Universal tree of life

The tree branches quickly into three domains  

Eukarya - cells containing membranes and nuclei (e.g. plants, fungi and animals). 

Archaea a distinct type of organism with different basic properties and cell wall structures. 

Finding the root of the tree is hard, especially as we do not know the sequence of the RNA from the common ancestor. However, there are sequences that are propagated similarly in early organisms and show us which species are closest to the common ancestor. The first major divergence was between the bacteria and the archaea but no living species is close to the root, implying that all life has evolved significantly from the common ancestor. However, all species closest to 

The formation of life and how to recognise it is the central problem in astrobiology. All searches for other life forms will be prejudiced horribly by the study of the only example we know to date - life on Earth. Despite attempts to classify the general roles of molecules in definitions of life as biomarkers, there have been many discussions of possible biomarkers, including  

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Schopf JW (1998) Tracing the Roots of the Universal Tree of Life. In Brack A (Ed) The Molecular Origins of Life. Cambridge University Press, pp 336-362 Schopf JW (1999) Cradle of Life. Princeton University Press, Princeton Schopf JW, Kudryavtsev AB, Agresti DG, Wdowiak TJ, Czaja AD (2002a) Nature 416 73... 

A universal tree of life has been derived from this analysis (Figure 9.10) for all species alive on Earth today that enables a genetic distance to be determined between species but not necessarily a historical distance. 

Universal tree of life Studies of the genetic history and length of intron DNA lead to a universal tree of life and a common genetic ancestor - a hypothermophile bacterium... 

Universal tree of life The categorisation of species on Earth due to its genetic material producing a genetic distance from a common genetic ancestor. 

Forterre P. and Philippe H. (1999) Where is the root of the universal tree of life BioEssays 21, 871-879. 

Figure 10 A rooted universal tree of life, showing the three domains of life. The tree is based on sequence comparisons of ribosomal RNA, analysed by Carl Woese and his colleagues. The order and length of branches are proportional to the sequence similarities within and between the domains and the kingdoms of life — in other words, they are directly proportional to the genetic similarities between species. It is humbling to note that the animals, plants and fungi account for just a small comer of the Eucarya domain, and that there is less variation in ribosomal RNA sequences within the entire animal kingdom than there is between different groups of methanogen bacteria.

The universal tree of life represents a hierarchical phylogenetic classification of the living organisms based on comparative analysis of biosequences encoding rRNA and several proteins (Doolittle, 1999). The two major problems with inferring phytogenies from biosequences are ... 

ArchaeaFEMS Microbiology Reviews 1998 18 225-236. Forterre, Patrick Institut Pasteur Paris France The universal tree of life an update. Front Microbiol 2015 6 717. Csurds, Miklos University Montreal Quebec Canada Ancestral reconstruction by asymmetric Wagner parsimony over continuous characters and squared parsimony over distributions (in print). 

Cooper, G.M. (2003). The Cell A Molecular Approach. Sinauer Associates, Inc., Sunderland, MA. Cracraft, J. and Donoghue, J. (eds.) (2004). Assembling the Tree of Life. Oxford University Press, New York... 

The repartition in the universal phylogenetic tree of life, of the direct and indirect pathways for Gln-tRNA and Asn-tRNA biosynthesis in bacterial lineages, is shown in Figure... 

Cracraft, J. and Donoghue, M.J. (2004) Assembling the Tree of Life. Oxford University Press, Oxford, UK. 

Martin W (2005) Woe is the tree of life. In Sapp J (ed) Microbial phylogeny and evolution concepts and controversies. Oxford University Press, New York Martin W, Muller M (1998) The hydrogen hypothesis for the first eukaryote. Nature 392 37-41... 

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