Deck 26: Biogeochemical Cycling

Question 1

Microbial degradation of hydrocarbons cannot take place using ____________ as the electron acceptor.

A) oxygen
B) carbon dioxide
C) nitrate
D) sulfate

Answer 1

B

Question 2

Ferroplasma acidarmanus is

A) capable of oxidizing iron.
B) capable of growth at pH 0.
C) lacking a cell wall.
D) all of the choices

Answer 2

D

Question 3

Which of the following microbes can oxidize ferrous iron while using chlorate or perchlorate as the electron acceptor?

A) Pseudomonas denitrificans
B) Thiobacillus ferrooxidans
C) Ferribacterium limneticum
D) Dechlorosoma suillum

Answer 3

D

Question 4

Inorganic phosphorus complexed with cations in the environment is most available to microbes at pH 4 and below because of solubility considerations.

Question 5

The use of sulfate as a terminal electron acceptor by Desulfovibrio is an example of assimilatory sulfate reduction.

Question 6

Nitrogen fixation is an energy-yielding process.

Question 7

___________ have been defined as communities of organisms and their physical and chemical environments that function as self-regulating units.

Question 8

Which of the following is not an example of symbiotic nitrogen fixation?

A) Rhizobium with leguminous plants
B) Azotobacter with certain photosynthetic protists
C) Anabaenea with a water fern
D) Frankia with woody shrubs

Question 9

The process of nitrogen fixation involves the transformation of

A) ammonia to organic matter nitrogen.
B) nitrogen gas to ammonia.
C) nitrate to nitrogen gas.
D) ammonia to nitrate.

Question 10

Which organisms would most likely be present on the bottom or closest to the actual surface of a complex microbial biofilm?

A) anaerobic sulfate-reducing bacteria
B) cyanobacteria
C) facultative chemoorganotrophs
D) eukaryotic protists

Question 11

Because of the high requirement for reducing power in nitrogen fixation, the nitrogenase enzyme that carries out the reaction is very sensitive to the presence of

A) light
B) carbon dioxide
C) oxygen
D) none of the choices

Question 12

The release of excess nitrogen into the environment when certain complex organic substrates are used to make new microbial biomass is called

A) mineralization.
B) nitrification.
C) denitrification.
D) dissimilation.

Question 13

Nutrients are often transformed and cycled by oxidation-reduction reactions that can change the chemical and physical characteristics of the nutrients.

Question 14

Which of the following does not contribute to the increasing levels of methane in the atmosphere?

A) methane production in termites
B) methane production in rice paddies
C) methane production at sewage treatment plants
D) methane production beneath an aerobic water column

Question 15

Less than ________ percent of all microbial species have been cultured, identified, and studied.

A) one
B) two
C) five
D) ten

Question 16

Microbes sometimes make metals such as mercury more volatile and lipid soluble by

A) phosphorylation.
B) aggregation.
C) methylation.
D) none of the choices

Question 17

Some microbes convert iron to magnetite which is then used as an internal compass to help position the microbe correctly in its environment.

Question 18

An example of biomagnification is the ability of Desulfovibrio to catalyze production of methyl mercury, which is lipid soluble, thereby increasing the concentration of mercury in the food chain.

Question 19

Degradation of organic matter is influenced by

A) nutrient availability
B) abiotic conditions
C) the nature of the microbial community present
D) all of the choices

Question 20

The carbon cycle begins with

A) the conversion of carbon dioxide to methane.
B) carbon dioxide fixation.
C) aerobic respiration
D) anaerobic respiration

Question 21

Since the beginning of the twentieth century, the rate at which ________ and other so-called greenhouse gases have entered the atmosphere has been faster than at any other time in the known history of life on Earth.

Question 22

Forests are generally regarded as CO₂

A) sources.
B) sinks.
C) both a source and a sink.
D) none of the choices

Question 23

A single outbreak of a tropical infectious disease in a temperate climate is considered evidence of the effects of global climate change on infectious disease epidemiology.

Question 24

Sulfate and sulfite reductions carried out by Desulfovibrio and related microorganisms are assimilatory processes.

Question 25

Dimethylsulfonopropionate is used by bacterioplankton (floating bacteria) as a sulfur source for protein synthesis and which is then transformed to dimethylsulfide, a volatile sulfur form that can affect atmospheric processes.

Question 26

In the anammox process

A) anaerobic oxidation of ammonia is coupled to the reduction of nitrite.
B) nitrogen gas is evolved.
C) all reactions must take place in the absence of O₂.
D) all of the choices

Question 27

Bacterioplankton (floating bacteria) use ________________ as a sulfur source for protein synthesis.

Question 28

Ecologists have documented the extinction over the last 20 years of ___________ of the 110 species of harlequin frogs (Atelopus) native to tropical America.

A) 100%
B) 15%
C) 67%
D) none of the choices

Question 29

When a usable organic electron donor is present, sulfate serves as a terminal electron acceptor during anaerobic respiration by a variety of microbes

A) Desulfovibrio
B) Desulfonema
C) Archaeoglobus
D) all of the choices

Question 30

Biological nitrogen fixation is carried out

A) by prokaryotes and some protists.
B) only by prokaryotes in symbiotic relationships with plants.
C) only in totally anaerobic environments.
D) only by a limited number of prokaryotes.

Question 31

A major fully reduced form of carbon, important in biogeochemical cycling is

A) carbon dioxide.
B) carbohydrate.
C) methane.
D) hydrogen sulfide.

Question 32

The oxidized form of inorganic iron that results from microbial oxidative processes is

A) ferrous ion.
B) ferric ion.
C) sulfate ion.
D) nitrate ion.

Question 33

Peat bogs occur in flooded areas because the rate of decomposition of which compound will be slower under anaerobic conditions?

A) starch
B) lignin
C) protein
D) lipids

Question 34

Methane is usually released directly to the atmosphere in environments without an overlying ________ water zone.

Question 35

Microbes such as Geobacter metallireducens obtain energy from organic matter under anaerobic conditions by using ferric iron as a(n) __________ __________.

Question 36

The removal of nutrients from nutrient cycling when those nutrients are converted to biomass is referred to as nutrient _____________________ .

Question 37

Biomagnification involves compounds having higher relative concentrations in

A) lower trophic levels.
B) higher trophic levels.
C) top consumers.
D) top consumers or higher trophic levels.

Question 38

The manufacture of fertilizer is an energy-intensive process that uses __________ gas to reduce N₂ to NH₄⁺ at high temperature and pressure.

Question 39

When nitrate is reduced to dinitrogen gas (N₂), nitrogen is removed from the ecosystem and returned to the atmosphere through a series of reactions collectively known as

A) nitrogen fixation.
B) denitrification.
C) anammox reaction.
D) all of the choices

Question 40

The process of denitrification involves the transformation of

A) ammonia to organic matter nitrogen.
B) nitrogen gas to ammonia.
C) nitrate to nitrogen gas.
D) ammonia to nitrate.