What is the main source of carbon in an ecosystem? a. nitrifying bacteria b. the atmosphere c. photosynthesis d. cells and tissues

The source of the carbon found in living matter is carbon dioxide (CO2) in the air or dissolved in water. Algae and terrestrial green plants (producers) are the chief agents of carbon dioxide fixation through the process of photosynthesis, through which carbon dioxide and water are converted into simple carbohydrates.

b. atmosphere

Explanation:

The main source of carbon in an ecosystem is atmosphere.  The plants absorb the carbon in the form of carbon dioxide from the atmosphere, which they use as a reactant of photosynthesis to produce food in the form of carbohydrates which are indirectly called as the products of carbons. The plants are consumed by many herbivores , other animals, microbes and humans.