Question 1

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

Accepted Answer

Geosmin is primarily produced by the genus Streptomyces, a group of soil bacteria known for their ability to produce diverse secondary metabolites. Other microorganisms such as blue-green algae can also produce geosmin, but Streptomyces is the main producer.

Question 2

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

Accepted Answer

It is estimated that less than 1% of microorganisms present in soils can be cultured in the laboratory using traditional methods. The majority of microorganisms in soil are believed to be unculturable or difficult to culture.

Question 3

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

Accepted Answer

Vascular plants are the primary terrestrial producers that contribute to organic matter in soils. While cyanobacteria and photosynthetic protists also contribute to organic matter, they are generally found in aquatic environments or as components of soil crusts, and do not contribute as much organic matter as vascular plants. Therefore, the best choice is B.

Question 4

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

Accepted Answer

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

Question 5

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.

Accepted Answer

The answer of The common building block of ___________ is...

Question 6

Protozoa in soils utilize bacteria as a nutrient source.

Accepted Answer

Protozoa in soils are known to feed on bacteria and other microorganisms as a source of nutrients.

Question 7

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

Accepted Answer

Bog soils, being waterlogged and predominantly anoxic, actually slow down the decomposition rate of lignin-cellulose complexes due to the lack of oxygen, which is necessary for the decomposition process carried out by microorganisms.

Question 8

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

Accepted Answer

A mineral soil is primarily made up of inorganic mineral particles, while an organic soil is formed primarily from the decomposition of organic matter. The amount of organic carbon in mineral soil is typically less than 20 percent, while an organic soil contains at least that amount of organic carbon.

Question 9

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

Accepted Answer

Clays in the soil have a negative charge that attracts positively charged ions, such as ammonium (NH4+). Therefore, ionized ammonia will be effectively retained in the soil.

Question 10

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

Accepted Answer

Enzymes can retain their catalytic activity outside the organism and can function independently as long as the environmental conditions are suitable for their activity.

Question 11

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

Accepted Answer

Fungi have a network of fine, branching filaments called hyphae that can extend for long distances in soil. It is not uncommon for there to be several hundred meters of hyphae per gram of soil.

Question 12

Mycorrhizae are formed by the association of plants with

Accepted Answer

Mycorrhizae are formed by the association of plants with fungi.

Question 13

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

Accepted Answer

A carbon to nitrogen ratio of 20 or less indicates that there is more nitrogen available in the soil, which can result in the loss of soluble nitrogen from the system. This can occur through leaching, volatilization, or denitrification. A higher C/N ratio can lead to nitrogen being immobilized in the soil, which can limit plant growth.

Question 14

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

Accepted Answer

Filamentous fungi are able to form hyphae that extend and connect soil particles, allowing for the transfer of nutrients and water between them. This can improve soil structure and fertility.

Question 15

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

Accepted Answer

Oxygen-impermeable structures including sclerotia and hyphal cords are unique to terrestrial filamentous fungi and are used for survival during periods of stress, such as drought or low nutrient availability. These structures are not found in aquatic fungi as they do not face the same environmental stressors. Flagellated spores and highly invaginated cristae in mitochondria are not unique features to terrestrial fungi.

Question 16

An average gram of forest soil contains about

Accepted Answer

The passage states that an average gram of forest soil contains about 4 x 10^17 bacteria and archaea. The other answer choices mention different types of microorganisms, but there is no information in the passage to support those numbers.

Question 17

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

Accepted Answer

Oxygen diffuses through air much faster than through water, not the other way around. In dry soil, which contains air spaces, oxygen diffusion is faster compared to waterlogged soil.

Question 18

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

Accepted Answer

Streptomyces is a well-known genus of gram-positive aerobic actinomycetes commonly found in soil. Species of Streptomyces are important producers of antibiotics and other bioactive compounds.

Question 19

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

Accepted Answer

Molecular techniques have shown that Crenarchaeota are indeed present in soil.

Question 20

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

Accepted Answer

Microorganisms in soil require oxygen for their growth and metabolism, which is found in the thin water films on particle surfaces in the soil.

Quiz 31: Microorganisms in Terrestrial Ecosystems