Living world

• There is a wide range of living types and extraordinary habitats in which living organisms are found
• The number of species that are known and described range between 1.7-1.8 million
• As we explore new areas, and even old ones, new organisms are continuously being identified
• Nomenclature

  The process of standardising the naming of living organisms so that a particular organism is known by the same name all over the world
• Identification


  The process of describing an organism correctly and knowing to what organism the name is attached
• Binomial nomenclature


  • Each scientific name has two components - the Generic name and the specific epithet
  • This naming system given by Carolus Linnaeus is being practised by biologists all over the world
• Rules of biological nomenclature


  • Biological names are generally in Latin and written in italics
  • The first word in a biological name represents the genus while the second component denotes the specific epithet
  • Both the words in a biological name, when handwritten, are separately underlined, or printed in italics to indicate their Latin origin
  • The first word denoting the genus starts with a capital letter while the specific epithet starts with a small letter
• Classification


  The process of grouping anything into convenient categories based on some easily observable characters
• Taxa


  The scientific term for the categories used to study organisms
• Taxa can indicate single categories at very different levels, e.g. 'plants', 'wheat', 'animals', 'mammals', 'dogs'
• Taxonomy


  • The process of characterisation, identification, classification and nomenclature of organisms
  • It takes into account external and internal structure, cell structure, development, evolution and ecological information of organisms
• Systematics


  The branch of study that deals with the identification, nomenclature and classification of organisms, taking into account their evolutionary relationships
• Taxonomic categories and hierarchy represent a hierarchy of steps in the classification process, with each step representing a rank or category
• Nomenclature


  The system of scientific naming of organisms
• Classification


  The arrangement of organisms into groups based on their similarities
• Systematics


  The study of the diversity of organisms and their evolutionary relationships
• Systematics takes into account evolutionary relationships between organisms
• Taxonomic categories


  The hierarchy of ranks or units used in the classification of organisms
• Classification is not a single step process but involves a hierarchy of steps
• Each taxonomic category represents a rank or unit of classification
• Taxonomic categories and hierarchy can be illustrated by an example of insects
• Taxonomical studies have led to the development of common categories such as kingdom, phylum, class, order, family, genus and species
• The basic requirement for placing an organism in various categories is the knowledge of its characters
• Species


  A group of individual organisms with fundamental similarities
• Genus


  A group of related species which have more characters in common compared to species of other genera
• Family


  A group of related genera with still less number of similarities as compared to genus and species
• Order


  The assemblage of families which exhibit a few similar characters
• Class


  A category that includes related orders
• Phylum


  The next higher category after class, comprising animals like fishes, amphibians, reptiles, birds and mammals
• Kingdom


  The highest category in the classification system, comprising all animals or all plants
• As we go higher from species to kingdom, the number of common characteristics goes on decreasing
• Lower the taxa, more are the characteristics that the members within the taxon share
• Higher the category, greater is the difficulty of determining the relationship to other taxa at the same level
• The problem of classification becomes more complex as we go higher in the taxonomic hierarchy
• Taxonomic categories of some common organisms


  • Housefly
  • Man
  • Mango
  • Wheat