Question 1

Which of the following best describes the difference between species richness and species abundance in a microbial ecosystem?

Accepted Answer

Species richness refers to the total number of different species present, while species abundance refers to the proportion of each species in the ecosystem.

Question 2

A lake experiences a sudden influx of agricultural runoff, leading to a bloom of cyanobacteria. What is the most likely immediate effect on the lake's oxygen levels and microbial community?

Accepted Answer

Oxygen levels decrease due to increased respiration, and species richness decreases while abundance of cyanobacteria increases.

Question 3

Which of the following is a defining characteristic of a microbial guild?

Accepted Answer

A group of metabolically related microbial populations that share a similar niche.

Question 4

Biofilms are important in both medical and industrial contexts. Which of the following is NOT a typical consequence of biofilm formation?

Accepted Answer

Biofilms increase the solubility of oxygen in water.

Question 5

In the context of soil horizons, which layer is characterized by the highest microbial activity and organic material?

Accepted Answer

A horizon

Question 6

Which of the following statements about the deep terrestrial subsurface is correct?

Accepted Answer

Microbial life in the deep subsurface is typically nutrient-limited and dominated by small cells.

Question 7

Which equation correctly represents the process carried out by oxygenic phototrophs in the photic zone of a lake?

Accepted Answer

$$6 \mathrm{CO}_2 + 6 \mathrm{H}_2O \rightarrow \mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6 \mathrm{O}_2$$

Question 8

During summer stratification in a temperate lake, which layer is most likely to become anoxic and why?

Accepted Answer

The hypolimnion, because oxygen is consumed and not replenished due to limited mixing.

Question 9

Which process is measured by the biochemical oxygen demand (BOD) in aquatic environments?

Accepted Answer

The microbial oxygen-consuming capacity of a body of water.

Question 10

What is the primary reason that oxygen minimum zones (OMZs) are expanding in the world’s oceans?

Accepted Answer

Increased nutrient input leads to higher oxygen demand and depletion.

Question 11

Which group of microorganisms is most abundant in the open ocean surface waters?

Accepted Answer

Bacteria

Question 12

What is a major ecological consequence of eutrophication in coastal marine environments?

Accepted Answer

Intermittent anoxia due to removal of $$\mathrm{O}_2 by $$respiration and production of $$\mathrm{H}_2\mathrm{S} by $$sulfate-reducing bacteria.

Question 13

Which of the following best explains why deep-sea hydrothermal vent communities can thrive in the absence of sunlight?

Accepted Answer

Chemolithotrophic prokaryotes utilize inorganic materials from the vents for energy.

Question 14

Which phylum is most commonly found in both soil and freshwater lake microbial communities?

Accepted Answer

Proteobacteria

Question 15

A scientist is studying a microbial mat in the Rio Tinto, Spain, where ferrous iron ($$\mathrm{Fe}^{2+}) is $$oxidized to ferric iron ($$\mathrm{Fe}^{3+}). $$Which type of metabolism is primarily responsible for this process?

Accepted Answer

Chemolithotrophy

Question 16

Which of the following adaptations is most likely found in deep-sea piezophiles?

Accepted Answer

Pressure-regulated gene expression and specialized porins.

Question 17

Which of the following is a plausible reason why viruses are considered the most abundant microorganisms in the oceans?

Accepted Answer

Viral concentrations can reach $$10^8$$ virions/mL, affecting prokaryotic populations and diversity.

Question 18

Which of the following equations represents the process of methanogenesis in anoxic sediments?

Accepted Answer

$$\mathrm{CO}_2 + 4 \mathrm{H}_2 \rightarrow \mathrm{CH}_4 + 2 \mathrm{H}_2O$$

Question 19

Which of the following best describes the role of primary producers in aquatic ecosystems?

Accepted Answer

They produce organic material and oxygen, supporting heterotrophic microbial activity.

Microbial Ecosystems: Structure, Diversity, and Function in Terrestrial and Aquatic Environments

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