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Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a byproduct of splitting water molecules, unlike other organisms that conduct anoxygenic photosynthesis such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated to 1.6 to 1.7 billion years ago. [11]
The first autotrophic organisms likely evolved early in the Archean but proliferated across Earth's Great Oxidation Event with an increase to the rate of oxygenic photosynthesis by cyanobacteria. [8] Photoautotrophs evolved from heterotrophic bacteria by developing photosynthesis. The earliest photosynthetic bacteria used hydrogen sulphide.
The species Difflugia that contain endosymbionts are not considered to be heterotrophs, but instead mixotrophs because they combine being autotrophic and heterotrophic. The source of food depends on the environment but across the genus it is found to be mainly algae and fungi.
They include algae (autotrophs which make their own food) and protozoans (heterotrophs which eat the algae for food). In recent years, researchers have discovered many protists are mixotrophs , which can function in both modes.
Heterotrophic organisms have to take in all the organic substances they need to survive. All animals, certain types of fungi, and non-photosynthesizing plants are heterotrophic. In contrast, green plants, red algae, brown algae, and cyanobacteria are all autotrophs, which use photosynthesis to produce their own
In an ecological context, phototrophs are often the food source for neighboring heterotrophic life. In terrestrial environments, plants are the predominant variety, while aquatic environments include a range of phototrophic organisms such as algae (e.g., kelp), other protists (such as euglena), phytoplankton, and bacteria (such as cyanobacteria).
Heterotrophic microbes likely originated at low H 2 partial pressures. Bases, amino acids, and ribose are considered to be the first fermentation substrates. [32] Heterotrophs are currently found in each domain of life: Bacteria, Archaea, and Eukarya. [33]
Scenedesmus is known to have high biomass productivity among green algae, and has been actively researched for its use for biodiesel production. Its heterotrophic production of biomass and lipid in optimized conditions is reported to have higher efficiency than its autotrophic production.