Systematics: History, Basics of Study and Types

In this article we will discuss about:- 1. Meaning of Systematics 2. History of Systematics 3. Basics of Study 4. New Systematics or Modern Taxonomy.

Meaning of Systematics:

Systematics is a branch of Biology that deals with cataloguing plants, animals and other organisms into categories that can be named, remembered, compared and studied. Study of only one organism of a group provides sufficient information about the remaining members of that group. Scientists connected with the study of systematics are called systematises or taxonomists.

The terms systematics, taxonomy and classification are often held as syn­onyms but technically they carry different meanings. Simpson, (1961) has defined system­atics as the branch of biology that deals with the diversity of organism at every level of classification.

Taxonomy, systematics or classification of organisms is based on the study of their comparative morphology (form, external and internal structure), cytology, embry­ology, fossil relatives, biochemical analysis and ecological relationships.

The knowledge is required by all biologists working in different fields, e.g., agriculture, forestry, industry, ecology, medicines, genetics, physiology, etc. It also helps in developing evolutionary rela­tionships, with or without the help of taxonomic studies of fossils.

History of Systematics:

Early classifications were concerned entirely for easy identification of useful and harmful plants and animals. Hippocrates (460-377 BC, father of medicine) and Aristotle (384-322 BC, father of zoology) arranged animals on the basis of habitat into aquatic, terrestrial, aerial animals.

On the basis of single character, Greek scholars divided animals into four major groups— insects, birds, fishes and whales. Theophrastus (father of botany, У10-285 BC) divided plants on the basis of form, texture and habit into four groups— trees, shrubs, under-shrubs and herbs. He described 480 plants in his book ‘Historia Plantarum’.

Pliny the Elder (28-79 A.D.) introduced the first system of artificial classification. His book, Historia Naturalis (c75 AD), mentions over 1,000 economic plants with about 2,000 items. More and more organisms were discovered and named. John Ray (1627-1705), English naturalist, described about 18600 plants in three volumes ‘Historia Generalis Plantarum’ between 1686-1704.

The naturalist introduced the word “species” in its present sense for the first time. John Ray defined species as an assemblage of individuals with similar par­entage and having ability to pass the parental traits to the offspring. Swedish naturalist Carolus Linnaeus developed the scientific system of naming species.

It is known as binomial system of nomenclature. Linnaeus described 5900 species of plants in his book Species Plantarum (1753) and 4326 species of animals in Systema Naturae (1758). The word sys­tematics is derived from Latin word ‘systema’ which means systematic arrangement of organisms. Linnaeus used syszterma Nature as the title of his book.

Right from Aristotle to Linnaeus, every systematic employed limited number of traits for classification of organisms. Therefore, the systems proposed by them remained artificial. Later on with increased in-depth study of various biological domains, more and more char­acters were taken into consideration by taxomonists.

It brought out natural affinities amongst organisms. This represented the phase of classical taxonomy which produced natural systems of classification. A modification of this system is numerical taxonomy or phonetics which came into existence during 1950s. Simultaneously biologists began to find out evolutionary and genetic relationships.

This resulted in development of phylogenetic clas­sification or cladistics (Gk. klaclos- branch, L. dados- branch). In cladistics organisms are arranged in historical order in which they evolved as branches of the parent stock. This phase is known as new systematics or biosystematics. Father of new systematics is Sir Julian Huxley (1940).

Basics of Systematic Study:

1. Characterization:

The organism to be studied is described for all its morphological and other characteristics.

2. Identification:

Based on the studied characteristics, the identification of the organ­ism is carried out to know whether it is similar to any of the known group or taxa.

3. Classification:

The organism is now classified on the basis of its resemblance to different taxa. It is possible that the organism may not resemble any known taxa or groups. A new group or taxon is raised to accommodate it.

4. Nomenclature:

After placing the organism in various taxa, its correct name is determined. If the organism is new to systematics, it is given a new name based on rules and conventions of nomenclature.

Classical Taxonomy:

It is taxonomy based on observable morphological characters with normal individuals considered to be expression of the same while their variations are believed to be imperfect expressions. Classical taxonomy originated with Plato followed by Aristotle (father of Zool­ogy), Theophrastus (Father of Botany) up to Linnaeus (father of Taxonomy) and his contem­poraries,

1. Species are delimited on the basis of morphological characters.

2. Only a few characters are employed for classification.

3. A few individuals or their preserved specimens are used for study. It is called typological concept.

4. Species are believed to be static or immutable.

5. Species is centre stage of study. Its subunits are not important.

New Systematics or Modern Taxonomy:

The term new systematics was coined by Julian Huxley (1940). New systematics is systematic study which takes into consideration all types of characters including those from classification morphology, anatomy, cytology, physiology, biochemistry, ecology, genetics, development (embryology), behaviour, etc. of the whole population instead of a few typo­logical specimens.

In contrast classical systematics is based on the study of mainly mor­phological traits of one or a few specimens with supporting evidences from other fields. New systematics is also called population systematics and biosystematics. It strives to bring out evolutionary relationships amongst organisms.

1. New systematics is based on the study of all types of variations in the species.

2. Along with morphological characters, other investigations are also carried out to know the variety of traits.

3. Delimitation of species is carried out on the basis of all types of biological traits. It is also called biological delimitation.

4. Traits indicating primitiveness and advancement are found out.

5. Inter-relationships are brought out.

6. Species are considered dynamic.