Question 1

It is estimated that the mass of bacteria and fungi in the top six inches of an acre of soil is
A) 2 tons.
B) 100 lbs.
C) 10 tons.
D) 500 lbs.
E) 2 kilograms.

Accepted Answer

The mass of bacteria and fungi in the top six inches of an acre of soil is typically estimated to be around 2 tons.

Question 2

Streptomyces
A) may produce antibiotics.
B) may produce antivirals.
C) are typically found in the air.
D) are frequently transmitted by vectors.
E) will swarm together to form fruiting bodies.

Accepted Answer

E

Question 3

The region of the earth inhabited by living organisms is called the
A) biosphere.
B) niche.
C) ecosystem.
D) community.
E) environment.

Accepted Answer

The biosphere refers to the global sum of all ecosystems on Earth, including all living organisms and their communities in the air, on land, and in water. It is the region of the earth inhabited by living organisms.

Question 4

Geosmins are
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.

Accepted Answer

Geosmins are secondary metabolites produced by certain bacteria and fungi, and they are responsible for the earthy and musty odor of soil. They do not refer to a specific bacterial strain or group of bacteria such as Bacillus, nitrogen-fixing bacteria, or Rhizobium.

Question 5

The term used to describe the interrelationship between the living and non-living environments in an area is called a(n)
A) group.
B) community.
C) ecosystem.
D) ecological niche.
E) habitat.

Accepted Answer

An ecosystem is the term used to describe the interrelationship between the living and non-living environments in an area. It includes all living organisms (biotic factors) interacting with each other and their physical (abiotic) environment. A group refers to a collection of individuals or things, a community refers to a group of interacting living organisms, an ecological niche refers to the specific role and position an organism occupies within its habitat, and a habitat refers to the physical environment where an organism lives.

Question 6

The bacteria cultured from a soil sample typically represents
A) all the bacteria present in that sample.
B) a very small number of bacteria present in that soil.
C) all the metabolically active bacteria.
D) all the metabolically inactive bacteria.
E) most of the types of bacteria in that soil.

Accepted Answer

The bacteria cultured from a soil sample represents only a small number of bacteria present in that soil. This is because only certain types of bacteria can grow under specific laboratory conditions and not all bacteria are culturable. Therefore, the cultured bacteria do not represent all the bacteria present in that sample.

Question 7

Nutrient poor waters are described as being
A) hypoxic.
B) oligotrophic.
C) autotrophic.
D) eutrophic.
E) anoxic.

Accepted Answer

Nutrient poor waters are typically low in nutrients such as nitrogen and phosphorus, which limits the growth of algae and other photosynthetic organisms. This condition is referred to as oligotrophic.

Question 8

The role that an organism plays in its environment is called its
A) role.
B) niche.
C) position.
D) ecosystem.
E) habit.

Accepted Answer

The term "niche" refers to the specific role that an organism plays in its environment, including its interactions with other organisms and its use of resources. A niche includes factors such as what an organism eats, where it lives, and how it reproduces.

Question 9

The environment immediately surrounding an individual cell is called its
A) macroenvironment.
B) microenvironment.
C) microniche.
D) colony.
E) macrohabitat.

Accepted Answer

The term "microenvironment" refers to the immediate surroundings of an individual cell, including nearby cells, extracellular matrix components, and signaling molecules. This term is commonly used in the field of cell biology to describe the local conditions that can influence cell behavior and function. The other options, such as macroenvironment, microniche, colony, and macrohabitat, either refer to larger scales or are not directly related to individual cells.

Question 10

The major effect of excess water in the soil is to
A) increase the level of oxygen.
B) lower the amount of oxygen.
C) reduce the pH.
D) increase the amount of nitrogen.
E) reduce the amount of carbon.

Accepted Answer

Excess water in soil can lower the amount of oxygen available to plant roots, leading to oxygen deficiency and potentially harmful conditions such as root rot.

Question 11

Which group is composed of autotrophs?
A) Primary consumers
B) Secondary consumers
C) Decomposers
D) Rotters
E) Primary producers

Accepted Answer

Autotrophs, also known as primary producers, are organisms that can produce their own food using photosynthesis or chemosynthesis. Therefore, the correct choice is E, which is the option for primary producers. The other options (A, B, C, and D) are all heterotrophic groups that obtain their food from other sources.

Question 12

Bacteria survive adverse conditions by forming
A) zygotes.
B) capsules.
C) endospores.
D) glycocalyx.
E) capsules AND endospores.

Accepted Answer

Bacteria survive adverse conditions by forming endospores, which are highly resistant structures that can remain dormant for long periods of time. Endospore formation allows bacteria to survive extreme temperatures, droughts, and other adverse conditions.

Answer E is also acceptable as some bacteria survive by forming capsules, which protect them from host defenses and desiccation. However, endospore formation is a more specific and widely applicable answer to the question.

Question 13

An early contributor to the understanding of nitrogen fixation was
A) Hooke.
B) Pasteur.
C) Winogradsky.
D) Beijerinck.
E) Lister.

Accepted Answer

Winogradsky was an early contributor to the understanding of nitrogen fixation. He discovered that certain bacteria can convert atmospheric nitrogen into ammonia, which can then be used by plants.

Question 14

A microbial mat
A) is a form of biofilm.
B) is poorly organized.
C) contains only obligate anaerobes.
D) is constructed to prevent interactions between the various layers of microorganisms.
E) is a form of biofilm AND is poorly organized.

Accepted Answer

A microbial mat is a type of biofilm, which is a community of microorganisms that adhere to a surface and produce extracellular polymeric substances. Microbial mats are highly organized and structured, and include both aerobic and anaerobic microorganisms. They are found in a variety of environments, including aquatic and terrestrial habitats, and play important roles in biogeochemical cycling and nutrient cycling.

Question 15

The organic matter in soil is referred to as
A) mineral soil.
B) humus.
C) inorganic substance.
D) bedrock.
E) mulch.

Accepted Answer

Organic matter in soil is commonly referred to as humus, which is the decomposed remains of plants and animals.

Question 16

Eutrophic waters
A) are nutrient rich AND contain 3.5% salt.
B) may become hypoxic AND lack phosphate, nitrate, and iron.
C) lack phosphate, nitrate, and iron AND contain 3.5% salt.
D) contain 3.5% salt AND are alkaline.
E) are nutrient rich AND may become hypoxic.

Accepted Answer

Eutrophic waters are defined as nutrient-rich waters that support high levels of primary productivity. This means that they contain significant levels of phosphates, nitrates, and other nutrients that encourage the growth of algae and other aquatic plants. However, when these plants die and decompose, they consume oxygen, which can lead to hypoxia (low oxygen levels) in the water. While eutrophic waters may have other characteristics (such as salinity or alkalinity), the key defining feature is their nutrient richness and potential for hypoxia.

Question 17

Which of the following soil organisms play a major role in decomposing plant matter?
A) bacteria AND fungi
B) bacteria AND viruses
C) fungi AND protozoa
D) protozoa AND viruses
E) viruses AND fungi

Accepted Answer

Both bacteria and fungi play major roles in decomposing plant matter. Bacteria break down the simplest organic compounds, while fungi can break down more complex organic compounds, such as lignin and cellulose, found in plant cell walls. Viruses, protozoa, and other microorganisms can also contribute to decomposition, but bacteria and fungi are the primary decomposers.

Question 18

Biofilms are likely to be found in environments
A) that are nutrient rich.
B) that are relatively warm.
C) with rapidly flowing water.
D) with low nutrients.
E) with abundant nutrients.

Accepted Answer

The answer of Biofilms are likely to be found in...

Question 19

The problem of not being able to cultivate most microorganisms has led to the use of
A) FISH.
B) microscopy with fluorescent dyes.
C) 16s rRNA analysis.
D) FISH and 16s rRNA analysis.
E) All of these methods help identify microorganisms in the environment.

Accepted Answer

All of these methods, including FISH (Fluorescence In Situ Hybridization), microscopy with fluorescent dyes, and 16S rRNA analysis, are used to identify and study microorganisms that are difficult or impossible to cultivate in a laboratory setting. These techniques allow for the analysis and identification of microbial communities directly from environmental samples.

Question 20

The practice of cells turning on the production of some enzymes and turning off others in response to a changing environment is called
A) compromise.
B) adaptation.
C) metabolism.
D) nutritional metabolism.
E) quorum sensing.

Accepted Answer

The practice of cells adapting to a changing environment by turning on the production of some enzymes and turning off others is called adaptation. This allows the cell to respond to its surroundings and optimize its metabolism accordingly. The other choices are not as accurate to describe this process.

Quiz 28: Microbial Ecology

It is estimated that the mass of bacteria and fungi in the top six inches of an acre of soil is

Streptomyces

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

Geosmins are

The term used to describe the interrelationship between the living and non-living environments in an area is called a(n)

The bacteria cultured from a soil sample typically represents

Nutrient poor waters are described as being

The role that an organism plays in its environment is called its

The environment immediately surrounding an individual cell is called its

The major effect of excess water in the soil is to

Which group is composed of autotrophs?

Bacteria survive adverse conditions by forming

An early contributor to the understanding of nitrogen fixation was

A microbial mat

The organic matter in soil is referred to as

Eutrophic waters

Which of the following soil organisms play a major role in decomposing plant matter?

Biofilms are likely to be found in environments

The problem of not being able to cultivate most microorganisms has led to the use of

The practice of cells turning on the production of some enzymes and turning off others in response to a changing environment is called