Nitrogen is the most common element in the air. Why do bacteria play a role in the nitrogen cycle?

Explanation:

The bacteria’s helps in breaking down the organic materials which has nitrogen in it, and helps in giving the nitrogen back to the cycle. Bacteria helps in breaking down of the leaves and then it diffuses the nitrogen to the soil. Prokaryotes also plays an important role in the nitrogen cycle. The nitrogen fixing bacteria present in the root zone of plants basically in the soil, helps in conversion of the nitrogen into ammonia. Then the nitrifying bacteria converts the ammonia to the nitrites or can say nitrates.  

the sun creates it's own light, also gives light and life to bunch of stuff like plants,animals,humans etc.photosyntesis is the process of making food which needs sun,water,nutrients etc.