How Animals are Related to One Another

First of all you should realize that many specialists can't even agree on whether certain organisms are plants or animals, or something else -- and there is debate about whether viruses are alive or not! Therefore, here we can't give any absolute answers. However, what we have here is good enough if you're doing a term paper or just trying to understand the basics.

Now, the Animal Kingdom, if we exclude one-celled organisms, is divided into about 20 to 35 phyla (singular phylum), depending on who your expert is. An amazing fact to keep in mind is this: If someone should ask you to name all the animals you could, the vast majority of your listed animals would probably belong to just one of those 20 to 35 or so phyla. That one super-important phylum is this one:

the phylum Chordata

In the Chordata we find "animals with backbones" --all birds, frogs, toads,snakes, lizards, turtles, rodents, cows, horses, pigs, dogs, cats, apes, humans, and much more. All these animals belong to the phylum Chordata. Click here for more info on the Chordata.

If all you want is some help organizing your thoughts and maybe information for homework, and if you keep in mind that other interpretations exist and that the outline shown below is somewhat outdated, then what's below should serve you well. It's from a college textbook published way back in 1996.

The ANIMAL KINGDOM
Adapted from Biology, Fourth Edition, by
Peter Raven & George Johnson,
Wm. C. Brown Publishers, 1996

SUBKINGDOM Parazoa (lack symmetry, no tissues or organs
- PHYLUM Porifera (Sponges)
SUBKINGDOM Eumetazoa (symmetrical, with tissues, organs)
- PHYLUM Cnidaria (Corals, Jellyfish, Hydras)
- PHYLUM Ctenophora (Comb Jellies & Sea Walnuts
- PHYLUM Platyhelminthes (Flatworms)
- PHYLUM Rhynchocoela (Ribbon Worms)
- PHYLUM Nematoda (Nematodes, Eelworms, Roundworms)
- PHYLUM Rotifera (Rotifers)
- PHYLUM Loricifera (tiny animals living in sand)
- PHYLUM Bryozoa (Bryozoans)
- PHYLUM Brachiopoda (Brachiopods)
- PHYLUM Phoronida (Phoronid Worms)
- PHYLUM Mollusca (Molluscs)
  - CLASS Polyplacophora (Chitons)
  - CLASS Gastropoda (Snails, Slugs)
  - CLASS Bivalvia (Bivalves -- clams, oysters, etc.)
  - CLASS Cephalopoda (Octopuses, squids, etc.)
- PHYLUM Annelida (Annelids, or segmented worms)
- PHYLUM Arthropoda (Arthropods)
  - CLASS Arachnida (Arachnids -- spiders, ticks, etc.)
  - CLASS Merostomata (Horseshoe Crabs)
  - CLASS Pycnogonida (Sea Spiders)
  - CLASS Crustaceae (Crustaceans -- crabs, etc.)
  - CLASS Diplopoda (Millipedes)
  - CLASS Chilopoda (Centipedes)
  - CLASS Insecta (Insects)
- PHYLUM Pogonophora (Giant Tube Worms)
- PHYLUM Onychophora (strange wormlike animals)
- PHYLUM Echinodermata (Echinoderms -- Sea Stars, etc.)
- PHYLUM Chaetognatha (Arrow Worms)
- PHYLUMM Hemichordata (Acorn Worms)
- PHYLUM Chordata
  - SUBPHYLUM Urochordata (Tunicates)
  - SUBPHYLUM Cephalochorata (Lancelets)
  - SUBPHYLUM Vertebrata
    - CLASS Agnatha (Agnathans)
    - CLASS Chondrichthyes (Sharks, Skates, Rays)
    - CLASS Osteichthyes (Bony Fishes)
    - CLASS Amphibia (Amphibians)
    - CLASS Reptilia (Reptiles)
    - CLASS Aves (Birds)
    - CLASS Mammalia (Mamals)

One way to sensitize yourself to the mind-boggling diversity represented above is to Google the phyla names -- use the Google Search Engine to look for pages describing the kinds of organisms you don't know anything about. For instance, I wonder if you can visualize these animals:

Rotifers

Bryozoans

Phoronid Worms

Chitons

Giant Tube Worms

Onychophora

Arrow Worms

Tunicates

Lancelets

Just pick any good-sounding but mysterious animal name from anyplace on this page, type it into the box below, then hit the Google Search button, and see what comes up:

To see another outline of the Animal Kingdom, with all the phyla listed on one page, with certain subphyla, classes and orders listed below the most important phyla, visit the Biosis "Guide to the Animal Kingdom for Students and Educators."