Study Notes
Nutrient cycles involve the recycling of essential elements like carbon and nitrogen to sustain life on Earth.
- Carbon Cycle — the process by which carbon is exchanged between the atmosphere, organisms, and the Earth. Example: Carbon dioxide is used by plants for photosynthesis and released back into the atmosphere through respiration and combustion.
- Nitrogen Cycle — the process by which nitrogen is converted between its various chemical forms. Example: Nitrogen fixing bacteria convert nitrogen gas into nitrates, which plants can absorb.
- Decomposition — the breakdown of dead organisms and waste, returning nutrients to the soil. Example: Decomposers break down proteins into ammonium compounds.
- Nitrification — the conversion of ammonium compounds into nitrates by bacteria. Example: Nitrifying bacteria convert ammonium into nitrites and then nitrates.
- Denitrification — the conversion of nitrates back into nitrogen gas by bacteria. Example: Denitrifying bacteria in poorly aerated soils convert nitrates to nitrogen gas.
Exam Tips
Key Definitions to Remember
- Carbon Cycle
- Nitrogen Cycle
- Decomposition
- Nitrification
- Denitrification
Common Confusions
- Confusing the roles of nitrifying and denitrifying bacteria
- Misunderstanding how nitrogen is fixed from the atmosphere
Typical Exam Questions
- What is the role of photosynthesis in the carbon cycle? Photosynthesis removes carbon dioxide from the atmosphere and incorporates it into organic molecules.
- How do nitrogen fixing bacteria contribute to the nitrogen cycle? They convert nitrogen gas from the atmosphere into nitrates in the soil.
- What happens during nitrification? Ammonium compounds are converted into nitrites and then nitrates by bacteria.
What Examiners Usually Test
- Understanding the steps of the carbon and nitrogen cycles
- The role of microorganisms in nutrient cycles
- The impact of human activities on these cycles