Diversity in the Living World & the Need for Classification
Look around and you see an astonishing variety of living organisms - trees, insects, birds, fungi, microbes. So far, biologists have identified and described about 1.7-1.8 million species, and many more remain undiscovered. Each distinct type is referred to as a kind of organism.
If we simply describe every organism separately, the information becomes unmanageable. To study this enormous diversity, we must classify organisms into groups and sub-groups - and to talk about them unambiguously across the world, we must give each one a standardised name.
Why common names are not enough
The same organism has different local/common names in different regions and languages. One plant may be called by a dozen names in a single country. A common name cannot be understood worldwide and may refer to different organisms in different places. Scientists therefore agreed on standardised scientific names so that one organism has one name, understood everywhere.
Nomenclature and the Binomial System
Nomenclature is the process of standardised naming of organisms such that the same organism is known by the same name all over the world. Nomenclature is only possible after an organism is correctly identified (knowing what it actually is).
Scientists have agreed on international codes for naming:
- Plants → ICBN (International Code for Botanical Nomenclature; now the International Code of Nomenclature for algae, fungi and plants).
- Animals → ICZN (International Code of Zoological Nomenclature).
Binomial nomenclature
The system in use was given by Carolus Linnaeus. In binomial nomenclature, each scientific name has two components:
- the Genus (generic name), and
- the specific epithet (species name).
Example: the mango is Mangifera indica - Mangifera is the genus, indica is the specific epithet.
Universal rules of nomenclature
- Biological (scientific) names are generally in Latin and written in italics (they are Latinised regardless of their origin).
- When printed, the name is in italics; when handwritten, the genus and species are underlined separately (to show their Latin origin).
- The first word is the genus, and it begins with a capital (upper-case) letter.
- The second word is the specific epithet, and it begins with a small (lower-case) letter.
- The name of the author appears after the specific epithet, i.e., at the end, written in an abbreviated form - e.g., Mangifera indica Linn. (Linn. shows Linnaeus first described this species).
A few standard scientific names
| Common name | Scientific name |
|---|---|
| Human | Homo sapiens |
| Housefly | Musca domestica |
| Wheat | Triticum aestivum |
| Mango | Mangifera indica |
| Lion | Panthera leo |
| Potato | Solanum tuberosum |