BioGalleries Animal Phyla
The Animal Phyla
By David Denning
Photographs by David Denning and Bruce Russell

There are about 30 different phyla of animals. How well do you know them? The images below show 25 different animal phyla. Move the cursor over a photo to see its phylum.

The Big Nine

The vast majority of all animal species (over 95%) belong to the phyla listed here, sometimes called the ‘Big Nine’. These groups are covered by our Biology Of series of video and DVD programs.

  • Phylum Nematoda
    (with coverage of other groups)
  • Phylum Mollusca
  • Phylum Annelida

Check these links for concise information about each group in our online program study guides.

How is life organized? ... How many phyla are there?

These and similar questions have fascinated nature-watchers for centuries. About 150 years ago, Charles Darwin revealed the basic principles for the development of species, and indeed for the organization of all life. Biologists then recognized that all organisms are related to one another through descent from common ancestors – ancestors that evolved at various times in the long (3-billion-plus) year history of life. They visualized a great 'tree of life' full of millions and even billions of branches (equating to species). Fossils in rocks such as the Burgess Shales showed that the animal portion of the tree of life is ancient – at least 500 million years old.

Looking at this Tree of Life, biologists realized that phyla are deep branches where at the very beginning of the branch ancestral organisms developed a fundamentally new and different body plan. They concluded that all the descendants of this ancestor, living and extinct, form a group that can be called a Phylum.

Even with this understanding, it has not been easy to group animals into a definitive pattern of phyla. Although most biologists now recognize about 30 animal phyla in total, there are still many questions such as: how the organisms in any one phylum evolved, how the phyla are related, and even whether some groups that have traditionally been recognized as distinct phyla should be combined together with other groups into another phylum.

In this gallery we will develop a series of short, illustrated essays addressing key questions about the animal phyla. The essays will be developed over time so bookmark this page and check back often. You can even contribute to these essays or to other questions if you like. Send your comments and ideas by e-mail to {tagcontactlinkid=1}.

{mosloadposition essays}
©2013 BioMEDIA ASSOCIATES, LLC  All Rights Reserved.
No other use of this material is allowed without written permission.
Powered By IRIS Education   v1.5.26.204.