Collegeboard: Nitrogen Chcle

Question 1

Nitrogen cycle

Answer 1

-Movement of atoms and molecules containing the element nitrogen between sources and sinks
-Biogeochemical cycle
-Can be disrupted by human activity
-Stabilize and regulate the flow of matter through ecosystems

Question 2

Importance of nitrogen

Answer 2

-Every living thing needs it
-In amino acids, proteins, nucleic acids, DNA
-A limiting factor
-Producers need nitrogen to grow

Question 3

Fixation

Answer 3

N2 fixed by lightning (abiotic) or microbes in soil/root nodules (biotic)

Question 4

Ammonification

Answer 4

NH3 converted to NH4+ by soil bacteria; NH3 can also be added by decay of organic material

Question 5

Nitrification

Answer 5

NH4+ converted into NO2- (nitrite); then NO3- (nitrate)

Question 6

Assimilation

Answer 6

NO3- (nitrate) uptaken by plants through roots (then to animals)

Question 7

Dentrification

Answer 7

NO3- can be converted back to N2- by soil bacteria

Question 8

Nitrogen reservoirs

Answer 8

-Primarily driven by microbial action
-Major reservoir is in the atmosphere (78%)
-Most reservoirs store nitrogen for short periods of time