Universal+Tree+of+Life



In the 1960s when researchers were learning the genetic code, they found that it was in all forms of life. They came to the to the conclusion that all present-day organisms must have a common ancestor. Scientists use two different criteria to identify regions of DNA molecules that can show where the branching patterns of the tree. The regions must have evolved slowly so that homologies between distantly related organisms can be detect and must be able to be sequenced. There are three domains on the tree of life. They are Bacteria, Archaea, and Eukarya. The first domain, Bacteria, consists of prokaryotes, including bacteria that is closely related to chloroplasts and mitochondira. The second domain, Archaea, is a group of diverse prokaryotic organisms that inhabit a variety of environments. They can use hydrogen as a energy source while others use deposits of natural gas that are found in Earth's crust. The third domain is Eukarya. In the Eukarya, the cells have true nuclei. This domain also includes groups of single-celled organisms to multicellular plants, fungi, and animals. The early history is not clear on these domains, but comparisons of complete genomes from the domains show that during the early history there had been substantial changes in genes between the organism in the domains. These changes took place through horizontal gene transfer. The genes are transferred from one genome to another through mechanisms like transposable elements and through fusions of different organisms(2).

(1). http://nanotransformation.com/nanotransformation/the-tree-of-life-morgellons-finish-it.html (2). AP Biology Book

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