Nitrogen cycle

Definition

The nitrogen cycle is a natural process that describes the movement of nitrogen through the atmosphere, lithosphere, hydrosphere, and biosphere. It plays a crucial role in ecosystem functioning as it transforms nitrogen from its atmospheric form into compounds usable by living organisms, and then back into the atmosphere, maintaining balance within the environment.

5 Must Know Facts For Your Next Test

1. The nitrogen cycle consists of several key processes: nitrogen fixation, nitrification, ammonification, and denitrification.
2. Nitrogen-fixing bacteria, found in root nodules of legumes or in the soil, play a critical role in converting atmospheric nitrogen into forms usable by plants.
3. Nitrification involves the conversion of ammonia to nitrites and then to nitrates, making nitrogen accessible to a wider range of plants.
4. Human activities, such as the use of fertilizers and fossil fuel combustion, have significantly increased nitrogen levels in ecosystems, leading to issues like water pollution and algal blooms.
5. The balance of the nitrogen cycle is essential for ecosystem health; disruptions can result in harmful environmental impacts including soil degradation and loss of biodiversity.

Review Questions

• How do human activities influence the nitrogen cycle, and what are the potential consequences of these influences?
  • Human activities, such as agricultural practices that utilize synthetic fertilizers and industrial processes that burn fossil fuels, dramatically alter the natural nitrogen cycle. These actions increase nitrogen levels in soil and waterways, leading to nutrient overloads that can cause water pollution, algal blooms, and loss of aquatic life. Understanding these impacts highlights the importance of sustainable practices to maintain ecological balance.
• Describe the key processes involved in the nitrogen cycle and their roles in supporting ecosystem health.
  • The nitrogen cycle consists of processes such as nitrogen fixation, where atmospheric nitrogen is converted into ammonia by bacteria; nitrification, which transforms ammonia into nitrates; ammonification, where organic waste is converted back to ammonia; and denitrification, which returns nitrogen gas to the atmosphere. Each process plays a vital role in making nitrogen available to plants for growth and supporting overall ecosystem health by maintaining nutrient balance.
• Evaluate the impact of disruptions to the nitrogen cycle on ecosystem functioning and biodiversity.
  • Disruptions to the nitrogen cycle can have profound effects on ecosystem functioning and biodiversity. Increased levels of nitrogen from human activities can lead to soil degradation and shifts in plant communities due to nutrient imbalances. This can reduce habitat diversity for various species, ultimately threatening ecosystems' resilience. Evaluating these impacts underscores the need for careful management of nitrogen inputs to preserve biodiversity and ensure healthy ecosystems.

Related terms

nitrogen fixation:

The process through which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related compounds, making it available for uptake by plants.

denitrification: A microbial process that converts nitrates (NO₃) and nitrites (NO₂) back into nitrogen gas (N₂), returning it to the atmosphere and completing the nitrogen cycle.

ammonification: The conversion of organic nitrogen from dead organisms and waste products into ammonia, which can then be further processed by bacteria in the soil.