Classification Classification in biology, is the identification, naming, and grouping of organisms into a formal system. The vast numbers of living forms are named and arranged in an orderly manner so that biologists all over the world can be sure they know the exact organism that is being examined and discussed. Groups of organisms must be defined by the selection of important characteristics, or shared traits, that make the members of each group similar to one another and unlike members of other groups. Modern classification schemes also attempt to place groups into categories that will reflect an understanding of the evolutionary processes underlying the similarities and differences among organisms. Such categories form a kind of pyramid, or hierarchy, in which the different levels should represent the different degrees of evolutionary relationship.
The hierarchy extends upward from several million species, each made up of individual organisms that are closely related, to a few kingdoms, each containing large assemblages of organisms, many of which are only distantly related. Carolus Linnaeus is probably the single most dominant figure in systematic classification. Born in 1707, he had a mind that was orderly to the extreme. People sent him plants from all over the world, and he would devise a way to relate them. At the age of thirty-two he was the author of fourteen botanical works. His two most famous were Genera Plantarum, developing an artificial sexual system, and Species Plantarum, a famous work where he named and classified every plant known to him, and for the first time gave each plant a binomial.
This binomial system was a vast improvement over some of the old descriptive names for plants used formerly. Before Linnaeus, Catnip was known as: “Nepeta floribus interrupte spicatis pedunculatis” which is a brief description of the plant. Linnaeus named it Nepeta cataria–cataria meaning, “pertaining to cats”. The binomial nomenclature is not only more precise and standardized; it also relates plants together, thus adding much interest and information in the name. For instance, Solanum relates the potato, the tomato and the Nightshade.
Binomial Classification Early on in naming species taxonomists realized that there would have to be a universal system of nomenclature. A system that was not affected by language barriers, and would also classify the millions of species throughout the world. Binomial classification in its simplest form is a way of naming a species by means of two names both in Latin. Latin was originally used because it was the language of the founders of the classification system, like Carolus Linnaeus, but it continues to be used presently because it is a “dead language”. This means that it is no longer changing or evolving, so it stays the same and can be used universally, without confusion.
Carolus Linnaeus (see Appendix A, Image 1) first introduced binomial classification, which is why he is known as the father of the modern day classification system. In Binomial classification the first name, which begins with a capital letter is known as the Genus it is always capitalized. The genus is a group of species more closely related to one another than any other group of species. The genus is more inclusive than the species because it often contains many species. The second part of the binomial represents the species itself and is always printed with all letters in lower case. A species is a group of individuals that are alike in many different ways. Individuals are in the same species if they are: 1. Are able to mate with those similar to themselves.
2. Produce young that are themselves able to reproduce. As an example, in the cat family, the genus Panthera is coupled with the species leo to form Panthera leo, the Lion. Likewise, Panthera is coupled with tigris, to form Panthera tigris the Tiger. In simplified terns both the Lion(see Appendix A, image 2) and Tiger share common traits and a common genus – Panthera, whilst clearly remaining separate species. To allow further subdivision, the prefixes sub- and super- may be added to any category.
In addition, special intermediate categories-such as branch (between kingdom and phylum), cohort (between class and order), and tribe (between family and genus)-may be used in complex classifications. Closely related species are a genus, closely related genera (plural form of genus) are grouped together in a family. Closely related families are grouped into an order, and so on, into more inclusive categories, or levels in the classification hierarchy. Taxonomic Hierarchy Approximately one and a half million species have been classified and there are estimates that over five million species remain to be discovered. For biologists to order this mass of information, a scientific system called taxonomy was introduced. The basic idea is to group species with similar characteristics together into families, and to group the families together into broader groupings. To this end, the taxonomic categories where devised, and they create the taxonomic hierarchy.
The hierarchy goes (with an example): *Categories Example Kingdom Animalia Phylum (Plural = Phyla) Cordata *In plants, this category is often called a division* Class Mammalia Order Carnivora Family Canidae Genus Canis Species Lupus (the Wolf) Every species is in only one genus. Similarly, every genus is in only one family, and so forth up the hierarchy. The most inclusive category for classifying groups of similar organisms is the Kingdom. It is argued exactly how many Kingdoms there are though. Up until recently, only two kingdoms were generally used, the plant and animal kingdoms. Now however there are 5 established kingdoms and one controversial unofficial kingdom.
The 5 kingdoms: 1. Kingdom Animalia (The Animal Kingdom) ex: Multi-cellular motile organisms, which feed heterotrophically (Humans) 2. Kingdom Plantae (The Plant Kingdom) ex: Multi-cellular organisms, which feed by photosynthesis (Tulips) 3. Kingdom Protista (The Protist Kingdom) ex: Protozoa and single-celled algae 4. Kingdom Fungi (The Fungus Kingdom) ex: Yeast 5.
Kingdom Monera (The Monera Kingdom) ex: Bacteria and blue-green algae Parallel to these Kingdoms, but not included, are the Viruses. These are acellular entities with many of the properties of other life forms, but are genetically and structurally too dissimilar to the species categorized above to fit into that scheme of taxonomy. Although this system is complex and intricate at times, its universality makes it a necessity. With out the system presently in use the world would be years and years behind in their task to name all of the living organisms on earth. This system is great but it is always possible that some new finding could cause the system to evolve to become more inclusive. This system is by no means set in stone, and Linnaeus would probably be astounded to see the way that it has evolved since his original system.
Appendix A Carolus Linnaeus (Image 1) Panthera leo (Image 2) Bibliography Berkely University. www.ucmp.berkeley.edu/history/linnaeus.html/ Galbraith, Don. Understanding Biology. John Wiley and Sons. Toronto. 1989, Microsoft.
Encarta Encyclopedia 97. Microsoft Corporation. 1997.