Endosymbiosis Hypothesis Essay

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Write a 400- to 600-word research report (about two double-spaced pages) evaluating the evidence that supports the endosymbiosis hypothesis for the origin of mitochondria and chloroplasts in eukaryotic cells. Provide at least two properly cited references in your research report. The endosymbiosis hypothesis, developed by Margulis (1970), suggests an explanation for the evolutionary origin of organelles, specifically mitochondria and chloroplasts, in eukaryotic cells. The many similarities between mitochondria and chloroplasts led biologists to wonder if they shared a common evolutionary origin, separate from the rest of the cell. These organelles are believed to have been absorbed in early pre-eukaryotic cells and ultimately developed a symbiotic relationship with the host cell over time. Essentially, mitochondria and chloroplasts are thought to be distant relatives of ancient, free-living prokaryotes, that sometime in the past, they were cells themselves. There is compelling evidence supporting this hypothesis. Bacteria routinely absorb other smaller bacteria and sometimes these are not fully digested. This is one of the main pieces of evidence used to support endosymbiosis. Take the Paramecium bursaria for example. This single-celled eukaryote demonstrates how easily organisms can become dependent on one another for survival, resulting in a permanent relationship. It does not possess its own chloroplasts and must swallow photosynthetic green algae in order to “borrow” these organelles. Paramecium bursaria chauffeurs the algae and in return, the algae shares the food it produces (Palmer). This is essentially what happened with endosymbiosis. Scientists believe mitochondria and chloroplasts originated from larger prokaryotic cells engulfing bacterial cells, whereas most membrane-enclosed organelles, such as the nucleus, ER, and Golgi, likely originated from

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