[Biology] Systematics

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INTRODUCTION

  • Systematics is the branch of biology that deals with the classification systems and nomenclature of living organisms.
  • Systematics is the basis of understanding evolution process of life

FIELDS OF SYSTEMATICS

The study of systematics is comprised of three distinctive fields which aid in the classification of organisms:

  • Identification
  • Classification
  • Nomenclature

IDENTIFICATION

  • Identification is used to recognize the correct place of an organism in a system of classification.
  • It is done with the aid of keys. An identification key, also termed as a taxonomic key, is a useful means of identifying unknown organisms. Keys are used for identification and are based on the alternate characters.

CLASSIFICATION

  • Classification is the system of arranging organisms into relevant groups.
  • Classification system helps the scientists to organize these organisms so that they can be studied easily.
  • Classification in Systematics can be divided into two closely related and interconnected levels of classification:
  • Taxonomic classification (known as the Linnaean System)
  • Phylogenetic classification

TAXONOMIC CLASSIFICATIONS

  • This type of classification groups living things together based on shared traits i.e. what they look like or what their bodies do.
  • For example, animals that lay eggs and have scales are called reptiles, and animals that have live births and have fur or hair are called mammals.
  • More specifically, all humans share the same characteristics and belong to a group (taxon) of the genus Homo, and species sapiens.

PHYLOGENETIC CLASSIFICATIONS

  • This type of classification uses the taxonomic names and further groups organisms on the basis of their evolutionary relationships
  • If you were to introduce someone to a group of people, you might start with his/her names (taxonomic classification), and then describe whose sister, brother, uncle, friend the person is or a total stranger (phylogeny).

NOMENCLATURE

  • Nomenclature is the system of naming organisms for easy identification.
  • Using the scientific name, an organism can easily be identified as well as information about its taxon can be derived from the name as well

TYPES OF NOMENCLATURE

  • Binomial nomenclature
  • Polynomials nomenclature
  • Trinomial nomenclature

BINOMIAL NOMENCLATURE

  • Binomial nomenclature is a binomial system of naming an organism.
  • Each organism’s name consists of two parts, the first name is genus and it starts with capital letter.
  • The second part’s name is species and it starts with the small letter.
  • This system was developed by Carolus Linnaeus and is used by biologists all over the world.

FOR EXAMPLE

  • Mangifera indica (Mango); here Mangifera is the generic name and indica is the specie name.
  • In terms of zoology, it is called binary nomenclature.
  • While in botanical terms, it is called a binomial classification system.

RULES FOR BINOMIAL NOMENCLATURE

There are certain rules for naming and classifying organisms to avoid any confusion and error:

  • Names should be in Greek or Latin language.
  • Generic name begins with capital letter (Mangifera) and is placed before species name, while species name begins with a small letter (indica).
  • The scientific name should be either underlined or italicized.
  • Name of the author should be written after species name in an abbreviated form. e.g., Homo sapiens Linn.
  • It indicates that the species is first described by Linnaeus.

POLYNOMIAL NOMENCLATURE

  • Before 1750, a polynomial nomenclature system was used.
  • In this nomenclature, the organism’s name consists of a series of Latin descriptive words.

FOR EXAMPLE

TRINOMIAL NOMENCLATURE

This system, devised by Lamarck, the organism is given a name consisting of three words i.e. genus, species, subspecies
FOR EXAMPLE: Brassica oleracea capitata (cabbage)

CODES OF BIOLOGICAL NOMENCLATURE

There are five codes of nomenclature which help to evade errors,

Duplication and uncertainty in scientific names:

  • International Code of Botanical Nomenclature (ICBN)
  • International Code of Zoological Nomenclature (ICZN),
  • International Code of Bacteriological Nomenclature (IC Вас N),
  • International Code of Viral Nomenclature (ICVN) and
  • International Code of Nomenclature for Cultivated Plants (ICNCP).

DIFFERENCE BETWEEN TAXONOMY AND SYSTEMATICS

REFERENCES

  • Arihant’s handbook of biology. The living world. Page no: 1-6.
  • NCERT biology; textbook for class 11. The living world. Page no: 1-62.
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