Systematic

• Classification, the arrangement of objects, ideas, or information into groups, makes things easy to find, identify, talk about, and study
• The system we use today was developed by the Swedish naturalist Carolus Linnaeus who separated animals and plants according to certain physical similarities and gave identifying names to each species
• Taxonomy


  The branch of biology which concerns with classification and somewhat intergrades with systematics
• Zoological classification is the ordering of animals into groups (or sets) on the basis of their relationships
• Procedure of classification


  1. Evaluates multitudes of characters from specific to general

  2. Deals with populations and aggregates of populations

  3. Grouping and ranking of organisms
• Identification is the determination of the taxonomic identity of an individual
• Classification deals with populations in an inductive procedure while identification deals with individuals based on deductive reasoning process
• Dichotomous key


  A device that can be used to easily identify an unknown organism. It consists of a series of two part statements that describe characteristic of organisms
• Steps to follow in using Dichotomous Key


  1. Begin by reading the first couplet or pair of contrasting statements

  2. Select the statement that fits the organism you are identifying

  3. Follow the number or figure indicated at the end of the statement

  4. Read the couplet identified and continue the selection process

  5. The name at the end identifies the organism
• Zoological nomenclature


  The application of distinctive names to each of the groups recognized in the zoological classification
• The International Code of Zoological Nomenclature (ICZN) is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals
• Gender agreement


  In the species group, the name of a species must be grammatically correct Latin and its ending must agree in gender with the name of the genus
• Higher taxa


  All higher taxonomic names have one part (uninominal) and are plural. Names of taxa of the family and genus groups must be unique
• The major goal of systematics is to infer the evolutionary tree or phylogeny - the evolutionary history of a species or group of related species
• Phenetic (or numerical taxonomy)


  Classification methods that group organisms based on the degree of overall similarity between them, without necessarily reflecting genetic similarity or evolutionary relatedness
• Cladistic (or phylogenetic)


  Classification methods that group organisms based on their evolutionary relationships, recognizing groups that share unique derived characteristics (synapomorphies)
• Cladistic groupings must possess the following characteristics: 1) All species in a grouping must share a common ancestor, 2) All species derived from a common ancestor must be included in the grouping
• Monophyletic grouping


  All species share a common ancestor and all species derived from that common ancestor are included
• Paraphyletic grouping


  All species share a common ancestor, but not all species derived from that common ancestor are included
• Polyphyletic grouping


  Species that do not share an immediate common ancestor are lumped together, while excluding other members that would link them
• Steps for Constructing a Cladogram

  1. Select a taxonomic group to be analyzed

  2. Determine observable traits (characters) and their states for each member

  3. Determine which trait state is ancestral (plesiomorphic) and which is derived (apomorphic)

  4. Group taxa by shared derived character states (synapomorphies)

  5. Choose the most parsimonious tree
• Homologous


  Shared characters that result from common ancestry
• Analogous


  Similarity in structure due to convergent evolution rather than shared ancestry
• Shared primitive (ancestral) character


  Homologous structure that predates the branching of a particular clade from other members of that clade
• Shared derived (advanced) character

  Evolutionary novelty unique to a particular clade
• Taxon


  Designated group of species
• Clade


  Taxon that includes all the evolutionary descendants of a common ancestor
• Outgroup


  Closely related, but not part of the group being examined (the ingroup)
• Animals are multicellular, eukaryotic and heterotrophic
• Major animal phyla


  • Porifera
  • Cnidaria
  • Platyhelminthes
  • Nematoda
  • Mollusca
  • Annelida
  • Arthropoda
  • Echinodermata
  • Chordata