂ released from the niche.
B) exceeds the rate of respiration.
C) is less than the respiration rate.
D) does not affect carbon cycling.
E) is inversely related to rate of respiration.

Question 18

Microbes participate in which step of wastewater treatment?

A) preliminary
B) primary
C) secondary
D) tertiary
E) every step

Question 19

The Blood Falls ecosystem is driven by microbes that reduce ________ and others that oxidize ________.

A) nitrogen; iron
B) phosphorus; nitrogen
C) iron; sulfur
D) sulfur; nitrogen
E) carbon; sulfur

Question 20

The sink of an element in the ecosystem

A) is the reservoir to which it returns during cycling.
B) is the most accessible reservoir of that element.
C) renders the element inaccessible.
D) releases the element into the subsurface.
E) is the source of the element for living organisms.

Question 21

Which of the following is NOT used as a biosignature?

A) metabolic activity
B) isotope ratios
C) microscopic imaging
D) mineral formations
E) microfossils

Question 22

Eolian sources of iron in marine systems are due to.

A) precipitation of Fe3+ by OH- or PO43-.
B) phytoplankton consumers.
C) iron-oxidizing bacteria.
D) wind-borne dust from dry land.
E) reduction of Fe3+ by anaerobic respiration.

Question 23

Wastewater treatment generates which of the following gases in quantities sufficient for recovery as fuel?

A) carbon dioxide
B) oxygen
C) nitrous oxide
D) methane
E) hydrogen sulfide

Question 24

Phosphorus is a fundamental element of which biological molecule?

A) cofactors for enzymes
B) siderophores
C) proteins
D) nucleic acids
E) peptidoglycan

Question 25

Which of the following organisms does NOT play a major role in secondary wastewater treatment?

A) Zoogloea
B) Flavobacterium
C) Escherichia
D) Pseudomonas
E) Nocardia

Question 26

Which of the following major biological elements has the highest number of oxidation states?

A) nitrogen
B) carbon
C) hydrogen
D) sulfur
E) oxygen

Question 27

In the anammox reaction, ________ is the electron donor and ________ is the electron acceptor.

A) dinitrogen gas; nitrite
B) nitrite; nitrate
C) ammonium ion; dinitrogen gas
D) dinitrogen gas; nitrate
E) ammonium ion; nitrite

Question 28

Microbes using nitrogen as a terminal electron acceptor would be performing

A) nitrogen fixation.
B) ammonification.
C) nitrification.
D) denitrification.
E) anammox.

Question 29

If an oligotrophic marine system has low concentrations of both nitrogen and phosphorus, it is said to be

A) eutrophic.
B) polluted.
C) high BOD.
D) colimited.
E) hypoxic.

Question 30

Acid mine drainage is caused primarily by the microbial genus

A) Thalassiosira.
B) Leptothrix.
C) Prochlorococcus.
D) Acidithiobacillus.
E) Desulfovibrio.

Question 31

In polluted ocean waters, what type of organisms may contribute significantly to global warming?

A) photosynthetic algae
B) methanogens
C) vent bacteria
D) marine mammals
E) denitrifying bacteria

Question 32

The following image is evidence supporting ________ on Mars.

A) life
B) past water
C) tectonic processes
D) current water
E) volcanic flow

Question 33

Which of these is involved in commercial chemical fertilizer production?

A) lightning strikes
B) the Haber process
C) cellular nitrogen fixation
D) nitrification
E) denitrification

Question 34

What do wastewater treatment plants have in common with wetland filtration (purification)?

A) The type of wastewater treated is the same.
B) The engineering designs and flow are similar.
C) They depend on microbes to remove nitrogen and carbon.
D) Chlorine is used to decontaminate pollutants.
E) They are both continually aerated.

Question 35

The highly potent greenhouse gas N₂O generates ________ the warming effect of CO₂.

A) 50X
B) 100X
C) 150X
D) 200X
E) 500X

Question 36

During wastewater treatment, the secondary treatment requires continual aeration to

A) suppress microbial growth.
B) select for anaerobic heterotrophs.
C) stimulate abiotic degradation.
D) increase microaerophilic filamentous bacteria.
E) maximize breakdown of molecules to CO₂ and nitrates.

Question 37

Which is the most stable form of nitrogen?

A) NO
B) NO₂-
C) N₂
D) NH3
E) NH

Question 38

What types of bacteria will carry out nitrification?

A) lithotrophs
B) heterotrophs
C) chemoorganotrophy
D) phototrophs
E) fastidious heterotrophs

Question 39

Dinitrogen gas constitutes ________ of the atmosphere.

A) 10%
B) 79%
C) 69%
D) 21%
E) 0.03%

Question 40

Which contaminant in water is especially prevalent in agricultural regions of the United States?

A) carbon
B) sulfur
C) phosphate
D) nitrate
E) magnesium

Question 41

Compare and contrast assimilatory and dissimilatory nitrate reduction.

Question 42

Which of the following is the most limiting element in marine ecosystems?

A) iron
B) sulfur
C) carbon
D) phosphorous
E) hydrogen

Question 43

If life is found on other planets, it will almost certainly be

A) thermophilic.
B) microbial.
C) barophilic.
D) psychrophilic.
E) multicellular.

Question 44

Which of the following does bacteria use for iron uptake?

A) ferrodoxin
B) protein A
C) hemoglobin
D) siderophores
E) lipoprotein

Question 45

Jupiter's moon ________ is a candidate for extraterrestrial life due to its subsurface oceans.

A) Io
B) Europa
C) Titan
D) Mimas
E) Deimos

Question 46

Which of the following is assimilated almost entirely in the oxidized state?

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

Question 47

On which of the following does humankind expect to find life because of the similarity of its geology to that of Earth?

A) Jupiter
B) Venus
C) Mars
D) Jupiter's moon Europa
E) Pluto

Question 48

Describe the difference between a source, sink, and reservoir of an element.

Question 49

The figure below shows the ignition of methane from what source? Why is this methane source a major concern for global warming?

Question 50

Which of the following spontaneously ignites with a green glow as it emanates from the ground?

A) pyrite
B) nitrous oxide
C) dimethyl sulfide
D) phosphine
E) dimethylmercury

Question 51

What would happen if household wastewater was emptied into local receiving rivers without prior treatment?

Question 52

Increased ________ is NOT needed to terraform Mars.

A) greenhouse gases
B) temperature
C) pH
D) air pressure
E) oxygen

Question 53

Modifications of ________ structure and composition represents a common microbial adaptation to limiting phosphorous concentrations.

A) membrane
B) protein
C) DNA
D) polysaccharide
E) the cell wall

Question 54

Why does the burning of fossil fuels have such a drastic impact on the atmospheric carbon reservoir?

Question 55

Compare and contrast carbon cycling in aerobic versus anaerobic terrestrial systems.

Question 56

What does the increase in nitrite (NO₂⁻) and nitrous oxide (N₂O) in the following figure indicate? Describe this process in detail.

Question 57

Predict the relative levels of biological oxygen demand (BOD) of water flowing into and out of a municipal wastewater treatment plant. Why is this difference desirable?

Question 58

How did Jill Mikucki test her hypothesis that a subsurface river of brine flows deep beneath the glaciers and permafrost of Taylor Valley, feeding Blood Falls?

Question 59

How are wetlands similar to or different from commercial wastewater treatment plants?

Question 60

Anaerobically, H₂S may be photolyzed to

A) sulfate.
B) sulfite.
C) sulfur dioxide.
D) sulfuric acid.
E) elemental sulfur.

Question 61

Astrobiology is the study of life in the universe. Why might our rDNA probes NOT be appropriate to detect extraterrestrial life?

Question 62

Discuss the concept of iron fertilization to remove excess CO₂ from the atmosphere.

Question 63

Discuss the difference in environmental availability of phosphorus versus sulfur and nitrogen.

Question 64

What are two mechanisms used by marine organisms to adapt to the scarcity of phosphorous?

Question 65

Explain how the Mississippi River drainage into the Gulf of Mexico off the coast of Louisiana leads to a large dead zone.

Question 66

What types of evidence suggest the past existence of water on Mars?

Question 67

What are the major limitations to nitrogen fixation? How do organisms overcome these limitations?

Question 68

Some bacteria are responsible for degrading concrete. How do they accomplish this?

Question 69

Discuss how human activities have perturbed the nitrogen cycle.

Question 70

What evidence suggests that the biochemistry of life elsewhere would resemble that on Earth?