Phylogenetics | Evolutionary Relationships & Classification (2024)

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Written by

Omar Sultan Haque Postdoctoral Fellow, Department of Psychology, Harvard University. He contributed several articles to SAGE Publications’Encyclopedia of Global Health (2008), which served as the basis for...

Omar Sultan Haque

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Related Topics:
evolution
phylogeny
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phylogenetics, in biology, the study of the ancestral relatedness of groups of organisms, whether alive or extinct.

History

Classification of the natural world into meaningful and useful categories has long been a basic human impulse and is systematically evident at least since time of ancient Greece. Dominant for close to 2,000 years in the West was the notion of a “Great Chain of Being,” or scala naturae, which emphasized a static notion of reality and depicted a hierarchy that started from matter and nature (such as rocks) and moved upward to humans, angels, and eventually and highest of all, God. Since Carolus Linnaeus, and especially since Charles Darwin, classificatory schemes have not only quickly put aside such notions as the scala naturae but also slowly moved away from postulating relationships between species based on either presumed essential traits or based on general physical similarity. The field of phylogenetics takes a functional and more scientific turn in its attempts to construct an objective depiction of evolutionary relationships between organisms based on genetic, molecular, archaeological, and historical studies and with the specific purpose of explaining, predicting, and testing similarities and differences between organisms.

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The “tree of life”

Ancestral relationships among species are commonly represented as phylogenetic trees (also called cladograms or dendrograms). A cladogram is a physical diagrammatic representation of a hypothesis of inferred relationship between species. The evolutionary relatedness between species is reflected by branching pattern of the tree and the relative distance between species on the tree. Any two species will have a common ancestor at the point where their respective branches are traced back to intersect. The more recent a common ancestor to humans, the more closely related it is to humans. For example, the common ancestor of modern humans and Neanderthals would be traced back to approximately 500,000 years ago. Similarly, the common ancestor of humans/Neanderthals and chimpanzees existed approximately 6.5 million years ago. Thus, since humans and Neanderthals share a common ancestor not shared by chimpanzees, we have reason to believe that humans are more closely related to Neanderthals than to chimpanzees. Similar retracing can be done farther and farther back on the branches of the tree of life to connect the common ancestry humans have with unicellular species some billions of years ago.

Estimating relatedness

Cladograms can be constructed with the aid of technologies that estimate molecular divergences in key sequences of DNA or protein amino acids. Similar to the progress seen in estimating the age of organic substances with the use of radioactive decay technologies and carbon dating, the advent of molecular biological technologies in the later half of the 20th century have increasingly allowed scientists to more accurately estimate the degree of evolutionary relatedness at the genetic level. Taking two hom*ologous DNA sequences in different species, one can estimate evolutionary distance by measuring the number of nucleotide substitutions that have occurred over time. Alternatively, using protein products of DNA expression, one can measure the number of amino acid substitutions that have occurred between hom*ologous protein sequences.

Omar Sultan HaqueThe Editors of Encyclopaedia Britannica
Phylogenetics | Evolutionary Relationships & Classification (2024)

FAQs

Phylogenetics | Evolutionary Relationships & Classification? ›

The field of phylogenetics

phylogenetics
phylogeny, the history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms.
https://www.britannica.com › science › phylogeny
takes a functional and more scientific turn in its attempts to construct an objective depiction of evolutionary relationships between organisms based on genetic, molecular, archaeological, and historical studies and with the specific purpose of explaining, predicting, and testing similarities ...

What is the relationship between classification and phylogeny? ›

The history of the evolution of a group of organisms or a particular kind of species is referred to as phylogeny. The study of phylogeny is called phylogenetics. Classification is the process of categorizing organisms into various groups based on some easily observable characteristics.

How do you describe phylogenetic relationships? ›

A phylogenetic relationship is a study of the relationship among organisms of a species or a population through evolution. These relationships are identified using the similarities in DNA, RNA, or protein sequences, or a comparison of the anatomical features.

What is evolutionary relationship with classification? ›

Evolutionary relationships are useful in classification because it can help show which species are more closely related and should be classified together. Species that evolved from each other will share genetic information, or DNA sequences.

What is the phylogenetic species concept and classification? ›

The phylogenetic species concept defines species as groups of organisms that share a pattern of ancestry and descent and which form a single branch on the tree of life (Fig 6.3).

What are the classification of phylogenetic relationships? ›

A phylogenetic classification involves placing organisms in a clade with their common ancestor. Consider the cladogram in Figure below. It groups birds in the same clade as reptiles, because a variety of evidence suggests that birds evolved from a reptile ancestor.

How does a phylogenetic tree relate to the system of classification? ›

Most modern systems of classification are based on evolutionary relationships among organisms – that is, on the organisms' phylogeny. Classification systems based on phylogeny organize species or other groups in ways that reflect our understanding of how they evolved from their common ancestors.

How evolution and classification are interrelated? ›

Classification and evolution are highly interlinked fields of study because the classification of an organism is influenced by its evolution. An organism may have a different type of look based on its morphology and are classified into a different group as compared to the other organism.

Which describes the relationship between evolution and classification? ›

The classification system tells something about the evolutionary relationships among species. Moving down through each level of classification, the number of species in the group decreases (Table 1.10). Two species within the same genus likely share a recent common ancestor in their evolutionary history.

What is the difference between phylogenetic and evolutionary classification? ›

Cladistics, also called phylogenetic systematics, is a taxonomic theory that is based on cladograms. All taxa must be monophyletic! Traditional Evolutionary taxonomy is based on common descent and the amount of evolutionary change to rank higher taxa.

What is the basis for classification based on phylogenetics? ›

As a result, phylogenetic classification is based on a group of entities' evolutionary descent. A phylogram and a cladogram are used to show relationships.

What is the phylogenetic system of classification? ›

A system of classification that names groups of organisms according to their evolutionary history. Like Linnaean classification, phylogenetic classification produces a nested hierarchy where an organism is assigned a series of names that more and more specifically locate it within the hierarchy.

What are the principles of phylogenetic classification? ›

The phylogenetic principle of classification is an evolutionary principle: in contrast to the phenetic principle, it classifies species according to how recently they share a common ancestor.

What is the relationship between phylogenetic and taxonomic? ›

Taxonomy is the description of species and larger groups, and the naming of these species and groups. Phylogeny is the relationships — the lines of shared descent — between these groups.

How phylogeny relates to taxonomy classification? ›

Today, biologists generally agree that we should group organisms based on how they are related to each other through evolution. This means that the taxonomy we use should reflect shared ancestry (that is, phylogeny), ideally by organizing individuals and species into monophyletic groups.

What is the relationship between taxonomy classification systematics and phylogeny? ›

Systematics is concerned both with Taxonomy, the naming and classification of life, and Phylogeny, the science and study of understanding the family tree of all life on Earth.

What is the relationship between taxonomy and phylogeny quizlet? ›

Taxonomy focuses on the characteristics of an organism, whereas phylogeny focuses more on the evolutionary relationship of a particular group of organisms.

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