Question 1

In a stratified lake, the warmer and less dense layer is called the
A) epilimnion.
B) hypolimnion.
C) hyperlimnion.
D) thermocline.

Accepted Answer

The epilimnion is the warmer and less dense layer of a stratified lake that is closest to the surface. It is characterized by relatively consistent temperatures and high oxygen levels, which support the growth of photosynthetic organisms such as algae and phytoplankton. The hypolimnion, on the other hand, is the colder and denser layer at the bottom of the lake, which is often devoid of oxygen and contains decomposing organic matter. The thermocline is the layer in between the epilimnion and hypolimnion, where there is a rapid change in temperature with depth. The hyperlimnion is not a commonly used term in limnology and does not refer to any specific layer in a stratified lake.

Question 2

Which is the correct order of increasing size in soil particles?
A) clay > sand > silt
B) clay > silt > sand
C) sand > clay > silt
D) silt > clay > sand

Accepted Answer

The correct order of increasing size in soil particles is clay < silt < sand. Choice B correctly identifies this order.

Question 3

Some nitrifying prokaryotes carry out metabolic cooperation by a process known as
A) competition.
B) niche partitioning.
C) syntrophy.
D) antagonism.

Accepted Answer

Syntrophy is a process in which a group of microorganisms cooperate in metabolizing a compound that none of them can break down individually. Some nitrifying prokaryotes are known to carry out metabolic cooperation through syntrophy.

Question 4

The chemical oxygen demand (COD) of a body of water is determined using a(n)
A) microelectrode.
B) oxygenator.
C) spectrophotometer to determine the OD₅₄₀nm.
D) strong oxidizing agent.

Accepted Answer

The chemical oxygen demand (COD) of a body of water is determined using a strong oxidizing agent such as potassium dichromate. The amount of oxygen consumed during the oxidation of the organic matter in the sample is measured and used to calculate the COD.

Question 5

The abundance of cyanobacterial mats has greatly declined due to the evolution of
A) antimicrobial-producing fungi.
B) bacteriophages.
C) animal grazers.
D) Proteobacteria.

Accepted Answer

Cyanobacterial mats are often consumed by animal grazers, leading to a decline in their abundance. This is supported by research that has found that grazing by snails, gastropods, and other invertebrates significantly reduces the biomass and diversity of cyanobacterial mats. Antimicrobial-producing fungi, bacteriophages, and Proteobacteria may play a role in shaping microbial communities, but there is no evidence to suggest that they are the primary drivers of the decline in cyanobacterial mats.

Question 6

A notorious biofilm former implicated in cystic fibrosis is
A) Bacillus subtilis.
B) Escherichia coli.
C) Lactobacillus acidophilus.
D) Pseudomonas aeruginosa.

Accepted Answer

Pseudomonas aeruginosa is a well-known biofilm-forming pathogen and is often associated with chronic infections in patients with cystic fibrosis. It has the ability to form biofilms on both biotic and abiotic surfaces, which makes it difficult to clear infections treated with antibiotics.

Question 7

The photosynthetic pigments bacteriorhodopsin and proteorhodopsin are present in ________ and ________, respectively.
A) Archaea / Bacteria
B) Bacteria / Archaea
C) Bacteria / Bacteria
D) Bacteria / Eukarya

Accepted Answer

Bacteriorhodopsin is found in Archaea, specifically in halophilic archaea, while proteorhodopsin is present in Bacteria, indicating their roles in different domains of life.

Question 8

According to bacterial abundance studies done so far on soils, the ________ represent the most abundant phylum.
A) Proteobacteria
B) Acidobacteria
C) Actinobacteria
D) Firmicutes

Accepted Answer

Proteobacteria are generally considered the most abundant phylum in soil bacterial communities, according to numerous studies on soil microbial diversity.

Question 9

A soil that lacks a dominate particle size is referred to as a(n)
A) aggregation.
B) bisequum.
C) loam.
D) mottled soil.

Accepted Answer

A loam soil contains a relatively even mixture of sand, silt, and clay particles, without one dominant particle size.

Question 10

Biofilm structure is determined by
A) nutritional factors.
B) signaling factors.
C) the local environment.
D) the local environment, nutritional factors, and signaling molecules.

Accepted Answer

The answer of Biofilm structure is determined by
A) nutritional factors.
B)...

Question 11

Which bacterial genus is responsible for producing ferrous iron (Fe²⁺) in groundwater?
A) Alteromonas
B) Aquifex
C) Geobacter
D) Loktanella

Accepted Answer

Geobacter is a genus of bacteria known for their ability to produce ferrous iron (Fe²⁺) in groundwater through a process known as dissimilatory metal reduction. They are anaerobic bacteria that use metals such as iron as electron acceptors in their metabolism. This process has important implications for groundwater quality and environmental remediation.

Question 12

An organism living in the bottommost region of a body of water is described as being
A) benthic.
B) litoral.
C) neritic.
D) pelagic.

Accepted Answer

The term "benthic" refers to organisms living on or in the bottom of a body of water. This can include both freshwater and marine environments.

Question 13

In the soil, oxygen concentrations are highly variable even within a soil particle. The center of the particle may be anoxic even if the outer portions are oxygen rich. In this context, facultative anaerobes could be found
A) at the surface of the particle.
B) in the center of the particle.
C) in the middle regions of the particle.
D) throughout the particle.

Accepted Answer

Facultative anaerobes are capable of living in both aerobic and anaerobic environments. Therefore, they could be found throughout the soil particle, regardless of the oxygen concentrations in different regions.

Question 14

A population consists of
A) all of the individuals of all species in the same area.
B) all of the individuals of one species in the same area.
C) all of the individuals that interact in different areas.
D) all of the individuals that interact in the same area.

Accepted Answer

The answer of A population consists of
A) all of the...

Question 15

During periods of stratification, transfer between surface and bottom waters is controlled by
A) mixing.
B) diffusion.
C) niche partitioning.
D) current.

Accepted Answer

During periods of stratification, mixing and currents are reduced, so diffusion becomes the main mechanism for transfer between surface and bottom waters. Niche partitioning may occur within the water column, but it does not directly control transfer between surface and bottom waters.

Question 16

The generation time of Escherichia coli in the human intestine is ________ in laboratory culture.
A) at about the same rate as
B) faster than
C) more optimal than
D) slower than

Accepted Answer

The generation time of Escherichia coli in the human intestine is slower than in laboratory culture. This is because laboratory conditions do not mimic the environment of the human intestine, which is more complex and provides different nutrients and conditions for growth.

Question 17

Which of the following represents increasing microbial diversity?
A) guild-community-population
B) population-guild-community
C) cell-community-population
D) community-guild-population

Accepted Answer

Population refers to organisms of the same species in a given area. A guild includes different species that exploit the same resources in similar ways. A community encompasses all the different species living in a particular area. Thus, moving from population to guild to community represents increasing microbial diversity.

Question 18

Which metabolic strategy is most common in chemolithotrophic mats?
A) ammonia oxidation
B) iron oxidation
C) nitrate reduction
D) sulfur oxidation

Accepted Answer

Chemolithotrophic mats primarily rely on oxidizing sulfur compounds for their energy generation. This is because sulfur compounds are abundant in their environment and can serve as electron donors in the absence of organic material.

Question 19

Assuming exposure to the same climate, which of the following aquatic systems would be most stratified?
A) 20 m deep freshwater river
B) 50 m deep marine water fjord
C) 200 m deep saltwater lake
D) 300 m deep freshwater lake

Accepted Answer

The answer of Assuming exposure to the same climate, which...

Question 20

Which metric describes the proportion of EACH species present in a community?
A) species abundance
B) species diversity
C) species evenness
D) species richness

Accepted Answer

The answer of Which metric describes the proportion of EACH...

Quiz 20: Microbial Ecosystems

In a stratified lake, the warmer and less dense layer is called the

Which is the correct order of increasing size in soil particles?

Some nitrifying prokaryotes carry out metabolic cooperation by a process known as

The chemical oxygen demand (COD) of a body of water is determined using a(n)

The abundance of cyanobacterial mats has greatly declined due to the evolution of

A notorious biofilm former implicated in cystic fibrosis is

The photosynthetic pigments bacteriorhodopsin and proteorhodopsin are present in and , respectively.

According to bacterial abundance studies done so far on soils, the ________ represent the most abundant phylum.

A soil that lacks a dominate particle size is referred to as a(n)

Biofilm structure is determined by

Which bacterial genus is responsible for producing ferrous iron (Fe²⁺) in groundwater?

An organism living in the bottommost region of a body of water is described as being

In the soil, oxygen concentrations are highly variable even within a soil particle. The center of the particle may be anoxic even if the outer portions are oxygen rich. In this context, facultative anaerobes could be found

A population consists of

During periods of stratification, transfer between surface and bottom waters is controlled by

The generation time of Escherichia coli in the human intestine is ________ in laboratory culture.

Which of the following represents increasing microbial diversity?

Which metabolic strategy is most common in chemolithotrophic mats?

Assuming exposure to the same climate, which of the following aquatic systems would be most stratified?

Which metric describes the proportion of EACH species present in a community?