Question

Assertion :- Crop production without use of chemical fertilizers is called organic farming.
Reason :- Cyanobacteria are autotrophic prokaryotes which are used as biofertilizers in paddy fields.

• A. Both assertion and reason are true and the reason is a correct explanation of the assertion
• B. Both assertion and reason are true but reason is not a correct explanation of the assertion
• C. The assertion is true but the reason is false
• D. Both assertion and reason are false

Answer 1

The correct option is B Both assertion and reason are true but reason is not a correct explanation of the assertion

Production of crops without the use of chemical fertilisers is called organic farming. In this technique, chemical fertilisers are replaced with biofertilisers. Biofertilisers are microorganisms which are used to increase the nutritional value of the soil for crops. These microorganisms could be bacteria, fungi, cyanobacteria, etc. Hence, the assertion is true.

Cyanobacteria are also known as blue green algae. These are believed to be the very first photoautotrophs. Autotrophs are the organisms which are capable of preparing their own food. Photoautotrophs use sunlight to prepare their own food. Anabaena is a cyanobacteria. It is used in paddy fields to increase crop production. Azolla is a small, free floating, fresh water fern which is found to have a cohabitual existence with rice and paddy plants. It doesn’t interfere with their growth. Anabaena is found in the leaf cavities of Azolla, and hence is associated with rice cultivation. Hence, the reason is true.
The reason is not the explanation of the assertion. It is because chemical fertilisers cause various types of pollution, because of which, they are replaced by biofertilisers.