Identify the sequence of steps of nitrogen cycle showing relationship between the three main nitrogen pools-atmospheric, soil and and biomass.

Options

A. Atmosphere `N_2 to`soil `N_(2)` Pool `to` plant biomass`to`animal biomass`to`decayng biomass
B. Animal biomass`to`decaying biomass`to`plant biomass`to`soil `N_(2)` Pool `to`atmospheric `N_(2)`
C. Soil `N_(2)` Pool `to` atmospheric `N_(2)to`decaying biomass`to`animal biomass
D. none of the above

Answer

### Step-by-Step Solution for the Nitrogen Cycle

1. **Atmospheric Nitrogen (N₂) Fixation**:
- The nitrogen cycle begins with atmospheric nitrogen, which is abundant in the atmosphere but not directly usable by most living organisms.
- Nitrogen fixation occurs, where atmospheric nitrogen is converted into ammonia (NH₃) by nitrogen-fixing bacteria (biological fixation) or through non-biological processes like lightning.

**Hint**: Remember that nitrogen fixation is essential for converting atmospheric nitrogen into a usable form for plants.

2. **Conversion to Soil Nitrogen**:
- The ammonia produced is then converted into nitrites (NO₂⁻) and nitrates (NO₃⁻) through a process called nitrification, facilitated by nitrifying bacteria in the soil.
- This process enriches the soil nitrogen pool, making it available for plant uptake.

**Hint**: Nitrification is crucial as it transforms ammonia into forms that plants can absorb.

3. **Plant Uptake**:
- Plants absorb nitrates from the soil through their roots. This is the primary way plants obtain nitrogen, which is essential for their growth and development.
- Once absorbed, nitrogen is incorporated into amino acids, proteins, and nucleic acids within the plant biomass.

**Hint**: Focus on how plants are the primary producers that convert nitrogen into organic forms.

4. **Animal Biomass**:
- Herbivores (primary consumers) eat the plants and obtain nitrogen from the plant biomass. This nitrogen is then used to build their own proteins and nucleic acids.
- Carnivores (secondary consumers) obtain nitrogen by consuming herbivores.

**Hint**: Animals rely on plants for nitrogen, highlighting the interdependence in the ecosystem.

5. **Decaying Biomass**:
- When plants and animals die, their bodies decompose. Decomposers like bacteria and fungi break down the organic matter, releasing nitrogen back into the soil in the form of ammonium (NH₄⁺) through a process called ammonification.
- This process returns nitrogen to the soil nitrogen pool.

**Hint**: Decomposition is vital for recycling nutrients back into the ecosystem.

6. **Return to Atmospheric Nitrogen**:
- Some nitrogen in the soil is converted back to atmospheric nitrogen through denitrification, a process carried out by denitrifying bacteria. This completes the nitrogen cycle by returning nitrogen to the atmosphere.

**Hint**: Denitrification is the final step that ensures nitrogen is cycled back into the atmosphere.

### Summary of the Sequence:
1. Atmospheric Nitrogen (N₂)
2. Soil Nitrogen (NH₃, NO₂⁻, NO₃⁻)
3. Plant Biomass
4. Animal Biomass
5. Decaying Biomass
6. Return to Atmospheric Nitrogen

### Final Answer:
The correct sequence of the nitrogen cycle showing the relationship between the three main nitrogen pools (atmospheric, soil, and biomass) is:
- Atmospheric Nitrogen → Soil Nitrogen → Plant Biomass → Animal Biomass → Decaying Biomass → Atmospheric Nitrogen.