Autotroph
From Freepedia
An autotroph (from the Greek eauton = self and trophe = nutrition) is an organism that produces organic compounds from carbon dioxide as a carbon source, using either light or reactions of inorganic chemical compounds as a source of energy. Plants and other organisms using photosynthesis are photolithoautotrophs; bacteria that utilize the oxidation of inorganic compounds such as hydrogen sulfide or ferrous iron as an energy source are chemolithoautotrophs.
There are some organisms that require organic compounds as a source of carbon, but are able to use light or inorganic compounds as sources of energy. Such organisms are not defined as autotrophic, but rather as heterotrophic. An organism that obtains carbon from organic compounds but obtains energy from light is termed a photoheterotroph, while an organism that obtains carbon from organic compunds but obtains energy from the oxidation of inorganic compounds is termed a chemoheterotroph.
Autotrophs are a vital part of a food chain. They take energy from the sun or from inorganic sources and convert it into a form (organic molecules) that they use to carry out biological functions including cell growth, and that other organisms (called heterotrophs) utilize as food. Thus, heterotrophs — animals, fungi, as well as most bacteria and protozoa — depend on autotrophs for energy and for the raw materials to make complex organic molecules. Heterotrophs obtain energy by breaking down organic molecules obtained in their food. Carnivorous animals ultimately rely on autotrophs because the energy and organic building blocks obtained from their prey comes from autotrophs eaten by the prey.
In simpler terms, an autotroph is an organism that uses energy and different raw materials to make its own food, an autotroph is a producer.
