Phylum (Phyla)

Animal Taxonomy Pyramid Diagram

Biology Definition:  Phylum is a taxonomic rank below Kingdom and above Class in biological classification, especially of animals. In plants, the corresponding rank is Division. Example: Phylum Chordata includes Class Mammalia (mammals), Class Aves (birds), Class Ascidiacea (sea squirts), etc. These animals have notochords at some point in their life cycle. Etymology: Greek “phylon”, from “phyle”, meaning “tribe”.

After animal kingdom, animal species usually fall into one of seven different phylum or phyla:

  1. Porifera – Marine animals more commonly known as sponges and found in every ocean on earth.
  2. Cnidaria – Mostly marine animals that include over 11,000 species. Examples include coral, jellyfish, and anemones
  3. Platyhelminthes – Typically parasitic flatworms. Lacking in any respiratory or circulatory system, oxygen passes through their bodies instead in a process known as diffusion. Examples include tapeworms and flukes.
  4. Annelida – More complex than Platyhelminthes, these are segmented and symmetrical worms containing a nervous system, respiratory system, and sense organs. Examples include the common earthworm and leeches.
  5. Mollusca – The second largest phylum by species count, and the largest marine phylum. Invertebrates with soft unsegmented bodies. It is estimated almost a quarter of marine life falls in this category. Examples include clams, mussels, and snails
  6. Arthropoda – Invertebrate animals with an exoskeleton and segmented bodies. Contains insects, crustaceans, and arachnids. This is the largest phylum by species count. Examples include scorpions, butterflies, and shrimp
  7. Chordata – Vertebrates. Animals that develop a notochord, a cartilaginous skeletal rod that supports the body in the embryo and can often become a spine. Most animals we are familiar with, including dogs, horses, birds, and humans fall into this category.


  • Austin, S. (2023, January 30). Classification of Animals: The Complete Guide. A-Z-Animals. Retrieved September 25, 2023, from Link
  • Encyclopædia Britannica, Inc. (2023). Animal Taxonomy [Photograph]. Britannica. Link
  • Phylum. (2023, May 29). In BiologyOnline. Link

Additional Sources of Information

  • NatureFiji-MareqetiViti is Fiji’s only domestic NGO working solely for the conservation and sustainable management of Fiji’s unique natural heritage – Link


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