The bacteria can chemically combine nitrogen with hydrogen to form ammonia (NH3). This combining process is called nitrogen fixation.

Which group of organisms chemically combines nitrogen with hydrogen in a process called nitrogen fixation?

bacteria

birds and reptiles

only aquatic plants

all mammals

Bacteria

Explanation:

Nitrification fixation takes place by nitrogen-fixing bacteria like Azotobacter, Klebsiella, Bacillus etc which convert atmospheric nitrogen gas into fixed-nitrogen compounds like nitrates or ammonium ions for the plants to readily absorb.

The nitrogen fixing bacteria can be free-living like cyanobacteria or live with symbiotic relationship with plants and fungi.

The chemical conversion of di-nitrogen to ammonia takes place with the help of enzymes like nitrogenase in combination with leghahemoglobin, a protein through a reduction reaction.

1. is geographic distribution

2 is increasing complexity

3 is transitional forms