Classification of Organisms. Plant Classification, Artificial, Natural and Phylogenetic Systems of classification complete notes for NEET/ Bsc/ Msc/ TGT/PGT Exams with MCQ questions.

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 Basics of Classification

  • The arrangement or grouping of organisms is called as Classification.
  • The organisms are recognized and assembled into groups on the basis of certain resemblance.
  • Taxonomy is the science of identifying, naming and classifying living organisms.
  • Scientific classification is a system of taxonomy used to organise group of organisms based on how closely they are related.
  • The groups thus formed and arranged are assigned to various levels, having a fixed sequence of arrangement.
  • There are several different levels of scientific classification between kingdom to species.
  • The largest group is KINGDOM or DIVISION.
  • The group assigned to the highest category is generally a division and the lowest category is usually a species.
  • The process is repeated until finally all the organisms have been assembled into a single, largest most inclusive group. These groups called as Taxonomic groups or Taxa. The orderly arrangement of taxa is called as taxonomic hierarchy.
  • TYPES OF PLANT CLASSIFICATION
  • ARTIFICIAL SYSTEM OF CLASSIFICATION
  • In artificial classification Plants are categorized on basis of easily observable characters like plant color plant habit etc.
  • Because many plants in a category are not closely related to each other by a common ancestor and they separated from their natural relatives simply as they differ in flower color and habit.
  • The system of classification was based on one or few easily observable morphological characters without giving any importance to affinities or interrelationship. More generally it includes single character
SEXUAL system of classification
  • Linneaus system: Linnaeus proposed his own artificial classification. With the goal to describe and classify all plants—and other living beings—that were “put on Earth by the Creator,” he grouped them based on the number and arrangement of stamens and pistils within flower.
  • He called this classification a “sexual system,” referring to the fundamental role of flowers in sexual reproduction. 
  • Based on the huge collection of plants during the exploration, he classified the plants and proposed a system of classification which is as a matter-of-fact artificial system or sexual system of classification.
  • This is exactly what the sexual system of Linnaeus achieved with merit. His Species plantarum (1753) marks the starting point of botanical nomenclature
  • In Species plantarum, he listed and described all the known species of plants. 
For each species there was:
(i) a generic name;
(ii) a polynomial descriptive phrase or phrase-name commencing with generic name and of up to twelve words, intended to serve as description of the species;
(iii) a trivial name or specific epithet on the margin;(
iv) synonyms with reference to important earlier literature; and

NATURAL SYSTEM OF CLASSIFICATION

  • Natural system of Classification was planned to reflect the relationship among plants.
  • Plants are classified according to their related affinities.
  • It is modern interpretation of past classification.
  • It reflects on the natural relationships of individuals.

George Bentham & Sir J.D. Hooker Classification

  • The system of classification of seed plants presented by Bentham and Hooker, two English botanists, represented the most well-developed natural system
  • The Genera plantarum of Bentham and Hooker provided the classification of seed plants describing 202 families and 7569 genera. They estimated the seed plants to include 97,205 species.

PHYLOGENETIC system of classification

  • Grouping of plants based on their evolutionary relationships(Phylogeny) and shared features from a common ancestor
  • Phylogeny refers to evolutionary history of group of organisms
  • Phylogeny is represented in form of a phylogenetic tree.
  • Example: Engler and Prant system of classification
Some MCQ questions:



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