Class 11 NEET Biology Biological Classification Questions Part 1

(d) : Symbiosis is a mutually beneficial relationship or interaction between individuals of two different species with none of the two capable of living separately. e.g., Rhizobium is associated with root nodules of legumes. It fixes nitrogen for the plant and the plant provides it food and shelter. Azotobacter is a free-living bacteria which occurs in the soil and fixes nitrogen directly. Bacillus is also a free living bacteria which acts upon nitrogenous excretions and proteins of dead bodies of living organisms. These are therefore, non-symbiotic N2 fixing bacteria.