During monsoon days, a blue green layer was developed on moist soil of village streets making them slippery. On the instruction of science teacher Ghanshyam collected this upper slippery layer of soil from the village street and dried it. Then he added this powder to this crop field. He got very good crop yield without using any fertilizers
(i) Which group of organisms is responsible for this blue green layer ?
(ii) What is the possible reason for increased crop yield after addition of blue green layer to the fields
(iii) Name one blue green alga which do nitrogen fixation
(iv) Name one blue green alga which is a good source of protein.

Answer

N/a

Explanation

(i) Blue green algae (Cyanobacteria)
(ii) Many blue green algae are known to fix atmosphere nitrogen (called biological nitrogen fixation) and improve the fertility of the soil
(iii) Anabaena
(iv) Spirulina.