How does photosynthesis keep humans alive?

Photosynthesis keeps trees alive and trees give us oxygen as we give carbon dioxide

Explanation:

Because photosynthesis is important to living organisms because it is the number one source of oxygen in the atmosphere.

Explanation:

So we need it to breath basically.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.