Question

the nitrogen cycle discussion questions
the atmosphere is 80% nitrogen: why do you think plants and animals cant use nitrogen as it is found in the atmosphere?
explain what is meant by nitrogen fixation.
what is the role of bacteria in the nitrogen cycle?
why dont legumes need nitrogen - containing fertilizers?
why is nitrogen so important for living things?

Explanation:

1. The nitrogen in the atmosphere is in the form of N₂, a very stable molecule with a triple - bond. Plants and animals lack the enzymes to break this strong bond to use the nitrogen atoms, so they can't use atmospheric nitrogen directly.
2. Nitrogen fixation is the process of converting atmospheric nitrogen (N₂) into ammonia (NH₃) or other nitrogen - containing compounds that can be used by living organisms. This can be done by lightning, industrial processes, or nitrogen - fixing bacteria.
3. Bacteria play multiple roles in the nitrogen cycle. Nitrogen - fixing bacteria convert N₂ into ammonia. Nitrifying bacteria convert ammonia into nitrites and then nitrates. Denitrifying bacteria convert nitrates back into N₂, returning it to the atmosphere.
4. Legumes have a symbiotic relationship with nitrogen - fixing bacteria (Rhizobium) in their root nodules. These bacteria fix atmospheric nitrogen for the legumes, so legumes don't need additional nitrogen - containing fertilizers.
5. Nitrogen is important for living things as it is a key component of proteins, nucleic acids (DNA and RNA), and many other biological molecules. Proteins are essential for cell structure, function, and regulation, and nucleic acids are crucial for genetic information storage and transfer.

Answer:

1. Plants and animals can't use atmospheric nitrogen because N₂ has a strong triple - bond and they lack the enzymes to break it.
2. Nitrogen fixation is the conversion of atmospheric N₂ into ammonia or other usable nitrogen - containing compounds.
3. Bacteria fix nitrogen, nitrify ammonia, and denitrify nitrates in the nitrogen cycle.
4. Legumes don't need nitrogen - containing fertilizers due to symbiotic nitrogen - fixing bacteria in their root nodules.
5. Nitrogen is important for living things as it is a key component of proteins and nucleic acids.