About Tree of Life Pages
This page gives a brief introduction to the different categories of ToL Pages, it explains how the pages are connected to one another, and it gives a preview of the future design and functionality of ToL Pages:
- Branches, Leaves, and Accessory Pages
- Connections Between ToL Pages
- The Future of Tree of Life Pages
Branches, Leaves, and Accessory Pages
The Tree of Life ("ToL") project consists of various explanatory pages (such as the home page, and this page), as well as three classes of pages authored by contributors: the branch pages and leaf pages, which together form the main body of the Tree, and accessory pages, which are additional pages that are attached to the Tree's branches and leaves.
Branch pages are all of the ToL pages that have (or will eventually have) ToL pages descended from them. These pages all show a phylogeny or classification of subgroups. The vast majority of pages in the ToL are branch pages, and include those for amniotes, Ascomycota (sac fungi), the Bembidion (Bracteon), and jumping spiders. Branch pages that comprise the path from the root of the Tree up into prominent groups (e.g. into mammals, flowering plants, insects) are called trunk pages.
Leaf pages are the ToL pages presenting information about individual species. They are the terminal pages on the Tree, attached to apical branches. An example leaf page is that for Bembidion levettei.
Accessory pages are pages that are attached to either branch or leaf pages of the ToL, but are not themselves part of the Tree structure. They do not provide the primary information about the groups of organisms (this is provided on the branch or leaf pages), but instead contain additional information, perhaps including more detailed descriptions of structure, comprehensive discussions of phylogenetic relationships, more pictures, identification keys, etc. While links to many additional pages can be made from a ToL branch or leaf, only those linked pages that are specially designated and included in the EXTRAS menu of ToL branch or leaf pages are considered ToL accessory pages. See Michel Laurin's terrestrial vertebrates page for an example of a branch page that has several accessory pages attached to it (these include a page on Breathing in Terrestrial Vertebrates and Phylogeny of Terrestrial Vertebrates).
Treehouses are a special kind of accessory page that is designed for children or the young at heart. Our goal is to have treehouses sprinkled throughout the Tree, as authors' time and resources permit. Currently, there is one treehouse available on the ToL, the Beetle Treehouse.
Connections Between ToL Pages
The branch and leaf pages of the ToL are linked to each other hierarchically, in the form of the evolutionary tree that connects the different groups of organisms. All ToL pages (except the root page of the entire Tree) have an immediate containing group. The ToL page of this containing group has a tree or taxon list that provides links to the subgroups immediately descending from this particular containing group.
In the example given in the previous section, the family is the immediate containing group for the genera, and each genus is the immediate containing group for several species. Of course, the family is also a containing group for all the species descending from its descendent genera, but at a deeper level in ToL page universe. All branch pages on the ToL will eventually have descendent pages. Leaf pages are, however, terminal on the Tree, i.e., they do not have any descendents and are therefore not containing groups for other groups.
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The Future of Tree of Life Pages
The new ToL Database system brings with it a new way of looking at ToL pages. In the old ToL, branches and leaves were represented by static HTML files, each composed by an author or a group of authors, and linked together according to the authors' preferred phylogenetic hypotheses. In the future, the presentation of ToL content will become much more flexible, with different page components (text sections, images, phylogenetic hypotheses, references, etc.) treated as self-contained modules that can be displayed more or less independently of one another. While there will always be a default version of the Tree of Life web site, featuring ToL pages similar to those that are currently presented, the new system will allow us to serve alternative, customized versions of ToL pages based on the needs and preferences of a diverse user community. For further information on this topic see the page about Customizing Your View of the Tree of Life.
The ToL will also become capable of serving alternative tree topologies; i. e., visitors will have the option to browse ToL pages based on a number of different phylogenetic hypotheses. Alternative tree topologies may be derived from different methods of inference (including supertree algorithms) or from different kinds of data (e. g., molecular versus morphological versus combined). In order to realize these new capabilities, the current architecture of the ToL project is based on a model of hierarchically interconnected nodes (representing groups of organisms) to which a variety of objects (e. g., taxon names, modular text objects, images and other media, etc.) can be attached. For more background information about these issues, refer to our pages about the Future Design of the Tree of Life Project.