Deck 29: Microorganisms in Terrestrial Ecosystems

Question 1

Microorganisms in soil are located in thin water films on particle surfaces where oxygen is present at high levels.

Answer 1

True

Question 2

Oxygen diffuses through water approximately 4,000 times faster than through dry soil.

Answer 2

False

Question 3

A mineral soil contains less than 20 percent organic carbon while an organic soil contains at least that amount.

Answer 3

True

Question 4

Fungi can be present at up to several hundred meters of hyphae per gram of soil.

Question 5

The vast majority of microorganisms found in soils have been successfully cultured in the laboratory.

Question 6

Filamentous fungi found in soils are able to form bridges across aggregates and facilitate nutrient transfer processes.

Question 7

In bog soils, the decomposition rate of lignin-cellulose complexes is accelerated by the water-logged, predominately anoxic conditions.

Question 8

Lignin degradation by basidiomycetes is an aerobic process that is catalyzed by phenoloxidases.

Question 9

Molecular techniques have shown that Crenarchaeota are not present in soil.

Question 10

One of the more important genera of gram-positive aerobic actinomycetes found in soils is

A) Streptomyces.
B) Bdellovibrio.
C) Acinetobacter.
D) Pseudomonas.

Question 11

Protozoa in soils utilize bacteria as a nutrient source.

Question 12

Most organic matter found in soils results from primary producers such as

A) cyanobacteria.
B) vascular plants.
C) photosynthetic protists.
D) none of the choices

Question 13

The common building block of ___________ is the phenylpropene unit, which consists of a hydroxylated six-carbon aromatic benzene ring and a three-carbon linear side chain.

Question 14

A carbon to nitrogen (C/N) ratio of 20 or less in soil results in the loss of soluble nitrogen from the system.

Question 15

Enzymes, once released from plant and animal cells, can remain present and function independent of the organisms that synthesized them.

Question 16

A unique feature of terrestrial filamentous fungi not found in aquatic fungi is

A) oxygen-impermeable structures including sclerotia and hyphal cords.
B) formation of flagellated spores that aid in spore dispersal.
C) mitochondria with highly invaginated cristae that permit more rapid diffusion of oxygen for oxidative phosphorylation.
D) all of the choices

Question 17

Mycorrhizae are formed by the association of plants with

A) algae.
B) actinomycetes.
C) cyanobacteria.
D) fungi.

Question 18

An average gram of forest soil contains about

A) 2 $\times$ 10⁹ bacteria and archaea.
B) 4 $\times$ 10⁷ bacteria and archaea.
C) 4 $\times$ 10⁷ protists.
D) 2 $\times$ 10⁹ fungi.

Question 19

Ionized ammonia applied to soil is effectively retained because clays in the soil have a charge that is

A) positive.
B) negative.
C) uncharged.
D) none of these

Question 20

Geosmin, which contributes to the characteristic earthy odor of soils, is produced primarily by the genus

A) Streptomyces.
B) Paramecium.
C) Caenorhabditis.
D) Armillaria.

Question 21

Microbes that live on the surface of plants are called __________ .

Question 22

The ____________ mycorrhizae are the most common type of mycorrhizae.

A) arbuscular
B) ericaceous
C) orchidaceous
D) monotropoid

Question 23

Rhizobium and Bradyrhizobium are significant contributors to which process when engaged in a symbiotic relationship with leguminous plants?

A) nitrification
B) nitrogen fixation
C) denitrification
D) sulfate reduction

Question 24

A major organism involved in associative nitrogen fixation in the rhizosphere of many plants is

A) Azospirillum.
B) Rhizobium.
C) Frankia.
D) Pseudomonas.

Question 25

When rhizobia approach a plant root, the plant initially responds by

A) an oxidative burst.
B) an increase in exudate.
C) releasing flavonoid inducer molecules.
D) producing leghemoglobin.

Question 26

Ti plasmids in the species Agrobacterium tumefaciens

A) is required for nitrogen fixation.
B) causes the formation of tumors.
C) carries the genes needed for root nodule development.
D) carries the genes needed for formation of bacteroids.

Question 27

In the process of forming a root nodule, species of Rhizobium differentiate to form a type of cell called a

A) lymph node.
B) bacteroid.
C) nucleoid.
D) vesicle.

Question 28

Which of the following statements is correct?

A) All plants maintain a mycorrhizal relationship.
B) Most plants maintain a mycorrhizal relationship.
C) Some plants maintain a mycorrhizal relationship.
D) Only a few plants maintain a mycorrhizal relationship.

Question 29

Most ectomycorrhizae produce signaling molecules that limit the growth of root hairs.

Question 30

An important bacterial mediated process that occurs on the surface of plant roots is called _________ nitrogen fixation.

Question 31

Actinorrhizae can benefit the plant by providing it with the products of

A) nitrification.
B) denitrification.
C) nitrogen fixation.
D) sulfate reduction.

Question 32

Agrobacterium has the ability to infect plants and produce tumor-like growths.

Question 33

The stems and leaves of plants, called the ___________, provide a habitat for a wide variety of microorganisms.

A) plant crust
B) rhizosphere
C) phyllosphere
D) microbivory

Question 34

A common resident of the rhizosphere that can enhance plant growth is

A) Arthrobacter.
B) Erwinia.
C) Sphingomonas.
D) Pseudomonas.

Question 35

The formation of an infection thread is an important initial part of microbial interactions with plants in the process of

A) nitrification.
B) nitrogen fixation.
C) denitrification.
D) sulfate reduction.

Question 36

One of the most common bacterial genera cultured from plant leaves is

A) Nocardia.
B) Cellulomonas.
C) Sphingomonas.
D) Arthrobacter.

Question 37

Mycorrhizal fungi can either be intracellular or extracellular.

Question 38

The plant leaf surface is called the rhizosphere.

Question 39

In a mycorrhizal relationship, the fungal component can assist in providing phosphorus and water to the plant. The plant in turn provides the fungus with

A) metal cofactors.
B) organic carbon.
C) nitrogen.
D) carbon dioxide.

Question 40

The region of soil in the immediate vicinity of the roots of plants is called the

A) plant crust.
B) rhizosphere.
C) phyllosphere.
D) microbivory.

Question 41

A substance that promotes binding of Rhizobium to plant root hairs is called a __________ factor.

Question 42

In the shallow subsurface, surface waters often move through ________, which are porous geological structures below the plant root zone.

Question 43

The surface of a plant root is called the __________.

Question 44

Recent studies indicate that active prokaryotic assemblages are present in high-temperature oil reservoirs, including such genera as

A) Thermotoga
B) Thermoanaerobacter
C) Agrobacterium
D) only Thermotoga and Thermoanaerobacter

Question 45

Porous geological structures below the plant root zone where water flows are known as glaciated subterranean lakes.

Question 46

Microbial processes take place in

A) shallow subsurface where water flowing from the surface moves below the plant root zone.
B) regions where organic matter, originating from the Earth's surface in times past, has been transformed by chemical and biological processes to yield coal.
C) zones where methane is being synthesized as a result of microbial activity.
D) all of the choices

Question 47

Except for a shallow surface layer, the earth's crust is known to be free of microorganisms.

Question 48

A large reserve of methane is found in a pocket below the ocean floor and isotope analysis revealed that the ¹³C/¹²C ratio is lower than that predicted by the natural occurrence of these isotopes. This finding suggests that the methane was produced by

A) a geochemical process.
B) the metabolic activity of microorganisms.
C) a radioactive decay process.
D) oxidation of sulfite.

Question 49

Legume plants provide certain amino acids to the ___________ so that they do not need to assimilate ___________. In return, the bacteroids shuttle amino acids bearing the fixed nitrogen back to the plant.

Question 50

Bacteroids are terminally differentiated-they can neither divide nor revert back to the nondifferentiated state.