Biology 7.1

• Taxonomy


  The science that deals with the description, identification, nomenclature, and classification of organisms
• Taxonomy takes into account how organisms are related, but it does not totally reflect evolutionary relationships
• Description


  The basic procedure in taxonomy that entails the assignment of characteristics to an organism for use in the succeeding steps
• Identification


  The step that determines whether an organism already falls under a previously identified organism
• Classification


  The step that involves the assignment of an organism to a particular level or rank in the taxonomic hierarchy
• Nomenclature


  The procedure in taxonomy in which organisms are named by using a standardized system, where formal scientific names should be in Latin
• Taxonomic hierarchy


  The system used to classify organisms, starting from the domain down to the species level
• Taxonomic classification groups organisms according to their relatedness
• Taxonomic levels


  • Domain
  • Kingdom
  • Phylum
  • Class
  • Order
  • Family
  • Genus
  • Species
• Organisms are more distantly related at the domain level and tend to share more similarities as we go down the taxonomic hierarchy
• Taxonomic traits


  The characters used to classify organisms according to their taxonomic groups, which are important in quantifying the degree of relatedness of species with one another
• Ancestral traits


  Evolutionary traits that are homologous within groups of organisms, which are expected to have descended from a common ancestor and are useful in classifying organisms at the domain, kingdom, or phylum level
• Ancestral traits are not informative in classifying organisms into the genus or species level
• Taxonomic characters


  Characters used to classify organisms according to their taxonomic groups
• Taxonomic characters


  • They are very important in quantifying the degree of relatedness of species with one another
• Categories of taxonomic characters

  • Ancestral traits
  • Derived traits
• Ancestral traits


  Evolutionary traits that are homologous within groups of organisms
• Ancestral traits are expected to be shared by organisms descended from a common ancestor
• Ancestral traits


  They are useful in classifying organisms up to the domain, kingdom, or phylum level
• Ancestral traits are not informative in classifying organisms at the genus or species level
• Ancestral trait


  • Presence of jaws in fishes, birds, and mammals
• Derived traits


  Characters that are present in a species but absent in their ancestor
• Derived traits are useful in studying the evolution of organisms
• Derived traits are usually products of evolutionary changes that allow organisms to adapt to their environment
• Derived traits are useful in classifying organisms into their specific taxonomic groups
• Derived traits


  • Presence of hair and milk production in mammals
• Derived traits are helpful in identifying species-specific traits
• Morphological traits


  The set of physical features of living organisms, both external and internal, that are useful for classification
• Taxonomists look for homology or similarities in the body structure when using morphological traits
• Homology in vertebrate forelimbs


  • Presence of related bones like humerus, radius, ulna, carpals, metacarpals, and phalanges
• Morphological traits are the main foundation of classical taxonomic science and remain useful in constructing the taxonomic tree of life
• Developmental traits


  The set of developmental features that can be used for the classification of organisms, observed during embryonic development
• Taxonomic groups may have minimal similarities in morphological features during adulthood but share homologous developmental traits
• Developmental stages can be useful as supplementary evidence for the classification of some groups
• The development of organisms is relevant in understanding their evolutionary path
• Developmental traits in vertebrates

  • Presence of distinct head, body, and tail region during early embryonic stages
  • Presence of pharyngeal slits
• Physiological traits


  Functional features of structures, focused on comparing the functions of body parts among organisms
• Physiological traits can be useful in constructing convergent evolutionary parts among distantly related organisms
• Analogous structures


  • Wings of birds and insects
  • Ant and horse legs
  • Pectoral fins in bony fishes and flippers of dolphins
• Genetic traits


  Specific sequences of the DNA molecule in organisms, useful in delineating organisms to the species or subspecies level