Final answer:
A chemoheterotroph is an organism that requires external sources of organic compounds for energy and carbon, as it lives in environments without light and cannot perform photosynthesis.
Step-by-step explanation:
The organism that depends on an external source of organic compounds is known as a chemoheterotroph. Such organisms rely on chemical sources of energy and consume organic compounds for their carbon source, as they cannot photosynthesize due to living in lightless environments. The term heterotroph comes into play here because these organisms obtain their carbon from organic compounds other than carbon dioxide, which differentiates them from autotrophs that can use inorganic carbon dioxide to synthesize their own food.
The organism that depends on an external source of organic compounds is a heterotroph. Heterotrophs rely on complex organic carbon compounds as nutrients, which are initially provided by autotrophs. Many organisms, including humans and prokaryotes, are heterotrophic.