1. chemotrophs Chemotrophs are organism that obtain energy by the oxidation of electron donating molecules in their enviroments.these molecules may be organic (organotrophs) or inorganic molecules(lithotrophs). It is two types: chemoautotrophs chemoheterotrophs

2. chemoautotrophs Chemoautotrophs generally use only inorganic energy sources. Synthesize all necessary organic energy compounds from carbondioxide. Chemotrophs generally falls in several groups :methanogen, halophiles, sulphur reducers, nitrifiers, anammoxbacteria, and thermoacidophiles.

3. chemoheterptrophs Must ingest organic building blocks that they are capable of creating on their own. Most chemoheterotrophs derive energy from organic molecules like glucose.

4. Heterotrophs A heterotroph is a an organism that uses organic carbon for growth. This contrast with autotrophs, such plants which able to directly use source of energy, such as light to produce organic substrate from inorganic carbondioxide. Herterotrophs are known as consumers in food chain. All animals are heterotrophs.

5. Types of heterotrophs 1) Phototrophs : obtain energy from light, but needs carbon in an organic form for growth. 2) Chemoheterotrophs – need an organic source of carbon for both energy source and growth.

6. Organotrophs and lithotrophs These terma are refers to the chemical that are involved in biosynthesis process or respiration. Phototrophs and chemotrophs can be either lithotrophs or organotrophic.

7. Photoheterotrophs Organism that use light for energy, use organic compounds from the environment to satisfy their carbon requirements. They use carbohydrates, fatty acid, and alcohols as their food organic “ food”. E.g purple non sulphur bacteria, green non sulphur bacteria and helicobacteria.