Can you explain the need for cycling of carbon, oxygen, nitrogen, phosphorus, and hydrogen in living ecosystems?

Last week i was assigned a thematic. we have groups of three but the people i was assigned with haven't been in school for days. i would appreciate if anyone can me with my thematic . i highlighted most of the important steps and i circled my thematic topic. in desperate need : ( its due on february 19

What maintain homeostasis when a persons internal body temperature is 97.5°f

The cluster of developing cells from conception until birth is called an