Question

directions: color in the features in the nitrogen - cycle diagram. use the word bank to label the diagram.
word bank
ammonium (nh₄⁺)
assimilation
atmospheric nitrogen (n₂)
decomposers
denitrifying bacteria
lightning fixation
nitrates (no₃⁻)
nitrifying bacteria
nitrites (no₂⁻)
nitrogen - fixing bacteria
directions: define the terms in the table below.

term	definition
2. nitrification
3. denitrification
4. assimilation
5. nitrogen fixation
6. lightning fixation

Explanation:

1. Ammonification: The process by which decomposers break down organic - nitrogen compounds (like proteins) in dead organisms and waste products, releasing ammonium ($NH_4^+$) into the soil.
2. Nitrification: A two - step process where nitrifying bacteria first convert ammonium ($NH_4^+$) into nitrites ($NO_2^-$) and then into nitrates ($NO_3^-$), making nitrogen more available for plant uptake.
3. Denitrification: The process in which denitrifying bacteria convert nitrates ($NO_3^-$) back into atmospheric nitrogen ($N_2$), returning nitrogen to the atmosphere.
4. Assimilation: The process by which plants and animals incorporate nitrogen - containing compounds (such as nitrates and ammonium) into their tissues. Plants absorb nitrates and ammonium from the soil and use them to build proteins and other nitrogen - containing biomolecules, and animals obtain nitrogen by eating plants or other animals.
5. Nitrogen fixation: The conversion of atmospheric nitrogen ($N_2$) into ammonia ($NH_3$) or other nitrogen - containing compounds that can be used by living organisms. This can be done by nitrogen - fixing bacteria (either free - living or symbiotic with plants like legumes) or by non - biological means like lightning.
6. Lightning fixation: During a lightning strike, the high temperatures and pressures cause nitrogen ($N_2$) and oxygen ($O_2$) in the atmosphere to react, forming nitrogen oxides. These nitrogen oxides dissolve in rainwater and are carried to the soil, where they can be converted into forms usable by plants.

Answer:

1. The process of decomposers releasing ammonium from organic - nitrogen compounds.
2. Bacterial conversion of ammonium to nitrites and then nitrates.
3. Bacterial conversion of nitrates to atmospheric nitrogen.
4. Incorporation of nitrogen - containing compounds into plant and animal tissues.
5. Conversion of atmospheric nitrogen into usable compounds by bacteria or lightning.
6. Nitrogen and oxygen reaction during lightning to form nitrogen oxides for plant use.