Phylogenetic Tree- Introduction, Mode of Classification
- 2. What is the Phylogenetic Tree? It is defined as a diagrammatic representation of evolutionary relationships among living organisms. This diagrammatic representation represents how different species evolved from a series of common ancestors. The phylogenetic tree can also be defined as the two- dimensional graph representing the evolutionary relationship between an organism from various other organisms. The phylogenetic tree is also called the “Tree of Life” or “Dendrogram” The idea of a phylogenetic tree arose from an ancient concept of a ladder-like progression from moderate to powerful forms of life. The term Phylogenetic or Phylogeny is derived from the ancient Greek word, which refers to race, origin or lineage.
- 3. Construction of the Phylogenetic tree There are two different methods based on which the phylogenetic tree is constructed. Character-based method This method is based directly on the sequence characters, therefore it is also called the discrete method. The character-based method uses the aligned characters for constructing the phylogenetic tree. These aligned characters include either the DNA or protein sequences during the tree inference. The two most popular character-based methods: Maximum parsimony. Maximum likelihood. Distance-based method This method is based on the amount of the distance or the dissimilarity between the two aligned sequences. In this method of constructing the phylogenetic tree, the sequence data is
- 4. Steps for preparing the Phylogenetic Tree Selection of an organism or a gene family ↓ Selection of appropriate molecular markers ↓ Amplification ↓ Sequencing ↓ Assembly ↓ Alignment ↓ Evolutionary model ↓ Phylogenetic Analysis ↓ Construction of a Tree ↓ Evolution of a Phylogenetic Tree
- 5. Types of Phylogenetic Trees 1. Rooted tree 2. Un-rooted tree
- 6. 3. Bifurcating tree 4. The multifurcating tree
- 7. Importance of Phylogenetic Tree It is the fundamental tool to derive their most-useful evidence from the fields of anatomy, embryology, palaeontology and molecular genetics. Other significances of the phylogenetic tree are: Used in the search for a new species. Used to study evolutionary histories. To study how the species were spread geographically. To study the common ancestors of extant and extinct species. It is used to identify the most recent common ancestors and to recognize how closely related species are. To relate the milestones of the evolution of major life forms to the tree of life. To represent evolutionary relationships between organisms that are believed to have some common ancestry. With the help of the phylogenetic tree, the infectious microbes can be traced along with their evolutionary histories.