Before going into details we should know about these terms:

Phylogeny: It is related to evolution dealings in the evolutionary development of a species. It is represented by different ways vertical or slanted.

Phylogenesis: It refers to the evolutionary relationships among species.

Phylogenetics: It is determination or estimation of evolutionary relationships among groups of species, organisms and genes.

Phylogenetics is a field of biology which is used to find relationships among different organisms. This relationship is showing through a tree (used to model actual evolutionary relationship of organisms). Ancestral divided into two descendant species because closely related organisms are shown in near branches. If there is too much divergence between two species its mean they are not closely related.

The history of speciation (one species becomes divided into more than one new species) tells us how these species are related to each other. If they evolve to be separate species relatively recently then they are "closely relative" similarly if they evolve to be separate specie long above then they are "distant relatives". For example orthologs are genes in different species that evolved from common ancestor gene by speciation; they retain same function in the course of evolution.

Objective of Phylogenetics:

1. Determine the closest relative of organism we are interested in for example new strain of bacteria.
2. Predict protein-protein interactions.
3. Determine three dimensional structure of protein by phylogenetic analysis.
4. Estimate time of divergence.
5. Follow the changes in rapidly changing species for example flu a viral disease.
6. Predict a function of a gene through BLAST.

Phylogenetics is based on two types of data; morphological data (includes characters) and molecular data (includes DNA protein sequences). There are some benefits of molecular data when compared with morphological data. In molecular data sequences are evolve in a much more regular manner than morphological data. It can be used for any organism.

Terms related to phylogenetics:

Systematic: is the study of diversity of life on planet earth, both past and present and the relationship among living things through time.
Taxonomy: is classification of organism groups and change according to evolutionary history or similarity. Carl Gustor who is the father of taxonomy.

Mostly scientists prefer phylogenetics classification as it only names the clad (a type of tree which should have ancestors and descendants) and does not follow rank to hierarchy.

Conclusion

In the summary, phylogenetics analysis allows us to determine closest relationship among different organism. Evolutionary relationships can be constructed by similarity in sequences. We can find how these organisms evolve from each other. By drawing a tree we can get better idea about the related species. This field will provide us better way for the determination of evolutionary relationships among different groups of organism.

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