The Nitrogen Cycle worksheet for educational purposes, featuring labeled steps and key points about nitrogen transformation in ecosystems.

Let's solve this step by step.

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Step 1: Understand the Nitrogen Cycle

The nitrogen cycle is a biogeochemical cycle that describes how nitrogen moves through the atmosphere, soil, and living organisms. Key processes include:

- Nitrogen fixation: Conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) or ammonium (NH₄⁺) by certain bacteria.
- Nitrification: Conversion of ammonium to nitrites (NO₂⁻) and then to nitrates (NO₃⁻) by nitrifying bacteria.
- Assimilation: Plants absorb nitrates via their roots and use them to make amino acids and proteins.
- Consumption (Feeding): Animals eat plants and incorporate nitrogen into their own proteins.
- Ammonification (Decomposition & Death and waste): When organisms die or excrete waste, decomposers break down organic nitrogen into ammonium.
- Denitrification: Denitrifying bacteria convert nitrates back into nitrogen gas (N₂), releasing it into the atmosphere.

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Step 2: Label the Numbered Boxes

We are given the following terms to use:
- Denitrifying Bacteria
- Nitrifying Bacteria
- Decomposition
- Death and waste
- Nitrogen Fixation
- Uptake by roots
- Feeding

Now let’s analyze each number:

#### Box 1
- Arrow from "Nitrogen in the air" → to "Bacteria in root nodules"
- This represents Nitrogen Fixation, where bacteria convert atmospheric nitrogen into usable forms.
✔ 1 = Nitrogen Fixation

#### Box 2
- Arrow from "Ammonium ions" → to "Nitrate ions", with bacteria involved
- This is nitrification — conversion of ammonium to nitrate by nitrifying bacteria.
✔ 2 = Nitrifying Bacteria

#### Box 3
- Arrow from "Nitrate ions" → to plant (flower)
- This is the process where plants absorb nitrates through their roots.
✔ 3 = Uptake by roots

#### Box 4
- Arrow from plant → animal (rabbit)
- This is feeding — animals consume plants for nutrients.
✔ 4 = Feeding

#### Box 5
- Arrow from rabbit → dead animal (or waste)
- This shows the death and waste of organisms, leading to release of nitrogen compounds.
✔ 5 = Death and waste

#### Box 6
- Arrow from dead animal → "Ammonium ions"
- This is decomposition by decomposers breaking down organic matter into ammonium.
✔ 6 = Decomposition

#### Box 7
- Arrow from "Nitrate ions" → back to "Nitrogen in the air", with bacteria
- This is denitrification, where denitrifying bacteria convert nitrates back into nitrogen gas.
✔ 7 = Denitrifying Bacteria

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✔ Final Answers for the Diagram:

| Box | Label |
|-----|-------|
| 1 | Nitrogen Fixation |
| 2 | Nitrifying Bacteria |
| 3 | Uptake by roots |
| 4 | Feeding |
| 5 | Death and waste |
| 6 | Decomposition |
| 7 | Denitrifying Bacteria |

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Step 3: Fill in the Key Points

We are given words to use:
legumes, nitrate, bacteria, roots, denitrifying, fixing

#### 1. A key type of organism involved in the cycling of nitrogen are bacteria.

✔ Answer: bacteria

#### 2. Nitrogen-______ bacteria are found in the root nodules of ______ and can convert inert nitrogen gas into nitrogen-containing ions.

- Nitrogen-fixing bacteria live in root nodules of legumes (like beans, peas).
- They fix atmospheric nitrogen into ammonia.

✔ Answer: fixing, legumes

#### 3. Nitrifying bacteria can convert ammonium ions to ______ ions, which can be taken up by the ______ of plants.

- Nitrifying bacteria convert ammonium → nitrate.
- Plants take up nitrate via their roots.

✔ Answer: nitrate, roots

#### 4. Some bacteria, found in water-logged soils, convert nitrates back into nitrogen gas, these are known as ______ bacteria.

- These are denitrifying bacteria.

✔ Answer: denitrifying

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✔ Final Answers for Key Points:

1. A key type of organism involved in the cycling of nitrogen are bacteria.
2. Nitrogen-fixing bacteria are found in the root nodules of legumes and can convert inert nitrogen gas into nitrogen-containing ions.
3. Nitrifying bacteria can convert ammonium ions to nitrate ions, which can be taken up by the roots of plants.
4. Some bacteria, found in water-logged soils, convert nitrates back into nitrogen gas, these are known as denitrifying bacteria.

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✔ Summary

Diagram Labels:
- 1: Nitrogen Fixation
- 2: Nitrifying Bacteria
- 3: Uptake by roots
- 4: Feeding
- 5: Death and waste
- 6: Decomposition
- 7: Denitrifying Bacteria

Key Points:
1. bacteria
2. fixing, legumes
3. nitrate, roots
4. denitrifying

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