key term - Nitrogen fixation

Definition

Nitrogen fixation is the process by which atmospheric nitrogen (N₂) is converted into a form usable by living organisms, typically ammonia (NH₃) or related compounds. This vital process is primarily carried out by certain bacteria, which play a crucial role in converting inert nitrogen gas into biologically available forms that can be used by plants and, subsequently, the entire food web.

5 Must Know Facts For Your Next Test

1. Nitrogen fixation is essential for maintaining soil fertility, as it replenishes the nitrogen content that plants need to grow.
2. Some key bacteria involved in nitrogen fixation include Rhizobium, which forms symbiotic relationships with legumes, and Azotobacter, which lives freely in the soil.
3. Nitrogen-fixing bacteria can either be free-living in the soil or form symbiotic relationships with certain plants, particularly legumes.
4. The Haber-Bosch process artificially fixes nitrogen on an industrial scale, producing fertilizers that significantly impact agriculture.
5. Without nitrogen fixation, ecosystems would suffer from nitrogen deficiency, leading to decreased plant growth and lower agricultural yields.

Review Questions

• How do nitrogen-fixing bacteria contribute to soil health and plant growth?
  • Nitrogen-fixing bacteria play a vital role in enhancing soil health by converting atmospheric nitrogen into ammonia, a form that plants can use for growth. By forming symbiotic relationships with certain plants like legumes, these bacteria not only provide necessary nutrients but also help improve soil structure and fertility. The presence of these bacteria enables plants to thrive even in nitrogen-poor soils, thus supporting a diverse array of ecosystems.
• Discuss the ecological significance of the relationship between legumes and nitrogen-fixing bacteria.
  • The relationship between legumes and nitrogen-fixing bacteria is ecologically significant because it allows for the efficient use of atmospheric nitrogen. As legumes host these bacteria in their root nodules, they benefit from increased access to ammonia for their growth. In turn, the legumes provide carbohydrates and a habitat for the bacteria. This mutualistic relationship enhances soil fertility and promotes sustainable agricultural practices by reducing the need for synthetic fertilizers.
• Evaluate the impact of human intervention through the Haber-Bosch process on natural nitrogen fixation processes in ecosystems.
  • The Haber-Bosch process has dramatically increased the availability of fixed nitrogen in agricultural systems by producing synthetic fertilizers. While this has led to higher crop yields and food production, it has also disrupted natural nitrogen cycles and resulted in issues such as nutrient runoff, water pollution, and soil degradation. The reliance on artificial fixation can overshadow natural processes like biological nitrogen fixation, potentially harming ecosystem balance and biodiversity due to changes in nutrient dynamics.

Related terms

ammonification: The process by which organic nitrogen from dead organisms and waste products is converted into ammonia by decomposer bacteria.

nitrification:

The biological process where ammonia is converted into nitrites (NO₂⁻) and then into nitrates (NO₃⁻), making it accessible to plants.

legumes: A family of plants that have symbiotic relationships with nitrogen-fixing bacteria in their root nodules, enhancing soil fertility.