Question

How do plants and animals depend on each other for their requirements of oxygen and carbon di oxide.

Answer 1

because get food from sunlight and animals depend on plants like cow eat grass

Answer 2

plant need carbon dioxide and give out oxygen to make their own food,where as animal need oxygen to respire and give out carbon dioxide .The carbon dioxide released by animal is inhaled by plant and oxygen released by plant is inhaled by animal.
Hope it helped.