Ecology Biogeochemical Nutrient Cycles 2 — Questions and Answers
Question 1: Which process converts dissolved nitrate (NO₃⁻) back into atmospheric nitrogen gas (N₂)?
- Nitrification
- Denitrification (Correct answer)
- Ammonification
- Nitrogen fixation
Correct answer: Denitrification
Denitrification is carried out by anaerobic bacteria that reduce nitrate to N₂, returning nitrogen to the atmosphere.
Question 2: In the phosphorus cycle, which reservoir holds the largest long-term store of phosphorus?
- Ocean water
- Living biomass
- Sedimentary rocks (Correct answer)
- Soil organic matter
Correct answer: Sedimentary rocks
Sedimentary rocks are the primary long-term reservoir for phosphorus, which is released slowly through weathering.
Question 3: What is the term for the release of nutrients from decomposing organic matter back into inorganic form?
- Immobilization
- Mineralization (Correct answer)
- Assimilation
- Volatilization
Correct answer: Mineralization
Mineralization is the microbial decomposition of organic compounds that converts nutrients into inorganic forms available to plants.
Question 4: Which gas released from wetlands and rice paddies is a significant product of the carbon cycle and a potent greenhouse gas?
- Carbon dioxide (CO₂)
- Nitrous oxide (N₂O)
- Methane (CH₄) (Correct answer)
- Hydrogen sulfide (H₂S)
Correct answer: Methane (CH₄)
Methane (CH₄) is produced by methanogenic archaea under the anaerobic conditions found in wetlands and flooded rice paddies.
Question 5: Sulfur enters the atmosphere naturally in large quantities primarily through which process?
- Forest fires
- Volcanic eruptions (Correct answer)
- Ocean evaporation
- Animal respiration
Correct answer: Volcanic eruptions
Volcanic eruptions release large amounts of sulfur dioxide (SO₂) into the atmosphere as part of the natural sulfur cycle.
Question 6: Which type of symbiosis is responsible for the majority of biological nitrogen fixation in terrestrial ecosystems?
- Parasitism between fungi and roots
- Mutualism between Rhizobium and legumes (Correct answer)
- Commensalism between algae and mosses
- Competition between soil bacteria
Correct answer: Mutualism between Rhizobium and legumes
Mutualistic Rhizobium bacteria living in legume root nodules fix the most atmospheric nitrogen in terrestrial ecosystems.
Question 7: When a nutrient is taken up by microorganisms and incorporated into their biomass, making it temporarily unavailable to plants, this is called:
- Leaching
- Immobilization (Correct answer)
- Mineralization
- Adsorption
Correct answer: Immobilization
Immobilization occurs when microbes assimilate inorganic nutrients into their cells, temporarily reducing nutrient availability to plants.
Ecology Biogeochemical Nutrient Cycles 2
Which process converts dissolved nitrate (NO₃⁻) back into atmospheric nitrogen gas (N₂)?