1. Nitrogen Cycle
• All animals require Nitrogen to make
a.a., which then make proteins.
• Atm contains 80% N2 gas.
• N2 gas (most abundant form) can not
be used by most living things.
• Bacteria are the only organisms that
use nitrogen directly from the
atmosphere.

2. Nitrogen
Cycle

3. Nitrogen Cycle Terminology
• Nitrogen Fixation –
– Nitrogen gas in atm to ammonia (bacteria in soil)
• Nitrification-
– ammonia to nitrate (bacteria in soil)
• Assimilation-
– Absorption of ammonia and nitrate by plants
• Ammonification-
– break down of dead organisms returns “unused nitrogen” to
soil
• Decomposer-
– Organism that breaks down organic matter into simpler
compounds.
• Denitrification
– Conversion of nitrates back to nitrogen gas (returns to air
bacteria)

4. Why is the nitrogen cycle
important?
• Why is nitrogen important to living things?
• Used to make proteins.
• How do plants obtain nitrogen?
• Absorb it from soil.
• How do animals obtain nitrogen?
• Eat plants or other animals. Absorbed
from bacteria.
• Nitrogen is also released by
decomposition.