Autotrophs: Organisms that can make their own food from carbon dioxides and water under the action of sunlight and in the presence of chlorophyll are called autotrophs.
Example: All Green plants.
Heterotrophs: Organisms which cannot make their own food by the process of photosynthesis and are dependent on others*for food are called heterotrophs.
Example: All Animals.
Decomposers : Organisms that decompose the complex molecules present in the dead remains of plants and animals are called decomposers. Example: Bacteria, Fungi.