phylogenetic tree.pptx
- 1. Phylogenetic tree By Ms. Apoorva Udayashankar Assistant professor Department of Life Sciences Kristu Jayanti Autonomous College Bangalore
- 2. A phylogenetic tree is a diagram that represents evolutionary relationships among organisms based on the similarities and differences in their genetic and evolutionary characteristics The pattern of branching in a phylogenetic tree reflects how species or other groups evolved from a series of common ancestors. The phylogenetic tree is also called the “Tree of Life” or “Dendrogram”
- 4. 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.
- 8. Rooted tree: The rooted tree is described as a phylogenetic tree sharing the common ancestor on the node. Therefore the classification ends at one point usually on the node which is the common ancestor of all the branches of the tree. Unrooted tree: Contrary to the rooted tree, the non-rooted tree doesn’t have a common ancestor. The unrooted phylogenetic tree is always prepared from the rooted tree by excluding the common ancestor or the node of the tree.
- 9. Bifurcating tree The phylogenetic tree only has two branches or we can say leaves are known as bifurcating trees. It is also classified in rooted bifurcation trees and unrooted bifurcating trees. Multifurcating tree: The multifurcating tree is described as having multiple branches on a single node. Again it is classified into a rooted multifurcating tree and an unrooted multifurcating tree.
- 10. In phylogeny, the node is also known as a “clade” as well. Though there are so many different variations of the phylogenetic tree, every method of making a tree depicts the same type of information. Take a look at various trees shown in the figure Keep in mind that whatever the shape, topology or structure of the tree is, it must have a common node if rooted and branched. To read a tree, start with the tip of the branches and see where the branch ends (the node), based on that information you can depict or conclude which organism is nearer or closer and which are distantly related.
- 13. Applications of a phylogenetic tree: The phylogenetic tree is constructed to make an evolutionary link between various organisms. By doing so, we can get an idea about how and from whom different organisms are evolved. Also, it helps to classify organisms and species in different taxa and groups based on their DNA sequence and phenotypic similarities and differences. In addition to this, it is useful to study the force of evolution and characteristics of different organisms. it is applicable to study the events occurring during the course of evolution and to classify species based on the divergence of structure and function.
- 14. Limitations of a phylogenetic tree: Firstly, the manual process of constructing a phylogenetic tree is a tedious and time-consuming process. We need special software to create one! With this to construct a tree based on the DNA or protein sequence variations, a lot of lab work is needed prior to making it. or instance, if we want to construct a phylogenetic tree of 100 different organisms for a couple of genes. DNA extraction, amplification, and DNA sequencing are performed on all 100 samples prior to proceeding for phylogeny. The biggest limitation of the present technique is its accuracy. The Phylogeny methods to differentiate organisms or species are not so accurate. In addition to this, not all the characteristics can be taken into account for constructing a single tree, it will confuse things and will not give accurate divergence. Another limitation of the present technique is that we can’t quantify the divergence between two species. For instance, get back to example 1 at the starting of the article. Taxon 1 and 2 share common ancestor node 1 and taxon 3 and 4 share common ancestor node 2 but in which amount taxa 1 and 2 carry the diversity we don’t know. Furthermore, It is also difficult to explain which organism can be placed first in the sister group.
- 15. Barry G. Hall, Building Phylogenetic Trees from Molecular Data with MEGA, Molecular Biology and Evolution, Volume 30, Issue 5, May 2013, Pages 1229–1235, https://doi.org/10.1093/molbev/mst012.