Information AboutPhylogenetics |
| CATEGORIES ABOUT PHYLOGENETICS | |
| phylogeneticsphylogenetics | |
| bioinformatics | |
| evolutionary biology | |
| scientific classification | |
| genetics | |
|
Phylogeny (or phylogenesis) is the origin and Evolution of a set of organisms, usually a set of species. A major task of Systematics is to determine the ancestral relationships among known species (both living and Extinct ). The most commonly used methods to infer phylogenies include Cladistics , Phenetics , Maximum Likelihood , and MCMC -based Bayesian Inference . 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. ERNST HAECKEL'S RECAPITULATION THEORY During the late 19th Century , Ernst Haeckel 's Recapitulation Theory , or biogenetic law, was widely accepted. This theory was often expressed as " Ontogeny recapitulates phylogeny", i.e. the development of an organism exactly mirrors the evolutionary development of the species. The early version of this hypothesis has since been rejected as being oversimplified. However, most modern biologists recognize numerous connections between ontogeny and phylogeny, explain them using evolutionary theory, or view them as supporting evidence for that theory. HORIZONTAL GENE TRANSFER New developments in the understanding of Horizontal Gene Transfer have complicated the matter a bit. :Sequence comparisons suggest recent horizontal transfer of many genes among diverse species including across the boundaries of phylogenetic "domains". Thus determining the phylogenetic history of a species can not be done conclusively by determining evolutionary trees for single genes. {Link without Title} TAXON SAMPLING Due 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 . 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 . It has been argued that this is an important reason to incorporate data from fossils into phylogenies where possible. Using simulations, Zwickl and Hillis (2002) found that increasing taxon sampling in phylogenetic inference has a positive effect on the accuracy of phylogenetic analyses. SEE ALSO REFERENCES
EXTERNAL LINKS |
|
|