Nitrogen Cycle Processes Overview

What is the primary process through which nitrogen-fixing bacteria convert atmospheric nitrogen into a usable form for plants?

Which type of bacteria is responsible for converting ammonia into nitrites during nitrification?

In the nitrogen cycle, what form of nitrogen do plants primarily absorb?

What is the main role of decomposers like bacteria and fungi in the nitrogen cycle?

Which process completes the nitrogen cycle by converting nitrates back into atmospheric nitrogen?

What impact do nitrogen-based fertilizers have on aquatic ecosystems?

How does burning fossil fuels affect the nitrogen cycle?

What is the primary consequence of land use changes like deforestation on the nitrogen cycle?

Nitrogen Fixation

Certain bacteria and organisms, including those in legume roots, convert atmospheric nitrogen (N₂) into ammonia (NH₃) or ammonium ions (NH₄⁺). This is called nitrogen fixation.
Lightning can also fix nitrogen, creating nitrogen oxides (that become usable forms like nitrate (NO₃⁻)).

Nitrification

Nitrifying bacteria (like Nitrosomonas) convert ammonia into nitrites (NO₂⁻).
Other nitrifying bacteria (like Nitrobacter) convert nitrites into nitrates (NO₃⁻).
Plants primarily absorb nitrates, making them essential.

Assimilation

Plants absorb nitrates or ammonium from the soil to build essential compounds like proteins.
Animals get nitrogen by consuming plants or other animals, and incorporate it into their own biological molecules (proteins and DNA).

Ammonification (Decomposition)

When organisms die, decomposers (bacteria and fungi) break down organic matter, releasing nitrogen as ammonia (NH₃) or ammonium (NH₄⁺).
This released nitrogen can be utilized by plants or further processed.

Denitrification

In oxygen-poor environments (like waterlogged soil), denitrifying bacteria convert nitrates (NO₃⁻) back into nitrogen gas (N₂).
This released nitrogen gas returns to the atmosphere, completing the cycle.

Human Impact

Excessive use of nitrogen fertilizers can lead to nitrate runoff, harming aquatic ecosystems (eutrophication) and contaminating water sources.
Burning fossil fuels and industrial processes release nitrogen oxides (NOₓ), causing air pollution and acid rain.
Changes in land use (e.g., deforestation) disrupt this natural cycle.

Explore the key processes of the nitrogen cycle, including nitrogen fixation, nitrification, assimilation, and ammonification. Learn how these processes contribute to the ecosystem and the importance of nitrogen in biological systems. This quiz is essential for understanding nutrient cycles in biology.