Phylogenetic groups, or taxa, can be monophyletic, paraphyletic, or polyphyletic. A taxon (plural taxa) or taxonomic unit, is a name designating an organism or a group of Organisms In Biological nomenclature according to A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all In Phylogenetics, a Taxon is polyphyletic ( Greek for "of many races" if the trait its members have in common evolved separately in different

In biology, phylogenetics (Greek: phyle = tribe, race and genetikos = relative to birth, from genesis = birth) is the study of evolutionary relatedness among various groups of organisms (e. Foundations of modern biology There are five unifying principles Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly eVolution is the third Album by eLDee, it was due to be released in 2008 g. , species, populations). In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. Also known as phylogenetic systematics or cladistics, phylogenetics treats each species as a group of lineage-connected individuals^[1]. Cladistics is the hierarchical classification of Species based on evolutionary ancestry Cladistics is the hierarchical classification of Species based on evolutionary ancestry Taxonomy, the classification of organisms according to similarity, has been richly informed by phylogenetics but remains methodologically and logically distinct. Taxonomy is the practice and science of classification The word comes from the Greek, taxis (meaning 'order' 'arrangement' and, nomos ^[2]

Evolution is regarded as a branching process, whereby populations are altered over time and may speciate into separate branches, hybridize together, or terminate by extinction. Speciation is the Evolutionary process by which new biological Species arise In Biology, hybrid has two meanings The first meaning is the result of interbreeding between two animals or plants of different taxa. In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa. This may be visualized as a multidimensional character-space that a population moves through over time. See also Visualization and Information graphics Visualization is any technique for creating Images Diagrams or Multidimensional scaling ( MDS) is a set of related Statistical techniques often used in Information visualization for exploring similarities or dissimilarities The problem posed by phylogenetics is that genetic data are only available for the present, and fossil records (osteometric data) are sporadic and less reliable. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is FOSSIL is a standard protocol for allowing serial communication for Telecommunications programs under the DOS Operating system. Osteometry is the study and Measurement of Human or Animal Skeleton, especially in an Anthropological or Archaeological Our knowledge of how evolution operates is used to reconstruct the full tree. ^[3]

Cladistics provides a simplified method of understanding phylogenetic trees. Cladistics is the hierarchical classification of Species based on evolutionary ancestry There are some terms that describe the nature of a grouping. For instance, all birds and reptiles are believed to have descended from a single common ancestor, so this taxonomic grouping (yellow in the diagram) is called monophyletic. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor "Modern reptile" (cyan in the diagram) is a grouping that contains a common ancestor, but does not contain all descendents of that ancestor (birds are excluded). Cyan (saɪæn from Greek κυανός / kyanos, meaning "blue" may be used as the name of any of a number of a range of colors in the blue/green part of This is an example of a paraphyletic group. In Phylogenetics, a group of organisms is said to be paraphyletic if the group contains its most recent common ancestor but does not contain all A grouping such as warm-blooded animals would include only mammals and birds (red/orange in the diagram) and is called polyphyletic because the members of this grouping do not include the most recent common ancestor. In Biology, a warm-blooded Animal species is one whose members maintain thermal Homeostasis; that is they keep their body temperature at a roughly constant In Phylogenetics, a Taxon is polyphyletic ( Greek for "of many races" if the trait its members have in common evolved separately in different

The most commonly used methods to infer phylogenies include parsimony, maximum likelihood, and MCMC-based Bayesian inference. Computational phylogenetics is the application of computational Algorithms methods and programs to phylogenetic analyses Parsimony is a 'less is better' concept of frugality economy stinginess or caution in arriving at a hypothesis or course of action Maximum likelihood estimation ( MLE) is a popular statistical method used for fitting a mathematical model to some data Bayesian inference is Statistical inference in which evidence or observations are used to update or to newly infer the Probability that a hypothesis may be true Distance-based methods construct trees based on overall similarity which is often assumed to approximate phylogenetic relationships. Phenetics should not be confused with Phonetics, the study of speech sounds despite the similarity in pronunciation All methods depend upon an implicit or explicit mathematical model describing the evolution of characters observed in the species included, and are usually used for molecular phylogeny where the characters are aligned nucleotide or amino acid sequences. Note The term model has a different meaning in Model theory, a branch of Mathematical logic. Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this

Ernst Haeckel's recapitulation theory

During the late 19th century, Ernst Haeckel's recapitulation theory, or biogenetic law, was widely accepted. The 19th century of the Common Era began on January 1, 1801 and ended on December 31, 1900, according to the Gregorian calendar Ernst Heinrich Philipp August Haeckel ( February 16, 1834 — August 9, 1919)also written von Haeckel, was an eminent German The theory of recapitulation, also called the biogenetic law or embryological parallelism, and often expressed as Ontogeny recapitulates Phylogeny This theory was often expressed as "ontogeny recapitulates phylogeny", i. Ontogeny, as opposed to Phylogeny, refers to the history of an organism from birth as opposed to its genetic makeup e. the development of an organism exactly mirrors the evolutionary development of the species. Haeckel's early version of this hypothesis (that the embryo mirrors adult evolutionary ancestors) has since been rejected, and the hypothesis amended as the embryo's development mirroring embryos of its evolutionary ancestors. Most modern biologists recognize numerous connections between ontogeny and phylogeny, explain them using evolutionary theory, or view them as supporting evidence for that theory. Evolutionary developmental biology ( evolution of development or informally evo-devo) is a field of Biology that compares the developmental processes Donald Williamson suggested that larvae and embryos represented adults in other taxa that have been transferred by hybridization (the larval transfer theory)^{[4] [5]}

Gene transfer

Organisms can generally inherit genes in two ways: from parent to offspring (vertical gene transfer), or by horizontal or lateral gene transfer, in which genes jump between unrelated organisms, a common phenomenon in prokaryotes. Donald Williamson may refer to Don Williamson, Michigan politician Donald I The prokaryotes (proʊˈkærioʊts singular prokaryote /proʊˈkæriət/ are a group of Organisms that lack a Cell nucleus (= karyon or any other

Lateral gene transfer has complicated the determination of phylogenies of organisms since inconsistencies have been reported depending on the gene chosen.

Carl Woese came up with the three-domain theory of life (eubacteria, archaea and eukaryotes) based on his discovery that the genes encoding ribosomal RNA are ancient and distributed over all lineages of life with little or no lateral gene transfer. Therefore rRNA are commonly recommended as molecular clocks for reconstructing phylogenies.

This has been particularly useful for the phylogeny of microorganisms, to which the species concept does not apply and which are too morphologically simple to be classified based on phenotypic traits.

Taxon sampling and phylogenetic signal

Owing to the development of advanced sequencing techniques in molecular biology, it has become feasible to gather large amounts of data (DNA or amino acid sequences) to estimate phylogenies. Molecular biology is the study of Biology at a molecular level For example, it is not rare to find studies with character matrices based on whole mitochondrial genomes. However, it has been proposed that it is more important to increase the number of taxa in the matrix than to increase the number of characters, because the more taxa, the more robust is the resulting phylogeny. This is partly due to the breaking up of long branches. Long branch attraction (LBA is a phenomenon in Phylogenetic analyses (most commonly those employing Maximum parsimony) when rapidly evolving lineages are inferred It has been argued that this is an important reason to incorporate data from fossils into phylogenies where possible. Using simulations, Derrick Zwickl and Hillis^[6] found that increasing taxon sampling in phylogenetic inference has a positive effect on the accuracy of phylogenetic analyses. Dr Derrick Zwickl is a researcher in the field of Phylogenetics.

Another important factor that affects the accuracy of tree reconstruction is whether the data analyzed actually contain useful phylogenetic signal, a term that is used generally to denote whether related organisms tend to resemble each other with respect to their genetic material or phenotypic traits. ^[7]

See also

References

1. ^ Speer, Vrian (1998). A body plan, or bauplan, is essentially the blueprint for the way the body of an organism is laid out Bioinformatics is the application of information technology to the field of molecular biology For use of basic artimethics in Biology see relevant topic such as Serial dilution. Cladistics is the hierarchical classification of Species based on evolutionary ancestry In Genetics, coalescent theory is a retrospective model of population genetics that traces all Alleles of a Gene in a sample from a population to a single The EDGE of Existence programme is a research and conservation initiative that focuses on species deemed to be the world’s most Evolutionarily Distinct and Globally Endangered Anatomy Commentary on Anatomy in Avicenna's Canon List of language familiesA language family is a group of Languages related by descent from a common ancestor called the Proto-language of that family Maximum parsimony, often simply referred to as "parsimony" is a non-parametric statistical method commonly used in Computational phylogenetics for estimating The International Code of Phylogenetic Nomenclature, known for short as the PhyloCode, is a developing draft for a formal set of rules governing Phylogenetic A phylogenetic tree, also called an evolutionary tree, is a tree showing the Evolutionary relationships among various biological Species or other A phylogenetic network is any graph used to visualize evolutionary relationships between species or organisms This list of phylogenetics software is a compilation of Computational phylogenetics software used to produce Phylogenetic trees Such tools are commonly used in Phylogeography is the study of the historical processes that may be responsible for the contemporary geographic distributions of individuals Phylogenetic comparative methods (PCMs use information on the evolutionary relationships of organisms (phylogenetic trees to compare species (Harvey and Pagel 1991. Biological systematics is the study of the diversity of Life on the planet Earth both past and present and the relationships among living things through time UCMP Glossary: Phylogenetics. UC Berkeley. Retrieved on 2008-03-22. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 238 - Gordian I and his son Gordian II are proclaimed Roman emperor.
2. ^ A.W.F. Edwards & L.L. Cavalli-Sforza (1964). Anthony William Fairbank Edwards (born 1935 is a British Statistician, Geneticist, and Evolutionary biologist. Luigi Luca Cavalli-Sforza (born January 25, 1922) is an Italian population geneticist born in Genoa, who has been a professor at in Systematics Assoc. Publ. No. 6: Phenetic and Phylogenetic Classification: Reconstruction of evolutionary trees, 67-76.  
3. ^ L.L. Cavalli-Sforza and A.W.F. Edwards (Sep. Luigi Luca Cavalli-Sforza (born January 25, 1922) is an Italian population geneticist born in Genoa, who has been a professor at Anthony William Fairbank Edwards (born 1935 is a British Statistician, Geneticist, and Evolutionary biologist. , 1967). "Phylogenetic analysis: Models and estimation procedures". Evol. 21 (3): 550-570.  
4. ^ Williamson, D. I. (2003) The Origins of Larvae. Kluwer. Dordrecht. xviii + 261 pp.
5. ^ Williamson, D. I. (2006) Hybridization in the evolution of animal form and life-cycle. Zoological Journal of the Linnean Society 148: 585-602.
6. ^ Zwickl DJ, Hillis DM (2002). "Increased taxon sampling greatly reduces phylogenetic error". Systematic Biology 51: 588-598. doi:10.1080/10635150290102339. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
7. ^ Blomberg SP, Garland T Jr, Ives AR (2003). "Testing for phylogenetic signal in comparative data: behavioral traits are more labile". Evolution 57: 717-745.  

External links

• The Tree of Life
• Interactive Tree of Life
• PhyloCode
• UCMP Exhibit Halls: Phylogeny Wing
• Willi Hennig Society
• Filogenetica.org in Spanish
• PhyloPat, Phylogenetic Patterns
• Phylogenetic inferring on the T-REX server
• Mesquite
• NCBI - Systematics and Molecular Phylogenetics