A student is setting up a model to study the carbon cycle and natural sources of carbon dioxide. They create a microenvironment that contains soil, leaf debris, an earthworm, heterotrophic bacteria, and a sun lamp. What natural source of carbon dioxide and major metabolic process was left out of the model

Fossil fuels, forest fires, and respiration and major metabolic process photosynthesis are left out of the model.                

Explanation:

The carbon cycle model contains all the activities but some points are missing in it. Oceans, the burning of fossil fuels should be explained.  Natural elements such as coal and natural gas are the main elements of the carbon cycle.Because they are important compounds of the carbon cycle. The process of photosynthesis is very important in the carbon cycle. The process of volcanic eruption should be explained in the carbon cycle.        

Tolerance to high levels of salinity