Question 1

Which process is primarily responsible for the formation of mid-ocean ridges?

Accepted Answer

Seafloor spreading at divergent plate boundaries

Question 2

What is the main energy source for chemolithoautotrophic ecosystems at hydrothermal vents?

Accepted Answer

Chemical energy from reduced minerals

Question 3

Why is the term 'chemoautotrophic ecosystem' considered partly flawed when describing hydrothermal vent communities?

Accepted Answer

Because some vent organisms are heterotrophic

Question 4

Which equation best represents the oxidation of hydrogen sulfide ($$\mathrm{H_2S}) by $$oxygen ($$\mathrm{O_2$}) at $$hydrothermal vents?

Accepted Answer

$$\mathrm{2H_2S + O_2$ \rightarrow 2S + 2H_2O}$$

Question 5

What is the role of thermodynamic disequilibrium in hydrothermal vent ecosystems?

Accepted Answer

It provides energy for ecosystems independent of photosynthesis

Question 6

Which group of microorganisms is most likely to thrive in the highest temperature zones of hydrothermal vents?

Accepted Answer

Hyperthermophiles

Question 7

A black smoker at a hydrothermal vent is formed when:

Accepted Answer

Cold, oxygenated seawater mixes with hot, mineral-laden vent fluid

Question 8

Which of the following best describes the energy metabolism of methanogens found at hydrothermal vents?

Accepted Answer

Reduction of carbon dioxide ($$\mathrm{CO_2$}) $$with hydrogen ($$\mathrm{H_2$})$$

Question 9

Which of the following is a plausible reason why hydrothermal vents are considered 'oases' on the seafloor?

Accepted Answer

They support dense biological communities in otherwise nutrient-poor regions

Question 10

Which chemical reaction is most likely to occur in the anaerobic zones of hydrothermal vents?

Accepted Answer

$$\mathrm{CO_2$ + 4H_2 \rightarrow CH_4$ + 2H_2O}$$

Question 11

How might the study of hydrothermal vent ecosystems inform our search for life on other ocean worlds?

Accepted Answer

It demonstrates that life can thrive using chemical energy in the absence of sunlight

Question 12

Which of the following is NOT a typical electron donor for energy metabolism at hydrothermal vents?

Accepted Answer

Oxygen ($$\mathrm{O_2$})$$

Question 13

A scientist discovers a microorganism at a vent that uses $$\mathrm{NO_3$^-} as an $$electron acceptor and $$\mathrm{H_2$} as an $$electron donor. Which metabolic process is this organism most likely performing?

Accepted Answer

Denitrification

Question 14

Which environmental factor is most critical in creating thermodynamic disequilibrium at hydrothermal vents?

Accepted Answer

Gradients of temperature and geochemistry

Question 15

Which of the following best explains why hydrothermal vent ecosystems can be (partly) independent of photosynthesis?

Accepted Answer

They utilize chemical energy from inorganic compounds

Question 16

Which of the following is a plausible multi-step process for the formation of a hydrothermal vent?

Accepted Answer

Seafloor spreading creates fractures, seawater percolates and heats, mineral-laden fluid is ejected, forming a vent

Question 17

Which of the following taxa is most likely to be found in the mesophilic temperature range (20-40°C) at hydrothermal vents?

Accepted Answer

Epsilonproteobacteria

Question 18

What is the primary reason that hydrothermal vent ecosystems are considered important for understanding the origin of life?

Accepted Answer

They demonstrate that life can originate and persist in extreme, energy-rich environments without sunlight

Question 19

Which of the following reactions is most likely to occur in the presence of both hydrogen ($$\mathrm{H_2$}) $$and carbon dioxide ($$\mathrm{CO_2$}) at a $$hydrothermal vent?

Accepted Answer

$$\mathrm{CO_2$ + 4H_2 \rightarrow CH_4$ + 2H_2O}$$

Chemolithoautotrophy at Hydrothermal Vents: Microbial Life and Ecosystem Function

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