Biology: The Endosymbiotic Theory Essay example

of the food chain. This would cause their numbers to rise, which would lead to irreparable damage to the ever-fragile ecosystem.

Endosymbiosis is the theory that eukaryotic cells were formed when a prokaryotic cell ingested some aerobic bacteria. The first step of the evolution of a eukaryotic cell is the infolding of the cellular membrane. This process takes place when the plasma membrane folds inwards and develops an envelope around a smaller prokaryotic cell. Once the smaller cell is engulfed, it becomes dependent upon its host cell. It relies on the host cell for organic molecules and inorganic compounds. However, the host cell also benefits because it has an increased output of ATP for cellular activities and becomes more productive. This ATP comes from the mitochondrion (the aerobe) that is engulfed.

With surely convincing evidence researchers have been able to compile in support of the endosymbiosis theory, it becomes hard for one to deny the possibility that cilia, mitochondria and chloroplasts once existed as bacterial organisms (later to be taken up by host cells by endosymbiosis).

Before eukaryotic cells contained organelles and worked symbiotically as one, life consisted of free-living bacteria. Organelles, such as chloroplasts and mitochondria, that are currently found in eukaryotic cells are theorized to have been separate bacteria before the evolutionary success of the eukaryotic cell. Such idea is proven through the endosymbiotic theory. This concept provides an evolutionary origin for the mitochondrion and chloroplast seen in organisms of today. This theory is held together by DNA evidence found within the organelles themselves. The mitochondrion alone contain its own genome enclosed in the form of circular DNA, as well as their own ribosomes and transfer RNA. Similarly, the chloroplasts have their own genome. When compared to their bacterial ancestors, these DNA sequences resemble that of the respective organelles. The DNA sequences of these genes provide clear evidence to the evolutionary success of the eukaryotic cell.

1st photosynthetic organisms may have been bacteria with clusters of photosynthetic enzymes and other molecules embedded in infoldings of plasma membrane

The mitochondria and chloroplasts display similar attributes with bacteria that ultimately led to the endosymbiotic theory. The theory began as an early ancestor of eukaryotic cells engulfed an oxygen-using non-photosynthetic prokaryote, which became the mitochondria. The engulfed cell eventually began to form a “relationship” with the host cell, becoming an endosymbiont, meaning a cell living within another cell. As evolution took its course, they merged into a single organism. Along the way, at least one organism containing the

Evolution, the process by which populations have changed and modified over generations, is the key to explaining the phenomenon that allowed single celled prokaryotes to be the ancestors to all life on earth. The first life on earth was believed to be prokaryotic cells, which lacked a nucleus to encase their DNA, while animals are multicellular, heterotrophic, eukaryotes, whose DNA and other organelles are encased. Somehow, the populations of prokaryotes on the early earth became more complex organisms such as animals over the generations, through evolution. To begin to comprehend this process, one must first look at how cells evolved from prokaryotes into the eukaryotes that make up the animal body.

The endosymbiotic model suggests that eukaryotic cells came from mutually beneficial (symbiotic) relationship between different kinds of prokaryotic cells. That is, ancient bacterial cells enveloped smaller bacterial cells, and they functioned together as a unit. The model suggests that they evolved together, eventually becoming present-day eukaryotic cells. This model is supported by the fact that mitochondria and chloroplasts contain enzymes, ribosomes, and membranes that are similar to those of existing prokaryotes.

Maybe the most vital distinction in the middle of essential and optional Endosymbiosis is that on account of essential, the inundated

As indicated by the theory of endosymbiosis, convincing confirmation recommends that chloroplasts were once primitive bacterial cells that shaped an endosymbiotic relationship with other prokaryotic cells. Over numerous years of development, they have turned into a perpetual piece of their host cell and could no longer exist

The principal branches of the tree of life are Bacteria, Archaea, and Eukarya. These three branches distinct and are very much alike to each other. Bacteria and Archaea are comparable in size, shape, generative procedure and amount of chromosomes. Both recreate using binary fission and they only have one chromosome. Bacteria and Archaea both lack a nucleus and other organelles. Eukarya have diversified chromosomes and a nucleus. Archaean cells have dissimilar lipid bonds than both Bacteria and Eukarya. In addition to both Bacteria and Eukarya have greasy acids in their cells but, Archeans do not. Nevertheless all of them have RNA, even though Archaea have more complex RNA polymerases than Bacteria. All three branches on the Tree of Life are

From studies of both the Archezoan and Symbiogenetic Scenarios, the latter theorizes that the mitochondrion and the eukaryotic cell evolved together as the result of a symbiosis between two prokaryotes. The host was an autotrophic methanogenic archaeon and the symbiont was an -proteobacterium capable of living both anaerobically and aerobically. This provides explanations for the need of an endosymbiont and why gene transfer was an essential part of the process. Studies of MROs such as the hydrogenosome show that it and the mitochondrion share a system for protein transport and hydrogenosomes have now been found in species that were previously thought to have separated from other eukaryotes before the mitochondrial endosymbiosis. Further research with a broadening base of organisms will continue to question whether all eukaryotes contain a mitochondrial ancestor, highlighting the important role that mitochondrial endosymbiosis has played in eukaryotic

Introduction: - The mitochondria is a double membrane organelle that is found in all eukaryotic organisms. There is some evidence that proves some eukaryotes lack mitochondria, but there is no true evidence about complete lack of mitochondria in the organisms. Mitochondria is known as a power house of the living body cell. They store energy in the cell and release it as needed. Every structure in Mitochondria have their own specific roles which helps in storing energy (See Figure 1 for details). Evidence shows that mitochondria evolved from primitive bacteria. Did mitochondria evolve from primary bacteria or were they the new adaptation in the plants and animals? In this paper we are going to see how Mitochondrion have been evolved in different species and what methods have been used to prove that evolution. There is still debate between scientists about whether mitochondrion really evolved from bacteria or if it was present in the cells before bacteria were present.

Interestingly, like organisms chloroplasts have ancestors too. These are called “cyanobacteria”. Cyanobacteria are morphologically complex organisms which belong to the family of eubacteria, also known as ‘true bacteria’. Chloroplasts evolved from these organisms by the ‘endosymbiont hypothesis’ which is the same mechanism that explains how mitochondria evolved. According to this theory, chloroplasts were not just mere structures once, in fact they were individual organisms and that is the reason that they contain their own genome. Not only were they quite similar to cyanobacteria, they also had a close relationship with plants cells, an interaction known as a symbiotic relationship. One can wonder, what exactly happened to chloroplasts then? Why didn’t they remain an individual species? Over time, these ‘photosynthetic bacterial cells’  formed the chloroplasts

The primitive eukaryotic cell was also eventually able to eat prokaryotes, a marked improvement to absorbing small molecules from its environment ("Endosymbiosis - The Appearance of the Eukaryotes", 2017). This whole process of endosymbiosis started when the eukaryote engulfed and could not digest an autotrophic bacterium; there is evidence suggesting that this bacterium was alphaproteobacteria, which uses photosynthesis for energy. This opened up a new trend where the eukaryote provided protection and nutrients to the prokaryote, and in return the prokaryotic endosymbiont returned the favour by providing additional energy to its eukaryotic host through respiratory cellular mechanism. In the long run this became a permanent arrangement in completing the endosymbiosis process because the endosymbiont lost genes it previously used for its independent life and transferred others to eukaryotes’ nucleus as it became more dependent on its new host for organic molecules and inorganic