The Tree of Life shows how all living organisms have evolved since life began on Earth. In this image, pictures at top of the tree represent the diversity of creatures alive today. The base of the tree indicates the time when life on Earth first appeared. Numbers along the left side indicate the billions of years before the present. Although simplified, this Tree of Life image is based on data from thousands of researchers using the most up-to-date tools of molecular biology.
We are All Related
Monarch butterflies, monkeys and microbes are all related. LUCA, the last universal common ancestor of life, is indicated at the bottom of this image. Surprising discoveries suggest that this ancestor may actually be not a single organism, but rather a group of organisms that freely exchanged their DNA via horizontal gene transfer.
Cooperation and Gene Sharing Drives Evolution
This image shows the powerful role of cooperation in evolution. This occurs through symbiosis and gene transfer. The convergence of a bacterium (seen as red) with a eukaryote gave rise to mitochondria, the energy powerhouses of our cells. Another symbiosis of a green, photosynthesizing cell with a eukaryote gave rise to all the plants. Horizontal gene transfer, the swapping of DNA between distantly related organsims, is indicated by converging lines. This sharing of genes also drives evolution.
Tree Or Network
In the first millions of years of life on Earth, the tree of life is more like a network than a tree. Genes passed freely from one species to another. Today, Bacteria and Archaea continue to swap their genes. Gene swapping withing species of Eukarya during meiosis drives rapid evolution. Gene swapping between species is rare in the Eukarya.
Life Over Time
The numbers on the left indicate the billions of years ago that events occurred (approximately). At this scale, humans emerged only in the last few pixels of red in the animal line. Dinosaurs went extinct several more pixels back.
To help us understand the relationships of all living things, scientists classify organisms into groups. This image shows only one of several classification schemes. The six different colored branches correspond to the domains and kingdoms of living organisms. The blue Bacteria and yellow Archaea are "domains" of microbes that lack a nucleus. The plants, animals, fungi, and protists are all kingdoms in the domain of "Eukarya", those organisms with a defined nucleus.
DNA Is the Most Reliable Evidence
This tree is based on comparisons of DNA sequences from genes of thousands of diverse creatures. Humans, amoebas, strawberries and E. coli all share several hundred similar genes. (For comparison, humans have between 20,000 -25,000 genes.)
Pruning the Tree
Lines that end before the top of the tree depict branches in the tree of life that have been pruned by extinction. More species have gone extinct than exist today. The good news for us as humans, is that we are among the survivors! Furthermore, we are the first creatures to evolve that have the foresight that may well help us prevent calamities, such as the meteor strike that wiped out the dinosaurs.
Origin of Life is Speculative
The base of this tree has a question mark that indicates that the origin of life is still unknown.
All Models Are Wrong, Some Models Are Useful
This tree of life is vastly simplified for the sake of a presenting a clear overview. It provides a useful summary of the relationships of all creatures to one another and roughly when they appeared in time. This tree has several limitations. For example, it does not show the actual numbers of living creatures and it depicts only a limited number of instances of interspecies gene transfer. As more information becomes available, the branches of this tree will surely change. The origin of life is purely speculative. It may have occured once or several times. This tree also is a very rough approximation as to when various events occured. Despite these limitations, this tree does give viewers a snapshot of how life on Earth evolved.
A Rose by Any Other Name
The information presented on this tree comes from many different, fast-moving disciplines. Many of the names given on this tree have alternate names. For example, the Bacteria, Protists and Archaea are also known as Eubacteria, Protoctista, and Archaebacteria.
Horizonal Gene Transfer - The transfer of DNA from one species of organism to a different species. Horizontal gene transfer, (also known as lateral, or interspecies gene tranfer) is common among bacteria and Arcaheae and rare among eukaryotes.
© Cathy Russell, www.epicofevolution.com
Due to enthusiastic response, this image of the Tree of Life is now available as a poster and greeting card at Zazzle.com.
Classification and the Tree of Life - Creatures may be classified in many ways. Check out this interactive to see various ways to classify creatures.
Other Trees of Life:
Tree of Life Web Pages - The Tree of Life Web Project is a collection of information about biodiversity compiled collaboratively by hundreds of expert and amateur contributors.
Evogenao -Gorgeos Tree of Life portrayed from a human perspective. Leonard Eisenberg created this wonderful tree based on information from Richard Dawkins' book, The Ancestor's Tale.
Interactive Tree of Life - s an online tool for the display and manipulation of phylogenetic trees
Encyclopedia of Life - a global effort to document all 1.8 million named species of animals, plants, and other forms of life on Earth. For the first time in the history of the planet, scientists, students, and citizens will have multi-media access to all known living species, even those that have just been discovered.
Discover Life - Tree of Life - This interactive Tree of Life contains contains links to major groups of living things. Discover Life provides free on-line tools to identify species, share ways to teach and study nature's wonders, report findings, build maps, process images, and contribute to and learn from a growing encyclopedia of life that now has 1,197,759 species pages.
3-Domains - A huge breakthrough in understanding the tree of life arrived with the comparison of DNA sequences from diverse organims. In 1977, Carl Woese was the first to publish his observations that the Tree of Life had three domains, one of which was previously considered to be closely related to bacteria. To the left is the "Big Tree" created by Norm Pace as an elaboration of Woese's original work.
Tree of Life Poster - Beautiful Tree of Life poster featuring images of various creatures. The author, Neal Olander, allows you to download a 24"x48" poster in pdf format. Includes a timeline.
Diversity Of Life: The Illustrated Guide to the Five Kingdoms 1999. ISBN #0763708623.
by Lynn Margulis, Karlene Schwartz and Michael Dolan. This coloring book is packed with information about the vast variety of life on Earth.
Doolittle, W. Ford (February, 2000). "Uprooting the tree of life". Scientific American 282 (6): 90–95.
Woese, Carl, The universal ancestor, Proceedings of the National Academy of Sciences, Vol. 95, Issue 12, 6854-6859, June 9, 1998, http://www.pnas.org/cgi/content/full/95/12/6854
News of the Death of the Tree of Life Has Been Greatly Exaggerated - This concise, well-written report by Steven Schafersman, Ph.D. on behalf of Texas Citizens for Science shows how scientific disputes taken out of context have been used to discredit the science of evolution. 2009 February 7.