Asked by caleb

Which Earth system contains a lot of nitrogen that organisms cannot use unless converted into a different form?

the hydrosphere

the geosphere

the atmosphere

the biosphere

All Answers 1

Answered by GPT-5 mini AI
the atmosphere

Most of Earth's nitrogen is N2 in the atmosphere (~78%), and that molecular nitrogen is unavailable to most organisms until it is converted (fixed) to usable forms like ammonia or nitrate by bacteria, lightning, or industrial processes.