Phylogeny: Definition, Types, & Examples

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Phylogeny Definition

Phylogeny refers to an organism’s or taxonomic group’s development through evolutionary history. These evolutionary histories and relatedness of different species can be depicted in form of a tree known as a phylogenetic tree that represents phylogenetic relationships. This tree is based on the information collected through molecular sequencing of biomolecules like proteins or nucleic acid or on morphological data matrices.

What is Phylogeny?

Phylogeny is usually interchangeably used with phylogenesis as both pertain to the taxonomic group or organism’s evolutionary history. But the biological process is referred to as phylogenesis that is responsible for the existence of a particular taxon.

Phylogenetics pertains to the scientific extensive study of phylogeny that involves different techniques like analytical and molecular techniques. Phylogeny represents all the evolutionary processes and the evolutionary history. It is shown in the form of a tree called the phylogenetic tree that shows the relatedness of different species and groups.

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Phylogeny vs Ontogeny

Phylogeny and ontogeny deal with the development and origin of organisms and their developmental histories. Ontogeny differs in terms of timeline, it utilizes its own timeline to analyze the developmental history of an organism from its simplest to complex form. Whereas in phylogeny evolutionary history is also considered along with development.

Phylogeny vs Taxonomy

Phylogeny is involved in evolutionary history and relatedness but is not involved in identification or classification. This area comes under taxonomy that deals with naming, identification, and classification that places the organism in a taxonomical rank in a hierarchy. This classification is based not only on morphology but also on the information derived from phylogenetics. Whereas phylogenetic classification is solely derived from molecular sequencing.

Molecular Phylogeny

This branch of phylogenetics employs techniques like molecular sequencing to understand evolutionary history and relationships. This technique helps to understand the evolutionary history of different taxa. Earlier taxa were classified and grouped based on anatomy, morphology, life cycle, and physiology.

The grouping is relatively easy as the traits considered can be utilized in classification based on their variations. But these variations may be vague, as species that were placed in the same taxa based on similarities may be put into different taxa after analyzing their genome that shows less relatedness.

More reliable and advanced techniques emerged for studying and determining phylogeny. One such tool was molecular sequencing of RNA, proteins, and DNA that can be analyzed to understand the history and the evolutionary origins. Such techniques generate large data that can be computed and compared by employing computer programs and algorithms that can help to analyze relatedness between taxa.

This can help to understand and determine whether the species are distant or evolutionarily related. rRNA like 16S rRNA have been employed as tools to understand molecular phylogeny.

Phylogeny Diagrams

It is depicted in form of an evolutionary tree and describes the relatedness or relationship among different taxa. It is created based on molecular phylogenic analytics. The organisms are also compared based on their morphology and the similarities and differences are used to describe a relationship between different taxa in a tree diagram.

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This evolutionary tree is of 2 types based on the inclusion of a common ancestor in the tree, it may be unrooted or rooted. In a rooted tree, the common ancestor is depicted and their descendants and closely related groups can be seen branching from this common ancestor.

While in the case of unrooted the common ancestor is lacking, but the relationship between closely related taxa can be inferred from the taxa. This tree is critical as it has various cope in different areas like ecology, genetics, evolution, and biodiversity. The length and position of the branches and nodes help us in understanding relatedness.

The hypothetical common ancestor is indicated by the internal nodes. Tree of life This tree shows the evolution of all organisms whether living or extinct in a schematic model. The modern metagenomics tree of life was suggested back in 2016 that includes 26 archaeal phyla, 92 bacterial phyla, and all 5 eukaryotic supergroups.

The most recent organisms can be seen at the furthermost branches while the last common ancestor of the whole organisms can be speculated from the root or bottom region of the tree.

Microbial Phylogeny

It illustrates the development and evolutionary history of microorganisms. Like other phylogenies, the morphology of microbes and their structure were utilized to draw the tree diagrams. This developed around the 1960s, the construction of trees started based on molecular comparative studies on proteins and nucleic acid.

Carl Woese determined evolutionary relatedness by comparing the small subunit of rRNA of different microbes. Based on this he believed that archaebacteria differed from bacteria, which eventually lead to the development of a 3 domain classification system. This system includes the domain Archaea, domain Eucarya, and domain bacteria. Approximately about 92 phyla have been discovered in bacteria by phylogenetics.

Animal Phylogeny

This tree depicts the evolution and development of animal organs. Thus, based on organ system organization, the relatedness and relationship between different lineages can be studied. As an instance, the digestive system evolved 600 mya, and the liver evolved in the case of vertebrates after a hundred million years later.

Importance of Phylogeny

Phylogenetic studies highlight the relationship between different taxa and their evolutionary history. It is basic to other disciplines like taxonomy for identification and classification, genetics, and ecology.

Limitations of Phylogeny

There are constraints on the data observed from phylogenetics as some errors can be present in the data. For instance, the data used may be erroneous as when horizontal gene transfers occur between organisms. For phylogeny, the data should be sources from different genomic sources like mtDNA or cpDNA, instead of focusing only on 1 single protein and gene. There may be limited or insufficient DNA samples of extinct species.

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