And this includes us humans. These types of organisms are known as organotropes, while those organisms that obtain their electron source from non organic or inorganic materials, those are known as lithotrophs. So basically, we have the source by which we obtain our carbon. We have either autotrophs or heterotrophs. Autotrophs basically means we create or synthesize our organic molecules from inorganic starting materials such as carbon dioxide. Heterotropes means to actually obtain that organic material, we cannot synthesize it.