Problem 10 - Biology

Question

The conversion of ammonia to nitrate, known as is a two-step process performed by soil bacteria. (a) nitrogen fixation (b) nitrification (c) assimilation (d) ammonification (e) denitrification

Step-by-Step Solution

Answer

The process is (b) nitrification.

Step 1: Identify the Process

To determine which two-step process in soil bacteria converts ammonia to nitrate, we need to identify the steps involved.

Step 2: Review Bacterial Processes

Recall that nitrification is the process in which ammonia is converted first to nitrite, then to nitrate, both by different groups of bacteria. This matches the description of a two-step process.

Step 3: Understand Other Terms

Understand that nitrogen fixation is the conversion of nitrogen gas to ammonia. Assimilation involves incorporating nitrates into organic molecules. Ammonification recycles organic nitrogen back to ammonia, and denitrification converts nitrate to nitrogen gas. These do not match the described process.

Step 4: Conclusion Based on Analysis

The two-step conversion of ammonia to nitrate by soil bacteria is called nitrification.

Key Concepts

Ammonia

Ammonia is a colorless gas with a distinct pungent smell, and it is chemically represented as NH₃. It plays a vital role in the nitrogen cycle, acting as a starting point for nitrogen compounds beneficial to plant growth. When ammonia is introduced into the soil, either through natural processes or as a fertilizer, it is at the beginning of a transformative process.

• Ammonia serves as a source of nitrogen, an essential nutrient for plants.
• Nitrogen obtained from ammonia helps in the synthesis of amino acids, which are the building blocks of proteins.
• It is crucial for chlorophyll production, essential for photosynthesis in plants.

In agriculture, ammonia is often directly applied to the soil to ensure crops have enough nitrogen to support their growth. This application requires understanding of how ammonia is further processed in the soil to form more usable compounds, especially the role of nitrification.

Nitrate

Nitrate, represented chemically as NO₃⁻, is the final product of ammonia transformation through nitrification. It is a more stable form of nitrogen which plants can readily absorb and use from the soil.

• Nitrate is highly soluble in water, making it easily transportable within the soil.
• It is directly taken up by plants through their root systems, contributing to robust growth.
• Once inside the plant, nitrate is converted into useful organic molecules such as amino acids and proteins.

The process of nitrification is crucial because it turns ammonia into nitrate, which is in a form that plants can efficiently utilize. However, because nitrates are so soluble, they can also leach into waterways, potentially causing environmental issues if not managed carefully.

Soil Bacteria

Soil bacteria are microscopic organisms that play an essential role in the nitrogen cycle, particularly in the nitrification process. These tiny yet powerful organisms drive the conversion of ammonia into nitrate, making nitrogen available to plant life.

• The nitrification process involves two groups of bacteria: Nitrosomonas and Nitrobacter.
• Nitrosomonas bacteria first convert ammonia (NH₃) to nitrite (NO₂⁻).
• Then, Nitrobacter bacteria convert the nitrite into nitrate (NO₃⁻).

This two-step transformation is essential for keeping nitrogenous substances in forms that plants can use. Without these soil bacteria, the nitrogen cycle would be incomplete, and plant growth would be impaired due to nitrogen deficiency.

Nitrogen Cycle

The nitrogen cycle is a complex process describing how nitrogen moves through the atmosphere, soil, and living organisms. It's a crucial ecological cycle that ensures the availability of nitrogen, an imperative nutrient for life on Earth. The nitrogen cycle includes several key processes:

• Nitrogen Fixation: Atmospheric nitrogen ( N_2) is converted to ammonia (NH₃) by natural phenomena such as lightning or symbiotic bacteria in legumes.
• Nitrification: A two-step process where ammonia is oxidized to nitrate (NO₃⁻) by soil bacteria, making nitrogen accessible to plants.
• Assimilation: Plants absorb nitrate and incorporate it into organic molecules essential for growth and development.
• Ammonification: Decomposition of organic matter returns nitrogen to the soil as ammonia.
• Denitrification: Nitrate is converted back into gaseous nitrogen (N₂), completing the cycle and returning nitrogen to the atmosphere.

Understanding the nitrogen cycle is vital for managing soil health and ensuring sustainable agricultural practices. It highlights the interconnectedness of natural processes and the importance of each step, including nitrification, in maintaining ecological balance.