Answer:
Chlorophyll
Explanation:
Chlorophyll is needed for photosynthesis in plants so the ammount of chlrophyll will limit the rate of photosynthesis because its needed for it
Any area in a damp or closed surface.
Im not 100% sure but the best answer I can give is Prokaryotes because they came to be around the time oxygen did as well.
Search up labels of a animal cell
