EndosymbiosisBefore the 1960s many biologists pondered as to how eukaryotic cells evolved. Some scientists believed that these complex organisms evolved from prokaryotic cells. However, this theory begged the question, why are prokaryotic cells still functioning if evolution occurred? Darwin's theory of evolution proves against this theory but in the 1960s biologist Lynn Margulis formed the endosymbiotic theory. This theory she created would have much evidence to help prove its truth.
In 1967, Dr. Margulis hypothesized a theory of eukaryotic evolution. She "proposed that aerobic bacteria (that require oxygen) were ingested by anaerobic bacteria (poisoned by oxygen), and may each have had a survival advantage as long as they continued their partnership." (Biology. Com). The endosymbiotic theory states that eukaryotic cells originated from engulfing bacteria (prokaryotic) cells and forming a symbiotic relationship between cells. An animal cell would surround an aerobic bacteria cell to form mitochondria, while a plant cell would surround blue-green algae to form chloroplast.
(Berkley). This theory explains why animals cells are able to perform cellular respiration and plant cells are able to perform photosynthesis. Aerobic bacteria cells and blue-green algae cells are able to breathe on their own and create wastes. When the cells were engulfed, the new eukaryotic cells formed a symbiotic bond between the two separate parts. In a symbiotic relationship, cells benefit from one another. In animal cells the process which benefits both cells is cellular respiration. In plant cells the process is photosynthesis. These sharing cells each have a copy of DNA. The actual cells with the nucleus contain a separate copy from the mitochondria or the chloroplast. (Telic). The DNA is similar but not exact.
The endosymbiotic theory shows how cells became independent through phagocytosis. The swallowing of bacteria by a cell allows the new cell to become much more complex...