What is phylogeny in biology?

In biology, phylogeny is the study of the evolutionary history of species or groups, especially regarding lines of descent and the relationships between broad groups of organisms. Phylogenies show that the tree of life results from a historical process of evolution and that degrees of resemblance correspond to degrees of relationship from common ancestors. Scientists use paleontology , comparative anatomy, embryology, and molecular genetics to develop phylogenies. Evolutionary trees are models that reconstruct the evolutionary history of taxa, such as species, genera, families, or orders. These trees show branching relationships that reflect ancestry and the changes that have occurred along each lineage.

Why do scientists study phylogeny?

Scientists study phylogeny to understand the evolutionary history of species and their relationships. Taxonomy, the science of classifying organisms, relies on phylogeny to reflect the natural relationships among living things. Phylogenetic analyses have practical applications in various fields, including tracing infectious disease origins, identifying evolutionary distinctiveness in endangered species, and determining parentage in captive breeding programs. Biologists use evidence from paleontology, comparative anatomy, embryology, and molecular genetics to develop phylogenies. By studying similarities and differences in molecular structures like DNA, they can measure how species have diverged from common ancestors.

How are organisms grouped in a phylogenetic tree?

Phylogenetic trees, also known as evolutionary trees, illustrate the evolutionary relationships among a group of organisms that share a common ancestor. The ancestor is represented as the tree's trunk, while its descendants appear at the branch tips. The distance between groups on the tree indicates the degree of relationship, with closely related groups located on nearby branches. These trees use cladogenesis and anagenesis to show the relative relationships of ancestry and the changes that have occurred along each lineage. Taxonomy, which is the science of classifying organisms, is based on phylogeny . Organisms are grouped by apparent similarity, with the data gathered from paleontology, comparative anatomy, comparative embryology, and molecular genetics.

What information do scientists use to build phylogenies?

Scientists construct phylogenies, or evolutionary trees, using data from various fields. These trees illustrate the relationships and lines of descent among species or groups, based on the proposition that different species originate from common ancestors. The most useful evidence for building phylogenies comes from: * Paleontology, especially the fossil record, which helps to determine the phylogeny of groups containing hard body parts and to date divergence times of species. * Comparative anatomy and embryology, which analyze similarities and differences between species, distinguishing between homologies (similarities inherited from a common ancestor) and analogies (similarities arising from similar habits). * Molecular genetics, which measures the degree to which species have diverged by counting differences in the sequence of units that make up protein and DNA molecules. * Geographic distribution of flora and fauna.

How does phylogeny help us understand evolution?

Phylogeny, the study of the evolutionary history of species, helps us understand evolution by showing lines of descent and relationships among organisms. Evolutionary trees, which are models that reconstruct the evolutionary history of species, use cladogenesis and anagenesis to show these relationships. Cladogenesis demonstrates ancestry, while anagenesis indicates changes along lineages. By studying homologies, or similarities inherited from a common ancestor, and using data from paleontology, comparative anatomy, embryology, and molecular genetics, we can build phylogenies that show the history of life and the degrees of relationship between groups. These phylogenies have practical applications in medicine, conservation, and even legal contexts. For example, phylogenetic methods can trace the source of infections.

What is the difference between a phylogenetic tree and a family tree?

A phylogenetic tree is a diagram that shows the evolutionary connections among a group of organisms derived from a common ancestor. It is a hypothesis based on evolutionary change and ancestry, useful in studies with any related groups. A family tree represents the genealogy and line of ancestors from whom a person is descended. The branching relationships in phylogenetic trees reflect ancestry, while family trees represent a line of descent.

phylogeny

References & Edit History Related Topics

Images

Diagram comparing the forelimb bone structures of a human, horse, dolphin, box turtle, fruit bat, and chicken, with color-coded bones showing homologous parts to illustrate evolutionary relationships.

A branching phylogenetic tree diagram shows evolutionary relationships among various organisms, from Neurospora mold to humans, based on differences in cytochrome c gene sequences. Each branch is labeled with nucleotide substitution values and illustrated with animal or organism icons along the tree.

A summary of probable lines of plant evolution.

Hypothetical relationships in the animal kingdom.

Diagram comparing two phylogenetic trees based on molecular changes: one tree shows evolutionary relationships among four species using myoglobin changes, and the other compares humans, rhesus monkeys, and horses using cytochrome c changes, with arrows and numbers indicating the amount of molecular change between branches.

At a Glance

phylogeny summary

phylogeny

biology

Written by

John L. Gittleman

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Britannica Editors

Last updated

Oct. 10, 2026 •History

Top Questions

What is phylogeny in biology?
In biology, phylogeny is the study of the evolutionary history of species or groups, especially regarding lines of descent and the relationships between broad groups of organisms.

Phylogenies show that the tree of life results from a historical process of evolution and that degrees of resemblance correspond to degrees of relationship from common ancestors. Scientists use paleontology, comparative anatomy, embryology, and molecular genetics to develop phylogenies.

Evolutionary trees are models that reconstruct the evolutionary history of taxa, such as species, genera, families, or orders. These trees show branching relationships that reflect ancestry and the changes that have occurred along each lineage.
2 Britannica Sources
1. phylogeny
2. evolution: Distance methods
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
Why do scientists study phylogeny?
Scientists study phylogeny to understand the evolutionary history of species and their relationships. Taxonomy, the science of classifying organisms, relies on phylogeny to reflect the natural relationships among living things.

Phylogenetic analyses have practical applications in various fields, including tracing infectious disease origins, identifying evolutionary distinctiveness in endangered species, and determining parentage in captive breeding programs. Biologists use evidence from paleontology, comparative anatomy, embryology, and molecular genetics to develop phylogenies. By studying similarities and differences in molecular structures like DNA, they can measure how species have diverged from common ancestors.
1 Britannica Source
1. phylogeny
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How are organisms grouped in a phylogenetic tree?
Phylogenetic trees, also known as evolutionary trees, illustrate the evolutionary relationships among a group of organisms that share a common ancestor. The ancestor is represented as the tree's trunk, while its descendants appear at the branch tips.

The distance between groups on the tree indicates the degree of relationship, with closely related groups located on nearby branches. These trees use cladogenesis and anagenesis to show the relative relationships of ancestry and the changes that have occurred along each lineage.

Taxonomy, which is the science of classifying organisms, is based on phylogeny. Organisms are grouped by apparent similarity, with the data gathered from paleontology, comparative anatomy, comparative embryology, and molecular genetics.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What information do scientists use to build phylogenies?
Scientists construct phylogenies, or evolutionary trees, using data from various fields. These trees illustrate the relationships and lines of descent among species or groups, based on the proposition that different species originate from common ancestors.

The most useful evidence for building phylogenies comes from:
* Paleontology, especially the fossil record, which helps to determine the phylogeny of groups containing hard body parts and to date divergence times of species.
* Comparative anatomy and embryology, which analyze similarities and differences between species, distinguishing between homologies (similarities inherited from a common ancestor) and analogies (similarities arising from similar habits).
* Molecular genetics, which measures the degree to which species have diverged by counting differences in the sequence of units that make up protein and DNA molecules.
* Geographic distribution of flora and fauna.
5 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
How does phylogeny help us understand evolution?
Phylogeny, the study of the evolutionary history of species, helps us understand evolution by showing lines of descent and relationships among organisms.

Evolutionary trees, which are models that reconstruct the evolutionary history of species, use cladogenesis and anagenesis to show these relationships. Cladogenesis demonstrates ancestry, while anagenesis indicates changes along lineages.

By studying homologies, or similarities inherited from a common ancestor, and using data from paleontology, comparative anatomy, embryology, and molecular genetics, we can build phylogenies that show the history of life and the degrees of relationship between groups. These phylogenies have practical applications in medicine, conservation, and even legal contexts. For example, phylogenetic methods can trace the source of infections.
3 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.
What is the difference between a phylogenetic tree and a family tree?
A phylogenetic tree is a diagram that shows the evolutionary connections among a group of organisms derived from a common ancestor. It is a hypothesis based on evolutionary change and ancestry, useful in studies with any related groups.

A family tree represents the genealogy and line of ancestors from whom a person is descended.

The branching relationships in phylogenetic trees reflect ancestry, while family trees represent a line of descent.
4 Britannica Sources
Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

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.

Fundamental to phylogeny is the proposition, universally accepted in the scientific community, that plants or animals of different species descended from common ancestors. The evidence for such relationships, however, is nearly always incomplete, for the vast majority of species that have ever lived are extinct, and relatively few of their remains have been preserved in the fossil record. Most phylogenies therefore are hypotheses and are based on indirect evidence. Different phylogenies often emerge using the same evidence. Nevertheless, there is universal agreement that the tree of life is the result of organic descent from earlier ancestors and that true phylogenies are discoverable, at least in principle.