The Wonderful World of Kingdom Animalia

Recall the characteristics that make an animal and animal...

Kingdom Animalia: An Overview

Let's look at our old pal, the (incomplete) phylogenetic tree of Animalia:

Note the emergence of each new character, and how it separates the monophyletic taxa.

Subkingdom Parazoa: The Sponges

Subkingdom Eumetazoa - All Other Animal Phyla
In the Eumetazoans...

  • Endoderm, ectoderm and mesoderm are the EMBRYONIC tissue layers. These develop into the complex tissues of the adult animal, which may include:

  • animals can be classified by the anatomy of their internal body cavity (located between the ectoderm and endoderm). From primitive to derived, the three possible animal body plans are:

    Let's look...

  • If a true coelom is present, the animal is further classified (by the characteristics of its embryonic development) into one of TWO MAJOR LINEAGES:

    In something said to be worth 1000 words...


  • Some animal phyla exhibit an important anatomical innovation: SEGMENTATION (also known as "metamerism", with each segment called a "metamere" or "somite"). In each segment, muscles, organs and other anatomical structures are repeated in a serial fashion.

    As evolution proceeded, some animals that had segmented ancestors secondarilyi lost their segmentation. Can you see any part of your body that's a remnant of your segmented ancestral heritage?


  • Bilaterally symmetrical animals have an advantageous anatomical feature: CEPHALIZATION. This is the presence of a "head end" at the front of the body, where the sense organs are concentrated.

    Where did Animals come from? Animals are believed to share a most recent common ancestor with the primitive protists known as CHOANOFLAGELLATES.

    Sponges actually have "collar cells" that are extremely similar to these choanoflagellates, and since they are the first type of cell to develop in sponges, there is strong evidence that other types of animal cells may be been derived from choanoflagellate cells.

    The earliest animal fossils appear during the late PreCambrian - early Cambrian (about 545 mya), and a rapid diversification lasting about 40 million years followed.

  • Most of these early fossils are Cnidarians (The phylum containing jellyfish, sea anemones and corals)
  • shell-less molluscs also present
  • other related groups, such as "worms" (which is sort of a catch-all term)
  • Almost all the major animal Body Plans show up in the fossil record by the Cambrian, about 545-525 mya, a result of the so-called "Cambrian explosion" of animal diversity.

    There are 32 animal phyla (sometimes more, depending on which systematist you talk to...), and we'll be visiting representatives of only a handful of these phyla.

    Animals within each phylum exhibit a series of distinctive characters that set them apart from other taxa, and the overall body form seen in a given taxon is sometimes called the BAUPLAN of that group.

    The literal translation of the German bauplan is "a structural plan or design." But when the word is applied to animal groups...