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Phylogeny is the evolutionary history of a characteristic, individual, population, species, or group of species. It is most often depicted as a branching tree analogous to a family tree. The complete phylogeny tree for all living organisms is called the Tree of Life, a metaphor dating back over 100 years.
Phylogeny could be considered the "facts" of evolution, and evolution in turn is the central unifying principle of biology. As such, phylogeny has several major uses within the biological sciences.
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Phylogeny and Classification
Phylogeny is used extensively in biological classification. In fact, it is now the primary factor considered by taxonomists, although not the only one. In traditional Linnaean classification, non-phylogenetic groups are allowed. One glaring example is Class Reptilia, which is a paraphyletic group. If it were a true monophyletic group, meaning that it accurately reflects the phylogeny of all members and descendants, then it would include birds and mammals, both of which descended from reptiles.
Even so, Linnaean classification does give heavy weight to phylogeny when considering how organisms should be placed. And Linnaean classification is not the only option for taxonomists. A new proposed classification scheme, the PhyloCode, uses phylogeny exclusively. It does away with ranks, allowing an unlimited number of groups in an organism's classification -- useful for species that are the result of extensive radiation and therefore have heavily branched phylogenies.
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Molecular Phylogeny, Infectious Disease, and Biotransformation
The study of the phylogeny of biochemical characteristics, such as genes and proteins, is called molecular phylogeny. This field helps broaden our understanding of biochemistry by allowing researchers to measure rates of evolution of biological molecules.
Molecular phylogeny has direct applications for medicine, especially in the field of infectious disease. Researchers can investigate the phylogeny of disease organisms and/or their constituent molecules and determine their rates of evolution. They can also study the direction of evolution. By determining where a disease organism, such as a bacterium or virus, has been, scientists can make predictions about where it is going.
Biotransformation refers to the process of living cells modifying molecules. Biotransformation is useful in diverse fields ranging from bioremediation (the use of bacteria to clean up environmental pollutants) to drug manufacturing. Selecting a bacterial strain to use in biotransformation can be a tedious trial-and-error process. Studying the phylogeny of different bacterial strains can enable researchers to select the appropriate strain for a given biotransformation, a procedure called "intelligent screening."
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Phylogeny: Used For Theory and Technology
Phylogeny is an integral part of a broad, unified view of biology, but it is more than just knowledge for knowledge's sake. It can be applied to human understanding of life, of biochemistry, and of evolution. Biotechnology applications also benefit from studies of phylogeny, and applications in the field of medicine may directly impact patients' lives. Phylogeny and its methods, such as cladistics, are an important field of science.