Biological Nomenclature

In previous articles, I have talked about how scientists name living organisms. In this article, I will discuss how organisms are organized into groups according to how they are related.

Aristotle, the Greek philosopher who lived from 384 to 322 BCE, is often called the "father of biological classification." He recognized that organisms ranged from the relatively simple to much more complex. He believed that all living organisms could be arranged on a scale of increasing complexity, which is referred to as the scala naturae or "scale of nature." Aristotle believed that each form along this ladder of life had an alloted rung, and that species did not change with time. This view of life prevailed for close to 2,000 years.

Aristotle's scala naturae was a very simple way of dividing organisms into groups. He looked at their outward appearance and grouped them accordingly. He used criteria such as: two-footed versus four-footed, hairy versus feathers, with or without an outer shell, etc. However, Aristotle did delineate the major groups of animals, like the mammals, fish, birds, whales, and insects.

In the 1700's, the Swedish physician and scientist Carl Linnaeus developed a different filing system for living organisms which he called the Systema Naturae or natural system. His system was similar to Aristotle's in that he also grouped organisms according to their outward appearance. His major improvement to Aristotle's classification system was that he developed groups that were further divided into smaller subgroups. With some modifications, this is the system that we still use today; Linnaeus is often called the "father of taxonomy."

Linnaeus's technique was to first divide organisms into separate Kingdoms. Linnaeus only recognized the Kingdoms Animalia (animals), Plantae (plants), and Protista (microscopic organisms). Today, we recognize these three Kingdoms, plus the Monera (bacteria) and Fungi (mushrooms and other fungi).

The Kingdoms are then further divided into Phyla (the plural of Phylum), which are divided into Classes. Each Class is then divided into Orders, which are divided into Families. The Families are then divided into Genera (the plural of Genus), which are then divided into species. A good way to remember the order the divisions come in is to think, "Kings play chess on Fridays, generally speaking." Sometimes the divisions can be further divided into Sub-groups and Super-groups, such as Subphyla, Subspecies and Superfamilies.

Linnaeus and Aristotle both based their systems of organization only on outward appearance, but today biologists use the classifcation system to group organisms together according to how they are related. Often, plants or micro-organisms might look very similar but not be closely related at all. And sometimes animals or plants that look very different may be very closely related. DNA analysis is a very helpful tool for determining these relationships.

Go To Page: 1 2

Articles in this Topic    Discussions in this Topic