Problem 10 - Biology Today and Tomorrow with Physiology

Question

_________ convert nitrogen gas to a form producers can take up. a. Fungi b. Bacteria c. Mammals d. Mosses

Step-by-Step Solution

Answer

Bacteria convert nitrogen gas to a form producers can use.

Step 1: Understand the Nitrogen Cycle

The nitrogen cycle is a natural process by which nitrogen gas is converted into forms that are usable by living organisms. This cycle includes several steps such as nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. Producers, such as plants, primarily take up nitrogen in the form of ammonium (NH₄⁺) and nitrate (NO₃⁻).

Step 2: Identify Nitrogen-Fixing Organisms

In the nitrogen cycle, certain microorganisms are responsible for converting atmospheric nitrogen (N₂) into ammonia (NH₃) through a process called nitrogen fixation. This ammonia can be further converted into forms usable by plants. The primary microorganisms involved in nitrogen fixation are certain bacteria, and some of them are found in association with the roots of leguminous plants.

Step 3: Evaluate the Options

Given the options: a. Fungi b. Bacteria c. Mammals d. Mosses we need to determine which of these groups is responsible for converting nitrogen gas into a form producers can use. Fungi, mammals, and mosses are not involved in nitrogen fixation. Bacteria, on the other hand, play a crucial role in this process.

Step 4: Draw a Conclusion

Since bacteria are the group of organisms that can convert atmospheric nitrogen into a form plants can uptake, they are the correct answer to the question.

Key Concepts

Nitrogen Fixation

Nitrogen fixation is the process by which certain organisms transform nitrogen gas (N₂) in the atmosphere into ammonia (NH₃), a form that is accessible to plants. This is crucial because living organisms cannot use nitrogen gas directly. Instead, they rely on this conversion to obtain the nitrogen necessary for building essential molecules like proteins and nucleic acids.
It's primarily carried out by specific types of bacteria and archaea, with some forming close associations with plant roots. This synergy is seen in legumes, where root nodules house nitrogen-fixing bacteria. These bacteria take nitrogen from the air and convert it into ammonia, enriching soil fertility and benefiting plant growth. This is why legumes are often used in crop rotations to naturally boost soil nitrogen levels.

Bacteria in Nitrogen Cycle

Bacteria are superheroes in the nitrogen cycle, playing several key roles beyond nitrogen fixation. After ammonia is produced, other specialized bacteria in the soil convert ammonia into nitrites (NO₂⁻) and then into nitrates (NO₃⁻) through a process called nitrification. Nitrates are a major form of nitrogen that plants use to grow.
Two main types of bacteria facilitate this process: Nitrosomonas bacteria transform ammonia to nitrites, and then Nitrobacter convert nitrites to nitrates. These bacteria are essential, ensuring the continuous flow and transformation of nitrogen through its various forms in the ecosystem.

Role of Microorganisms in Nitrogen Conversion

Microorganisms, particularly bacteria, play a central role in the conversion of nitrogen into various forms within the nitrogen cycle. This cycle is critical for sustaining life as it facilitates the recycling of nitrogen, a building block of proteins and DNA.

• **Nitrogen Fixation**: This is initiated by nitrogen-fixing bacteria, which convert N₂ from the atmosphere into ammonia.
• **Nitrification**: Bacteria like Nitrosomonas and Nitrobacter convert ammonia into nitrites and nitrates, which are then used by plants.
• **Assimilation**: Plants absorb nitrates and ammonium, incorporating them into their biological molecules.
• **Ammonification**: When plants and animals die, decomposers (also microorganisms) convert organic nitrogen back into ammonia.
• **Denitrification**: Finally, other bacteria convert nitrates back to N₂ gas, releasing it into the atmosphere and completing the cycle.

Without these microorganisms, the transformation and movement of nitrogen would stagnate, severely impacting all life forms dependent on nitrogenous compounds.