go to the 
Tree of Life home page

Quality Assurance

Status of Tree of Life Pages

The Tree of Life is a work in progress, and ToL pages vary in their completeness, profundity, and review status. ToL content development is supervised by professional biologists and science educators of the ToL editorial staff, and ToL materials are divided into a number of broad categories, which are subject to different levels of scrutiny.

Scientific Content

ToL leaf pages, branch pages, and other articles, are classified according to one of five page status levels, and the status of each page is indicated in the top right corner of the content box.

page status is 
indicated in the top right corner of a page

Page Status Levels:

temporary page
Only leaf or branch pages can be published in temporary status. The main purpose of temporary ToL pages is to designate the position of associated groups in the hierarchy of life and to provide navigation routes connecting more complete ToL pages.
Temporary pages usually contain only references, internet links, and pictures, and, in the case of branch pages, a tree diagram or list of subgroups. Trees shown on temporary pages are based on the scientific literature. They have been selected by ToL editors, who are professional biologists, but not necessarily experts in any given group. In order to emphasize the fact that the a given phylogenetic hypothesis has not yet been reviewed by a specialist author, trees on temporary pages are printed in a lighter color.
under construction
ToL pages in under construction status are authored by specialists, but they have not yet been reviewed by other biologists. The under construction status allows ToL scientific contributors to gradually develop the content of a page while making work in progress available to the public. The amount of content on ToL pages under construction thus varies greatly, ranging from only a couple of text sections to pages that are fully fleshed out but still awaiting review.
complete check
A ToL page is elevated to complete status when it has been reviewed and approved by a ToL editor. ToL editors are professional biologists with Ph. D. degrees; however, they are not necessarily experts for every group they review. In order to be eligible for complete status, a ToL page has to fulfill certain content requirements, which vary according to page category. For example, a complete ToL branch page generally has to have at least an Introduction, Characteristics section, and Discussion of Phylogenetic Relationships.
tol-reviewed check check
A complete ToL page can be marked tol-reviewed, if its content has been reviewed by both ToL editors and coordinators. In some ways, tol-review is equivalent to peer-review, since tol-reviewed pages have undergone scrutiny by an author's professional colleagues who are experts in the group at hand. However, authors generally know who their ToL coordinators are, so the tol-review process is not anonymous. We therefore feel the need to discriminate between ToL internal peer-review and the more formal peer-review process involving external, anonymous reviewers.
peer-reviewed check check check
In addition to reviews by ToL editors and coordinators, peer-reviewed pages have been evaluated by external, anonymous, reviewers. For more details about the peer-review process, see the Peer Review page.

ToL scientific contributors also have the option to publish smaller contributions in the form of ToL notes. These brief accounts, keys, lists, and collections are not subject to the standard ToL review process. Their publication is, however, supervised by ToL editors who may consult with area specialists if necessary.



ToL treehouses are marked with a treehouse icon in the upper right corner of the content box. Treehouses may be authored by students of all ages, teachers, or other science enthusiasts. Treehouse contributions are checked for general accuracy and quality by teachers and ToL editors, however, treehouses are not usually reviewed by expert biologists.

We are planning to soon implement a special, open review system for treehouses, which will allow ToL contributors and visitors to provide feedback about treehouse content. This initiative will help treehouse contributors to improve the accuracy of their contributions, and it will encourage discussions among ToL users about their areas of interest.

About the Tree of Life

About ToL

ToL News

Goals of the ToL


Structure of the ToL

ToL Home Picture



Citing the ToL