Nitrification: The Nitrogen Cycle Explained
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Nitrification: The Nitrogen Cycle Explained
Understanding the crucial process of ammonia oxidation NCEA Level 3 Biology - Standard 91393 Year 13 Biology
What happens to nitrogen in our ecosystems?
Think about fertilizers on farms Dead plant and animal matter How does nitrogen move through the environment?
The Nitrogen Cycle Overview
Nitrogen fixation - converting N₂ to ammonia Nitrification - oxidizing ammonia to nitrates Assimilation - plants uptake nitrogen compounds Ammonification - decomposition releases ammonia Denitrification - nitrates back to N₂ gas
Nitrification Definition
The biological oxidation of ammonia (NH₃) or ammonium (NH₄⁺) to nitrite (NO₂⁻) and then to nitrate (NO₃⁻) by specialized bacteria
Two-Step Nitrification Process
{"left":"Step 1: Ammonia Oxidation\nNH₃ + O₂ → NO₂⁻ + H⁺ + H₂O\nPerformed by ammonia-oxidizing bacteria (AOB)\nExamples: Nitrosomonas, Nitrosospira","right":"Step 2: Nitrite Oxidation\nNO₂⁻ + ½O₂ → NO₃⁻\nPerformed by nitrite-oxidizing bacteria (NOB)\nExamples: Nitrobacter, Nitrococcus"}
Key Bacteria in Nitrification
Nitrosomonas - converts ammonia to nitrite Nitrobacter - converts nitrite to nitrate Nitrosospira - also oxidizes ammonia Nitrococcus - marine nitrite oxidizer These are chemolithotrophic bacteria They gain energy from chemical oxidation
Environmental Factors Affecting Nitrification
Nitrification in Action
Work in pairs to trace nitrogen through a farm ecosystem Start with animal manure containing ammonia Identify where each step of nitrification occurs Predict what happens to the nitrates formed Consider environmental factors that might affect the process
Importance of Nitrification
Makes nitrogen available to plants as nitrates Nitrates are easily absorbed by plant roots Essential for protein synthesis in plants Supports food web productivity Can lead to soil acidification Nitrates can leach into waterways
Summary and NCEA Connections
Nitrification = 2-step bacterial oxidation process Ammonia → Nitrite → Nitrate Requires oxygen and specific bacteria Environmental factors affect the rate Critical for ecosystem nitrogen availability Understanding helps with agricultural management