Endosymbiosis Essay

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Introduction: This essay is based on the endosymbiont Hypothesis which suggests that key organelles of eukaryotes originated as symbioses between separate single celled organisms and according to this theory and my understanding, the chloroplasts and possibly other organelles, represent cells that were formerly free-living bacteria that were absorbed into other cells as endosymbionts. There is molecular and biochemical evidence that suggests the mitochondrion developed from proteobacteria and the chloroplasts from cyanobacteria. Endosymbiosis is a discovery of great importance as it enables us to understand the evolution of plants and animals cell from the common evolutionary ancestor. This essay will focus on the early evolution of our eukaryote ancestor during Precambrian period, including the plastids origin along the algae family due to second endosymbiosis, discuss the evidence that supports the theory and give an example of endosymbiosis. Endosymbiosis has a primary and secondary phase. The primary phase of endosymbiosis involves the engulfment of a bacterium by another free living organism ant the secondary phase of endosymbiosis occurs when the product of primary endosymbiosis is itself engulfed and retained by another free living eukaryote. Secondary endosymbiosis has occurred several times and has given rise to extremely diverse groups of algae and other eukaryotes. Some organisms can take opportunistic advantage of similar processes, where they engulf an algae and use the products of its photosynthesis, but once the prey item dies off the host returns to a free living state.(Pagel) The process of secondary endosymbiosis left its evolutionary signature within the unique topography of plastid membranes. Secondary plastids are surrounded by three (in euglenophytes and some dinoflagellates) or four membranes (in haptophytes, heterokonts, cryptophytes,
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