Examples of Heterotrophs

1. Fungi

• Fungi are a group of eukaryotes that depend on dead and decaying matter for their food as well as energy.
• Fungi are organoheterotrophic organisms that use complex organic compounds as their electron source.
• Fungi make up the decomposers in the food chain, where they consume dead and decaying organisms and release simpler molecules so that those can be utilized by the autotrophs.
• These are mostly found in dry and arid environments, and these occur in the soil where most dead and decaying components are located.
• There is a large number of fungal species that can be aerobic or anaerobic, and depending on the availability of oxygen, these produce different levels of energy from organic compounds.

2. Photoheterotrophic cyanobacteria

• Photoheterotrophic cyanobacteria are a group of microorganisms that have superior photosynthetic efficiency and minimum growth requirements.
• These bacteria cannot use carbon dioxide as a source of carbon, but they can use solar energy for the transfer of electrons in the electron transport chain.
• The bacteria occur in aquatic or damp environments where they feed on the organic compounds produced by autotrophic aquatic organisms.
• These are increasingly studied due to their ability to produce a large amount of energy in the presence of sunlight.

3. Iron-reducing bacteria

• Iron-reducing bacteria are bacteria that metabolize reduced iron to oxidized iron compounds to produce energy.
• The energy obtained from the process is then utilized for absorption of carbon source and metabolism.
• These bacteria have been proposed to be used for decontamination of metal or metalloid polluted environments.
• Even though iron-reducing organisms are associated with extreme environments, these can occur in other areas as well.
• The occurrence of these bacteria in extreme environments is due to the occurrence of the inorganic compounds in such environments.

4. Animals

• Animals make up the most important group of heterotrophs in the environment as these occupy the maximum number of trophic levels in the food chain.
• All animals are heterotrophic, but their dependency on the autotrophs might differ as some depend on autotrophs while others are indirectly dependent.
• Herbivorous animals feed on autotrophic organisms like plants and phytoplanktons to obtain both energy as well as food.
• Carnivores, in turn, feed on herbivores, indicating an indirect dependency on the autotrophs.
• The organic compounds are taken up by the organisms, which are then broken down into simpler molecules by different mechanisms.