A biology teacher takes fish, algae, pond weed, invertebrates, and bottom muck from a local pond and establishes them in an aquarium. When the system is stable, the teacher seals it into a large, airtight glass box and leaves the box in a sunny location. After three months, the organisms in the aquarium appear alive and healthy. Which of the following statements about the experiment is true? a. During the three months, the biomass of animal life was greater than the biomass of plant life.
b. Some of the energy in the system has moved from one organism to another.
c. The air in the glass box contains no carbon dioxide.
d. No energy has entered or left the glass box.