Autotrophs and Heterotrophs
An autotroph is an organism that is able to form nutritional organic substances from simple non-organic substances such as carbon dioxide.
A heterotroph is an organism deriving its nutritional requirements from complex organic substances.
Autotrophs can produce their own food using light but heterotrophs can not. Heterotrophs have to depend on animals and plants for nutrition. Food chain level: heterotrophs: Primary Secondary and Autotroph: tertiary
An autotroph can be bacteria, plants or algae. But heterotrophs can be animals or us, humans.