PPT 2

• Taxonomy


  Formal system for organizing, classifying, and naming living things

  
• When Carl von Linné (also known as Linnaeus; 1701-1778), a Swedish botanist, laid down the basic rules for classification and established taxonomic categories, or taxa (singular, taxon)


  More than 250 years ago
• Linnaeus realized early on that a system for recognizing and defining the properties of living beings would prevent chaos in scientific studies by providing each organism with a unique name and an exact slot in which to catalog it
• This classification would then serve as a means for future identification of that same organism, and permit workers in many biological fields to know if they were indeed discussing the same organism
• This system of classification served well in categorizing the millions of different kinds of organisms that have been discovered since that time, including organisms that have gone extinct
• Primary concerns of taxonomy

  • Classification
  • Nomenclature
  • Identification
• Nomenclature (L. nomen, name, and clare, to call)


  A system of naming; is the assignment of scientific names to the various taxonomic categories and individual organisms
• Classification


  Attempts the orderly arrangement of organisms into a hierarchy of taxa (categories)

  
• Identification


  Is the process of discovering and recording the traits of organisms so that they may be recognized or named and placed in an overall taxonomic scheme
• Main taxa, or groups, in a classification scheme

  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• All the members of a domain share only one or few general characteristics, whereas members of a species are essentially the same kind of organism—that is, they share the majority of their characteristics
• Scientific name


  Also known as the specific epithet, is assigned by using a binomial (two-name) system of nomenclature
• Binomial scientific name


  Combination of the generic (genus) name followed by the species name
• The generic part of the scientific name is capitalized, and the species part begins with a lowercase letter. Both should be italicized (or underlined if italics are not available)
• An organism's scientific name is sometimes abbreviated to save space, as in H. capsulatum, but only if the genus name has already been stated
• The source for nomenclature is usually Latin or Greek. If other languages such as English or French are used, the endings of these words are revised to have Latin endings
• In general, the name first applied to a species will be the one that takes precedence over all others
• Phylogeny


  The natural relatedness between groups of living things
• Biologists can apply their knowledge of phylogenetic relationships to develop a system of taxonomy
• Evolution


  The scientific principle that living things change gradually through billions of years and that these changes result in various types of structural and functional adaptations through many generations
• Natural selection


  The process where changes that most favor the survival of a particular organism or group of organisms tend to be retained, and those that are less beneficial to survival tend to be lost
• The occurrence of evolution is supported by a tremendous amount of evidence from the fossil record and from the study of morphology (structure), physiology (function), and genetics (inheritance)
• Evolution accounts for the millions of different species on the earth and their adaptation to its many and diverse habitats
• Premises of evolution


  • All new species originate from preexisting species through inheritance of traits
  • Closely related organisms have similar features because they evolved from common ancestral forms
• Robert Whittaker developed a five-kingdom system in the 1960s that remained the standard for many years
• Using new molecular methods, Carl Woese and George Fox proposed a classification system that some have likened to a shrub of life rather than a tree
• In this system, organisms are most broadly classified as belonging to one of three domains