CLASSIFYING LIVING THINGS

• Taxonomy is a branch of Biology that classifies all living things. Let us study more about this. According to the history of biological classification, Aristotle, a Greek philosopher classified different animals based on their habitat, characteristic, etc.
• Taxonomic hierarchy refers to the sequence of categories in increasing or decreasing order
• Archaea are single-celled organisms like bacteria, some live in extreme environments
• Swedish botanist Carolus Linnaeus introduced Taxonomic Hierarchy Categories


  18th Century
• The word “Taxonomy” is derived from a Greek word – “taxis”, meaning arrangement or division, and “nomos”, meaning method
• On 1735, the kingdom is the highest rank and species is the lowest rank in the hierarchy
• (1735) In this system of classification, the kingdom is always ranked the highest followed by division, class, order, family, genus, and species
• Taxonomy is a branch of Biology that classifies all living things
• In 1990, domain is the highest rank of organisms
• Each level of the hierarchy is called the taxonomic category or rank
• Chordata includes animals with a dorsal nerve cord, Porifera are sponges, and Arthropoda are arthropods
• Examples of Phyla in the kingdom Animalia

  • Porifera
  • Chordata
  • Arthropoda
• Five kingdoms

  • Animalia
  • Plantae
  • Fungi
  • Protista
  • Monera
• A taxon is referred to as a group of organisms classified as a unit
• Phylum is the next level of classification, more specific than the kingdom
• Three domains of life

  • Bacteria
  • Archaea
  • Eukarya
• Aristotle, a Greek philosopher, classified different animals based on their habitat, characteristics, etc
• Class was the most general rank in the taxonomic hierarchy until phyla were introduced
• Kingdom is the 2nd to the highest level of classification, divided into subgroups at various levels
• Eukarya includes every living thing on Earth that is not a bacteria or archaea
• Classes used today are different from those proposed by Linnaeus and are not used frequently
• Kingdom Animalia includes 108 classes including Mammalia, Reptilia, Aves, etc
• Before domains were introduced, the kingdom was the highest taxonomic rank
• Taxonomy is a branch of Biology that refers to the process of classifying different living species
• Species can be further divided into sub-species
• Classes of plants today are different from those used by Linnaeus and classes are not always used in botany
• Order


  A more specific rank than class, constitutes one or more than one similar family
• Species is the lowest level of the taxonomic hierarchy, refers to a group of organisms similar in shape, form, reproductive features
• Classes of plants from Linnaeus are based on

  • Attributes like the arrangement of flowers but not on the relatedness of each
• Scientific name for humans is Homo sapiens. Homo is the genus name, sapiens is the species name
• Kingdom Animalia includes

  • 108 classes including class Mammalia, reptilia, aves, etc.
• While each genus name is unique, the same species names can be used for different organisms
• Orders still used today

  • Lepidoptera (butterflies and moths), Cetaceans (whales and dolphins), Carnivora and Chiroptera (bats), Primates (lemurs and chimpanzees)
• Components of DNA

  • Four bases (adenine, guanine, cytosine, thymine), sugar (deoxyribose), phosphate groups
• Species name is always italicized but never capitalized, the only taxonomic rank not capitalized
• Orders in class Mammalia include


  • Primates, Carnivora, etc.
• Families under the order Carnivora include

  • Canidae (dogs, wolves, foxes), Felidae (cats), Ursidae (bears)
• DNA tells the cell’s components to make proteins, the order of the four DNA bases determines which proteins are made
• DNA is the blueprint of life, contains instructions for making a living organism
• Genus


  A group of similar species, some monotypic (one species), some polytypic (more than one species)