Guest Author - Lisa Shea






The Four Kingdoms of Life


Life is extremely hard to categorize. Just what is a platypus? How about a Venus Fly Catcher? Scientists struggle with how to group live into various categories.

Biologists are constantly learning more about life and the creatures which inhabit this Earth, from the hot springs of Yellowstone National Park to the deepest depths of the oceans and the most frigid extremes of the poles. Each time they find a new creature, they expand our knowledge of animal life even further.

Scientists currently divide living life on earth up into four Kingdoms: Viruses, Archaea, Bacteria, and Eukaryotes. Probably all life that you can see and identify in your normal day to day existence is part of the fourth group. Eukaryotes are living things which have a nucleus in its cells, and similar cellular biology. The Eukaryotes are the animals, plants, fungus and other smaller creatures in our world. Each of these sub-groups is called a Phyla, and the phyla which contains all animals is the Metazoan Phyla.

In essence, creatures in the Metazoa phyla are those which come from eggs. It doesn't matter if this egg then forms the baby within the mother's body, or whether the mother pushes the egg out for it to hatch later on. With only few exceptions, the egg is the defining role for membership in this group.

There are 36 types of Metazoa - or classifications. These are the different types of animals you might find. For example, there are:

Chordata: perhaps the best known classification, this contains all animals with a spinal cord. This includes humans, cats, dogs, birds, frogs, fish, snakes, and reptiles.

Arthropoda: creatures with pairs of legs and a hard shell. This includes insects, scorpions, centipedes and so on.

Mollusca: soft-bodied creatures. These include snails, octopus, squid, mussels.

Cnidaria: creatures containing nematocysts, or stinging cells. These include jellyfish, sea anemones, and corals.

Learn more about the classifications that apply to your favorite animals, and what makes each animal unique!