Is this an experiment? If so, if you have a small environment, compare it to a larger one, like your backyard for instance. Does the small environment have the same things as your backyard? Are they different? Compare them both like the backyard would have trees and with bird nests, and bushes, and all sorts of living organisms. More than your small environment would right? Your small environment gets the same nutrients as the large environment such as Carbon Dioxide, Sunlight, Water. Does your small environment have any animals or insects? You could use that as a comparison too.
I Hope This Helped!
