The scientific classification of life, otherwise known as 'biological classification', is the method used by biologists to group organisms together by type.
Carl Linnaeus, a Swedish botanist, physician, zoologist and ecologist, is also known as the 'father of modern taxonomy.' Linnaeus grouped species together according to a system based on shared or similar physical characteristics. Born in 1707, Linnaeus graduated from Uppsala University and became a botany lecturer there in 1730. He then went abroad to study and research, and it was during this period (1735 - 1738) that he first published his 'Systema Naturae.'
In the 1740s Linnaeus returned to Sweden and made more research trips throughout the country to find and classify new plants and animals. This work continued through to the 1760s, and he published several more volumes relating to his classification work. The first edition of Systema Naturae was a twelve page work. By its 10th edition in 1758, it classified 4,400 species of animals and 7,700 species of plants.
What Linnaeus did was systematically categorize all known organisms. The different levels are called taxa. The different taxa are:
Kingdom is the broadest of the taxa. All animals are in Kingdom Animalia. All plants are in Kingdom Plantae.
Linnaeus attempted to name organisms in a way that would make sense to all scientists. For example, the group "Mammalia" were named for the mammary glands with which they nurse their young. Linnaeus' system recognized two 'Kingdoms' - Vegetabilia and Animalia. Today, most biologists utilize a six Kingdom system, as follows:
Animalia - All members of this Kingdom are multicellular, heterotrophic (they must ingest other organisms for sustenance), and are motile (able to move spontaneously and independently).
Plantae - Includes organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae.
Fungi - Includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.
Chromista - Includes all algae whose chloroplasts contain chlorophylls a and c, as well as various colorless forms that are closely related to them.
Protozoa - Generally refers to a unicellular heterotrophic organism, such as the amoeba and ciliates. The term algae is used for protozoans that photosynthesize.
Bacteria - A large group of single-celled microorganisms.
Domain, a level above Kingdom, has become popular in recent years. A three-domain system was first proposed in 1990, but has not yet been generally accepted amongst biologists.
A Memory Aid
The easiest way to remember the different levels of biological classification is to remember the phrase "King Philip Came Over For Good Soup." In this sentence, the first letter of each word stands for a different level, as follows:
King = Kingdom
Philip = Phylum
Came = Class
Over = Order
For = Family
Good = Genus
Soup = Species