The Nitrogen Cycle worksheet illustrating key stages including nitrogen fixation, nitrification, decomposition, and uptake by roots, designed for educational use.

Task: Label the numbered boxes in the nitrogen cycle diagram and answer the key points.

#### Step 1: Understand the Nitrogen Cycle
The nitrogen cycle is a biogeochemical cycle that describes how nitrogen moves through the environment. Key processes include:
- Nitrogen Fixation: Conversion of atmospheric nitrogen (N₂) into ammonia (NH₃) by certain bacteria.
- Uptake by Roots: Plants absorb nitrate ions (NO₃⁻) from the soil.
- Feeding: Animals consume plants, incorporating nitrogen into their bodies.
- Decomposition: Breakdown of organic matter by decomposers.
- Nitrification: Conversion of ammonia (NH₃) to nitrite (NO₂⁻) and then to nitrate (NO₃⁻) by nitrifying bacteria.
- Denitrification: Conversion of nitrate (NO₃⁻) back to nitrogen gas (N₂) by denitrifying bacteria.

#### Step 2: Label the Diagram
We will label the numbered boxes based on the processes and organisms involved in the nitrogen cycle.

1. Box 1: This process involves the conversion of nitrogen in the air into a form usable by plants. This is Nitrogen Fixation.
- Label: Nitrogen Fixation

2. Box 2: These are the bacteria responsible for converting ammonia (NH₃) into nitrate (NO₃⁻). These are Nitrifying Bacteria.
- Label: Nitrifying Bacteria

3. Box 3: This is the process by which plants absorb nitrate ions (NO₃⁻) from the soil. This is Uptake by roots.
- Label: Uptake by roots

4. Box 4: This is the process by which animals obtain nitrogen by consuming plants. This is Feeding.
- Label: Feeding

5. Box 5: This is the process where dead organisms and waste products are broken down by decomposers. This is Decomposition.
- Label: Decomposition

6. Box 6: These are the bacteria found in waterlogged soils that convert nitrate (NO₃⁻) back into nitrogen gas (N₂). These are Denitrifying Bacteria.
- Label: Denitrifying Bacteria

7. Box 7: This is the process where legumes (plants with root nodules) fix nitrogen from the atmosphere. This is part of Nitrogen Fixation.
- Label: Nitrogen Fixation

#### Step 3: Answer the Key Points
Using the labeled diagram and the provided words, we can fill in the key points.

1. A key type of organism involved in the cycling of nitrogen are _________.
- The key organisms are bacteria.
- Answer: bacteria

2. Nitrogen _______ bacteria are found in the root nodules of _________ and can convert inert nitrogen gas into nitrogen-containing ions.
- The bacteria found in root nodules are nitrogen-fixing bacteria, and they are found in legumes.
- 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 ions (NH₄⁺) to nitrate ions (NO₃⁻), which are absorbed by plant roots.
- Answer: nitrate, roots

4. Some bacteria, found in waterlogged soils, convert nitrates back into nitrogen gas; these are known as ______________ bacteria.
- These bacteria are denitrifying bacteria.
- Answer: denitrifying

#### Final Answer
- Labeled Diagram:
1. Nitrogen Fixation
2. Nitrifying Bacteria
3. Uptake by roots
4. Feeding
5. Decomposition
6. Denitrifying Bacteria
7. Nitrogen Fixation

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

Final Answer Box:
\boxed{
\text{1. Nitrogen Fixation, 2. Nitrifying Bacteria, 3. Uptake by roots, 4. Feeding, 5. Decomposition, 6. Denitrifying Bacteria, 7. Nitrogen Fixation}
}