Kingdom Animalia: Part One

(Note: the following post was penned while looking at this book, although I tried my hardest not to copy anything verbatim. I’m not even pretending I have all of this information memorized yet. Yay for my lab instructor and Sapphire’s former professor!)

Good evening, ladies and gentlemen. It’s the post you’ve all been waiting for. That’s right, it’s the dreaded taxonomy post! Do you love Latin words, vague animals and parasites? Then you’ve come to the right place! If you don’t, you’re a semi-normal person, and you probably aren’t liking Bio II a lot if you’re taking it.

I’m just going to cut right to the chase. I’ll give you the taxonomy as my lab manual outlines it, because, honestly, this stuff is always subject to change (and I really don’t get why we have to learn it in the first place).


Domain Eukarya

Kingdom Animalia

Here are some characteristics of this kingdom that we should know.

All members of this kingdom:

  • Are eukaryotic
  • Are heterotrophic
  • Are multicellular
  • Most commonly reproduce by sexual reproduction
  • Store carbohydrates as glycogen
  • Have no cell walls

Subkingdom Parazoa

Phylum Porifera

Common Name: Sponges

Sponges are hermaphroditic filter feeders that are porous and sessile (non-motile). These have no true tissues, although they have two types of specialized cells, choanocytes (“collar cells”) and amoebocytes. Choanocytes are flagellated, motile cells that are responsible for moving water through the sponge, trapping food particles, and performing digestion. The products of digestion are passed from these to the amoebocytes, which distribute food to different parts of the sponge by movement through the mesohyl. Amoebocytes can also get rid of waste products and store food. These also act as “sponge stem cells.”

Symmetry: Asymmetry.

Body Plan: Sac.

Important Features: Chondrocytes, amoebocytes, lack of tissues.

Class Calcarea

Sponges having calcium carbonate spicules.

Class Hexactinellida (“Glass Sponges”)

Sponges having silica spicules.

Class Demospongiae

Sponges having spongin spicules.

Subkingdom Eumetazoa

Phylum Cnidaria

Cnidarians are types of animals that show true tissues and the presence of nerves. These employ extracellular (“outside of cell”) digestion. Many members of this phylum alternate between polyp (sessile) and medusa (motile) stages. This phylum is named for the presence of cnidocytes, cells that contain a barb-like structure that can be used to sting. (This “stinger” is called a nematocyst.)

Symmetry: Radial.

Important Features: Nerve net, gastrovascular cavity.

Class Hydrozoa

Typical Organism: Obelia

Also known for the genus of organisms known as Hydra.

These exist primarily as polyps, with the medusa stage used for sexual reproduction. Obelia is colonial, while Hydra, which exists only as a polyp, is solitary. My text also thinks it important to mention that their larvae are called planula.

Class Scyphozoa

Common Name: True Jellyfish

The medusa is the dominant life form in these organisms.

Class Cubozoa

Common Name: Box Jellies

Sea turtles can eat these. This class includes Chironex fleckeri, which my text says is one of the deadliest organisms. That’s fun!

Class Anthozoa

Common Name: Corals and Anemones

These only exist in the polyp stage. The skeletons of corals form coral reefs.

Phylum Ctenophora

Common Name: Comb Jellies

These are named for the comblike structures of cilia used for swimming. (My text says these are the largest animals to use cilia for locomotion.) Some of these can be bioluminescent, and these have “sticky” cells instead of stinging cells.

Symmetry: Radial.

Important Features: Cilia “comb.”

Phylum Platyhelminthes

Common Name: Flatworms

This is a phylum of triploblastic acoelomates that are dosal-ventrally flattened. These have extra- and intercellular digestion, branched gastrovascular cavities, nerve cords with ganglia, and protonephridia (“before kidneys,” or rudimentary structures that perform functions similar to kidneys). Perhaps the most well-known of these are parasitic, but some are free-living.

Symmetry: Bilateral.

Body Plan: Tube-in-tube.

Important Features: Protonephridia with flame cells, branched gastrovascular cavities, nerve cords with ganglia, mesoderm.

Class Turbellaria

Known For: Planeria

These are mostly free-living and are capable of primitive learning. They also have eyespots. Planaria are well known for their regenerative abilities.

Class Trematoda

Common Name: Flukes

These are all parasites. (Yaaaayy…)

Class Cestoda

Common Name: Tapeworms

These have a head region called a scolex and packets of reproductive structures called proglottids. Can have multiple hosts.

Phylum Rotifera

Common Name: Rotifers

These are called “water bearers.” These are multicellular organisms that resemble protists. They have distinct organs, a grinding organ called a mastax and a constant number of cells. These can be found in freshwater, marine and terrestrial habitats. Rotifers are pseudocoelomates.

Symmetry: Bilateral.

Body Plan: Tube-in-tube.

Important Features: Mastax, distinct organs, cell-constancy, triploblasty, pseudocoelom.

Phylum Nematoda

Common Name: Roundworms

These are free-living or parasitic pseudocoelomates that can be found in many habitats. (My lab instructor, upon introducing these, said, “… I can’t think of any of these that you really want to have.”) These have longitudinal muscles, organs, and a hydrostatic skeleton. Included here is Trichinella, the causative agent of trichinosis. (Cook your pork, people!)

Symmetry: Bilateral.

Body Plan: Tube-in-tube.

Important Features: Longitudinal muscles, organs, hydrostatic skeleton, triploblasty, pseudocoelom.

Phylum Nemertea

Common Name: Ribbon Worms

These are pseudocoelomates with one-way digestive tracts and a simple circulatory system. There is a debate surrounding this fact, but these are currently accepted as being coelomates. These have muscles.

Symmetry: Bilateral.

Body Plan: Tube-in-tube.

Important Features: One-way digestive tract, circulatory system, muscles, coelom.

Okay, I don’t know if you’re exhausted, but I am. Now do you understand why I complain about taxonomy? Still, there are some interesting things about these organisms: cutting a Planaria head in half will result in it growing two heads, for example (Google it.) There are many more interesting things to be learned, but for now, I take a break. Next we delve into the taxonomy of the two biggest phyla in Kingdom Animalia: Phylum Mollusca and Phylum Anthropoda.

Questions? Comments? Put them below. Corrections? Yes, I know my taxonomy is probably out of date… [cries forever]


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