Figure 2: Comparing the nitrogen cycle and carbon cycle β different elements, different key organisms, different processes.
| Feature | Carbon Cycle | Nitrogen Cycle |
|---|---|---|
| Element cycled | Carbon (C) | Nitrogen (N) |
| Main atmospheric form | COβ (0.04%) | Nβ (78%) |
| How plants access it | Directly as COβ via stomata | As nitrates via roots (bacteria convert Nβ first) |
| Key process removing it from atmosphere | Photosynthesis | Nitrogen fixation (by bacteria) |
| Key process returning it to atmosphere | Respiration, combustion, decomposition | Denitrification (by bacteria) |
| Role of bacteria | Decomposition only (releases COβ) | Essential at EVERY stage (fixation, nitrification, ammonification, denitrification) |
| What it is used for in organisms | Energy (respiration), structure (glucose, starch, cellulose) | Proteins, DNA, chlorophyll |
| Human impact | Fossil fuel burning increases atmospheric COβ | Fertiliser overuse leaches nitrates into waterways (eutrophication) |
This comparison covers Nitrogen Cycle vs Carbon Cycle within The Nitrogen Cycle for GCSE Biology. The nitrogen cycle: nitrogen-fixing, nitrifying, denitrifying bacteria, ammonification, and the role of legumes It is section 6 of 14 in this topic. Use this comparison to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for The Nitrogen Cycle
What percentage of the atmosphere is made up of nitrogen gas (Nβ)?
Explain the difference between nitrifying bacteria and denitrifying bacteria, including the conditions in which each type thrives.
Quick recall flashcards
What is nitrogen fixation?
The conversion of atmospheric nitrogen gas (Nβ) into ammonia (NHβ) by nitrogen-fixing bacteria. This is the entry point of atmospheric nitrogen into the food chain.
What is ammonification?
The process by which decomposers (bacteria and fungi) break down nitrogen-containing molecules (proteins and DNA) in dead organisms and waste products, releasing ammonia into the soil.