Which of the following organisms does nitrogen fixation?
A Fungi.
B Bacteria.
C Algae.
D Rodents.
The correct answer and explanation is:
The correct answer is:
B. Bacteria.
Explanation:
Nitrogen fixation is the biological process by which atmospheric nitrogen gas (N₂), which is inert and unavailable to most organisms, is converted into ammonia (NH₃) or related nitrogenous compounds that plants and other organisms can use. This process is essential for life because nitrogen is a critical component of amino acids, proteins, nucleic acids, and other cellular constituents.
Why bacteria?
Certain bacteria possess an enzyme called nitrogenase that can break the very strong triple bond in nitrogen gas (N₂), allowing it to be converted into ammonia. These bacteria are called nitrogen-fixing bacteria. They can be free-living in soil or water or form symbiotic relationships with plants.
- Examples of nitrogen-fixing bacteria:
- Rhizobium species, which form symbiotic relationships with leguminous plants (like peas, beans, and clover) in root nodules.
- Azotobacter species, which are free-living in soil.
- Cyanobacteria (sometimes called blue-green algae, but actually bacteria) such as Anabaena can also fix nitrogen.
Why not the others?
- A. Fungi:
Fungi do not fix nitrogen. They are decomposers and help break down organic matter but do not convert atmospheric nitrogen to a usable form. - C. Algae:
Algae generally do not fix nitrogen. While some cyanobacteria (historically called blue-green algae) can fix nitrogen, true algae (like green algae or diatoms) cannot. - D. Rodents:
Rodents are animals and cannot fix nitrogen. They obtain nitrogen by consuming plants or other animals but do not convert atmospheric nitrogen into usable forms.
Importance of Nitrogen Fixation:
- Nitrogen fixation is a key step in the nitrogen cycle.
- It replenishes soil nitrogen levels, supporting plant growth.
- Without nitrogen-fixing bacteria, ecosystems would be limited by the availability of nitrogen.
- It reduces the need for synthetic nitrogen fertilizers in agriculture, which are energy-intensive to produce and can cause environmental damage.
In summary, nitrogen fixation is primarily carried out by certain bacteria, making option B the correct choice.