Question 1

During aerobic decomposition of organic matter the primary gas produced is

Accepted Answer

A)   oxygen.
B)   hydrogen sulfide.
C)   nitrogen.
D)   carbon dioxide.
E)   ethylene dioxide.

Question 2

Which group is composed of autotrophs?

Accepted Answer

A)   Primary consumers
B)   Secondary consumers
C)   Decomposers
D)   Rotters
E)   Primary producers E

Question 3

How can the biomass of fungi in soil be greater than that of bacteria, considering that bacteria are more numerous?

Accepted Answer

A)   Fungi are always multicellular organisms, while bacteria are unicellular. As such, biomass of fungi would always be larger than that of bacteria, since they possess more cells in each individual organism.
B)   This is a matter of size. Fungi, whether unicellular or multicellular, are eukaryotic and are generally larger than bacteria (which are prokaryotic) . This means that, even with a lower overall number, they will have more total biomass.
C)   It depends on where they grow. Fungi generally grow in the most moist areas near the top of soil, giving them an advantage over bacteria. They may not be as numerous, but this advantage in location and nutrients is what makes them larger than the bacteria (and therefore having more biomass) . 
D)   Fungi are capable of incorporating the dead materials around them into themselves as nutrient sources. This capacity allows them to greatly increase their biomass per each organism, well beyond what a simple bacterial cell could hold. This capability is what allows them to achieve higher biomass than bacteria.
E)   Bacteria may be more numerous, but in soil they exist mostly in a dehydrated state. Because they lack moisture, they weigh less than fungi, which may occur in lower numbers but are heavier because they are well hydrated in all soil environments.

Question 4

Azotobacter

Accepted Answer

A)   are the chief suppliers of fixed nitrogen in grasslands.
B)   form symbiotic associations with algae.
C)   have a very low respiratory rate.
D)   are methanogens.
E)   are the chief suppliers of fixed nitrogen in grasslands AND form symbiotic associations with algae.

Question 5

The conical sea floor vents that spout sulfide-rich, super-heated water at temperatures up to 300ºC are called

Accepted Answer

A)   hydrothermal vents.
B)   yellow smokers.
C)   warm vents.
D)   hot vents.
E)   hyperthermophiles.

Question 6

How do bacteriocins benefit bacteria in their natural habitat?

Accepted Answer

A)   They protect the bacteria from the effects of antibiotics in the environment.
B)   They provide a source of nutrients during adverse environmental conditions.
C)   They allow bacteria to compete against other bacteria that may attempt to use the same or similar resources.
D)   They are protective structures that allow bacteria to survive adverse environmental conditions.
E)   They induce resistance in the bacteria, helping them survive when medications are introduced into their habitat.

Question 7

An early contributor to the understanding of nitrogen fixation was

Accepted Answer

A)   Hooke.
B)   Pasteur.
C)   Winogradsky.
D)   Beijerinck.
E)   Lister.

Question 8

Geosmins are

Accepted Answer

A)   a strain of Bacillus.
B)   nitrogen-fixing bacteria.
C)   metabolites that give soil its odor.
D)   produced by Rhizobium.
E)   metabolites that give soil its odor AND produced by Rhizobium. F)  metabolites that give soil its odor AND produced by Bacillus.

Question 9

Mycorrhizae are a symbiotic association of

Accepted Answer

A)   bacteria and algae.
B)   plant roots and fungi.
C)   bacteria and virus.
D)   fungi and virus.
E)   plants roots and bacteria. B

Question 10

Which of the following may be used by prokaryotes, under anaerobic conditions, as terminal electron acceptors?

Accepted Answer

A)   nitrate
B)   nitrite
C)   sulfate
D)   carbon dioxide
E)   All of the choices are correct.

Question 11

Turning inorganic carbon into organic carbon is called

Accepted Answer

A)   mineralization.
B)   eutrophication.
C)   respiration.
D)   carbon fixation.
E)   carbonation. D

Question 12

The nitrogen in our atmosphere is only usable to us after it is converted to

Accepted Answer

A)   ammonia.
B)   amino acids.
C)   fertilizer.
D)   nitrous oxide.
E)   oxygen.

Question 13

Nitrogen is

Accepted Answer

A)   an important constituent of carbohydrates AND primarily fixed by fungi.
B)   turned into ammonia by microorganisms AND ultimately used in making amino acids and nucleotides.
C)   primarily fixed by fungi AND ultimately used in making amino acids and nucleotides.
D)   ultimately used in making amino acids and nucleotides AND an important constituent of carbohydrates.
E)   turned into ammonia by microorganisms AND ultimately used in making bacterial capsules.

Question 14

The zone of soil that surrounds the roots and contains a variety of organic exudates is called the

Accepted Answer

A)   mycorrhizae.
B)   rootsphere.
C)   rhizosphere.
D)   geosmin.
E)   biosphere.

Question 15

Oligotrophic waters are usually hypoxic.

Accepted Answer

A) True 
 B)False

Question 16

Sulfur occurs in all living matter primarily as a component of carbohydrates.

Accepted Answer

A) True 
 B)False

Question 17

Many orchids require fungi for seeds to germinate.

Accepted Answer

A) True 
 B)False

Question 18

The region of the earth inhabited by living organisms is called the

Accepted Answer

A)   biosphere.
B)   niche.
C)   ecosystem.
D)   community.
E)   environment.

Question 19

Bacteria are the most numerous soil inhabitants, but the biomass of fungi is greater.

Accepted Answer

A) True 
 B)False

Question 20

Protozoa, algae, and fungus are typically found near the surface of soil.

Accepted Answer

A) True 
 B)False

Exam 28: Microbial Ecology

During aerobic decomposition of organic matter the primary gas produced is

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Which group is composed of autotrophs?

Correct AnswerverifiedE

How can the biomass of fungi in soil be greater than that of bacteria, considering that bacteria are more numerous?

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Azotobacter

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The conical sea floor vents that spout sulfide-rich, super-heated water at temperatures up to 300ºC are called

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How do bacteriocins benefit bacteria in their natural habitat?

Correct AnswerverifiedShow Answer

An early contributor to the understanding of nitrogen fixation was

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Geosmins are

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Mycorrhizae are a symbiotic association of

Correct AnswerverifiedB

Which of the following may be used by prokaryotes, under anaerobic conditions, as terminal electron acceptors?

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Turning inorganic carbon into organic carbon is called

Correct AnswerverifiedD

The nitrogen in our atmosphere is only usable to us after it is converted to

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Nitrogen is

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The zone of soil that surrounds the roots and contains a variety of organic exudates is called the

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Oligotrophic waters are usually hypoxic.

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Sulfur occurs in all living matter primarily as a component of carbohydrates.

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Many orchids require fungi for seeds to germinate.

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The region of the earth inhabited by living organisms is called the

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Bacteria are the most numerous soil inhabitants, but the biomass of fungi is greater.

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Protozoa, algae, and fungus are typically found near the surface of soil.

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B

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D

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