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The classification system used today was created in the 18th century by Swedish biologist Carl von Linne (Linnaeus). In this system organisms are grouped on the basis of common features into categories of increasing similarity. To find out more about Linnaeus try www.ucmp.berkeley.edu/history/linnaeus.html
The broadest categories in common use are called kingdoms with each kingdom being further divided in the following way: |
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Organisms in a kingdom are divided into phyla.
Organisms in a phylum are divided into classes.
Organisms in a class are divided into orders.
Organisms in a order are divided into families.
Organisms in a family are divided into genera.
Organisms in a genus are divided into species.
Five Kingdoms of Life
Although early classification systems recognised only two kingdoms, the plant and animal kingdoms, one more recent system in common use recognise five kingdoms:
- Monera (Greek moneres - single)
Microscopic, single-celled organisms with simple cells - bacteria and blue-green algae.
- Protista (Protoctista) (Greek protos - first)
Mainly microscopic, single-celled organisms but with complex cells. Marine examples include diatoms, dinoflagellates and seaweeds (algae).
- Plantae (Latin planta - plant)
Includes multi-celled organisms such as mosses, ferns, conifers and flowering plants but not seaweeds (algae).
Once part of the plant kingdom, organisms such as mushrooms and toadstools are now placed in their own kingdom.
- Animalia (Latin anima - breath, soul)
The animal kingdom includes multi-cellular animals with backbones and those without.
To find out more about classification try www.ucmp.berkeley.edu/alllife/threedomains.html
The Concept of a Species
In Linnaeus's classification system, a species is the narrowest (most specific) grouping of organisms. However, a group of organisms within one species are not identical. They are similar enough for us to think of them as one ‘kind' or species. A more formal definition of a species states:
A species is a group of individuals that are more or less alike, and that are able to interbreed and produce fertile offspring under natural conditions.
Naming species
With almost 1.8 million species known to science and many more being discovered and described all the time, it is no wonder that biologists use a system of classification to organise and deal with earth's extraordinary biological diversity.
In Linnaeus's classification system, each species has two Latin names - its genus and species names. The first letter of the genus name is capitalised and the whole name is either printed in italics or underlined.
As far as the use of Latin and common names in school programs is concerned, we would like to encourage the use of both. The use of Latin names can become a worthwhile exercise if the names are broken into their component parts and ‘translated' into English. To this end, a list of Latin roots commonly used in Etymology in Marine Biology.
Next: Etymology in Marine Biology
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