Concept of Taxonomy
Taxonomy is the area of the biological sciences devoted to the identification, naming and classification living things according to apparent common characteristics. In terms of real life application, taxonomy, on the one hand is related to the entire world of life on “earth”. Taxonomists are responsible for identifying, naming, classifying all these species. Systematics is a discipline of biology that explicitly examines the natural variation and relationships of organisms. It also deals with relationships of different groups of organisms, as most systematicists strive to construct natural classification systems reflecting evolutionary relationships.
How it works.
Taxonomy in context.
The term taxonomy is actually just one of several related words describing various aspects of classification itself. Classification simply refers to the act of systematically arranging ideas or objects into categories according to specific criteria.
Phylogeny and nomenclature.
The two other terms that one is likely to run across in the study of taxonomy are phylogeny and nomenclature.
Phylogeny is the evolutionary history of organisms, particularly as that history refers to the relationships between life forms and the broad lines of decent that unite them. Some scientists called phylogeny the “tree of life”, meaning that its represents the underlying hierarchical structure by which life-forms evolved and are related to one another while nomenclature is the act or process of naming as a system of names, particularly one used in a specific science or discipline.
Homologous and Analogous Features.
Before going on to discuss methods of classification, it is important to note just characteristics of an organism’s morphological aspects (life structure) are important to scientists working in the field of taxonomy. In theorizing relationships between species, taxonomists are not interested in what are known as analogous features, those characteristics that are superficially similar but not as a result of any common evolutionary origin. Rather, they are interested in homologous features, or features that have a common evolutionary origin even though they may differ in terms of morphological form. An example of shared evolutionary characteristic is the pentadyctal limb, a five-digit appendage common to mammals and found in modified form among birds. This is a homologous feature, indicating a common ancestor that likewise it had limbs with five digits at the end.
Definition of species.
Before taxonomists can identify, name and classify organisms, they need to agree on a definition of the concepts of species. Most biologists basically concept, but argue that it really an idealized concept. Thus, in practice, nearly all biologists think of specifics as morphologically distinct groups of organisms.
Nomenclature (from the latin term nomenclatura, indicating the procedure of assigning names) is the naming of organisms for many centuries naturalists used latinized names to refer to different species of plants and animals in their scientific writings following the lead of swidish naturalists Car von Linne (17007-1778) Carolus Linnaeus began using a binomial (two words) latinized name for all species. The first word is the genus name and the second word is the specific epithet also called the trivial name. occasionally, additional groups are added to this classification scheme such as sub phylum, subclass, or suborder e.g human beings (Homo sapiens) are placed into the following categories.
Kingdom – Animalia
Phylum – Chordata
Subphylum – vertebrata
Class – mammalia
Order – primate
Family – Hominoidea
Genus – Homo
Species – Sapiens
Taxonomic classification is the grouping together of different organisms into different taxa (taxonomic categories) such as family, genus and species of classification as they relate to systems and innovations introduced by the Greek philosophy Aristotle (384-322 B.C), the Swedish botanist Carolus Linnaeus (1707-1778), and English naturalist Charles Darwin (1809-1882), The three most important men in the history of taxonomy part of what is known as the obligatory taxonomy. These ranks are kingdom, phylum, class, order, family, genus, & species.
Identification is the recognition of the identity or essential character of an organisms. Taxonomists are often present organized written descriptions of characteristics of similar species so that other biologists can identify unknown organisms. These organized are descriptions are referred to as taxonomic keys.
Methods of classification
The three most commonly used methods are phonetics, cladistics and evolutionary taxonomy. Some taxonomists use a combination of several of these different methods.
Phonetics also known as numerical taxonomy which classifies organisms based on overall form and structure or genetic similarity. First, many different characteristics of a group of organisms are measured. These measurements are then used to calculate similarity coefficients between all pairs of organisms and is between number ‘0’ and ‘1’ where 1 indicates absolute identity and 0 indicates absolute dissimilarity, it is used to develop a classification system.
Cladistics taxonomy: it classifies organism strictly based on branching points, focuses on shared relatively recent characteristics that are common to the species being studied also called phylogenetic taxonomy. It was first proposed inn 1950s by Willi Hennig, a german entomologist. It is currently the most widely used method of classification. It is important to note that a cladistics classification is not based on the amount of evolutionary change after the branching off of an evolutionary line.
Evolutionary taxonomy which classifies organisms based on a combination of branching and divergence also called traditional taxonomy. It is a mixture of phonetics and cladistics. The major limitations of evolutionary taxonomy is that it requires a highly arbitrary judgment about how much information about branching pattern to use.
Binomial system of nomenclature.
Linnaeus made another major contribution to organizing the natural world. He gave a two part scientific name to every living thing. The linnean system came to be called the binomial system of nomenclature and there are several strictly followed rules latin : genus and species to which an organism belogs – for its scientific name. binomial names are always underlined. The first letter of the genus is always underlined. The first letter of the genus is always capitalized, while the species is always written in lower case letters for instance, Homo sapiens is the scientific name for humans.
Kingdoms of organism.
In the past, biologists classified all organisms into the plant and animal kingdom. The five kingdom system based on proposals by ecologist Robert Whittaker in 1959 and 1969 is widely used as a framework.
Five kingdom system: according to the five kingdom system designated by L. Margulis and K.V Schwartz, all organisms are classified into one of five kingdoms:
- Monera (Single-celled prokaryotes e.g bacteria)
- Protista (single celled eukaryotes e.g algae, water molds)
- Fungi (multicellular eukaryotic organisms)
- Plantae (multicellular eukaryotic photosynthetic organisms)
- Animalia (multicellular, eukaryotic organisms)
Clearly, the five kingdom system does not segregate organisms according to their evolutionary ancestry. The monera and Protista are single celled organisms only distinguished by their intracellular organization. The Animalia, fungi and plantae are distinguished by their mode of nutrition. Plants are considered producers, fungi decomposers and animals considered consumers.
International Code of Botanical Nomenclature (ICBN)
In order to standardize terminology and promote effective communication among plant scientists, plants taxonomists have agreed to a set of formal guidelines to be used when naming plants known as the official references rules with which nomenclatural decisions about plants must be made. It serves as the basis for all naming of plant ranks from intraspecific taxa (variety subspecies) to species and to taxa of higher ranks (genus, family, order etc). there is also a separate code for the naming of cultivated plants, which has nomenclatural conventions very similar to that of the KBN.
At its founding, the ICBN agreed that plant nomenclature would officially begin with the work by Linnaeus, species plan-tarun, published in 1753. To avoid unnecessary duplication of names for the same species or to stabilize the way plant names are applied to the various taxonomic hierarchies.
- Analogous features: characteristics of organism that are superficially similar, but have different evolutionary organs.
- Homologous features: characteristics of organisms that have a common evolutionary history or lineage of an organism or group of related organisms.
- Taxon (plural taxa): taxonomic group such as species, genus or family.
- Taxonomic key: descriptions of the characteristics of species or other taxa organized in a manner to assist in identification of unknown organisms.
- Binomial nomenclature: a system of nomenclature in biological taxonomy whereby each type of plant or animal is given a two word name with the first name identifying the genus and the second species.
- Class: the third most general obligatory of the taxonomic classification ranks.
- Family: the third most specific of the seven obligatory ranks in taxonomy
- Systematics: the science of classifying and studying of organisms with regard to their natural relationships.
- Genus: the second most specific of the obligatory ranks in taxonomy.
- Classification – The Dinosaur FAQ (website). http://www.miketaylor.org.uk/dino/faq/index.html
- Why man, Kathryn. The animal kingdom: A guide to vertebrate classification and biodiversity. Austin, Tx: pain tree steck-vaughn, 1999.
- American society of plant taxonomist http://nowcsdi/tau.edu/flora/aspt/asptcarl.html
- Greuter, W. et al, eds. International code of botanical Nomenclature. Berlin: Regnum veg, 1988
- Gould, S.J. The pandas thumb New York, W.W. Norton, 1980
- Margulis, L. and K.V. Schwartz, five kingdoms New York: W.H freeman, 1988.