Tree of Life

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Tree of life or Universal Tree of Life is a metaphor, model and research tool used to explore the evolution of life and describe the relationships between organisms, both living and extinct, as described in a famous passage in Charles Darwin’s On the Origin of Species (1859).

The affinities of all the beings of the same class have some-
times been represented by a great tree. I believe this simile
largely speaks the truth. — Charles Darwin

Tree diagrams originated in the medieval era to represent genealogical relationships. Phylogenetic tree diagrams in the evolutionary sense date back to at least the early 19th century. The term phylogeny for the evolutionary relationships of species through time was coined by Ernst Haeckel, who went further than Darwin in proposing phylogenic histories of life.

In contemporary usage, tree of life refers to the compilation of comprehensive phylogenetic databases rooted at the last universal common ancestor of life on Earth. The Open Tree of Life, first published 2015, is a project to compile such a database for free public access. — Wikipedia

Encyclopædia Britannica




Taxonomy is the science of defining and naming groups of biological organisms on the basis of shared characteristics. Organisms are grouped together into taxa (singular: taxon) and these groups are given a taxonomic rank; groups of a given rank can be aggregated to form a super-group of higher rank, thus creating a taxonomic hierarchy. The principal ranks in modern use are domain, kingdom, phylum (division is sometimes used in botany in place of phylum), class, order, family, genus and species. The Swedish botanist Carl Linnaeus is regarded as the father of taxonomy, as he developed a system known as Linnaean taxonomy for categorization of organisms and binomial nomenclature for naming organisms.

With the advent of such fields of study as phylogenetics, cladistics, and systematics, the Linnaean system has progressed to a system of modern biological classification based on the evolutionary relationships between organisms, both living and extinct. — Wikipedia

Encyclopædia Britannica

Why should we care about species? (Jody Hey, Nature Education)
A list of 26 species ‘Concepts (John S. Wilkins, Evolving Thoughts Science Blog)

Tree of Life (Wellcome Trust)

OneZoom Tree of Life EXplorer

Tree of Life Web Project (David Maddison, Katja-Sabine Schulz, and Wayne Maddison)
Tree of Life Web Project (Wikipedia)
Web Lift to Taxa (University of California Museum of Paleontology)




Evolutionary biology is the subfield of biology that studies the evolutionary processes that produced the diversity of life on Earth, starting from a single common ancestor. These processes include natural selection, common descent, and speciation.

The discipline emerged through what Julian Huxley called the modern synthesis (of the 1930s) of understanding from several previously unrelated fields of biological research, including genetics, ecology, systematics and paleontology. — Wikipedia

Computational phylogenetics is the application of computational algorithms, methods, and programs to phylogenetic analyses. The goal is to assemble a phylogenetic tree representing a hypothesis about the evolutionary ancestry of a set of genes, species, or other taxa. For example, these techniques have been used to explore the family tree of hominid species and the relationships between specific genes shared by many types of organisms. Traditional phylogenetics relies on morphological data obtained by measuring and quantifying the phenotypic properties of representative organisms, while the more recent field of molecular phylogenetics uses nucleotide sequences encoding genes or amino acid sequences encoding proteins as the basis for classification. Many forms of molecular phylogenetics are closely related to and make extensive use of sequence alignment in constructing and refining phylogenetic trees, which are used to classify the evolutionary relationships between homologous genes represented in the genomes of divergent species. — Wikipedia

The Open Tree of Life
Synthesis of phylogeny and taxonomy into a comprehensive tree of life (Hinchliff, Cody E., et al., Proceedings of the National Academy of Sciences)
Automated assembly of a reference taxonomy for phylogenetic data synthesis (J. Rees & K. Cranston, Biodiversity Data Journal)

Edward O. Wilson (Museum of Comparative Zoology, Harvard University)
E. O. Wilson (Biodiversity Foundation)
E. O. Wilson (Encyclopædia Britannica)
E. O. Wilson (Wikipedia)




Paleontology is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene Epoch (roughly 11,700 years before present). It includes the study of fossils to determine organisms’ evolution and interactions with each other and their environments (their paleoecology). Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier’s work on comparative anatomy, and developed rapidly in the 19th century.

Paleontology lies on the border between biology and geology, but differs from archaeology in that it excludes the study of anatomically modern humans. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics, and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life, almost all the way back to when Earth became capable of supporting life, about 3.8 billion years ago. As knowledge has increased, paleontology has developed specialized sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates.

Body fossils and trace fossils are the principal types of evidence about ancient life, and geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave body fossils. Estimating the dates of these remains is essential but difficult: sometimes adjacent rock layers allow radiometric dating, which provides absolute dates that are accurate to within 0.5%, but more often paleontologists have to rely on relative dating by solving the “jigsaw puzzles” of biostratigraphy. Classifying ancient organisms is also difficult, as many do not fit well into the Linnaean taxonomy that is commonly used for classifying living organisms, and paleontologists more often use cladistics to draw up evolutionary “family trees”. The final quarter of the 20th century saw the development of molecular phylogenetics, which investigates how closely organisms are related by measuring how similar the DNA is in their genomes. Molecular phylogenetics has also been used to estimate the dates when species diverged, but there is controversy about the reliability of the molecular clock on which such estimates depend. — Wikipedia

K-12 Educational Materials (University of California Museum of Paleontology)
Introduction to Paleontolgy (Professor Stuart Sutherland, The Great Courses)
Paleontological Societies and Clubs (Glen J. Kuban)
How to become a paleontologist (Environmental Science)

The Linnaean collection (The Natural History Museum, London)
Carl Linnaeus (University of California Museum of Paleontology)
Carl Linnaeus (Wikipedia)
Linnaean taxonomy (Wikipedia)

Darwin Library, Now Online, Reveals Mind of 19th-Century Naturalist (Jie Jenny Zou, Chronicle of Higher Education)
My dear old friend: Darwin the man revealed as 40-year correspondence published online (University of Cambridge)
Darwin Correspondence Project (Cambridge University)

Darwin Manuscripts Project (American Museum of Natural History)
Looking for Darwin (Lloyd Spencer Davis)
Darwin’s Finches and Natural Selection in the Galapagos (Earthwatch)
Charles Darwin in the Galapagos (Galapagos Islands)
Charles Darwin (Encyclopædia Britannica)
Charles Darwin (Wikipedia)

Racing Extinction (Official Site)
Racing Extinction (Wikipedia)
Ocean Preservation Society (Official Site)
Ocean Preservation Society (Wikipedia)


Note: These are 360° videos — press and hold to explore them!

Paleontology (American Museum of Natural History Museum, New York)
American Museum of Natural History (YouTube Channel)

Smithsonian National Museum of Natural History (Washington, DC)
Smithsonian National Museum of Natural History (YouTube Channel)
Smithsonian National Museum of Natural History (Wikipedia)

Harvard Museum of Natural History (Cambridge, MA)
Field Museum (Chicago, IL)

Museum’s Library

Rare Book Room (Field Museum in Chicago)
Biodiversity Heritage Library


WorldCat, Library of Congress, UPenn Online Books, Open Library





Crash Course Biology (YouTube Channel)

Crash Course Ecology (YouTube Channel)

OER Commons: Open Educational Resources


News, NPR Archives









Charles Darwin in the Galapagos (Galapagos Islands)


Visual Arts

Tree of Life (Pinterest)


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Here are links to pages about closely related subjects.

Knowledge Realm


Sphere Land, Ice, Water (Ocean), Air
Ecosystem Forest, Grassland, Desert, Arctic, Aquatic

Life Cell, Gene, Tree of Life
Plant Flower, Tree
Invertebrate Cuttlefish, Octopus, Ant, Bee, Butterfly, Spider, Lobster
Vertebrate Fish, Seahorse, Ray, Shark, Frog, Turtle, Tortoise, Dinosaur
Bird, Ostrich, Owl, Crow, Parrot
Mammal Bat, Rabbit, Giraffe, Camel, Horse, Elephant, Mammoth
Whale, Dolphin, Walrus, Seal, Polar Bear, Bear, Cat, Tiger, Lion, Dog, Wolf
Monkey, Chimpanzee, Human


1.   The resources on this page are are organized by a classification scheme developed exclusively for Cosma.