Photosynthetic Organisms: Their Existence in Evolutionary Prospective

Photosynthesis is a very old process on this Earth. Based on fossil discoveries and chemical evidence, cyanobacteria first appeared 2.5–2.6 billion years ago (bya). Their evolution was undoubtedly continued by a number of anaerobic, photosynthetic bacterial life forms. Carbon isotope data revealed that autotrophic carbon fixation may have begun at least a bya. It is unclear, nevertheless, what the earliest photosynthetic organisms were like. The primary elements of the photosynthetic system are the carbon fixation mechanism, electron transport complexes, antenna complexes, and reaction centers. It is most likely true that these components have not all evolved at the same point in time. Consequently, it is better to think of the photosynthetic apparatus as a mosaic made up of numerous structural components, each with its own unique evolutionary background. One early instance of a cyanobacterium’s endosymbiotic absorption by a heterotrophic organism appears to have been the source of the chloroplasts seen in yellow-green algae, glaucophytes, brown algae, cryptophytes, red algae, and other algae in the “red” line of development. The variety of species present in the algae’s “red line” is the outcome of a single secondary endo-symbiotic occurrence in which an organism resembling red algae was ingested by another eukaryote. This “red line” is further expanded by tertiary (third-level) endosymbiotic events. Photosynthetic units are found in reaction centers involving complexes for gathering light. Two of these units are necessary for oxygenic photosynthesis, which currently accounts for the majority of biological transfer of energy in the various trophic levels of the biosphere. The emergence of photosynthesis utilizing oxygen among cyanobacteria, which paved the path for the formation of complex life forms with multicellular levels of organization, had a profound influence on the biology, geology, and environment of Earth. In this review, we have discussed the early evidence of photosynthesis, the origin of reaction centers, antenna, pigments, and how oxygenic photosynthesis came into existence. The origin of the chloroplasts is a necessary event that occurred earlier and was added to the history of photosynthetic origin in this review.