The Five Kingdoms and Classifying Organisms Study Guide (page 2)

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Updated on Sep 20, 2011

The Protist Kingdom

This Kingdom includes single-celled organisms that contain a nucleus as part of their structure. They are a relatively simple cell, but still contain many structures and perform many functions. This Kingdom includes organisms such as paramecium, euglena, amoeba, and slime molds. They often move around using cilia or flagellums.

The Moneran Kingdom

This Kingdom contains bacteria. All these organisms are single celled and do not contain a nucleus. They have only one chromosome for carrying genetic information, although sometimes they also transmit genetic information using small structures called plasmids. They also use flagella to move, like the protists, but their flagella has a different and simpler structure than the protists. They usually reproduce asexually. The bacteria E. coli (Escherichia coli) is a member of this Kingdom.

The Five Kingdoms and Classifying Organisms

Levels of Classification

A grouping as large as a Kingdom is not very specific and contains organisms defined by broad characteristics. Other levels of classification become gradually more specific until we define an actual specific organism. To classify organisms, we generally start out by grouping them into the appropriate Kingdom. Within each Kingdom, we further subdivide organisms into other groupings. As an example, let's take the wolf:

Kingdom: Animal

Phylum: Chordates (This means the wolf had a notochord that developed into its backbone.)
Class: Mammals (This means the wolf has hair, bears live young, and nurses them with mammary glands.)
Order: Carnivores (This means the wolf is a meat eater.)
Family: Canids (This means the wolf has nonretractable claws, a long muzzle, and separate toes.)
Genus: Canis (This means the wolf is a member of the dog family.)
Species: lupus (This refers to a particular type of wolf known as the European wolf.)


The previous categories form the most common scheme for classifying organisms, although other groupings and other categories are often used. The reason for developing a classifying system is so that we have consistency in how we refer to an organism. If we didn't have this system, then the European wolf described previously would be called wolf in English, lobo in Spanish, and loup in French. This leads to confusion and a loss of scientific accuracy.

Binomial Nomenclature

The system illustrated here is based on a system developed by Carlos Linneaus. It is called binomial nomenclature because in this system, any organism can be positively identified by two Latin words. The other words used previously illustrate where the named organism fits into the whole scheme, but it is only the last two, the Genus and species words, that specifically name an organism. The Genus name is always capitalized and written in italics, whereas the species name is written lowercase but also in italics. Thus, the European wolf is Canis lupus, Canis familiaris is the common dog, Felis tigrina is a tiger, Felis domesticus is a common cat, and humans are Homo sapiens.

How to Remember the Classification Scheme

Here is an easy way to remember the terms used in this classification scheme:

Kings Play Cards On Friday, Generally Speaking.

If you take the first letter of each word in the sentence and apply it to the proper term in the classification scheme, you will get the following:

Kingdom, Phylum, Class, Order, Family, Genus, Species

In Short

Biologists classify organisms based on shared characteristics among groups. The largest level of groupings is the Kingdoms, which consist of Animal, Plant, Fungi, Protist, and Moneran. The Kingdoms are further subdivided into Phylum, Class, Order, Family, Genus, and species. The Genus and species designations form a two-name system, called binomial nomenclature, that specifically identifies a particular organism (for example, humans are designated Homo sapiens).

Practice problems of this concept can be found at: The Five Kingdoms and Classifying Organisms Practice Questions

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