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3 Most Popular Methods in Classification •Evolutionary Systematics Ernst Mayr; G.G. Simpson phylogram •Phenetic Systematics Camin, Sneath, and Sokal phenogram •Cladistic Systematics Willie Hennig cladogram Evolutionary Systematics •Evolutionary systematics gives illustrations of the actual evolution of one species or higher taxon into another. •The method of reconstructing the evolutionary history (phylogeny) of a taxon by analyzing the evolution of major features along with the distribution of both SHARED PRIMITIVE and SHARED DERIVED characteristics Phenetics •Also called numerical taxonomy •Phenetics is a school of taxonomy that classifies organisms on the basis of overall morphological or genetic similarity •This mainly involves observable similarities and differences irrespective of whether or not the organisms are related •It involves grouping types together in clusters; types with many close relatives would be in a cluster •Unlike cladistics no attempt is made to distinguish between primitive from specialized (derived) characteristics. Cladistics (Phylogenetic Systematics) •Cladistics - also called Phylogenetic Systematics or Phylogenetic Taxonomy - is a method of classifying organisms by common ancestry, based on the branching of the evolutionary family tree •Based strictly on determining branching points in the ancestry of organisms, it establishes groups based on their shared, derived features, while ignoring primitive features inherited from ancestors •Organisms that share common ancestors (and therefore have similar features) are grouped into taxonomic groups called clades Practices under Taxonomy: 1. Identification 2. Classification 3. Nomenclature Characteristics of a Good Classification System 1. Universally accepted 2. Reflect real biological relationships Ultimate Purpose of Systematics “Provide a classification system that shows how biological diversity (past, present, and future) can be correlated into one another through evolutionary events and processes and that in turn provide basic knowledge on other fields of science such as agriculture, ecology, medicine, and most specially conservation biology” Schemes of Biological Classification • 2-Superkingdom-Scheme • 4-Kingdom-Scheme • 5-Kingdom-Scheme • 6-Kingdom Scheme • 3-Domain-Scheme 2-Super Kingdom Scheme Super kingdom Kingdom Age range Examples Prokaryota (Cell lacks nucleus) Monera 3500 my - Recent Bacteria & cyanobacteria ("blue-green algae") Eukaryota (Cell has a nucleus) Protista Late Precambrian - Recent Single-celled microfossils (diatoms, foraminifera) & multicellular seaweed Eukaryota Fungi Silurian Toadstools, fungi Eukaryota Plantae Silurian Plants. Multicellular Eukaryota Animalia Latest Animals. Biological Organization under 6-Kingdom SCHEME •Archaebacteria or Primitive Bacteria •Eubacteria or Modern Bacteria •Protista or Protists •Mycetae or Fungi •Plantae or Plants •Animalia or Animals 3 Domain Scheme