Endosymbiotic theory.

... Endosymbiotic theory: * Proposed by Dr. Margulis in 1981 in her book ìSymbiosis in Cell Evolutionî. * 1.6 billion years ago, blue-green algae, began releasing O2 into the atmosphere. * Aerobic bacteria developed (mitchondrial pre-cursor). * Anaerobic, heterotrophic cells (proto eukaryotes) engulfed the aerobic bacteria. * A mutually beneficial relationship between the two was formed. Endosymbiotic relationship: * The host cell provided essential nutrients to the engulfed aerobic cell. * In turn the aerobic cell used these nutrients to synthesize ATP energy molecules. * This ATP was used as an energy source by the host cell. * The aerobic cell was given a safe environment as well as receiving nutrients from the host cell. Evidence for Endosymbiosis: * The aerobic cell was given a safe environment as well as receiving nutrients from the host cell. * Mitochondria and bacteria are approximately the same size. * Mitochondria have a set of double membranes as do

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