Why are many ecological phenomena difficult to study

Ecosystems involve living organisms interacting with non-living things in a productive way; how is photosynthesis an example of this? answer, i will give brainiest to first person to get it right.

Which of the following produces carbon dioxide? a. plants b. animals c. decomposers d. all of the above

Which of the following is not a possible effectof increasimg carbon dioxide levels in the atmosphere ?