Organisms are often classified into two distinct categories regarding their ability to fix organic compounds for consumption. These two categories are heterotrophs and autotrophs. The bird in the photograph above is classified as a heterotroph. Autotrophs have the ability to self produce organic compounds such as carbohydrates, proteins, and fats from usually either inorganic compounds or the use of sunlight. Contrarily, heterotrophs are organisms that cannot fix inorganic carbon for consumption and use organic compounds to acquire energy and grow. By means of predation and consumption, heterotophs gather the reduced carbon compounds that they need to grow and preform standard functions. The majority of heterotrophs are classifed as chemoorganoheterotrophs or chemolithoheterotrophs. The first of the two consume plants and other animals to acquire their needed energy and carbon source. The latter of the two uses inorganic substances to produce ATP and the such. Heterotrophs make up a large portion of most environments in the world today.