Theory of Endosymbiosis

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The Theory of Endosymbiosis 09/12 Lynn Margulis developed the theory of Endosymbiosis during the 1960’s where she faced much criticism at the time from other Biologists for her new profound theory, however in time her theory has come to become universally accepted as one of the steps in the origin of life. In order for life itself to begin its evolution it required an important element, Oxygen. However 4 billion years ago oxygen was not present one Earth as it is today. This ultimately meant that for billions of years anaerobic bacteria were the dominant life on the planet and provided little hope of evolution past this primitive stage in life. Around 3 billion years ago however a new species of cell emerged, most probably from the tidal pools of the ocean, named ‘Cyanobacteria’ which kick started the evolution chain and changed the course of life on Earth. These new cells attained photosynthetic abilities in water, meaning that like plants today they could supply themselves with energy through the process of reacting carbon dioxide and water in the presence of light (photosynthesis) which also lead to the creation and output of Oxygen. This oxygen contaminated the oceans where the previous anaerobic bacteria, once content in isolation, was poisoned by the oxygen and ultimately destroyed. This event in the Earth’s history was important for the evolution of life as without this new up rise in cyanobacteria and oxygen, life would never have evolved. Around 2.5 billion years ago aerobic bacteria (mitochondrion) began to emerge and were engulfed by the anaerobic bacteria; most probably intended for digestion as a food source however through chance they were not and instead started a mutually beneficial relationship between the two cells (symbiosis). From here the

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