Taxonomy ultimately comes down to questions of origins. Some of the beginning of certain groups is surprisingly straightforward. Some involved steady adoptions to solely changing environment and conditions. In other situations dramatic changed in the conditions seem to force sudden and noteworthy changes to the evolution. And sometimes, a gigantic event makes a big splash in evolution. The origin of eukaryotes appears to have been a big splash in the form of endosymbiosis, a condition in which different organisms live together. The idea that endosymbiosis has been around since 1905 when a Russian biologist, C. Mereschkowsky, hypothesized that plastids, like chloroplasts, are decedents of bacteria like organisms. Another idea came up in 1927 when I. Wallin straightforwardly predicted that the mitochondria, discovered in the late 1800s, had evolved from a type of bacteria. The Endosymbiotic Theory was first proposed by former Boston University Biologist Lynn Margulis in 1967 and was later published in her book. With these findings the theory that life arose billions of years ago from a simple microbe similar to a prokaryote cell has been thought right. The theory basically states that some organelles in a eukaryotic cell were once prokaryote molecules.
The idea is that the first eukaryote was probably an amoeba-like cell with a nucleus formed from a piece of the cytoplasm membrane pinched off around the chromosomes. It was thought that some of the amoebic-like organisms ate absorbed a prokaryotic cell that survived within the organism. The mitochondria were formed when bacteria able of aerobic respiration were absorbed; chloroplasts formed when photosynthetic bacteria were ingested. In time they lost their cell walls and most of their DNA because they were not of use in the host cell.
Evidence has been found to support the idea. Mitochondria are the same size as a prokaryotic cell. It can also divide by binary fission. The chloroplast can also do this. The...
Citations: Lake, James A. "Evidence for an Early Prokaryotic Endosymbiosis." Macmillion Publishers
Limited, 20 Aug. 2009. Web. 22 Aug. 2010.
"Endosymbiosis and the Origin of Eukaryotes." 22 Aug. 2007. Web. 22 Oct. 2010.
Please join StudyMode to read the full document