Question

Some plants contain nitrogen-fixing bacteria Rhizobium in their root nodules. This relationship is known as ____________.

• A. aAn amensalism
• B. a commensalism
• C. a mutualism
• D. Interspecific competition

Answer 1

The correct option is C

a mutualism

The correct option is C
Explanation of the correct option:

1. Nitrogen fixation is the process of converting free atmospheric, molecular nitrogen gas into nitrogen compounds.
2. The process of conversion of free atmospheric nitrogen gas by the free-living bacterium like rhizobium is called biological nitrogen fixation.
   Rhizobium is a rod-shaped nitrogen-fixing bacterium that lives symbiotically within the roots of leguminous plants.
3. This biological relationship between nitrogen-fixing bacteria Rhizobium and the root nodules of leguminous plants is known as mutualism.
4. Mutualism is a type of association that occurs between two or more species in which each organism is benefitted.
5. The nitrogen compound produced by rhizobium is an essential plant nutrient as it is the main constituent of chlorophyll and amino acids. In return, rhizobium receives food and oxygen from the plant.

Explanation of the incorrect option:
Option A:

1. Amensalism is a type of association that occurs between two or more species in which one organism is hurt whereas the other one remains unaffected.
2. Penicillium notetum secretes penicillin for killing various bacteria. This is a prime example of amensalism.

Option B:

1. Commensalism is a type of association that occurs between two or more species in which one organism obtains food or other benefits from the other without either harming or benefiting it.
2. An example of commensalism includes tree frogs using plants as protection.

Option D:

1. Interspecific competition occurs between the organisms of different species.
2. Here, the organisms from different species compete for resources within the same ecosystem.
3. In ocean ecosystems, sharks, dolphins, and seabirds, for example, frequently eat the same sort of food.

Final answer:
Some plants contain nitrogen-fixing bacteria Rhizobium in their root nodules. This relationship is known as mutualism.