In a model of the carbon cycle containing soil, leaf debris, an earthworm, heterotrophic bacteria, and a sun lamp, what natural source of carbon dioxide or major metabolic process was left out of the model environment?

In a model of the carbon cycle containing soil, leaf debris, an earthworm, heterotrophic bacteria, and a sun lamp, what natural source of carbon dioxide or major metabolic process was left out of the model environment?

• A. Photosynthesis is included
• B. Decomposition
• C. Respiration by soil microorganisms
• D. There is no representation of photosynthesis in the model environment

Answer: (D)

This question hinges on how carbon moves in an ecosystem and the role of photosynthesis as a way to remove carbon dioxide from the air by building organic matter using light energy. In this model, there’s soil, leaf debris, an earthworm, heterotrophic bacteria, and a sun lamp. The organisms present besides plants are decomposers and detritivores that break down organic material and respire, releasing CO2 back into the environment. Leaf debris provides the carbon substrate for that decomposition and respiration. What’s missing is any photosynthetic organism to take CO2 from the air and convert it into organic matter. The sun lamp doesn’t automatically drive photosynthesis unless phototrophs are present to use that light. So there’s no representation of photosynthesis in the model, making it the missing process that would otherwise act as a CO2 sink in the carbon cycle.

This question hinges on how carbon moves in an ecosystem and the role of photosynthesis as a way to remove carbon dioxide from the air by building organic matter using light energy. In this model, there’s soil, leaf debris, an earthworm, heterotrophic bacteria, and a sun lamp. The organisms present besides plants are decomposers and detritivores that break down organic material and respire, releasing CO2 back into the environment. Leaf debris provides the carbon substrate for that decomposition and respiration.

What’s missing is any photosynthetic organism to take CO2 from the air and convert it into organic matter. The sun lamp doesn’t automatically drive photosynthesis unless phototrophs are present to use that light. So there’s no representation of photosynthesis in the model, making it the missing process that would otherwise act as a CO2 sink in the carbon cycle.