Genealogical Tree


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Genealogical Tree

 

in biology, a treelike representation of phylogenetic relationships within any natural group of organisms or within the organic world as a whole. The concept of a genealogical tree and the method for depicting it are borrowed from human genealogy.

The idea of a chain of beings preceded the concept of a genealogical tree. In 1766 the Russian scientist P. S. Pallas was the first to prove that the linear arrangement of organisms does not reflect the true relationship between animal classes, and consequently he proposed representing organic systems in the form of genealogical tables. This idea was particularly developed after the publication of C. Darwin’s The Origin of the Species (1859), in which the phenomenon of divergence was illustrated by means of genealogical trees. In the 19th century the genealogical tables of the animal and plant kingdoms were depicted by E. Heckel and others in the form of actual trees (hence the name) with group names arranged on the branches.

Genealogical trees are drawn only on the basis of a mono-phyletic development of living nature and cannot be used to illustrate a polyphyletic origin of the organic world. A genealogical tree is constructed to show the phylogenetic relationships and the level of organization of equally ranking groups, including phyla, classes, and orders. The relative level of organization of each group corresponds with its position on a genealogical tree. The origin of each group and its relation to other groups is designated by the point at which a particular branch departs from the common trunk or from a larger branch. If a genealogical tree is supposed to illustrate both phylogenetic ties and subordinate relationships in a group, the large unifying taxons (phyla, classes, orders, and families) are arranged closer to the base of the trunk (or the main taxon is at the trunk’s base) or they are arranged according to their rank on the primary or secondary lateral branches.

The end-shoots of a genealogical tree designate the lowest ranking categories, which are genera and sometimes species. Genealogical trees based on only modern forms reflect purely systematic relationships. If paleontological material is also used, genealogical trees are plotted on diagrams representing the subdivisions of geologic time. The point of divergence of a particular branch indicates the time that the corresponding taxon emerged.

True phylogenetic relationships among different groups of organisms and within individual groups are very complex and can only be approximated on a plane. Therefore, the two-dimensional flat representation of a genealogical tree is frequently replaced by a three-dimensional representation.

V. G. GEPTNER

References in periodicals archive ?
The influenza A(H5N1) virus genealogical tree notably contains long side branches; some lineages (mostly comprising hemagglutinin sequences from Southeast Asia, Africa, and southern Asia) persist for years.
Rolls began implementing this vision five years later, when he teamed up with Yiftah and Ilan Cohen to form Famillion, a startup that uses bio-informative methods and advanced programs to produce a platform where genealogical trees can be cross-checked and traced for compatibility.
It has permeable frontiers and extends beyond the individual proper, drawing substance and sustenance from the family and the community, for the genealogical tree does not represent the family in the narrow sense of the term, that generally accepted in Western culture.
The trees suggest to Marvell the pedigrees, the genealogical trees of Fairfax and Vere, two "ancient stocks" united by marriage.
The arrangement of branches of the new genealogical tree is reassuring, says Niels Kristensen of the University of Copenhagen, who was not involved in the study.
The team attempted to infect 35 species picked from different branches of the amphibian genealogical tree.
In particular, the Friedrich-Rothko comparison seemed to register convincingly - to me, at least, and apparently to many others - and I felt destined to fill in the historical blanks that might somehow connect these two painters, so far apart in time, space, and culture, with a convincing genealogical tree.
As recently as 30,000 years ago, the kangaroo genealogical tree had a branch called Sthenurinae.
A series of appendices provide a chronology of Melville's life and times and a bibliography of his works, list selected books and articles about Melville, present excerpts of contemporary reviews of his work, reprint some correspondence between Melville and Nathaniel Hawthorne, and present his family genealogical tree.
Comb jellies, with well-developed sensory cells and rapidly reacting ion channels, may be the most ancient surviving branch on the animal genealogical tree, the sister lineage to all other animals.
The ants he and Frederick identified as aquatic-capable were scattered among nonswimmers in several lineages in the genealogical tree, suggesting that the ability evolved independently each time.
He and Muir Eaton of Drake University in Des Moines, Iowa, worked backward along a genealogical tree of grackle relatives to reconstruct the history of male and female color differences.

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