Taxonomy NEET Notes | EduRev

Biology Class 11

NEET : Taxonomy NEET Notes | EduRev

The document Taxonomy NEET Notes | EduRev is a part of the NEET Course Biology Class 11.
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What is Taxonomy?

Taxonomy is a science that deals with the naming, describing, and classification of all living organisms including plants.

  • The word “Taxonomy” is derived from a Greek word – “taxis”, meaning arrangement or division, and “nomos”, meaning method.
  • Classification is based on behavioural, genetic, and biochemical variations.
  • Characterization, identification, and classification are the processes of taxonomy.
  • Carolus Linnaeus is considered the Father of Taxonomy. He is the one who developed a procedure to name and organize species. Even today this procedure is being followed. His contributions to taxonomy were:
    (i) Hierarchical classification system
    (ii) Binomial nomenclature system

What is Taxonomic Hierarchy?

Taxonomic hierarchy is the process of arranging various organisms into successive levels of the biological classification either in a decreasing or an increasing order from kingdom to species and vice versa.

  • Organisms are classified into similar categories namely kingdom, phylum, class, order, family, genus, and species.

Taxonomy NEET Notes | EduRev


Taxonomy includes the study of the following 4 points:

  • Identification: Identification of living organisms.
  • Nomenclature: Nomenclature of living organisms.
  • Classification: Classification of living organisms in groups.
  • Affinities: Study of the interrelationship between living organisms.

History of Taxonomy

Aristotle (382 B.C.)

  • Father of biology & father of zoology

Taxonomy NEET Notes | EduRevAristotle

Theophrastus

  • Time - 370 - 285 B.C. 
  • He is known as the father of ancient plant taxonomy and the father of botany. 
  • Both Theophrastus & Aristotle are Greek political philosophers.

Carolus Linnaeus [1707 - 1778] 

  • His real name was - Carl Von Linne.
  • On the basis of work in the Latin language, he changed his name to Carolus Linnaeus. He was a Swedish scientist.
  • He is known as the father of taxonomy, the father of plant taxonomy, and the father of animal taxonomy. 
  • Linnaeus gave the two kingdom system classification. He grouped plants and animals into kingdom Plantae and kingdom Animalia, respectively. 
  • Linnaeus wrote many books. Some important books are:
    (i) Hortus Uplandicus - First book
    (ii) Flora Lapponica
    (iii) Philosophia botanica
    (iv) Critica botanica
    (v) Systema Naturae (1737)
    (vi) Genera Plantarum
    (vii) Species Plantarum - last book (1753)

Try yourself:Taxonomy deals with
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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.

  • The study of only one organism of a group provides sufficient information about that group's remaining members. Scientists connected with the study of systematics are called systematists or taxonomists.
  • Linnaeus proposed the term "Systematics".
  • It includes a description of the external morphological characters of plants or living organisms.
    Example: Morphological characters of Root, Stem, Leaves, Flowers.


Taxonomy NEET Notes | EduRevLinnaean Classification System


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 organism's identification is carried out to know whether it is similar to any known taxa group.
  3. Classification: The organism is now classified based on 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 nomenclature rules and conventions.

Difference between Taxonomy & Systematics

Taxonomy NEET Notes | EduRev

Try yourself:The correct sequence of taxonomic study of a newly discovered organism is
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Nomenclature

1. Polynomial System

According to this system, the name of any plant consists of many words. 
Example: Caryophyllum–Caryophyllum saxatilis folis gramineus umbellatis corymbis.

2. Binomial System

  • Gaspard Bauhin first proposed the binomial system in his book - "Pinax Theatre Botanica."
  • Principle of Priority: The nomenclature done by the principle of priority. If two names are proposed for any plant after 1753, the valid name is the earlier name proposed just after 1 May 1753.

3. Trinomial System

  • Proposed by Huxley and Strickland.
  • According to this system name of any plant or species is composed of three names:
    (i) Generic name
    (ii) Specific name
    (iii) Subspecific name (Name of variety) 
  • When members of any species have large variations, then the trinomial system is used. Based on dissimilarities, this species is classified into subspecies.
    Example: Brassica oleracea var. botrytis (Cauliflower), Brassica oleracea var. Capitata (Cabbage), Brassica oleracea var. Caulerpa (Knol-Khol).

ICBN (International Code of Botanical Nomenclature)

  • ICBN - Book of rules of nomenclature.
  • The collection of rules regarding the scientific - Nomenclature of plants is known as ICBN.
  • ICBN was firstly proposed by – Sprague, Hitchcock, Green (1930). 
  • ICBN was first accepted in 1961. 
  • 12th International Congress, Leningrad, revised ICBN in 1975. 
  • After revision, it was republished in 1978. So that ICBN was published two times in 1961, 1978.
  • ICNB = International Code of Nomenclature for Bacteria.
  • ICVN = International Code of Viral Nomenclature.
  • ICNCP = International Code of Nomenclature for Cultivated Plants.

Main Rules of ICBN

  • According to the binomial system name of any species consists of two names:
    (i) Generic name - Name of the genus
    (ii) Specific epithet - Trivial name
    Example: Specific Name - Mango, Generic Name - Mangifera indica 
  • In-plant nomenclature (ICBN) tautonyms are not valid i.e. generic name and specific name should not be the same in plants.
    Example: Mangifera Mangifera
  • But tautonyms are valid in animal nomenclature (ICZN-International Code of Zoological Nomenclature).
    Example: Naja naja (Indian cobra), Rattus rattus (Rat) 
  • The generic name or specific name's length should not be less than 3 letters and not more than 12 letters.
    Example: Mangifera indica
  • The first letter of a generic name should be in capital letters, and the first letter of a specific name should be in small letters.
    Example: Mangifera indica
  • But if a specific name is based on some person's name, its first letter should be in capital letter.
    Example: Isoetes Pantai
  • When written freehand or typed, then the generic name and specific name should be separately underlined. But during printing name should be italicized.
  • The scientist's name (who proposed nomenclature) should be written in short after the specific name.
    Example: Mangifera indica Lin
  • The scientist's name should be neither underlined nor written in italics, but written in roman letters (simple alphabets).
  • If any scientist has proposed the wrong name, then it should be written in the bracket, and the scientist who corrected the name should be written after the bracket.
    Example: Tsuga canadensis (Lin.) Salisbury
    Note: Linnaeus named this plant Pinus Canadensis.
  • Scientific names should be derived from Latin or Greek languages because they are dead languages
  • The type specimen (Herbarium Sheet) of the newly discovered plant should be placed in the herbarium (Dry garden). 
  • The standard size of a herbarium sheet is 11.5 × 16.5 inches.

Try yourself:ICBN stands for
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Biological Classification

The art of identifying distinctions among organisms and placing them into groups that reflect their most significant features and the relationship is called biological classification. 
  • The purpose of biological classification is to organize the vast number of known organisms into categories that could be named, remembered, and studied.

According to"A.P. de Candolle", classification is of two types:

1. Empirical Classification 
Taxonomy NEET Notes | EduRev

Flora
  • In this type, the actual nature or character of plants is not considered. 
  • Plants are classified on the basis of their alphabetical order, i.e. on the basis of the name of the plant.
  • On the basis of name, the plant kingdom can be classified into 26 groups. (There are 26 alphabets in English - According to this classification, all plants having the same initial alphabet, are placed in one group.
    Example: If the name of plants, starts from 'A', then it is placed in "A -group". Similarly, if it starts with 'B', then it is placed in "B - group".
  • This is not a true classification. It has only one application:- "Listing of flora". 
  • If any scientist, writes the flora of a particular area, then he uses empirical classification.
  • Flora → Plants growing in a particular area. 
  • Two books in which flora of India is written:
    (i) Flora British Indica → By J.D. Hooker
    (ii) Flora Indica → By William Roxburgh

2. Rational Classification 

In this classification, plants are classified on the basis of their actual character or nature i.e. by viewing the characters.

Types of Rational Classification:

(a) Practical Classification

  • In this type of classification, plants are classified on the basis of their economic importance. In this type of classification, morphology of plants is not considered.
    Example: Oil yielding plants (Coconut, Walnut), Soybean Fibre yielding plants (Jute, Cotton), Medicinal plants (Rauwolfia, Cinchona, Eucalyptus)
    Example: Turmeric - Multi uses plant, it gives both medicines and spices.
  • Note: In this classification, any one plant can be a member of more than one group. 

(b) Artificial Classification

  • In this type of classification, plants are classified on the basis of one or two morphological characters. i.e. overall morphology is not considered.
    Example: Classification proposed by Linnaeus is Artificial Linnaeus classified the plant kingdom on the basis of only two characters: Stamens & Carpel 
  • On the basis of stamens and style, Linnaeus classified the plant kingdom into 24 classes 
    (i) Monandria — Those flowers in which only 1 stamen is present.
    (ii) Diandra —  2 stamens in a flower
    (iii) Triandria — 3 stamens in a flower
    (iv) Polyandria — Many stamens
    (v) Nonandria/Cryptogamia — No stamens

Note: Linnaeus divided flowering plants into 23 classes starting with class monandry with a single stamen, (Example - Canna) and plants with twenty or more stamens attached with calyx were assigned to class Icosandria.  He also included all non-flowering plants such as algae, fungi, lichens, mosses, and ferns in a separate class called Cryptogamia or Nonandria.

Try yourself:The classification of Linnaeus was mainly based on
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(c) Natural Classification

  • In this type, plants are classified on the basis of their complete morphological characters of the stem, root, leaves, flowers, etc. Maximum characters are taken as a base in this classification.

Taxonomy NEET Notes | EduRevBrassica Oleracea

(d) Adansonia System or Phenetic Classification or Numerical Classification

  • Numerical taxonomy was developed by Skol and Sneath.
  • It uses characters in the form of numbers, mathematical formulas, and statistics to study the relationship among organisms.
  • In this, importance to anyone character is not given, all characters have the same importance. While in natural classification, floral (reproductive) characters have more importance than vegetative (root, stem, and leaves) characters.

(e) The Phylogenetic System of Classification

  • It was first proposed by British scientist John Hutchinson.
  • The basis of the phylogenetic system of classification is the ancestral history of the organisms. It is based on the theory that organisms with the most common characteristics have originated from a common ancestor.
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