Oxygen is cycled between the tree and the fox through the processes of photosynthesis and respiration. Photosynthesis is the process by which plants use sunlight to convert carbon dioxide and water into glucose and oxygen. The oxygen produced by photosynthesis is released into the atmosphere, where it is used by animals for respiration. Respiration is the process by which animals use oxygen to break down glucose and produce energy. The carbon dioxide produced by respiration is released into the atmosphere, where it is used by plants for photosynthesis.

Here is a more detailed explanation of how oxygen is cycled between the tree and the fox:

1. The tree absorbs carbon dioxide from the atmosphere.

2. The tree uses sunlight to convert the carbon dioxide and water into glucose and oxygen.

3. The oxygen produced by photosynthesis is released into the atmosphere.

4. The fox inhales the oxygen from the atmosphere.

5. The fox uses the oxygen to break down glucose and produce energy.

6. The carbon dioxide produced by respiration is released into the atmosphere.

7. The tree absorbs the carbon dioxide from the atmosphere and the cycle begins again.

This cycle is essential for maintaining the balance of oxygen and carbon dioxide in the atmosphere. Without photosynthesis, there would be no oxygen for animals to breathe. Without respiration, there would be too much carbon dioxide in the atmosphere and plants would not be able to survive.