Nitrogen Cycle

Question 1

Why is N important to living organisms?

Answer 1

Macronutrient
Used to form amino acids, building blocks of proteins & nucleic acids, building blocks of DNA & RNA, used to build new cells

Question 2

Is it a limiting nutrient?

Answer 2

Yes

Question 3

Nitrogen cycle

Answer 3

Process nitrogen circulates among air, soil, water, plants, & animals in an ecosystem, the biosphere.

Question 4

Nitrogen fixation

Answer 4

Process converts nitrogen gas in atmosphere (N2) into forms of nitrogen that producers can use

Question 5

Nitrification

Answer 5

Conversion of ammonia (NH4+) into nitrite (NO2– ) & then into nitrate (NO3– )

Question 6

Assimiliation

Answer 6

Process which producers incorporate elements into their tissues

Question 7

Mineralization

Answer 7

Process which fungal & bacterial decomposers break down organic matter found in dead bodies & waste products & convert it into inorganic compounds

Question 8

Denitrification

Answer 8

Conversion of nitrate (NO3–) in a series of steps into gases nitrous oxide (N2O) & eventually nitrogen gas (N2), which is emitted into atmosphere

Question 9

Leaching

Answer 9

transportation of dissolved molecules through soil via groundwater

Question 10

Where do nitrogen-fixing bacteria live? How do they produce ammonia?

Answer 10

These bacteria live within roots of plants called legumes, which include beans, peas, & clover
Bacteria use sugar provided by legumes to produce nitrogen containing compounds such as nitrates
Excess nitrogen fixed by bacteria is released into soil
Atmospheric nitrogen is fixed by bacteria in soil and in root nodules to produce ammonia/ammonium (some by lightning)

Question 11

How do humans affect the nitrogen cycle?
Consider: Excess nitrogen in soils
Excess nitrogen in natural ecosystems
Burning of nitrogen -> nitric oxide

Answer 11

• Adding nitrogen to soils in fertilizers ultimately increases atmospheric concentrations of nitrogen in regions where fertilizer is applied
• can be transported through atmosphere & deposited by rainfall in natural ecosystems that have adapted over time to a particular level of nitrogen availability, altering the distribution or abundance of species in those ecosystems
• An influx of nitrogen due to human activities has favored colonization by new species that are better adapted to soils with higher fertility
• When fuel is burned, large amounts of nitric oxide is release into atmosphere
• In air, nitric oxide can combine with oxygen & water vapor to form nitric acid.
• Dissolved in rain or snow, the nitric acid falls as acid precipitation

Question 12

What is the primary sink for N?

Answer 12

atmosphere is the primary sink for nitrogen, N2