In a model of the carbon cycle, how would you label an arrow from the atmosphere to plants?

a. cellular respiration

b. photosynthesis

c. decomposition

d. consumption

Video transcript

Hi everyone. Let's look at our next question. It says in which the following cycles do respiration and photosynthesis play the most significant role. Well we can just recall from our content videos when we think about respiration and photosynthesis, we're thinking about the participation in a cycle. So you want to think what is do they use up? What do they produce? Of course respiration uses oxygen and produces carbon dioxide. Photosynthesis uses carbon dioxide, produces oxygen. When we look at our choices for cycles here and our answer choices. We've got carbon, nitrogen phosphorus and sulfur. We don't have oxygen here but we do have our carbon cycle of which both have a significant involvement. So our answer choice here is going to be choice. A carbon cycle photosynthesis of course removes a large amount of carbon from the atmosphere about equivalent to the amount that respiration respiration produces. So they are a very key part of the carbon cycle. Let's look at our other answer choices though. Just to go through them. When we have the nitrogen cycle, most nitrogen is in the atmosphere with some being fixed in the soil by nitrogen fixing bacteria. But not real involvement of respiration and photosynthesis. Plants do use nitrogen which they access from the soil where it's been fixed by that bacteria but not going to be a significant part of respiration. Not having respiration and photosynthesis play a significant role choice. See the phosphorus cycle again, plants do use phosphorus but most phosphorus is in soils and rocks. Um it has its solid normal temperature and pressure. So it doesn't have an atmospheric component in its cycle. So I'll just put no atmospheric and cycle uh Some is taken up by plants which then gets also incorporated into animals. Um phosphorus is key to us. We need it for our D N. A. R N A R A T. P. Um but only a little bit and it sort of progresses rapidly through plants and animals. Most of the phosphorus is in soils and rocks and respiration and photosynthesis don't play a significant role in that. So choice c not our answer. And finally, choice the the sulfur cycle um Again, not photosynthesis and respiration. Not playing a significant role here. Sulfur cycle. Most of it comes from weathering of rocks which causes it to go into the soil where some is taken up by plants. But again, we're talking very small amounts there and not really part of this respiration photosynthesis process. So again in which the following cycles do respiration and photosynthesis play the most significant role. And that would be choice a the carbon cycle. See you in the next video