Which molecules would you expect to find at the top of the diagram?

Oxygen. Oxygen because both plants and animals need oxygen to breath. When the inhale its carbon dioxide but when they exhale its oxygen.

Explanation: im so sorry if its wrong i did a test on tath like two weeks ago sorry ◑﹏◐

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.