Classification System

Classification System

1. Definition : Arrangement of organisms into groups or taxon based on mutual similarity or evolutionary relatedness

2. Ways of Classification

   • Phenetic classification
     • Mutual similarity of phenotypic characteristic
     • Regardless of ancestral lineage
     • Not dependant on phylogenetic relationships
     • Numerical taxonomy
       • Simple matching coeffecient
       • Jaccard coefficent
     • Unweighted COmparison
   • Phylogenetic classification
     • Based on evolutionary relationships
     • Base on specific gene (e.g. 16S rRNA)
     • Possibility due to :
       • Highly conserved genetic sequence
       • Advancement in sequencing technique
     • Phylogenetic tree
       • Nodes : individual species
         • Internal node : ancestor
         • External node : living species
       • Branches : represent the evolutionary distance in between 2 species
       • Rooted : shows the phylogenetic relationship and the common ancestor
       • Unrooted : shows the phylogenetic relationship
   • Genotypic classification
     • Compare genetic similarity between organisms (individual genes or whole genomes)