Biogeochemical Nutrient Cycles Flashcards

Which process converts dissolved nitrate (NO₃⁻) back into atmospheric nitrogen gas (N₂)?

Answer: Denitrification

Denitrification is carried out by anaerobic bacteria that reduce nitrate to N₂, returning nitrogen to the atmosphere.

In the phosphorus cycle, which reservoir holds the largest long-term store of phosphorus?

Answer: Sedimentary rocks

Sedimentary rocks are the primary long-term reservoir for phosphorus, which is released slowly through weathering.

What is the term for the release of nutrients from decomposing organic matter back into inorganic form?

Answer: Mineralization

Mineralization is the microbial decomposition of organic compounds that converts nutrients into inorganic forms available to plants.

Which gas released from wetlands and rice paddies is a significant product of the carbon cycle and a potent greenhouse gas?

Answer: Methane (CH₄)

Methane (CH₄) is produced by methanogenic archaea under the anaerobic conditions found in wetlands and flooded rice paddies.

Sulfur enters the atmosphere naturally in large quantities primarily through which process?

Answer: Volcanic eruptions

Volcanic eruptions release large amounts of sulfur dioxide (SO₂) into the atmosphere as part of the natural sulfur cycle.

Which type of symbiosis is responsible for the majority of biological nitrogen fixation in terrestrial ecosystems?

Answer: Mutualism between Rhizobium and legumes

Mutualistic Rhizobium bacteria living in legume root nodules fix the most atmospheric nitrogen in terrestrial ecosystems.

When a nutrient is taken up by microorganisms and incorporated into their biomass, making it temporarily unavailable to plants, this is called:

Answer: Immobilization

Immobilization occurs when microbes assimilate inorganic nutrients into their cells, temporarily reducing nutrient availability to plants.