Classification of Living Things : aka "taxonomy"

There are lots and lots and lots and lots and lots of different types of organisms out there. Taxonomy attempts to organize all of these organisms into increasingly smaller & smaller groups until you are left with a group of all the same type of organism (namely, a species).

Today's classification is based mostly on similarities in structure and evolutionary relationships.

Organisms first get classified into one of five KINGDOMS. Each kingdom has certain defining characteristics. The kingdoms, which are a large & varied group of organisms, then get divided up into smaller subgroups (called phyla), which in tern get subdivided, and so on ...
The 5 kingdoms & their characteristics is a pretty good chunk of info so I've placed it on a separate page. To get to it click here. You could finish working with this page first, or check out the kingdoms & come back, the order doesn't really matter. The bad news is that eventually you're responsible for understanding ALL of this ....

(it's OK, take it a little at a time).

A kingdom then, is the largest group. Within a kingdom you have organisms that share certain characteristics (see the table if you forgot). At the same time, organisms in the same kingdom can be very different from one another. For example humans, frogs, eagles, salmon, hydra, earthworms, grasshoppers, and clams are all animals, and yet they are all quite different from eachother.

So we take the wide variety of organisms in a kingdom and subdivide them into other groups. The subgroups (from largest to smallest) are :

KINGDOM, PHYLUM, CLASS, ORDER, FAMILY, GENUS, SPECIES

These groups can be remembered using this sentence :

King Phyl Came Over For Good Spaghetti.

(The first letter of each word in the sentence is the first letter of each
classification group & they're listed in the correct order.)

In order to illustrate these groups, let's look at the classification of a few animals.

GROUP NAME ORGANISM

HUMAN CHIMPANZEE HOUSE CAT LION HOUSEFLY

KINGDOM Animalia Animalia Animalia Animalia Animalia

PHYLUM Chordate Chordate Chordate Chordate Arthropoda

CLASS Mammal Mammal Mammal Mammal Insect

ORDER Primates Primates Carnivora Carnivora Diptera

FAMILY Hominidae Pongidae Felidae Felidae Muscidae

GENUS Homo Pan Felis Felis Musca

SPECIES sapiens troglodytes domestica leo domestica

Scientific Name Homo sapiens Pan troglodytes Felis domestica Felis leo Musca domestica

NOTES :
1) all 5 of the organisms are classified as animals because they are multicellular, have eukaryotic cells, are heterotrophic, & capable of moving (motile)

2) the human, chimp, cat & lion have enough similar characteritics that they are put in the same phylum & in the same class too

3) the defining characteritics of each subgroup (as you go down a column) become more & more specific. the shared characteritics of the members of a kingdom are broad, the shared characteritics of members of a species are very specific.

4) in order for two organisms to be in the same "small" group, they must also be in all the same "big" groups above it. for example : if two organisms are in the same ORDER, they must be in the same class, phylum & kingdom. even though the cat & the housefly have the same species group name (domestica), they CAN'T BE the same species because they are not in the same genus, family, order, etc. In fact, that last group name (species) doesn't really mean anything all by itself. The correct, full species name is the organism's two-part scientific name (see #5).

5) REALLY IMPORTANT : every organism is given a scientific name which consists of its genus name (1st) & species name (2nd). This is called binomial nomenclature (bi-nomial = 2-names) & is attributed to Carolus Linnaeus (remember him ?). so a human's scientific name is Homo sapiens, a lion's is Felis leo, a house cat's is Felis domesticas, etc. In a SCIENTIFIC NAME, the genus name should be capitalized & the species name lowercase, & both should be either italicized or underlined.

6) the closer the evolutionary relationship between two organisms, the more groups they have in common. so of the 5 in this chart, the cat & lion are most closely related (they are classified together in the first 6 groups). A human is more related to a chimp (4 groups in common) than to a lion (only 3 common groups).

Linnaeus' Seven Taxa of classification:

1. Kingdom : The most general of the seven taxa. At present there are 6 kingdoms.

2. Phylum : Phyla ( plural). Each kingdom is subdivided into small more specific groups called phyla. These organisms contain all the kingdom characteristics plus some other specific ones that set each phylum apart form the others in the kingdom.

3. Class : Each phylum is subdivided into smaller groups called classes. Classes contain phylum characteristics plus specific characteristics that separate one class from another in the phylum.

4. Order : Each class is subdivided into smaller groups called orders. Orders contain class characteristics plus specific characteristics that separate one order from another in the class.

5. Family : Each order is subdivided into smaller groups called families. Families contain order characteristics plus specific characteristics that separate one family from another in the order.

6. Genus : Each family is subdivided into smaller groups called genera. The genus contains phylum characteristics plus specific characteristics that separate one genus from another in the family.

7. Species : Each genus is subdivided into smaller groups called species. Genera contain species characteristics plus specific characteristics that separate one species from another in the genus. The species is the most specific taxon in the system.

Scientific Name of an Organism:

A scientific name of an organism contains two parts. The first name is the genus name and the second name is the species name. There are some simple rules in writing a scientific name:

a). The first letter of the Genus name must be capitalized.

b). The first letter of the species name is not capitalized.

c). Both names must be underlined or italicized.

Kingdom Classification Table

Kingdom	Archaebacteria	Eubacteria	Protista	Fungi	Plant	Animal
Cell Type	Prokaryotic	Prokaryotic	Eukaryotic	Eukaryotic	Eukaryotic	Eukaryotic
Cell Parts	Cell wall not containing peptidoglycan, Single chromosome	Cell wall containing peptidoglycan ,Single chromosome	Some contain a cell wall, All contain a nucleus and membrane bound organelles.	Cell wall containing chitin, Nucleus, and membrane bound organelles	Cell wall containing cellulose, Nucleus and membrane bound organelles	No cell wall, Nucleus, and membrane bound organelles
Body type	Unicellular	Unicellular	Some multicellular, most unicellular.	Multicellular	Multicellular	Multicellular
Nutrition	Heterotrophic and autotrophic	Heterotrophic and autotrophic	Heterotrophic and autotrophic	Heterotrophic	Autotrophic	Heterotrophic
Examples	Methanogens	E. coli	Ameba, Paramecium, Euglena.	Mushrooms, yeast,	Ferns, grasses, mosses	Man, dogs, worms