There is no doubt that photosynthesis is believed to be the only storage of the solar energy processes on earth, and as well as the source of food and energy resources (Blankenship 434). This understanding concerning the origin and evolution of photosynthesis is critical in explaining all the complex paths followed by photosynthetic process.
The origin of life and photosynthesis
The origin of life is traceable to the origin and evolution of the process of photosynthesis. It is believed that the early atmospheric originally composed of neutral gases, mainly carbon dioxide and nitrogen (Hartman 516). However, critics questioned the probability of the occurrence of the photosynthetic process in such neutral conditions. This uncertainty was overcome with the existence of abundant reducing agents such as ferrous ions and hydrogen peroxide. Hydrogen peroxide induced oxygenic photosynthesis while the presence of ferrous ions undermined the possibility of water being used as electron donors (Hartman 516). The possibility of oxygenic photosynthesis developed in the cyanobacteria present in bacterial fossils.
Evolution of Photosynthetic organelle from Cyanobacteria
Plasticids or chloplasts are believed to have evolved from cyanobacteria though the process of endosymbiosis. Nakayama and Archibald (1) argue that this evolution provided the greatest landmark as far as the benefits of photosynthesis is concerned (eukaryotes). Of particular importance is the conversation of solar energy into chemical energy that eventually influenced the process of evolution and the earth’s climate. Photosynthetic eukaryotes comprises of a diversified collection of organisms conjoined in a web of plastid-bearing lineages (Nakayama and Archibald 1). Despite the existence of this complexity, these plastid-bearing are traceable to a single history. This history is occurred from the endosymbiotic event between heterotrophic host eukaryote and cyanobacteria.
Cyanobacteria and Early Earth Photosynthesis
Cyanobacteria are a very vital group of bacteria. It is blue-green in color and exists in water. They existed in the years beginning of evolution but still exist to date at very large numbers. They are very small, exist in single celled bodies, and are mostly round or sometimes hollow. The coexist in colonies and are built in numerous layers that are popularly known as stromatolites (Falcón 778). They make their food from photosynthesis. Since they are very small, and need constant supply of sunshine and carbon dioxide from the atmosphere, they exist on the edge of oceans and other sources of water. Due to the constant current and disturbance, they live in thin layers that can float on the surface of the water. A string like substance that they secrete supports this it acts as a facilitator for them to glide across the water surface. This acts as an adoptive mechanism since if a single cyanobacteria trailed of alone, it would not be able to exist in alone and would ultimately die.
Cyanobacteria are mostly transparent but underneath they contain a layer of cells that absorb the UV rays that facilitate this amazing process.
Photosynthesis is noted to occur in homologous centers. Other bacteria like algae and other plants have similar forms and follow similar processes (Zhang, 323). They are characterized as anoxygenic organisms. Their structures are however, complex and it is for the sole reason that they were able to exist for so many years and are presently fossils. Their complex structures enable them perform photosynthesis and respiration at the same time and at the same place. They also fix oxygen in addition. The adaptive features enable them evolve to hardiness and capability to thrive under adverse climate. They were also rumored to be the founders of chloroplast. Most researchers were initially skeptical about this notion but have now embraced this notion and it is now an accepted hypothesis worldwide. They were the first organisms to perform photosynthesis and this led to aerobic Eukarya.
Falcón, (778) seeks to explore the beginning of existence of cyanobacteria. They attempt to use phylogenetic analysis as well as molecular clocks. Their origin after this study was traced to nitrogen fixing cyanobacteria that are subsection-I. This are believed to have existed in the Achaean period. At this period, cyanobacteria did not fix oxygen but nitrogen. They then evolved to oxygen fixing later on in time. Today, they are able to store starch after photosynthesis in their chloroplast through a process that has taken years if not centauries called endosymbiosis.
Zhang, however brings in different hypothesis of their origin. This article gives two different hypothesis of their evolution. The first purposes the evolution of light harvesting antennae in protein form that existed through oxygenated photosynthesis. This consequently gave rise to cyanobacteria CP43 antennae much later that led to the present cyanobacteria. The other suggests that the antennas of CP43 originated from a form of ancestral protein. To understand which was the more believable of the two, the study uses phylogenetic technique. This technique uses layers of membrane from the alleged proteins. The first hypothesis was highly approved and seemed to give the most satisfying results.
Cyanobacteria exist in the group of organisms technically renowned as hypolithic microbes. Another characteristic of these organisms is that they can exist in extremely harsh conditions as earlier noted (Tracy 592). These conditions include translucent rocks like quarts and agate that exist in the semi-arid region of Australia. This are the same conditions that supported them in even after evolution before other organisms started inhabiting this region of the universe. Tracy 593) choose to test the most diverse conditions that this hypothilic organisms can exist in. cyanobacteria exist in this region under this rocks and this could be considered their most extreme existence condition.
The most necessities for photosynthesis that is vital for the existence of these organisms as noted earlier are carbon dioxide, moisture, and UV-light. This area barely provides these conditions. Laboratory tests were conducted that showed the specific measures provided in this conditions. First was the carbon dioxide that is in plenty of supply in the atmosphere. Then was the minimum moisture content that is vital to this process. Findings after the experiments revealed that moisture content was 15% by mass, which was the minimum required content. The temperatures necessary revealed to be between -1 and 51 degrees Celsius. These temperatures befit photosynthetic conditions.
The study earlier noted confirmed the claim that this species could have existed very early in evolution due to the single fact that it could exist under extreme conditions that took years for other organisms took to adapt. In addition, its simple form ensured that it had very few processes but those vital for existence. Its ability to reproduce so fast was a winning factor for the highly adaptive and continuous existence. Notably, an offspring requires thirty minutes to come into existence (Tracy 595). Despite the fact that not all reproduced organisms survived, those that did not were used as a layer to protect the fittest from the harsh sunrays. This ensured that nothing went to waste and this is the reason behind large fossil material at researcher’s disposal on the present day. Notably, they were closely intertwined and the light harvesting forms were strategically placed to absorb maximum sunlight (Amunts, Drory, & Nelson).
The most neglected part of these organisms when studies are conducted is the benefit they continue to present to the environment. Since the beginning of the existence of organisms, this crucial hypothylics have continued to support the existence of other organisms in the ecosystem. The most obvious and yet most vital especially in the early years of this planet is oxygen and nitrogen fixing (Amunts, Drory, & Nelson) Especially, in water, most organisms rely on these simple forms for their daily existence since they supplement the much-needed component of water. Another is the adaptive features that were assimilated by other organisms that enabled their mare existence on this planet. This included cytoplasm and other light harvesting factors (Amunts, Drory, & Nelson). The process of photosynthesis is also an essential producer of organic matter on the planet.
Works cited
Amunts, Alexey, Drory, Omri and Nelson, Nathan. The structure of a plant photosystem supercomplex at 3.4A° resolution, 447 (2007).
Blankenship, Robert. Early evolution of photosynthesis. Future perspectives in Plant biology. Plant Physiology, 154 (2010): 434-438
Falcón, Luisa, et al. “Dating the cyanobacterial ancestor of the chloroplast. “ The ISME Journal 4 (2010): 777–783.
Hartman, Hyman. Photosynthesis and the origin of Life. Origins of Life and Evolution of the Biosphere, 28 (1998): 515-521
Nakayama. Takuro and Archibald, John. Evolving a photosynthetic organelle. BioMed Central Biology 10:35 (2012)
Tracy, Christopher, et al. Microclimate and Limits to Photosynthesis in a Diverse Community of Community of Hypolithic Cyanobacteria in Northern Australia, 12. 3 (2010): 592-607.
Zhang, Yinan, et al. Evolution of the Inner Light-Harvesting Antenna Protein Family of Cyanobacteria, Algae, and Plants, 64 (2007): 321-331.
