Classification is a general process related to categorization, the process in which ideas and objects are recognized, differentiated, and understood.
A classification system is an approach to accomplishing classification.
A taxon is a biological group of any rank. Taxonomy is, therefore, the study of grouping or classification. It provides evidences by use of which a system of classification is worked out.
Systematics is a wider term comprising identification of an individual organism, assigning a proper rank to the same and giving it a name. However, taxonomy and systematics are considered by many to denote the same thing and the terms are treated as synonymous
The aim of taxonomy, therefore, is:
(a) To classify the plant Kingdom and
(b) To identify and name a plant and fix its rank in a recognised system of classification. taken into consideration.
The latter is also known as “omega” taxonomy or “biosystematics” and concerns chromosome morphology, chromosome number, breeding behaviour and barriers.
Recent trend in taxonomy is to recognise character combination for taxonomical grouping. Here mathematical techniques are applied to assess similarity and disparity through diagrams and using mathematical coefficients. This is called “numerical” taxonomy.
To make use of the results of chemical analysis or tests of plant-parts and products in study of taxonomy is called Chemotaxonomy. This involves a This is done by using almost entirely the external morphological characters, i.e., gross morphology. Such taxonomy is called “classical” or “orthodox” or “alpha” taxonomy to distinguish it from “experimental” taxonomy where cytological or embryological evidences are also study of the starch grains and rap-hides, study of plant-products, e.g. alkaloids, resins, etc. and serological tests
Chemical characters, however, should not be regarded as more important than other characters. They are often affected by environmental factors such as temperature, mineral deficiencies, etc.
It is possible that chemical and morphological features may have followed different evolutionary pathways. Comparative chemistry and serology are aids to establishing consanguinity, not phylogeny proper, which involves the tracing of phyletic lines back into the past.
“Many different types of information can be and should be woven into classificatory scheme and there is no obvious advantage in attaching overriding importance to any one type.” Basic unit of classification is the species. Each species has a combination of characters peculiar to its own.
Therefore species is a group of plants having a combination of characters common to each individual in that group. Such characters are morphological, cytological, embryological, etc. Further the plants belonging to a particular species are capable of free interbreeding, and carry and express one or more gene pools.
A genus is a natural group of closely related species. When a species is more or less isolated the genus may often be monotypic, i.e., consisting of a single species only. Similarly a family is a natural group of closely related genera.
Closely related families are grouped into an order, orders into a- class and classes into a division, while the divisions are grouped under a kingdom. Intermediate subgroups are also recognised and Intra specific categories are also known.
Taxonomy is the science dealing with classification. In biology or in any other field, systematic classification is necessary to bring an order in the apparent chaos, so that the different types in a heterogeneous assemblage can be arranged into groups having common properties.
In biology, taxonomy aims at grouping organisms on the basis of mutual similarities into units called taxa (singular taxon). The taxonomic unit, taxon, may have different levels depending on the extent of similarities among the organisms included in it. Each level or rank has a different designation and these ranks form a hierarchical arrangement.
Objectives of Taxonomy:
Taxonomy aims at fulfilling three main objectives:
1. Firstly, taxonomy aims at classifying organisms into taxa on the basis of similarities in phenotypic (phenetic) characteristics i.e. the characteristics which are expressed in an organism and can be examined visually or can be tested by other means.
As each phenotypic characteristic is controlled by one or a group of genes, two individuals which possess similar phenotypic characteristic must have similar genes. Large number of similar phenotypic characteristic, therefore, reveals a genetic closeness between organisms.
Genetic closeness is also often linked with phylogenetic relatedness, because organisms having many common genes among them must have originated from a common stock during evolution. For instance, if two organisms, A and B, are phylogenetically closer than to another organism, C, it means that A and B have branched off from a common stock in more recent times than C which branched off earlier. Obviously, A and B will have more common genes between them than they will have with C.
2. The second objective of taxonomy is to assign each taxon a name. This naming of a taxon is known as nomenclature. Assigning a name to an organism is necessary for identifying it without confusion throughout the scientific world. Therefore, nomenclature needs to be made following certain internationally accepted rules. Scientific naming of bacteria is governed by the International code of nomenclature of bacteria (The Revised code of 1975). An updated edition of the Revised code has been published in 1992.
Like other organisms, bacterial names have two parts, — a genus name and a species name. Both names must be in Latinized form. This type of naming of biological organisms called, binomial nomenclature, was first introduced by Carl Linnaeus in 1753. The generic name is a Latinized noun starting with a capital letter and the specific epithet is generally a Latinized adjective qualifying the genus name.
The species name is written in small hand. As an international convention, the generic and specific names are italicized. To avoid confusion, a scientific name of an organism also requires the citation of the author’s name who first proposed the name. In assigning a name to a newly discovered bacterium, the author or authors must strictly observe the rules laid down by the International Code.
A new species is indicated by the abbreviation sp. nov. and a new genus by gen. nov. The authors describing a new bacterium are also required to deposit a culture of the organism in an authorized culture collection where it is maintained as the type culture of the particular organism for future reference. Each entry is provided with a separate index number by the collection authority.
Besides scientific names, bacteria are often known by their trivial or informal names. Some trivial names are often widely used. For example, Koch’s bacillus is the common name of Mycobacterium tuberculosis, pneumococci of Streptococcus pneumoniae, meningococci of Neisseria meningitidis etc.
3. The third objective of taxonomy is to serve as an instrument for identification of bacteria. A newly isolated organism can be assorted to its nearest allies or can be identified as a new hitherto unknown taxon. This makes taxonomy a dynamic branch of biology, because discovery of new organisms constantly demands changes in the existing classification.
Also, adoption of new techniques for classifying organisms often necessitates changes, sometimes thorough changes in the existing framework. For example, the developments in the molecular biological techniques, like DNA hybridization, have made a great impact on the taxonomy of bacteria. In fact, a new branch of taxonomy called molecular taxonomy has come into existence. The determination of homology of ribosomal RNA’s is another development which has revolutionized bacterial taxonomy.
Global biodiversity is being lost at an unprecedented rate as a result of human activities, and decisions must be taken now to combat this trend. But how do decision-makers decide where to establish protected areas if they don't know what is being protected? How can regulators identify and combat harmful invasive species if they cannot distinguish them from native species? How do developing countries ensure that they reap the benefits of the use of their biological diversity, if they don't know the biological diversity that is being used? Taxonomy provides basic understanding about the components of biodiversity which is necessary for effective decision-making about conservation and sustainable use.
Before the invention of microscope, and of course its super-cousin (SEM), the microscopic world was not visible to humans. Microscopes made it possible to study the vascular structures and their function in nutrient transport, as also cellular basis of growth. But minute and careful observation of plants in India dates back to a few thousand years. The ancient science of botany was quite developed in its understanding of the plant kingdom, as also in taxonomy. Below we give a glimpse of the various attempts in antiquity to classify plants according to their properties.
The beginning of relationship between humans and plants can be traced back to the prehistoric times. The Indus Valley people used to live in villages, cities and towns, wore clothes, cultivated crops including wheat, barley, millet, dates, vegetables, melon and other fruits and cotton; worshipped trees, glazed their pottery with the juice of plants and painted them with a large number of plant designs. They also knew the commercial value of plants and plant products. There are sufficient indications to show that Agriculture, Medicine, Horticulture, developed to a great extent during the Vedic Period. In the Vedic literature we find a large number of terms used in the description of plants and plant parts, both external features and internal structures; a definite attempt at classification of plants and evidence that use of manure and rotation of crops were practiced for the improvement of fertility of soil and nourishment of plants. Even Rgveda mentions that Vedic Indians had some knowledge about the food manufacture, the action of light on the process and storage of energy in the body of plants. In the post-Vedic Indian literature there is enough evidence to show that botany developed as an independent science on which was based the science of medicine (as embodied in the Charaka and Susruta Samhitas), Agriculture (as embodied in the Krsi-Parasara) and Arbori-Horticulture (as illustrated in the Upavana-vinoda as a branch of Botany). This science was known as the Vriksayurveda, also compiled by Parasara.
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