All the organisms require energy for their survival. Some obtain it directly from the environment whereas some cannot. Depending on the source of energy, organisms are broadly classified into two categories as autotrophs and heterotrophs.
| Sr. No | Autotrophs | Heterotrophs |
| 1 2 3 4 5 | They can harness the light energy from the sun. They can produce their own food by utilizing raw materials from the physical environment. They are also called producers. They form the base of most food chains and food webs. Examples include plants, algae, etc | They cannot harness the light energy form the sun. They cannot produce their own food by utilizing raw materials from the physical environment. They are also called consumers. They do not form the base of any food chain or food web. Examples include animals, fungi, etc. |