The main source of carbon dioxide in an ecosystem is the carbon dioxide gas present in the atmosphere. This carbon dioxide is used by the plants and animals in different ways.
The plants use this carbon dioxide to perform the process of photosynthesis.This is carried out by the help of green pigment called chlorophyll that absorbs light from the sun, water from soil and carbon dioxide from atmosphere.
The carbon in animals comes when they eat these plants.
Stratosphere is the correct answer
