alleryStart learning →Nitrogen gas makes up most of the air, yet plants cannot use it directly. What brings nitrogen into living things?
ANitrogen rich rainfall
BNitrogen storing fungi
CNitrogen fixing bacteria
DNitrogen fixing beetles
Answer & Solution
Correct answer: C. Nitrogen fixing bacteria
1. Atmospheric nitrogen is held together by a tight triple covalent bond.
2. Plants and phytoplankton cannot break that bond themselves.
3. Bacteria can, and they build the nitrogen into their own macromolecules.
4. Some are free living, such as Azotobacter, and some are symbiotic, such as Rhizobium in legume root nodules.
5. Cyanobacteria do the same job in most sunlit aquatic ecosystems.
_Source: OpenStax Biology 1e (CC BY 4.0), Chs 44 and 46, section 46.3 Biogeochemical Cycles_
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