Why is nitrogen fixation important to all organisms?

it breaks down dead organisms.

it converts nitrogen gas into a usable form for plants.

it converts energy from the sun into a usable form for plants.

it produces much of earth's oxygen.

It's because it converts nitrogen gas into a usable form for plants. Most organisms can't use nitrogen gas (N₂) as-is because it doesn't react easily with other compounds (due to the triple bond between the nitrogen atoms). Nitrogen has to be fixed (into ammonia (NH₃)) before it is accessible.

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