Thomas constructs a model by completing the following steps.
1. Draw a diagram that shows where oxygen is found on Earth, including the atmosphere, bodies of water, land, and living things.
2. Draw arrows to show how oxygen moves and changes form from one location to another.
3. Label each arrow.
Thomas has constructed an example of what type of ecological model?
A. biogeochemical cycle
B. food web
C. energy pyramid
D. geological system