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Tree of Life

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The Tree of Life (TOL) is a vast, collaborative project on the World Wide Web that offers information about the lines of evolutionary development of plants and animal species. TOL was created in response to the need by scientists for a more up-to-date and easier-to-use method for locating information about phylogeny and organismal diversity. The Tree's creators, Professors David and Wayne Maddison of the University of Arizona, decided to place the Tree on a Web site, and chose Macintosh technology, including Power Macintosh computers, for developing and maintaining it.

Key Benefits:

  • The Tree of Life Web site allows biologists to disseminate their findings in realtime.
  • Collaboration among biologists is enhanced.
  • The Web site functions as a forum for biologists to display and air differing opinions.
  • The Web site's ease of administration allows its creators to spend time improving the site.

The Tree of Life (TOL) is a vast, multi-authored project on the World Wide Web offering information about the lines of evolutionary development of plants and animal species.This work in progress is a resource for researchers, teachers and students of phylogeny and is meant to illustrate the diversity and unity of all life on earth. The Tree of Life was created by David and Wayne Maddison, systematic biologists at the University of Arizona at Tucson.

Problem: For scientists building an evolutionary tree, it can be quite tedious to conduct research on subjects such as gene sequences by wading through hundreds of journals. Also, by the time information is in print, it usually is out of date. The field needed a more up-to-date and easier-to-use method for locating information about phylogeny and organismal diversity. Also, as findings proliferated, there was a need for more rapid dissemination of information and a way for biologists to readily learn about and work off of each other's findings.

Solution: Realizing that the amount of information and data on organisms is too huge and unwieldy to be adequately described in print, the Maddison brothers decided to take advantage of possibilities offered by the World Wide Web. "With the arrival of the Internet, we saw an opportunity to present views about the phylogeny of life in a comprehensive and up-to-date creation by allowing biologists around the world to contribute to it." explains David Maddison. The Maddison brothers used a variety of Apple technologies to create their unique Web site: phylogeny.arizona.edu/tree/phylogeny.html.

The goal of the Tree of Life is the inclusion of genetic and evolutionary relationships, photographs, and life histories of every type of living organism. The Tree currently has over 1200 pages, with each containing information on a particular group of organisms. For example, the page on Terrrestrial Vertebrates has pictures of representative terrestrial vertebrates, an image of the evolutionary tree of the organisms, and text about the group and its characteristics. This page is linked to one on amniotes (a subgroup which includes reptiles, birds, and mammals).

The Tree of Life Web site is an extension of the Maddisons' earlier work to create an evolutionary Tree. Using Apple Macintosh technology, the brothers developed a graphical branching program called MacClade ("Mac" for the Macintosh and "Clade" from an ancient term for branch). This analysis program helps organize and visually display phylogenetic findings. MacClade creates trees that trace the evolution of specific traits in organisms and performs calculations relevant to phylogenetic biology. Professor Maddison who admits to "being a graphical person," was impressed with "the real world metaphors of the Mac" when the Macintosh was first introduced in 1984. For the Maddisons, the strong graphical interface of the Macintosh encouraged and allowed them to develop MacClade in 1985, first on a Macintosh 512, then on a Macintosh Plus, a Macintosh IIci, a Macintosh Centris 650, and ultimately on the Power Macintosh 7600.

The Maddisons created a searchable index for the Tree of Life using a specialized AppleScript Web crawler they customized. David Maddison initially considered creating his own search engine with Perl, but found that "I did not have the time to learn such a complex language." Because of the ease of use of HyperTalk and HyperCard, Maddison found that it was "trivial" to build an engine and created the index using a HyperCard stack. The index sits on a Power Macintosh 6100 and runs with the help of Webstar server software. Currently about 260 biologists are signed up as contributors. The project is hierarchically coordinated, with authors inviting other experts to contribute pages on their specialty. To create the Web site, MacClade was modified to allow scientist-authors to create Tree of Life pages in their own specialties (whether it's frogs, beetles, molluscs, etc.) in an easy -to-make HTML page. Once an author enters a page that is stored in a MacClade file, he or she either sends the Maddisons the MacClade file, or uses MacClade to generate the HTML page and store it on their own Web server. When the Maddisons receive files, they generate the HTML pages using MacClade on two Power Macintosh 7600 computers and place the pages on a UNIX machine. This server now stores 40 percent of all branches. In all, TOL branches are spread over 15 computers on two continents.

In addition to the Tree of Life's primary audience-evolutionary biologists- another audience has emerged: children and their teachers. The Maddisons have begun developing Tree Houses, mini-websites with information about life history and behavior oforganisms for these novice Tree climbers.

Benefits: The TOL has allowed biologists who study evolutionary origins and the development of plants or animals to disseminate their findings in realtime. For example, a researcher in California can now receive instant feedback from a colleague in Europe moments after her/his page is posted. By going online, evolutionary biologists have a means of collaborating much more effectively.

Because of the unlimited space offered by the Web site, the Tree of Life can function as a forum for biologists to air their differing opinions. When arguments arise about which organisms go on which branch, the Tree allows for alternative views to be expressed. It is not unusual to find a root page displaying two competing trees, accompanied by the authors' defense of each version.

The Web site's ease of administration allows its creators to spend their time enhancing the site. The Maddisons are working on producing more tools like searchable indices. Other plans include creating an automated glossary, attaching databases to branches, and allowing specific leaves to be analyzed with special Web crawlers.

As the virtual metaphor it is, the Tree of Life is growing very rapidly, with more branches being added every few days. How large will the the Tree get? "How many million of organisms are there? We can't even say we've scratched the surface," according to David Maddison.

See Also