taxonomy

• Scientists have estimated that there are around 8.7 million species of plants and animals in existence. However, only around 1.2 million species have been identified and described so far, most of which are insects.
• Taxonomy


  A science that deals with the classification of organisms based on shared characteristics
• Binomial nomenclature


  A two-word naming system developed by Carolus Linnaeus, a Swedish scientist (1730s)
• Each species is assigned a scientific name that has two words. Scientific names are written in italics. The first word begins with a Capital letter. The second word is lowercase.
• Genus

  A group of closely related species. The first part of the scientific name in binomial nomenclature.
• Specific epithet

  The second part of a scientific name that is unique to each species. This part of the name often describes an important trait or the organism's habitat.
• Dichotomous key


  A simple tool for classifying organisms that uses two opposite characteristics with help of following specific directions that can lead you to the identity of an organism or a system
• The Linnaean Classification System


  • Species
  • Genus
  • Family
  • Order
  • Class
  • Phylum
  • Kingdom
• Species


  A group of individuals that can interbreed and produce fertile offspring
• Genus


  A group of closely related species; the first part of the scientific name in binomial nomenclature
• Family


  A group of similar genera
• Order


  A group of closely related families
• Class


  A group of closely related orders
• Phylum


  A group of closely related classes
• Kingdom


  The largest and most inclusive group in the Linnaean classification system
• Classifying organisms based on traits that are easy to see can lead to problems. Barnacles and limpets look very similar, yet they are not closely related. Barnacles and crabs do not look alike, yet they are closely related.
• Phylogeny


  A natural system of classification based on the evolutionary history or genealogy shared by a group of organisms

  
• Cladistics


  An analytical method of refining the evolutionary classification of organisms that involves identifying shared derived characteristics

  
• Cladogram


  A drawing that shows relationships among species and larger taxa by showing how evolutionary lines branched off from a common ancestor

  
• Derived character


  A trait that arose in the most recent common ancestor of a group and was passed on to its descendants
• The similarities and differences in homologous genes can tell how closely related organisms are. The more similar the genes in two organisms are, the more recently they shared a common ancestor. In these comparisons, genes and mutations are used as derived characters.
• Linnaeus' original system had only two kingdoms: plants and animals. Animals were organisms that moved and used food for energy. Plants included everything that was not an animal.
• Five Kingdoms


  • Protista
  • Fungi
  • Monera
• Six Kingdoms


  • Eubacteria
  • Archaebacteria
• Three Domains


  • Bacteria
  • Archaea
  • Eukarya
• Domain Bacteria


  Single-celled prokaryotes with unusual cell membranes and cell walls that do not have peptidoglycan. They live in some of the most extreme environments on Earth.
• Domain Bacteria

  Single-celled prokaryotes that do not have a nucleus and have thick cell walls that contain a substance called peptidoglycan. Some live in the soil, some make their own food by photosynthesis, and some are parasites that cause deadly diseases.
• Examples in Domain Bacteria and Archaea

  • Escherichia coli
  • Methanogens
• Domain Eukarya


  Contains all of the organisms that have a nucleus, including Protists, Fungi, Plants, and Animals.
• Protists


  This kingdom is not monophyletic, so many members are not closely related. Most are single-celled organisms, but the brown algae are multicellular. Some are photosynthetic, others are heterotrophic.
• Fungi


  Heterotrophs that have cell walls containing chitin. Most feed on dead organisms. Most are multicellular, some are single-celled.
• Plantae


  Make their own food by photosynthesis and have cell walls that contain cellulose. Most are multicellular, including green algae.
• Animalia


  Multicellular and do not have cell walls. Animals are heterotrophic and feed on other organisms or their remains. Most can move from place to place, at least in part of their life cycle.