Nomenclature in Biology, Lecture notes of Biology

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FACULTY OF AGRICULTURAL SCIENCES AND ALLIED INDUSTRIES

INTRODUCTORY BIOLOGY UGR-

LECTURE- 03

NOMENCLATURE

 Nomenclature is giving distinct scientific names to various structures including living organisms for their identification.  The names are of two types - vernacular (common name) and scientific names.  The vernacular names are based on some peculiarity of the organisms, e.g., Kandali (a plant having spines).  Scientific names are distinct and specific, they have particular spellings which are not changed.

TYPES OF NOMENCLATURE

Three types of nomenclature are polynomial, binomial and trinomial. POLYNOMIAL SYSTEM According to this system, name of any plant consists of many words. For e.g., Caryophyllum saxatilis folis gramineus umbellatus corymbia which means Caryophyllum growing on rocks, having grass like leaves and umbellate corymb flowers. BINOMIAL SYSTEM  Carolus Linnaeus used this nomenclature system for the first time and proposed scientific name of all the plants and animals. He is the founder of binomial system.  Linnaeus proposed scientific name of plants in his book "Species plantarum".  In binomial nomenclature, each scientific name has 2 components - generic name (genus) and specific name (species). E.g., Solanum tuberosum (potato), Mangifera indica (mango)  The name indicates relationship of a species with others present in the same genus. TRINOMIAL SYSTEM  This system was proposed by Huxley and Stricklandt.  According to this system, name of any plant or species is composed of three names-  Subspecific name (Name of variety)  When members of any species have large variations then trinomial system is used. On the basis of Generic name  Specific name  dissimilarities, this species is classified into sub-species. Eg. Brassica oleracea var. botrytis (Cauliflower) Brassica oleracea var. capitata (Cabbage) Brassica oleracea var. caulorapa (Knol-Khol)

Binomial nomenclature and Classification

 Holotype : Herbarium sheet on which the first description of plant is based.  Lectotype : In case of holotype is lost, second herbarium sheet prepared from the original plant is called lectotype. Neotype : In case holotype and original plant is lost then herbarium sheet prepared from some other plant of same species is called neotype. Syntype : In case holotype and original plant is lost then many herbarium sheet prepared from many plants of same species is called syntype. Isotype : It is duplicate of holotype. In presence of holotype a second herbarium sheet prepared from the original plant is called isotype. Paratype : Additional herbarium sheet used in the first description of plant is called paratype. It is prepared from some other plant of same species having some variations.

Classification

TAXONOMIC CATEGORIES

There are 7 main taxonomic categories. They are obligate categories i.e., they are strictly used at the time of any plant classification. There are some extra categories, like sub division, sub order, sub family, tribe, sub tribe,. etc. They are not regularly used. They are used only when they are needed.  The sequence of arrangement of taxonomic categories in a descending order during the classification of an organisms is called taxonomic hierarchy.  Kingdom is the highest and species is the lowest category in this hierarchy.  Plant groups or animal groups included in categories are called taxon.

 Suffix for taxa (Taxon) Division – phyta Sub division – phytina Class – opsida, phyceae, ae Order – ales Sub-order – ineae Family – aceae Sub family – oideae Tribe – eae Sub tribe – inae Notes: There is no suffix for Genus, Species and Kingdom. SPECIES Species is the smallest taxonomic category. It is the basic unit of classification. John Ray proposed the term and concept of species (1942). BIOLOGICAL CONCEPT OF SPECIES  Mayr proposed the biological concept of species.  According to Mayr "all the members that can interbreed among themselves and can produce fertile offsprings are the members of same species"  But this definition of Mayr was incomplete because this definition is applicable to sexually reproducing living beings. There are many organisms that have only asexual mode of reproduction. E.g., Bacteria, Mycoplasma.  The main character in determination of any species is interbreeding. But this character is not used in taxonomy. In taxonomy, the determination of species is based on other characters. E.g., mainly morphological characters. STATIC CONCEPT OF SPECIES  The static concept of species was proposed by Linnaeus.  According to Linnaeus "species is unchangeable" i.e. there is no change in the character of species. The species of present day are same as they were in past and they will remains same in future.

 Families are characterized on the basis of both vegetative and reproductive features of plant species.  Three different genera Solanum, Petunia and Datura are placed in the family Solanaceae. Among animals for example, genus Panthera, comprising lion, tiger, leopard is put along with genus, Felis (cats) in the family Felidae. ORDER  Order being a higher category, is the assemblage of families which exhibit a few similar characters. The similar characters are less in number as compared to different genera included in a family.  Plant families like Convolvulaceae, solanaceae are included in the order polemoniales mainly based on the floral characters.  The animal order, Carnivora, includes families like Felidae and Cancidae. CLASS  A class is a subdivision within a phylum made of one or more related orders.  Order Primata comprising monkey, gorilla and gibbon is placed in class Mammalia along with order Carnivora that includes animals like tiger, cat and dog. Class Mammalia has other orders also. PHYLUM Classes comprising animals like fishes, amphibians, reptiles, birds along with mammals constitute the next higher category called phylum. All these based on the common features like presence of notochord and dorsal hollow neural system, are included in phylum Chordata. In case of plants, classes with a few similar characters are assigned to a higher category called Division. KINGDOM All animals belonging to various phyla are assigned to the highest category called Kingdom Animalia. The Kingdom Plantae, on the other hand, is distinct, and comprises all plants from various divisions. Table : Organisms with their Taxonomic Categories