Describe the sequence of events in the evolution of eukaryotic cells as described by the endosymbiotic hypothesis. List four pieces of evidence which support this theory

Question

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Answer 1

The endosymbiotic theory describes the evolution of eukaryotic cells as a series of sequential, cell-merging events between a eukaryotic ancestor and certain prokaryotes. First, a non-photosynthetic prokaryote merged with the ancestral cell. Over time, the prokaryote lost the ability to live independently and evolved into the mitochondria. Later, descendants of these cells merged again with a photosynthetic prokaryote which became the chloroplast. Evidence for the endosymbiotic theory include the following: mitochondria and chloroplasts each contain circular DNA and 70S ribosomes similar to those found in bacteria, they are bound by a double-membrane within the eukaryotic cell, they are similar in size to bacteria, and replicate by a process similar to binary fission. A number of mitochondrial genes resemble genes found in certain bacteria (namely rickettsial species) while genes in the chloroplast resembles genes found in cyanobacteria.