Question

Suppose there is no animal in the world how will it affect the amount of oxygen and carbon dioxide in the air

Answer 1

The absence of animals will affect the world in a small amount as plants require both oxygen and carbon dioxide. The take in oxygen to respire and they require carbon dioxide for photosynthesis. Although carbon dioxide is used in a large scale but when the plants die, the carbon in them oxidize to form carbon dioxide. This will maintain the ratio of oxygen and carbon dioxide in world for many years.