Lesson 1.5: The Nitrogen Cycle

A set of vocabulary flashcards covering the key stages, bacterial organisms, chemical transformations, and environmental impacts associated with the nitrogen cycle.

Nitrogen Cycle

The biogeochemical cycle in which nitrogen is constantly recycled between the atmosphere, living organisms, soil, and water in different chemical forms.

Biological Necessity of Nitrogen

The requirement of nitrogen by plants and animals to synthesize proteins and DNA, without which they cannot grow, reproduce, or survive.

Nitrogen Fixation

The process of converting atmospheric nitrogen gas ($N_2$) into ammonia ($NH_3 / NH_4^+$) by bacteria, or into nitrates ($NO_3^-$) through the energy of lightning.

Rhizobium

A genus of nitrogen-fixing bacteria found in soil and root nodules of legumes that converts atmospheric nitrogen ($N_2$) into ammonia ($NH_3 / NH_4^+$).

Lightning Nitrogen Fixation

The abiotic process in which lightning provides enough energy for atmospheric nitrogen ($N_2$) to react with oxygen, forming nitrates ($NO_3^-$) in rain that enter the soil.

Nitrification

The biological process in which soil bacteria convert ammonia/ammonium ($NH_3 / NH_4^+$) into nitrites ($NO_2^-$) and subsequently into nitrates ($NO_3^-$).

Nitrosomonas

A genus of nitrifying bacteria that converts ammonia into nitrites ($NH_3 \rightarrow NO_2^-$).

Nitrobacter

A genus of nitrifying bacteria that converts nitrites into nitrates ($NO_2^- \rightarrow NO_3^-$).

Ammonification

The process where decomposers (bacteria and fungi) break down organic nitrogen from dead organisms and waste (urine, faeces, leaf litter) into ammonia ($NH_3$) or ammonium ($NH_4^+$).

Denitrification

The process where denitrifying bacteria convert nitrates ($NO_3^-$) back into nitrogen gas ($N_2$) under anaerobic conditions, releasing it back into the atmosphere.

Pseudomonas

A genus of denitrifying bacteria that converts nitrates ($NO_3^-$) to nitrogen gas ($N_2$) in anaerobic conditions.

Eutrophication

Water pollution caused by excess nitrate runoff from synthetic fertilizers, leading to algal blooms and disrupted aquatic ecosystems.

Precision Agriculture, Hydroponics, and Vertical Farming

Agricultural solutions used in regions like the UAE to manage nutrient delivery efficiently without causing excessive fertilizer runoff and groundwater contamination.